Theoretical studies suggest that gravitational collapse can form either a black hole or a visible (naked) singularity. Identifying observational signatures that distinguish these two types of collapsed objects is a holy grail of physics. Here, we examine whether relativistic accretion disk spectra can provide such a test. We construct an additive table model for a thin accretion disk in the Joshi-Malafarina-Narayan (JMN-1) naked singularity geometry matched to a Schwarzschild exterior and fit it to NuSTAR X-ray data from the AGN MCG-06-30-15. Our results are compared with standard Kerr and Schwarzschild black hole models. We also include the relativistic reflection spectral component relxill. Despite their different underlying geometries, the spinning (Kerr) black hole and the non-spinning JMN-1 naked singularity provide similar spectral fits, which are significantly better fits than the Schwarzschild black hole. This degeneracy between the naked singularity and the Kerr black hole could lead to incorrect spin measurements of collapsed objects using disk spectra. The degeneracy could be broken with an independent spin measurement, which could also help identify a naked singularity. Our results could also have a role in different spin distributions of collapsed objects measured from gravitational-wave sources and X-ray binaries.

This document presents an overview of the design, implementation, and expected performance of the Advanced Virgo Plus (AdV+) upgrades in view of the O5 observing run. Following the experience gained during the O4 commissioning and operations, the Virgo Collaboration has revised the upgrade strategy to address limitations associated with marginally stable recycling cavities. The O5 upgrade program combines elements from the original AdV+ Phase II project with new design solutions, including the implementation of stable recycling cavities, a major modification to the central interferometer layout, and a comprehensive renewal of critical subsystems. The planned upgrades are organized in two steps, targeting progressive improvements in operational stability, noise reduction, and detector sensitivity. Key developments include new vacuum infrastructures, suspensions, mirrors, optical configurations, quantum noise reduction systems, and high-power laser technologies. The resulting configuration is expected to significantly enhance the interferometer performance, enabling a substantial increase in astrophysical reach and scientific return during O5.

According to the leading cosmological model, a first generation of stars called Population III (PopIII), condensed almost entirely out of hydrogen and helium, must have initiated the creation of all heavier chemical elements. Here we report the detection of ionised hydrogen (H$\gamma_{4342}$) with $S/N$=5.9 in a region about 3 pkpc (projected) North-East from the z~10.6 galaxy GN-z11, where line emission compatible with doubly ionised helium (HeII$_{1640}$) had been found. Our new JWST/NIRSpec-IFS G395H data confirm the authenticity of the previous detection, at a redshift of $z_{\rm H\gamma}$=$10.5862$$\pm$$0.0003$. H$\delta$ is marginally detected ($S/N$$\sim$$2$). No metal lines are detected in our observations spanning $\lambda_{\rm rest}$=$0.25$-$0.45\mu$m. We derive a $3\sigma$ upper limit on the gas phase metallicity of 12+log(O/H)$<$6.96 ($Z_{\rm gas}$$<$$0.019~Z_\odot$). Through comparison with NIRCam imaging, we constrain a lower limit on the equivalent width of EW$_0$(H$\gamma$)$>$350Å. We compare our emission line constraints to model predictions and find them compatible with photoionization by PopIII stars, possibly intermixed with next-generation (PopII) stars. We infer an upper limit on the dynamical mass of $M_{\rm dyn}$$\lesssim$$3$$\times$$10^8M_\odot$. Our data provide novel support for the presence of PopIII stars nearby GN-z11, 440 Myr after the Big Bang.

We report the confirmation of a HeII$\lambda$1640 emitter located at 3 pkpc from the galaxy GN-z11, at z=10.6. The detection, based on JWST NIRSpec-IFU high-resolution spectroscopy, confirms a previous claim based on medium-resolution spectroscopy. The HeII$\lambda$1640 identification is further supported by the independent detection of H$\gamma$ obtained by Übler et al. (2026) at the same location. The HeII emission is spectrally resolved in two components separated by 120 km/s. The Equivalent Width of the HeII emission is extremely high ($>$20 A). No metal lines are detected. Population III stars appear to be the most plausible explanation for the observed HeII emission. We also discuss the possible contribution from a Direct Collapse Black Hole, or a Primordial Black Hole - these scenarios are less plausible, but cannot be ruled out completely.

The properties of the first metal-free stars remain largely unknown, and so far, the only data-driven constraints on their mass distribution (IMF) come from near-field cosmology. Here, we interpret new observations of the C1 and C2 components of Hebe, the HeII emitter near the galaxy GN-z11. Using a locally calibrated model, we robustly confirm the pristine (PopIII) nature of both components, showing that the measured upper limits on metal lines can only be reproduced by galaxies with $>50\%$ of their stellar mass in PopIII stars. We find that C1 is consistent with a purely PopIII system and adopt a simple parametric approach to infer the implications for the PopIII IMF and stellar mass. The observed $\rm HeII/H_\gamma$ ratio excludes steep IMFs, favoring top-heavy distributions, especially for young stellar ages ($\leq 1$ Myr). Combined with the HeII luminosity, this implies a total PopIII stellar mass of $2 \cdot 10^4 < M_\star/M_\odot < 6 \cdot 10^5$. While degeneracies between IMF, stellar mass, and age remain, adopting the lower stellar masses predicted by simulations ($M_\star < 10^5\,M_\odot$) strengthens the preference for top-heavy IMFs. Combining these results with near-field constraints, which instead exclude the flattest IMFs, we define a data-driven range of viable PopIII IMFs, linking characteristic mass and slope. This work demonstrates that direct observations of high-$z$ PopIII systems can place independent constraints on the IMF of the first stars, opening a new window on their formation and properties.

We present the first detailed analysis of the effects of dissipative dark matter on stellar streams. As a concrete example, we generate a cosmological hydrodynamic zoom-in simulation of a Milky Way-mass galaxy, assuming that the dark matter consists of Cold Dark Matter (CDM) with a sub-component ($\sim6\%$) of Atomic Dark Matter (ADM). The ADM subcomponent behaves as collisional, efficiently dissipative gas and allows for the formation of dense compact objects that enhance the central density of satellite galaxies, making them more resistant to tidal disruption. We show that stellar streams with stellar mass $M_{\rm{tot}, \star} \gtrsim 10^{5.5} \ \text{M}_\odot$ form later and exhibit prolonged star formation throughout their evolution, as compared to their CDM counterparts. Changes to star formation history are reflected on the chemical tracks of the stellar stream stars, where the youngest have enhanced [Fe/H] and [Mg/Fe] in the presence of ADM. Furthermore, a population of low-mass satellites with high ADM mass fractions is identified at low pericenter distances, which may affect the population of streams at $M_{\rm{tot}, \star} \lesssim 10^{5.5} \ \text{M}_\odot$. The results of this study should generalize to other dark matter models that lead to inner-density enhancements in satellites, such as elastic self-interacting dark matter in the gravothermal collapse regime.

We present spectroscopic followup observations of binary systems from the Gaia Data Release 3 (DR3) binary catalog that were selected to have large enough mass functions for their companions to be black holes or neutron stars. The selection includes 20 stars that are astrometric and/or spectroscopic binaries, as well as 11 stars with large accelerations both in the plane of the sky and along the line of sight but no DR3 orbital solution. We provide classifications for this entire sample, including radial velocity orbital solutions for 11 binaries. Apart from the previously published binaries Gaia BH1, Gaia BH2, and Gaia NS1, we show that the Gaia orbits are incorrect for all of the stars with candidate dark companions above 2 Msun. We suggest more conservative cuts on the significance and goodness of fit parameters that may be useful for identifying reliable orbital solutions in the tail of the binary star distribution. Although we find no new confirmed black hole or neutron star companions, one accelerating system has a minimum companion mass of 1.16 +/- 0.01 Msun that is likely to be a neutron star or an ultramassive white dwarf. The acceleration catalogs may therefore provide a largely unexplored source of additional wide binaries containing compact objects.

In this paper, we extend the foundational work of Bondi (1952) to include the effects of radiative feedback in gas-pressure-dominated environments. We construct steady-state spherically symmetric accretion solutions including radiative heating and cooling. Under the simplifying assumption of a constant opacity, the solutions are controlled by four dimensionless parameters: the adiabatic index $\gamma$, optical depth through the Bondi radius $\tau_B$, dimensionless luminosity at infinity $\tilde{L}_\infty$, and a characteristic dimensionless cooling time $\beta$. We present numerical solutions across the dimensionless parameter space $(\tau_B, \tilde{L}_\infty, \beta)\in [10^{-3}, 10^3]$. Contrary to radiation-pressure-dominated environments, radiative feedback primarily operates to suppress accretion -- particularly at high $\tau_B$, $\tilde{L}_\infty$, and/or $\beta$. We also present analytic descriptions confirming the suppressive nature of this feedback and give the scalings for the accretion rate $\dot{M}\sim \tilde{L}_\infty^{-5/4}$ at large $\tilde{L}_\infty$, $\dot{M}\sim \tau_B^{-10/11}\beta^{-5/11}$ at large $\tau_B$, and $\dot{M}\sim (\tilde{L}_\infty\tau_B)^{-5/8}$ for large $\tilde{L}_\infty\tau_B$. We discuss the potential role of convection in these steady-state solutions, and the particular relevance to problems of planet formation where radiative heating is significant, but the system remains in the gas-pressure-dominated regime.

The final stages of stellar evolution can be constrained by studying pre-SN variability. The incredible amount of data coming from the upcoming Rubin Legacy Survey of Space and Time (LSST) will be fundamental to this type of work. However, robustly measuring pre-SN variability can be hard, as even state-of-the-art image subtraction pipelines struggle when the target is embedded in a bright nearby galaxy. We developed Detection Efficiency and Threshold Estimation for Characterization of Transients (DETECT) to tackle this problem. It performs a series of source injection, image subtraction, and forced photometry to obtain reliable detection thresholds tailored to a specific location within a given host galaxy. We first validate the pipeline using simulated data from Rubin DP0 and then apply it to a sample of 15 targets found in Rubin DP1. We demonstrate that DETECT is capable of identifying pre-SN variability while calculating reliable upper limits and suppressing false positives for targets embedded in bright host galaxies. Most of the false positives in this work occurred when the signal-to-noise ratio (SNR) was between 5 and 10, while no false positives were found when the SNR was greater than 10. Finally, even though DETECT was originally developed in the context of pre-SN variability, it is broadly applicable to any situation where detections are uncertain and robust upper limits are needed.

We present multi-wavelength observations and a comprehensive analysis of the nearby (D$\sim$14 Mpc) Type IIb supernova (SN IIb) 2024iss. Observations of SN2024iss include an early ZTF detection at $\sim$40 minutes after first light and the earliest Hubble Space Telescope UV spectrum for a SN IIb to date at 7 days after first light. With the bolometric light curve and He-star models, we estimate an ejecta mass range of $\sim 1.1-3.3~M_{\odot}$ and a $^{56}\textrm{Ni}$ mass of $0.11 \pm 0.01~M_{\odot}$. We fit shock-cooling emission models to the first peak in the light curve and estimate a progenitor radius of $100-320~R_{\odot}$ and a H-rich envelope mass of $0.07-0.46~M_{\odot}$. We also compared optical/UV spectra to binary progenitor model spectra, which indicate a stripped H-rich envelope mass of $0.19-0.28~M_{\odot}$. We use early-time X-ray detections to calculate CSM densities that are consistent with a progenitor mass-loss rate of $5\times10^{-4}~M_{\odot}$ ($v_w = 100~$km/s), corresponding to a period of significant mass ejection in the final ~2-5 years before core collapse. In the UV spectrum, we observe strong Mg II emission extending to $\sim15,000 ~$km/s as well as weak P-Cygni profiles of iron-group elements (e.g., Fe, Ti, Al, Ni) present in the outer SN ejecta during the end of shock cooling phase. We find that the overall spectroscopic evolution of SN2024iss is comparable to other SNe IIb, but that the increased brightness following the initial light curve peak is likely influenced by SN ejecta-CSM interaction. Finally, optical/NIR nebular spectroscopy of SN2024iss at $\sim 260-412~$ days reveals multi-peaked forbidden line profiles of O I and Mg I] indicative of inner ejecta asymmetry and/or clumping. We demonstrate the utility of a rich, multi-wavelength dataset for constraining the progenitor systems and explosion dynamics of SNe IIb.

In the core accretion model of giant planet formation, the late stages of runaway growth are regulated by the hydrodynamic infall of gas from the protoplanetary disk. For a subset of planet-disk pairings, this scenario is analogous to the classical Bondi problem, which has motivated a Bondi-like parameterization of accretion in some population synthesis models. Existing models and the associated classical Bondi rate however, are predicated upon an adiabatic equation of state. In reality, the planet and its associated accretion shock supply a luminosity that substantially heats the accretion flow. In Paper I of this series, we demonstrate that such radiative feedback can dramatically suppress accretion by orders of magnitude. Here we quantify this effect under realistic planet-forming conditions. We find that for planets forming in an unperturbed disk, accretion is suppressed by 1-2 orders of magnitude interior to $\sim 10$ AU. For planets that open a gap, this feedback is less dramatic and the effect is $\sim$ 1 order in magnitude. We investigate the effect of various assumptions regarding dust opacities, shock efficiency, and planet radius and find this radiative suppression mechanism to be fairly insensitive to these effects. We also perform full time-dependent simulations demonstrating that the associated adverse entropy profiles are accurate and stable to convection. A simple and flexible set of open-source tools are provided to incorporate this radiative feedback into existing accretion models and population synthesis frameworks.

High-energy (HE) neutrinos have been observed by the IceCube (IC) Neutrino observatory for over a decade. Nevertheless, the astrophysical origin and the responsible mechanisms producing these HE neutrinos are still a mystery, with many astrophysical phenomena as potential emitters. A plethora of previous studies have attempted to study the correlation between HE neutrinos and active galactic nuclei, finding inconclusive results. Tidal disruption events (TDEs) have been proposed as candidate HE neutrino emitters, yet there is only one prior statistical study for the correlation of the two due to the limited number of observed TDEs. For this reason we used TDECat, an optical TDE repository, to investigate the potential association of TDEs with IceCube HE neutrino events. We implemented a spatio-temporal algorithm, where the temporal constraint is based on the transient nature of TDEs. We also simulated two sets of TDEs, correlated differently with neutrinos, to further study their statistical correlation. Despite the individual cases of TDE AT2019dsg and AT2021lo, we find no statistical association between optical TDEs and HE neutrinos. We find jetted TDE Sw J2058+05 to be spatio-temporally associated with a neutrino event. However, a $\gamma$-ray-flaring, flat-spectrum radio quasar is also within the neutrino's sky error region. Although our findings indicate no statistical correlation between optical TDEs and HE neutrinos, this correlation should be further studied in the future. Upcoming surveys such as the Legacy Survey of Space and Time, coupled with next-generation neutrino observatories, such as KM3NET and IceCube-Gen2, will expand both TDE and HE neutrino populations, clarifying their potential correlation.

Fast astronomical transients were observed by the VASCO Project (Villarroel et al 2020) in photographic sky surveys conducted in the 1950s. Those searches analyzed the Palomar Observatory Sky Survey (POSS-I and POSS-II) digitized plates. In this article, we present a preliminary report on a similar but independent search using archival plates taken at the Hamburg Observatory with the Großer Schmidtspiegel 1.2-m Schmidt camera, also from the mid-1950s. These plates were digitized by the APPLAUSE Archive, which provides both images and tables of detected objects. By analyzing pairs of plates taken in rapid sequence (about 30 minutes apart) of the same sky regions, we find evidence of transients similar to those previously reported by the VASCO Project for POSS plates. While the analysis is ongoing, one notable result is that our findings independently confirm that these transients exhibit systematically narrow full width at half maximum (FWHM) compared to stellar point spread functions. This provides further support for their interpretation as sub-second optical flashes, consistent with reflections from flat, rotating objects in orbit around Earth.

In this work, we investigate dark matter (DM) detection in the context of weakly interacting massive particles (WIMPs). Upon annihilation, WIMPs generate cascades of secondary particles through various channels, many of which culminate in the production of gamma rays. As these gamma rays travel toward Earth, their spectra are reshaped by interactions with the intervening medium. While current models typically account for attenuation via pair production on the extragalactic background light, they often neglect the fate of the resulting electrons and positrons, specifically subsequent inverse Compton scattering of these secondary particles, which can regenerate high-energy gamma rays. Here, we revisit the predicted gamma-ray fluxes from WIMP annihilation by performing a more detailed treatment of propagation effects. We show that for distant sources and annihilation channels such as $\tau^+\tau^-$, the full treatments can significantly alter the observed gamma-ray flux, by up to a factor of three orders of magnitude for heavy WIMPs. This has an impact on current dark matter limits derived without taking into account propagation effects, depending on the considered WIMP mass and annihilation channel. Our study demonstrates the importance of a detailed propagation treatment for indirect dark matter searches, and the need to account for such effects in order to obtain accurate, more reliable dark matter signal predictions and exclusion limits.

Many intermediate-mass close binaries exhibit photometric cycles longer than their orbital periods, likely related to accretion-disk variability. Previous studies indicate that historical light curves (LC) provide key constraints on disk evolution and may help trace mass-transfer changes in these systems. We investigate the short- and long-term variability of the eclipsing system OGLE-LMC-DPV-062, with special emphasis on the long cycle. Our aims are to clarify the role of the accretion disk in these modulations, particularly on timescales of hundreds of days, and to determine the evolutionary state of the system in order to better understand its stellar components. We analyzed 32.3 years of photometric time series from OGLE in the I and V bands, and from MACHO in the BM and RM bands. Using data from multiple epochs, we modeled the accretion disk at 20 equally spaced phases of the long cycle. To solve the inverse problem, we applied an optimized simplex algorithm to derive the best-fitting parameters of the stars, orbit, and disk. The MESA code was used to assess the evolutionary stage of the system and predict its past and future evolution. We find an orbital period of 6.904858(15) d and a long cycle of 229.7 d. The orbital solutions reproduce the LC, but the quasi-conservative mass-transfer scenario yields rates too high to be compatible with the observed orbital-period stability. We find consistency with the observed orbital-to-long-period ratio under the magnetic dynamo hypothesis. The normalized mass-transfer rate follows the long cycle, reaching a maximum at minimum brightness. At that phase, the inner disk edge thickens, obscuring a larger fraction of the gainer star. Disk variability occurs mainly in its vertical extent, with a standard deviation of 69% of the mean value at the inner border, whereas changes in outer radius and temperature are smaller, 7% and 5%, respectively.

RR Lyrae stars (RRLs) are classical tracers of old stellar populations, yet growing evidence suggests the presence of a metal-rich ([Fe/H]>-0.5), intermediate-age (2-7 Gyr) sub-population in the Milky Way disc. Binary evolution, particularly stable mass transfer, has been proposed as a viable formation channel, predicting that most metal-rich, intermediate-age (<9 Gyr) RRLs should reside in binaries with orbital periods of ~900-2000 days. However, no genuine RRL binaries have been robustly identified, including in the Gaia DR3 astrometric binary catalogues, despite Gaia being sensitive to the predicted orbital-period range. We investigate whether the lack of detections in Gaia DR3 reflects an intrinsically low binary fraction or instead arises from observational biases. We analyse a carefully selected sample of 100 Gaia DR3 RRLs designed to trace the metal-rich population with thin-disc kinematics and compare them with predictions from binary evolution models. We generate realistic Gaia observation mocks, including variability-induced astrometric biases, and assess the detectability of binaries and the posterior constraints on the hidden binary fraction using astrometric quality indicators, such as RUWE, and a robust Bayesian inference. While current uncertainties prevent a definitive rejection of a high fraction of hidden binaries, our results reveal tensions between existing binary evolution predictions and the Gaia DR3 non-detections. This suggests either the presence of unaccounted systematics in the modelling of Gaia observations or the need to revise assumptions in binary evolution models. We predict that Gaia DR4 will significantly improve the binary detectability and provide powerful new constraints on the post-interaction binary populations.

The population of binary black hole (BBH) mergers observed by the LIGO-Virgo-KAGRA (LVK) collaboration offers a window into the cosmic evolution of compact binaries and their formation. We employ the semi-analytic population-synthesis code B-POP to model BBHs assembled through isolated binary evolution and dynamical interactions in young, globular, and nuclear star clusters. Our framework incorporates star formation history, metallicity evolution, and single and binary stellar evolution to quantify their impact on the observable properties of the BBH population and on the relative contribution of distinct formation channels. Our models are characterized by a merger rate, $\mathcal{R} = 17.5-24.1\mathrm{Gpc}^{-3}\mathrm{yr}^{-1}$, broadly consistent with LVK constraints. Moreover, the predicted distributions of primary mass, mass ratio, and effective inspiral spin parameter are compatible with those inferred from current LVK observations. Our primary-mass distribution is dominated by isolated binaries at $m_1 < 20$ M$_\odot$, while dynamically assembled first- and higher-generation mergers dominate at larger masses. As a consequence, the sub-population of mergers with $m_1 > 45$ M$_\odot$ exhibits a nearly flat mass-ratio distribution and distinctive spin properties. We leverage our models to explore how: (i) the fraction of stars in isolated binaries and the fraction of stellar mass bound in clusters regulate the merger rate; (ii) common-envelope physics shapes the primary-mass distribution and its redshift evolution; (iii) the inclusion of stellar-collision products enhances the formation of higher-generation mergers; and (iv) the natal spin distribution influences the effective spin. Using our models to assess possible origins of selected GW events, we illustrate how the complexity of the underlying astrophysical processes can hinder the possibility to draw definitive conclusions.

We develop an accurate simulation-based inference framework for high-mass ($\gtrsim\!10^7 \rm{M_\odot}$) black-hole binaries observable by LISA. The method is implemented within the DINGO gravitational-wave parameter-estimation code, extending its application from ground-based detectors to the LISA band. We train a normalizing-flow model using aligned-spin higher-mode waveform models and a low-frequency approximation of the detector response. After sampling, we importance-sample to the true posterior. We validate performance on simulated signals spanning the signal-to-noise regimes relevant for LISA observations and benchmark our new DINGO implementation against standard methods. We report robust agreement in the inferred posterior distributions up to signal-to-noise ratios of $\sim\!500$. At higher signal-to-noise ratios of $\sim\!1000$, we observe a reduction in sampling efficiency, while still yielding unbiased and tightly localized posteriors that can be used as a starting point for follow-up with traditional this http URL trained flow can generate 20 thousand posterior samples in less than a minute, establishing DINGO as a promising neural inference framework for rapid full-parameter estimation of massive black-hole binaries in the LISA band. The likelihood-free nature of this approach allows for straightforward generalizations, including a time-dependent detector response, non-stationary noise artifacts such as gaps and glitches, and low-latency parameter estimations.

Ultra-compact massive galaxies (UCMGs) exhibit elevated stellar-to-dynamical mass ratios when dynamical masses are estimated using standard virial prescriptions. This discrepancy has been interpreted as non-homology driven by their compactness. This study investigates how the stellar-to-dynamical mass ratio depends on compactness (C), velocity dispersion ($\sigma_*$), stellar population properties (age, metallicity, and [Mg/Fe]), and star formation histories (SFHs). The analysis is based on a homogeneous sample of 482 UCMGs from the INSPIRE and E-INSPIRE surveys, extending to smaller sizes than previously analysed samples. I first derive the compactness-mass relation assuming a constant virial coefficient (K=5). I then correct stellar masses for IMF variations and recompute stellar-to-dynamical mass ratios using an empirical prescription where the virial coefficient varies with radius and stellar mass. Finally, I test modulation by stellar kinematics and population properties, including the degree of relicness (DoR), quantifiying the extremeness of the SFH. A statistically significant anti-correlation between compactness and the IMF-corrected stellar-to-dynamical mass ratio is recovered under a constant virial coefficient, but the relation flattens when a structure-dependent K is adopted. The data define a structural-dynamical manifold in the logC-log$\sigma_*$ space. Velocity dispersion sets the dominant axis of variation, and the corresponding plane accounts for ~62% of the variance in stellar-to-dynamical mass ratio. The stellar-to-dynamical mass ratio in UCMGs is governed primarily by the depth of the gravitational potential traced by $\sigma_*$, rather than C alone. At fixed size, systems with higher velocity dispersion show lower stellar-to-dynamical mass ratios. Non-homology therefore reflects coupled dynamical and evolutionary processes rather than purely geometric compactness.

Interstellar objects are interlopers from other planetary systems, and their volatile compositions provide a glimpse into planet formation around their host star. We present near-infrared spectra of the coma of interstellar object 3I/ATLAS measured with the James Webb Space Telescope. Our results demonstrate an unexpectedly high $\mathrm{D}/\mathrm{H} = (3.31\pm0.34)\%$ for methane and represent an exceedingly rare detection of deuterated organic molecules in an interstellar object. This D/H ratio is a factor of $14\pm2$ higher than that measured in comet 67P/Churyumov-Gerasimenko by the Rosetta spacecraft, the only other comet for which CH$_3$D has been detected, yet the ratio of deuteration in methane compared with water is consistent for both comets within $1.2\sigma$. The D/H ratio in methane is observationally unconstrained in extrasolar sources to date, but the enriched ratio in 3I/ATLAS is most similar to those measured in other organic molecules toward primitive environments. The high D/H ratios of water and methane in 3I/ATLAS are a natural consequence of formation in a high D/H elemental ratio environment as a result of locally cold conditions in the protoplanetary disk and prior interstellar cloud. Thus, 3I/ATLAS formed in an environment very different from that in which our Sun and planets originated.

As many research papers in astronomy have been written since the beginning of the 21st century as had been written previously. This exponential growth has been accompanied by substantial changes in the structure of astrophysics research, which organizations perform it and where they are located. Using data from the Smithsonian/NASA Astrophysics Data System/Science Explorer (ADS/SciX) we have obtained an article number and citation based set of metrics as a function of the institutional affiliation of the first author; nearly every organization which has produced recent astronomy research is included. We use these data to examine changes in where astronomy research is being done. We demonstrate how to create custom rankings for the organizations. We develop a dashboard of key performance indicators (KPI) to examine the relative and absolute changes in the research performance for each of the 1949 organizations which have produced at least one first authored, refereed astronomy journal article since 1997. We also present KPI dashboards for 65 countries and three regions.

We report a survey of molecular emission from cometary volatiles using the James Webb Space Telescope (JWST) toward interstellar object 3I/ATLAS carried out on UT 2025 December 22 and 23 at a heliocentric distance ($r_H$) of $2.37-2.41$ au. These measurements of CO, CO$_2$, H$_2$O, CH$_3$OH, and CH$_4$ sampled molecular chemistry in 3I/ATLAS as it receded from its encounter with our Sun and entered the vicinity of the H$_2$O ice line -- the region between $r_H$ = $2-3$ au where the temperature becomes too low for H$_2$O to vigorously sublime and CO and CO$_2$ begin to control the overall activity. CO was the most abundant molecule, followed by H$_2$O and CO$_2$, whose molecular abundances with respect to CO were $(44.4\pm0.7)\%$ and ($42.4\pm0.9)\%$, respectively. This work presents spatial-spectral maps of column density and rotational temperature as a function of distance from the nucleus for all detected species. The spatial distributions of both quantities were highly anisotropic for the apolar species in the coma of 3I/ATLAS, yet were more nearly symmetric for the polar molecules. These results demonstrate how volatiles were segregated in the nucleus ices of 3I/ATLAS and reveal heating and cooling mechanisms in its coma. Derived maps of the ortho-to-para ratio (OPR) for H$_2$O were flat with increasing distance from the nucleus and consistent with a coma-averaged value $\mathrm{OPR}=2.7\pm0.1$, slightly less than the expected equilibrium value of three.

Eclipsing binary systems with a Delta (${\delta}$) Scuti component serve a vital role in deriving precise fundamental stellar parameters and testing stellar evolution models. This study mainly focuses on the Kepler target KIC 8569819, a detached eclipsing binary system that consists of a ${\delta}$ Scuti pulsating component. The quarter 9 photometric data observed by the Kepler mission were used for the analysis. The binary nature of the KIC 8569819 system was modeled using the Wilson-Devinney (WD) code and extracted new set of stellar parameters. This comprehensive study mainly focuses on the application of the Differential Correction (DC2015) process after the initial fitting done by the Light Curve modeling (LC2015) process for the disentanglement of the binary nature from the observed light curve. Subsequently, an improved set of stellar parameters for both primary and secondary components of the KIC 8569819 system was determined. The DC2015 modeling process yielded an orbital inclination of $i=89.88\pm0.03$ degrees, primary component luminosity $L=10.911\pm0.005$ $L_{\odot}$, the effective temperature of the primary component of $T_{eff,1}=7155\pm9$ K and the effective temperature of the secondary component of $T_{eff,2}=5956\pm7$ K. Additionally, the values for the radius 1.790 $R_{\odot}$ and 0.986 $R_{\odot}$, bolometric magnitude $2.56$ mag and $4.65$ mag, and surface gravity $4.17$ $cm s^{-2}$ and $4.46$ $cm s^{-2}$, were found as refined stellar parameters for both primary and secondary components of the KIC 8569819 binary system respectively. These results not only deliver an updated and highly accurate stellar model for KIC 8569819 but also provide reliable input for the future analysis of mode identification of pulsation frequencies in the field of Asteroseismology.

Context. Gravitational waves (GW) provide a unique probe of the explosion mechanism of massive stars and the evolution of nascent proto-neutron stars (PNS). Magnetorotational explosions are one of the promising non-canonical core-collapse supernova scenarios, possibly linked to magnetar formation and energetic supernova explosions. However, the GW signatures of such events remain incompletely understood presently. Aims. This study investigates the origin and nature of gravitational-wave polarization arising from a magnetorotational core-collapse model and examines its potential detectability by current gravitational-wave observatories. Methods. We perform a three-dimensional simulation of general-relativistic magnetohydrodynamics of a rapidly rotating, strongly magnetized 20 M$_\odot$ progenitor, including multi-energy neutrino transport. The polarization states of the GW signals are analyzed with Stokes parameters. Results. We find that strong circular polarization emerges along the rotation axis during the early post-bounce phase (<230 ms after core bounce). The characteristic GW spectrum peaks at ~90 Hz, consistent with the emission at twice the local angular velocity (~45 Hz) around the PNS surface at cylindrical radii of ~50 km. These features are attributed to the low-T/|W| instabilities and non-axisymmetric motions near the PNS, rather than to the magnetohydrodynamic jets themselves. The polarization signals lie within the sensitivity bands of current GW detectors. Conclusions. Our study demonstrates that models launching magnetorotationally driven jets can produce circularly polarized GW signals originating from the inner PNS region. This provides an observational signature that complements previous findings from non-magnetized rotating models. Thus, our novel findings establish that the GW polarization is a promising diagnostic of non-canonical core-collapse supernovae.

A significant fraction of white dwarfs, the degenerate remnants of low- and intermediate-mass stars, host strong magnetic fields; yet, the origin and evolution of these magnetic fields remain poorly understood. Building a large, statistically robust sample of these magnetic white dwarfs (MWDs) is crucial for testing competing theories of field generation. We used the white dwarf candidates catalog from Gaia DR3 to select objects with spectra from the first data release of the Dark Energy Spectroscopic Instrument (DESI) survey. We identified candidate MWDs through visual inspection of their spectra, searching for the characteristic Zeeman splitting of absorption lines. After cross-matching with the literature, we present the discovery of 137 new MWDs. Follow-up analysis and atmospheric modeling were used to determine magnetic field strengths ranging from approximately 1 to nearly 500~MG. Our findings demonstrate the exceptional capability of large-scale spectroscopic surveys, such as DESI, to uncover rare stellar populations and advance our understanding of compact-object astrophysics.

Magnetic fields play a fundamental role in protostellar collapse and disk formation, yet direct measurements of magnetic field strength in deeply embedded protostellar envelopes remain difficult. We present a new method to estimate both the vertical and total magnetic field strength in collapsing, pseudodisk- or sheetlet-dominated protostellar envelopes, derived directly from the magnetohydrodynamic momentum equation. The method relates the magnetic field strength to two observationally accessible quantities: the projected gravitational acceleration toward the center of collapse and the face-on column density of the pseudodisk, and two dimensionless parameters, $a_{b, R}$ and $\gamma_{zR}$, which characterize magnetic contribution to the force balance and the field geometry, respectively, through $|B_z|=(2\pi a_{b,R}\gamma_{zR}g_R\Sigma)^{1/2}$. Using non-ideal magnetohydrodynamic simulations, we verify the assumptions underlying the method, justify the adopted approximations, and calibrate the two key dimensionless parameters. We provide canonical estimates of these two parameters, and show that they exhibit only weak spatial and temporal variations, allowing robust field strength estimates even when detailed gas kinematics or high-resolution polarization information is unavailable. We show that the method is applicable in both turbulent and non-turbulent envelopes and is insensitive to the ambipolar diffusion coefficient, making it robust against uncertainties in the local turbulence strength and ionization rate. We apply the method to the Class 0 source L1157, using column-density and gravitational-acceleration estimates from the literature to estimate the magnetic field strength for L1157. Our result is broadly consistent with previous estimates from independent methods, demonstrating the utility of this approach for constraining magnetic fields in embedded protostellar systems.

We present a model for pulsar filaments - a class of narrow X-ray nebulae misaligned with the proper motion, powered by pulsar-generated $e^\pm$. We suggest that cosmic ray-enhanced turbulence drives pitch-angle scattering and dominates $e^\pm$ motion along the filament; highly amplified magnetic fields are not required. A simulation built on this picture, using analytic approximations for the turbulence growth and cosmic ray evolution, generates images and spectra matching observations of the three best-measured filaments. The model structure depends on interstellar medium properties, and fits to filament data require values similar to observed ISM values. In this model a substantial fraction of the filament $e^\pm$ escape, free-streaming for many pc, in contrast to the suppressed cosmic ray diffusion near pulsar TeV halos. Accordingly, nearby low-power filament-generating pulsars may make out-sized contributions to the local positron spectrum. Future X-ray observatories can make the sensitive spectral maps required to test this particle escape.

The relative brightnesses of strongly lensed quasar images, called flux ratios, respond to perturbations from low-mass dark matter halos, enabling tests of dark matter models. The quasar narrow-line region (NLR) is ideal for flux-ratio studies: large enough to be insensitive to stellar microlensing, yet compact enough to remain sensitive to dark matter halo substructure. While nuclear emission dominates NLR flux, many quasars show low surface brightness extended emission spanning kiloparsec scales that could bias measurements. To test this potential bias, we generated mock Keck OSIRIS AO observations of seven $z<1$, $L_\mathrm{bol}\sim10^{46}$\,erg\,s$^{-1}$ quasars characteristic of sources. Only one system shows detectable extended emission after lensing. We introduce a new pipeline for simultaneously fitting point sources (nuclear) + Sérsic elliptical profiles (extended [O\,III]). We show that we recover the true flux-ratios to $<5\%$ even when the extended emission is boosted to 100 times its original flux. We also demonstrate that visual inspection of lenses reliably determines whether to use point-source-only or include extended emission modeling in the pipeline; both achieve $<5\%$ accuracy -- which is below the typical spectral fitting precision. The new pipeline and fitting procedure ensures reliable flux-ratio measurements can be made of narrow-line flux ratios for the thousands of lenses which will be discovered by Euclid, Rubin and Roman Space Telescopes.

Polarization measurements of fast radio bursts (FRBs) probe the magnetized plasma surrounding their central engines. FRB~20240114A is an exceptionally active repeating source, with 17,356 bursts detected between 2024 January 28 and 2025 May 30 by FAST, enabling time-resolved polarimetric studies. In this work, we present a polarimetric catalog of 6,131 bright bursts (with a signal-to-noise ratio S/N $\geq$ 20, 35.3% of the total sample), including arrival time (MJD$_{\text{topo}}$), dispersion measure (DM), burst width (W$_{\text{eff}}$), bandwidth, Faraday rotation measure (RM), linear and circular polarization degrees (DOL, DOC), and intrinsic polarization angle (PA$_0$). We detect a clear temporal evolution of RM: after an initial stable phase, it decreases linearly by $\sim$200 $\rm rad\ m^{-2}$ over 200 days, forming a bimodal distribution, whereas DM remains stable at 528.9 $\rm pc\ cm^{-3}$. The linear polarization fraction is generally high, with the 3$\sigma$ lower bound around 76%, while circular polarization is low, with 1,157 of 17,356 bursts (6.67%) having DOC $\geq$10%. We perform a power-law fit between $|\textrm{V}|$/I and $|\textrm{RM}|$, which yields an index of $-2.98 \pm 0.80$. It is found that the combined 2D distribution of L/I versus V/I remains stable, implying that the emission mechanism is largely invariant. Our PA$_0$ measurements show a broad, non-uniform distribution, implying a complex emission geometry. These results suggest that FRB~20240114A resides in a dynamically evolving magneto-ionic environment. This catalog provides a foundation for studies of repeating FRB progenitors and their environments.

Although the deuterium fraction is known to be a powerful evolutionary tracer, its variation within individual molecular cloud cores is still poorly understood. The northern $\int$-shaped filament and 20 individual starless cores in the Orion A and B clouds were mapped in the deuterated molecules of DNC and DCO$^+$ with the Receiver 7BEE installed on the Nobeyama 45~m radio telescope. In a ~ 5' X 30' map of the northern $\int$-shaped filament in the Orion A cloud, the DNC emission is detected over the filament, whereas the DCO$^+$ emission is localized toward OMC-3, the northernmost region of the filament. The difference in distribution between DNC and DCO$^+$ can be attributed to that between N- and C-bearing molecules as previously suggested by Tatematsu et al. High DNC/HN$^{13}$C column density ratios were observed in OMC-2 and OMC-3, and low ratios in OMC-1. It seems that OMC-2 and OMC-3 still contain molecular gas close to the onset of star formation. In 3' X 3' maps of the individual starless cores in Orion, the column density ratios of DNC/HN$^{13}$C and DCO$^+$/H$^{13}$CO$^+$ are found to be rather constant locally within each core, although the core-to-core variation is not small. Similar timescales of deuterization, depletion, and dynamical evolution might explain the locally constant ratio.

Unveiling the launching and driving mechanisms of powerful jets in active galactic nuclei (AGNs) is crucial for understanding the co-evolution of supermassive black holes (SMBHs) and their host galaxies. 1156+295 is a blazar at a redshift of z=0.729 and exhibits significant variability in long-term radio monitoring. Using multi-frequency Effelsberg single-dish flux density data from 2007 to 2012, we performed synchrotron self-absorption (SSA) spectral modeling and extracted the turnover frequency and turnover flux density. By combining SSA spectral modeling with the core size and brightness temperature from quasi-simultaneous very long baseline interferometry (VLBI) images, we estimated the jet magnetic-field strength and magnetic flux, and investigated their temporal evolution in 1156+295. The evolution of radio flux density, spectral shape, and jet structure is consistent with the shock-in-jet framework. The inferred magnetic flux reaching or exceeding the magnetically arrested disk (MAD) threshold, together with evidence that magnetic energy release precedes the radio flares, supports a magnetically driven jet scenario. Overall, our results place magnetic-field measurements, spectral evolution, and inner-jet structural changes on a common timeline, providing observational constraints on their coupled evolution during flares.

Unlike the complicated X-ray and radio structure observed in the North Polar Spur area, the South-Eastern part of the eROSITA bubbles can be reasonably well described as a propagating forward shock, plausibly created by the transient energy release at the Galactic Center. In this model, the physical radius of the bubble is $R_{\rm b}\sim 7-8\,{\rm kpc}$ and the age of the outburst is $t_{\rm age}\sim 5-8\,{\rm Myr}$. The visible segment of the shock front (located at a distance of $\sim 10-12\,{\rm kpc}$ above the Galactic Disk and at a similar distance from the Sun) is currently expanding with the velocity $\sim 700\,{\rm km\,s^{-1}}$ through the gas with density $n_e\sim 3\times 10^{-4}\,{\rm cm^{-3}}$, and the abundance of heavy elements in this gas is $Z\lesssim 0.1 \times Z_\odot$. Unlike constraints derived from the line-of-sight-integrated quantities, these are effectively in situ measurements of the circumgalactic medium (CGM) properties. Given the simplifying assumptions used in deriving the density, we assign a factor of 2 systematic uncertainty to the final estimate. An eventual decisive test for the shock properties can be provided by the velocity measurements of the X-ray-emitting gas with soft X-ray bolometers. The extended forward shock propagating through low-metallicity gas is a favorable site to accelerate very high-energy cosmic rays, which might contribute to the observed proton-rich galactic cosmic ray component at PeV energies.

In this study, we investigate the scenario in which the stochastic signal arises from primordial gravitational waves. Within this framework, we consider two distinct possibilities: one in which the pulsar timing arrays (PTAs) signal corresponds to a stochastic gravitational-wave background (SGWB), and one in which it does not. Primordial gravitational waves can generate an SGWB spanning an exceptionally broad frequency range and are also a source of B-mode polarization in the cosmic microwave background (CMB). We combine CMB B-mode polarization data from BICEP/Keck (BK18), Planck (Planck18), and baryon acoustic oscillation (BAO) measurements with SGWB limits from PTAs to derive updated constraints on the tensor spectral index of the primordial power spectrum. Under the assumption of no detection of an SGWB from PTAs, the allowed parameter space excludes a large portion of the positive region. The constraint within PTA limits is $n_t= -0.165^{+1.20}_{-1.56}$ at $95\%$ confidence level, which are consistent with those obtained from the combined BK18+Planck18+BAO dataset, leading to tighter constraints on the tensor spectral index. Conversely, if the PTA signal is interpreted as an SGWB, the likelihood distribution for the tensor spectral index favors positive values, with $n_t= 2.39^{+1.46}_{-1.35}$ at $95\%$ confidence level, providing evidence for a blue-tilted primordial gravitational-wave power spectrum. In this case, the allowed parameter space excludes the negative region.

The Pillars of Creation in M16 represent an iconic star-forming region where stellar feedback shapes molecular cloud evolution. We present a detailed investigation of dust extinction and density structure in the Pillars of Creation using multiband photometric observations from \emph{JWST} NIRCam. A high-resolution (2\arcsec) extinction map reaching depths of $A_V\sim 100$ mag has been constructed using NIRCam filters F090W, F200W, F335M, and F444W. This map clearly reveals the intricate structure of dense gas within the molecular cloud in the Pillars of Creation region. Analysis of the column density probability distribution function (N-PDF) exhibits a characteristic lognormal distribution at intermediate extinctions ($A_V\approx10-30$\,mag), which transitions to a power-law tail at high extinctions ($A_V\gtrsim$ 30\,mag) where star-forming cores reside. The power-law slope $\alpha$ displays significant spatial variation, steepening from $\alpha\approx 2.0$ at the pillar tips facing the NGC 6611 cluster to $\alpha\approx$4.0 in regions distant from the cluster. This systematic gradient demonstrates that stellar feedback not only disperses molecular clouds but can also locally enhance the formation of dense, self-gravitating structures through radiative compression.

Based on Insight-HXMT observations, we present a detailed timing analysis and spectral evolution of a complete Main High state for Her X-1 in February 2020. We determine an accurate local ephemeris using the Rømer delay measured from five eclipses. We report the spin period of the neutron star at $P_{\rm spin}=1.23765212 \pm 0.00000026$ s with a spin period derivative of $\dot P_{\rm spin}=-(1.18\pm 0.04)\times 10^{-13}$ s\,s$^{-1}$. By combining the newly measured local values $T_{ecl}$ with those reported in the literature, we refine the orbital ephemeris of Her X-1, obtaining $T_{ecl} = 46359.871956 \pm 0.000010$ MJD and $P_{orb}=1.7001674990 \pm 0.0000000105$ day, then detect a continuous decrease in the orbital period with a rate of $\dot{P}_{\rm orb} = -(1.957 \pm 0.335)\times10^{-11}\,\mathrm{d\,d^{-1}}$. We also investigate the evolution of X-ray spectral parameters during the Main High state. The hydrogen absorption column density $N_{\rm H}$ increased monotonously during the phase, and the photon index kept nearly constant. The cyclotron absorption line was detected with a centroid energy around 38 keV, showing no significant evolution with luminosity. The spectral variations with the superorbital phase are discussed within the accretion disk precession scenario.

X-ray polarization observations of pulsar wind nebulae (PWNe) provide crucial insights into magnetic field structures and particle acceleration mechanisms. While the Imaging X-ray Polarimetry Explorer (IXPE) has made significant contributions to PWN studies, its limited effective area restricts observations to only the brightest sources, leaving many fainter nebulae unexplored. We evaluate the polarization capabilities of the enhanced X-ray Timing and Polarimetry mission (eXTP) for studying PWNe and establish a methodology for simulating eXTP Polarimetry Focusing Array (PFA) observations using modified IXPEOBSSIM. We develop and validate a simulation framework with appropriate response functions and instrumental background models, conducting comprehensive simulations of twelve PWNe selected from the SNRcat catalogue across various evolutionary stages and brightness levels. Our simulations demonstrate that eXTP provides approximately a factor of 2 improvement in minimum detectable polarization at the 99\% confidence level (MDP$_{99}$) compared to IXPE. For the brightest targets (N157B, G54.1+0.3, and Mouse), 1 Ms observations achieve MDP$_{99}$ values of 4-5\%. The area with significant polarization detection for extended sources like Vela PWN is nearly twice as large as achievable with IXPE. These enhanced capabilities will significantly expand the sample of PWNe with robust X-ray polarization measurements, enabling systematic studies of magnetic field structures, particle acceleration mechanisms, and PWN-environment interactions across different evolutionary phases.

Local primordial non-Gaussianity, parameterised as $f_{\rm NL}^{\rm local}$, will be stringently constrained using state-of-the-art methods applied to next-generation galaxy redshift survey data. In this paper, in preparation for the upcoming data sets, we demonstrate for the first time the joint field-level inference of $f_{\rm NL}^{\rm local}$, nuisance parameters, and the initial conditions in realistic halo catalogues, ones which are generated through full dark-matter-only $N$-body simulations. The field-level inference algorithm optimally constrains $f_{\rm NL}^{\rm local}$ through a Bayesian forward-modelling approach at the field level, which outperforms traditional methods by leveraging the full statistical power of the data at the scales considered. In addition, we assess its performance under various design choices in the forward model, including tests of the structure formation model and resolution. We demonstrate the robustness of our approach by applying it to a subset of the \textit{Quijote} simulation suite, performing the inference at scales down to $k_{\rm max} \approx 0.1 h \rm{Mpc}^{-1}$. Compared with a power spectrum and bispectrum estimator, we find a $\sim1.3$ improvement in $\sigma(f_{\rm NL}^{\rm local})$ when applying \borg{}, while marginalising over the initial conditions and bias parameters. From the small-scale information sensitivity tests, we show that the constraints on $f_{\rm NL}^{\rm local}$ improve as we increase the resolution of the inference. These findings underscore the transformative potential of field-level inference to leverage the information available in ongoing surveys such as \textit{Euclid}, providing accurate insights into the physics of cosmic inflation and the number of fields driving it.

Neutron stars serve as unique laboratories for studying ultra-dense nuclear matter. The equation of state of neutron star matter can be effectively constrained by their masses and radii. Particular attention has been paid to rapidly rotating neutron stars, where strong relativistic effects leave imprints on their electromagnetic emission. To model the emission of rotating neutron stars in more realistic situations, especially when their surface emission is further re-processed by a scattering medium, we develop Monk-NS, a customized version of the general relativistic Monte-Carlo radiative transfer code Monk. We validate the code through a series of benchmarking tests, including computing the energy spectrum, pulse profile, and polarisation of rotating neutron stars, and comparing the results with those of the established codes in the X-ray timing community, yielding consistent outcomes. As an example to demonstrate Monk-NS's capabilities, we apply it to investigate various models proposed to explain the low pulsation amplitude of neutron star low-mass X-ray binaries. Our findings indicate that the dependence of the X-ray polarisation degree on the observer's inclination can serve as a key factor in distinguishing these models. We also find that complex hotspot morphologies yield polarisation properties different from those of circular hotspots.

BK Peg is a double-lined detached eclipsing binary containing two late-F stars in an orbit with small eccentricity. We use light curves from the Transiting Exoplanet Survey Satellite (TESS) and spectroscopic measurements from previous studies to measure the physical properties of the companions to a high precision. We obtain masses of $1.411 \pm 0.004$\Msun\ and $1.254 \pm 0.004$\Msun, and radii of $1.990 \pm 0.004$\Rsun\ and $1.460 \pm 0.004$\Rsun, which are among the most precise measurements made for these quantities in normal stars. These properties match theoretical stellar evolutionary models for a solar chemical composition and an age of 2.65~Gyr. We also present an updated ephemeris of the system, as a result of our TESS measurements and a collection of mid-eclipse times from previous studies.

We present a turbulence index independent framework for simultaneously deriving solar wind velocity and coronal electron density in the near-Sun region using the spectral broadening of spacecraft radio signals. The formulation accommodates arbitrary turbulence spectral indices ($p$), providing a direct analytical link between the observed Doppler spectra and underlying plasma parameters without assuming a fixed turbulence regime. This generalization extends conventional radio occultation techniques and enables consistent interpretation across multiple radio frequencies. We apply the method to X-band ($\sim$ 8.41 GHz) radio occultation measurements from JAXA's Akatsuki spacecraft during the 2016 and 2022 Venus - Earth superior conjunctions, spanning heliocentric distances of 1.4 - 10 $R_{\odot}$ and sampling both equatorial streamer regions and mid-latitude coronal holes. The retrieved electron densities exhibit systematic trends consistent with empirical coronal models and in-situ observations. By coupling the measured spectral widths with a turbulence-based frequency-scaling relation, we obtain a compact expression that links spectral broadening, solar wind speed, and electron density, applicable for any turbulence index $p$. Fast-solar-wind intervals, characterized by nearly isotropic turbulence, yield speed estimates in close agreement with expectations, while the anisotropic nature of the slow solar wind introduces small but systematic deviations. Our results refine earlier work and demonstrate that explicit consideration of near-coronal turbulence anisotropy is essential for accurate solar-wind parameter retrievals.

Accurate distance measurements to supernova remnants (SNRs) are crucial for understanding their physical properties and evolution. We present a novel method that combines CO line observations with three-dimensional (3D) extinction maps to determine distances to SNRs (G93.7$-$0.2, G109.1$-$1.0, G156.2+5.7, and G166.0+4.3) through their associated molecular clouds. For each SNR, candidate CO velocity components corresponding to interacting molecular clouds are identified based on previous observational evidence with refinements: [$-$19, $-$3] km s$^{-1}$ for G93.7$-$0.2, [$-$51, $-$46] km s$^{-1}$ for G109.1$-$1.0, [$-$10, 0] km s$^{-1}$ for G156.2+5.7, and [$-$27, $-$15] km s$^{-1}$ for G166.0+4.3. By examining extinction-distance profiles along the sightlines and identifying extinction jumps that spatially coincide with CO emission features, we derive distances of 1.82$\pm$0.13 kpc for G93.7$-$0.2, 3.05$\pm$0.15 kpc for G109.1$-$1.0, 0.60$\pm$0.15 kpc for G156.2+5.7, and 3.44$\pm$0.23 kpc for G166.0+4.3. Our extinction-based distances are largely consistent with previous estimates while with better accuracy and robustness.

We present an analysis of the photometric data of new main belt comet P/2023 JN16 (Lemmon) observed with the 1.35-m SkyMapper telescope at Siding Spring Observatory in 2024 during July - September. The faint object showed dusty activity during a long period. Some photometric parameters, such as SkyMapper r band magnitudes, Afrho parameters, and absolute magnitude were estimated. We estimate the nuclear radius for comet P/2023 JN16 to be less than 0.5 km. The activity of the object is possible driven by the release of large, slow-moving particles.

In an inhomogeneous universe, the Hubble frame used to describe the cosmic expansion does not, in general, coincide with a geodesic matter flow. In this work, it is shown that within a fully covariant framework, a non-geodesic observer congruence introduces an additional contribution to the relation between affine parameter and observed redshift, proportional to the line-of-sight projection of the observer 4-acceleration. This induces a dipolar modulation of the redshift itself, which propagates to any observable expressed in redshift space. Unlike the standard kinematic dipole associated with a global Lorentz boost, this contribution is sourced by the kinematics of the observer congruence along the past light cone and can exhibit a non trivial redshift dependence. These results provide a direct framework to identify such signatures in cosmological data, with potential implications for the interpretation of large-scale dipoles and redshift-based inference.

We propose the synchrotron self-Compton (SSC) scenario coupled with filamentary jet model, to reproduce the very high energy $\gamma$-ray emissions from Cen A. With reference to self-similarity of knot-like features in the jet, we assume nonuniform magnetic field associated with current filaments having various transverse sizes. For energetic electron production, the diffusive shock acceleration at sites distributed over the kiloparsec-scale jet is considered. We show that maximum Lorentz factor of the electron steadily exceeds $10^{8}$ due to suppression of synchrotron loss of the electrons trapped in weak magnetic field of the thin filaments, and inhomogeneous SSC in the inner jet can dominantly contribute to establishment of the pronounced hardening of $\gamma$-ray flux detected by the H.E.S.S. It is also suggested that the spectral contribution from diffuse regions of the outer jet potentially amounts to the observed Fermi fluxes.

Central compact objects are radio-quite young neutron stars associated with supernova remnants. They have relatively small dipole fields, $B_{\rm p} \sim 10^{10}\,{\rm G}$ as inferred from their spin parameters. X-ray observations and theoretical arguments imply the presence of stronger internal magnetic fields. We argue that the dipole fields of these objects are very close to what they had inherited from the \textit{core} of the progenitor by flux conservation and their small initial rotation frequency does not allow for the $\alpha$-process to enhance their poloidal fields. Although a full-fledged dynamo process can not proceed, relatively strong toroidal magnetic fields, $B_\phi \sim 10^{13}\,{\rm G}$, can be generated from the seed poloidal fields via the $\Omega$-effect in the proto-neutron star stage. We present a simplistic model for these processes and further speculate that the reason why these objects are born relatively slow-rotating is that they were not spun-up by acquiring angular momentum from the fallback matter.

We report the first detection of GeV gamma-ray flaring activity from the compact symmetric object (CSO)-like source 4C 76.03, based on 17 years of Fermi-LAT observations. Its long-term, time-averaged gamma-ray properties are consistent with the 4FGL-DR4 catalog. However, a time-resolved analysis with 100-day binning reveals two prominent flares occurring on timescales of approximately 30 days and 20 days, separated by about 2.5 years, with nearly identical fluxes, test statistic (TS) values, and photon indices. The short-timescale variability indicates localized and transient energy dissipation in the nuclear region, likely associated with newly injected jet components. Although the gamma-ray emission does not directly trace the long-term jet power responsible for building the observed radio structure, it demonstrates that the central engine remains active. In the context of CSO evolution, 4C 76.03 may represent a rare transitional case, where repeated energy injections allow the source to exceed the canonical 500 pc scale of most CSOs, providing key insight into the early stages of radio jet evolution.

The classical radio-loudness parameter $R \equiv f_\nu(5\,\mathrm{GHz})/f_\nu(4400\,\textÅ)$ compares a prompt accretion tracer with a radio numerator that mixes rapidly varying compact-core emission, lobe plasma surviving over millions of years, and host-galaxy synchrotron emission. We introduce a time-domain radio-loudness (TDRL) framework that makes this timescale mismatch explicit. The radio numerator is decomposed into compact-core and extended-lobe contributions, each weighted by a recovered fraction that depends on observing frequency, angular resolution, and surface-brightness sensitivity. For a single intermittently jetted AGN population, a two-state jet duty cycle convolved with exponential lobe fading yields an exact stationary Beta distribution for the normalized extended-radio response, whose mean is $f_{\rm duty}$ and whose variance scales as $(1+\chi_\nu)^{-1}$ with $\chi_\nu\equiv\taunu/t_{\rm switch}$. This result serves as an analytic reference model, while precise inference will require population models matched to specific survey selections. In this minimal reference model, the familiar GHz valley near the classical radio-loud/quiet boundary can in principle arise from short radio memory alone, without invoking two intrinsic engine classes; metre-wave surveys that recover diffuse emission and model the host galaxy contribution should progressively fill that valley. In the $(R^{core}_\nu,R^{lobe}_\nu)$ plane a core--lobe mismatch index distinguishes triggering, sustained, and remnant jet phases. A complementary two-barrier phase diagram in event-horizon-threading magnetic flux and jet-escape parameter provides a heuristic organizing scheme for jet launching and propagation through the nuclear medium. The framework offers testable, frequency-dependent predictions for current and future radio surveys.

We present a model-independent reconstruction of the quintessence scalar field's dynamics-both its potential and kinetic energy-directly from the latest cosmological observations. Our analysis combines DESI DR2 baryon acoustic oscillation measurements with the Pantheon plus Type Ia supernova compilation, employing Gaussian process with four distinct covariance kernels to avoid theoretical priors on the potential's functional form. Key findings reveal a monotonically decreasing potential with redshift, consistent with thawing quintessence, and a kinetic energy that crosses zero near $z\sim 1$, marking the dark energy-matter equality epoch. Notably, while apparent negative kinetic energy values emerge at intermediate redshifts (0.5<z<1.0), these are statistical artifacts within uncertainties, arising from error amplification in derivative reconstruction rather than new physics. Our results demonstrate the power of non-parametric methods to constrain dynamical dark energy and show minimal dependence on the choice of cosmological priors, whether from local (SH0ES) or early-universe (Planck) measurements.

We present a cosmological model-independent framework for testing general relativity (GR) on galactic scales by combining baryon acoustic oscillation (BAO) angular scale measurements with 120 galaxy-scale strong gravitational lensing systems. Using artificial neural networks (ANNs) and cubic spline reconstruction, we reconstruct the BAO angular scale from SDSS, BOSS, eBOSS, and DESI Data Release 2 (DR2), and infer the angular diameter distances to lenses and sources. Crucially, All the quantities used in the GR test are derived from observations and are independent of cosmological parameters such as the Hubble constant, the sound horizon, or the dark energy equation of state, minimizing potential biases from model-dependent distance priors. These distances are then incorporated into the strong lensing likelihood to constrain the parameterized post-Newtonian (PPN) parameter $\gamma_{\rm PPN}$ under two lens mass models: a constant-density-slope model ($P_1$) and a redshift-evolving model ($P_2$). For the $P_1$ model, the ANN reconstruction yields $\gamma_{\rm PPN} = 1.102^{+0.148}_{-0.125}$, consistent with GR at $1\sigma$ confidence level, while the cubic spline gives $\gamma_{\rm PPN} = 1.150^{+0.139}_{-0.118}$, consistent with GR at $2\sigma$ confidence level. For the $P_2$ model, the ANN reconstruction gives $\gamma_{\rm PPN} = 1.315^{+0.181}_{-0.155}$, compatible with GR at $2\sigma$, while the spline gives $\gamma_{\rm PPN} = 1.485^{+0.193}_{-0.168}$, showing mild tension at $\sim2.5\sigma$. The constraints exhibit a clear dependence on the adopted lens mass model, underscoring the critical role of lens modeling. No significant correlation is observed between $\gamma_{\rm PPN}$ and the Einstein radius. Overall, current galaxy-scale observations are consistent with GR, providing no evidence for deviations from Einstein's theory on kiloparsec scales.

Polycyclic aromatic hydrocarbons (PAHs) are commonly used as proxies for star formation, molecular gas content, and other interstellar medium (ISM) properties in our Galaxy and other galaxies. Given their abundance and brightness, polarization measurements of PAH features could, in principle, provide a probe of the ISM magnetic field and intrinsic PAH properties; however, the diagnostic power of PAH polarization remains to be established. Previous studies reported that the $11.3\,\mu$m PAH emission line in the northwestern nebula of the Herbig Be star MWC 1080 was polarized at $1.9\pm0.2$%. This level of polarization was explained via the paramagnetic relaxation process, which may allow the characterization of magnetic fields in the ISM. Using the same observations, here, we re-analyzed the $8-13\,\mu$m spectro-polarimetric observations taken with CanariCam on the 10.4-m Gran Telescopio CANARIAS (GTC), and we measure a polarization of $0.5\pm0.6$% within $11.3\pm0.2\,\mu$m, consistent with an unpolarized source, $0.6\pm0.2$% (instrumental polarization). We reproduce the previously reported polarized PAH emission line if the polarization fraction spectrum is oversubtracted by a constant instrumental polarization and the polarization uncertainties, which is inconsistent with the fundamentals of polarimetric data analysis. Thus, the published $8-13\,\mu$m spectro-polarimetric data taken with CanariCam/GTC provide no statistical evidence for a polarized $11.3\,\mu$m PAH emission line, in agreement with current dust models.

Molecular inventories in starless cores are powerful tools for probing the physical and chemical structures at the earliest stages of star formation. Wide-band spectral scans are invaluable for obtaining a comprehensive view of the chemical composition. In this paper, we present the first results from the project Q/W-band Observations toward Starless Cores in Orion (QWOSCO), which uses the Yebes 40-m telescope to survey 23 starless cores in the Orion cloud at the Q (31.0--50.5 GHz) and W (71.1--91.4 GHz) bands with a total bandwidth of 40 GHz. We detect approximately 40 molecular species and derive their column densities, with each species exhibiting a characteristic spread of roughly one order of magnitude. The derived isomer and isotopologue column density ratios, including A/E, ortho/para, cyclic/linear, HNC/HCN, 12C/13C, 14N/15N, 16O/18O, 32S/34S, and D/H, are consistent with expectations for starless environments. Our results together with the literature suggest that the complex organic molecules (COMs) CH3OH and CH3CHO are both likely ubiquitous in starless cores. The column density ratio of CH3CHO with respect to CH3OH in starless cores are comparable or lower by a factor of around 25 than those in hot corinos at the protostellar stages if the CH3OH column density is directly derived or rescaled from that of 13CH3OH, respectively. Accordingly, we discuss the possible roles of methanol opacity and chemical mechanisms across the starless and protostellar stages.

Efficiently sampling from high-dimensional, multi-modal posteriors is a central challenge in Bayesian inference for astrophysics, especially gravitational-wave astronomy. Popular families of methods like Markov-chain Monte Carlo, nested sampling, and importance sampling all rely on proposal distributions to guide exploration. Because prior knowledge of the target is often limited, practitioners can adopt adaptive proposals that iteratively refine themselves using information gained from previously drawn samples. Traditional adaptive strategies, however, struggle in high-dimensional multi-modal settings: complex, non-linear correlations are hard to capture, and hyperparameters typically require tedious, problem-specific tuning. To address these issues, we introduce Parallel Adaptive Reweighting Importance Sampling (PARIS). PARIS models its proposal as a Gaussian mixture whose component centers are the existing samples and whose component weights match the current importance weights. New draws from the proposal therefore concentrate around high-weight regions, while candidate points in unexplored areas receive intentionally inflated weights. As the algorithm continuously reweights all samples up to the latest proposal, any initial over-weighting self-corrects once additional neighbor samples are collected. To enable rapid reweighting, we present an efficient update scheme and evaluate PARIS on illustrative toy problems and more realistic gravitational-wave parameter estimation tasks. PARIS achieves accurate posterior reconstruction and evidence estimation with substantially fewer function evaluations than competing approaches, highlighting its promise for widespread use in astrophysical data analysis.

Baikal-GVD is a new-generation neutrino telescope currently under construction in Lake Baikal, Russia. With an instrumented volume already at 0.7 km$^3$, Baikal-GVD is currently the largest neutrino telescope in the Northern hemisphere. A sub-degree angular resolution, made possible thanks to high purity of Baikal water, further enhances Baikal-GVD sensitivity to cosmic neutrino sources. In this work, we employ track-like events collected from the partially completed detector between April 2019 and March 2024 to search for muon neutrino fluxes from 92 astrophysical objects of interest. For this, a $\chi^2$-based track reconstruction method is used along with a cut-based analysis. The analysis uses upward-going muons only, providing coverage for declinations between -90$^\circ$ and +38$^\circ$. No significant excess has been found, so upper limits are reported. The obtained limits are competitive with those set by ANTARES and KM3NeT. We briefly comment on a possible low-significance indication of an excess from the direction of Westerlund 1. This work sets a major milestone on the way to full-scale scientific exploitation of Baikal-GVD data.

Hot Jupiters (HJs), especially the Ultra-Hot Jupiters (UHJs), are ideal targets for robust atmospheric characterization, thanks to their high equilibrium temperatures and large atmospheric scale heights, which result from their proximity to their host stars and intense stellar irradiation. Here, we present atmospheric studies of five planets, namely WASP-50b, WASP-117b, WASP-156b, WASP-167b, and WASP-173Ab. These five planets include two UHJs, two classic HJs, and one hot Neptune, with four of them just on the upper and middle borders of the Neptune desert, providing an interesting sample for investigating the connection between planetary atmospheric composition and bulk properties. We have not detected any significant absorption signals exceeding 3$\sigma$ in the three less-inflated, relatively high-density HJs (WASP-50b, WASP-156b, and WASP-173Ab). We marginally detect H$\alpha$ and Li I with 3.2$\sigma$ and 3.1$\sigma$ in WASP-117b, respectively. In WASP-167b, we report tentative detection of H$\alpha$ and Fe I at 4.6$\sigma$ and $\sim3.4\sigma$, receptively. In addition, Fe I is significantly detected with a max SNR of 7.3 $\sigma$ using the cross-correlation technique, which exhibits a blue-shifted signal. For WASP-167b, we perform an atmospheric retrieval and yield the abundances of Fe, Mg, Ca, Ti, V, and equilibrium temperature of ${2479^{+193}_{-174}}$K. Comparing WASP-173Ab and WASP-167b, both are UHJ, but with quite different extents of atmospheric signals, we propose that there may be a transition in $T_{\rm eq}$ between 1900 and 2300K.

We introduce a novel set of analytic approximations for five fundamental functions in spherically symmetric, inhomogeneous Lemaitre-Tolman-Bondi (LTB) cosmologies, derived via Symbolic Regression (SR). Focusing on the constrained Garcia-Bellido-Haugboelle (GBH) parameterization, we sample the four-dimensional LTB parameter space using the bubble LTB numerical code and apply SR to reconstruct closed-form expressions for the radial and transverse scale factors A_parallel(r,t) and A_perp(r,t), the corresponding Hubble functions H_parallel(r,t) and H_perp(r,t), and the angular diameter distance D_A(z). Our best-fit formulas reproduce the numerical data with high precision: the relative mean error across all quantities remains below 0.3 percent, except for the radial Hubble function, where it reaches 1.4 percent. These compact expressions enable rapid evaluation of LTB predictions, supporting fast parameter scans, likelihood analyses, and model comparisons without time-consuming integrations. We provide explicit coefficients and discuss the domain of validity, demonstrating that SR-driven approximations can serve as robust surrogates for exact LTB solutions in both theoretical investigations and observational analyses.

The IllustrisTNG simulation suite, particularly TNG50, was reported to have generated a notable population of elongated, bar-like structures within galaxies classified as Early-Type Galaxies (ETGs). In this work, we revisit the nature of these structures at $z=0$ using a morphology-agnostic census. We find that these features are ubiquitous ($f_{\rm bar} \sim 75-80\%$) in dispersion-dominated galaxies ($D/T < 0.2$) in TNG50-1. They are not prolate rotators (rotating around their long axis), but genuine non-axisymmetric instabilities characterized by coherent, albeit slow, pattern speeds. Unlike the fast bars found in Late-Type Galaxies, these bar-like structures in ETGs are physically longer ($\gtrsim 3$ kpc), rotate significantly slower ($\Omega_p \lesssim 20$ km s$^{-1}$ kpc$^{-1}$), and reside in red, gas-poor, dispersion-dominated systems. By tracing the evolutionary history of these systems, we demonstrate that such structures originate as typical fast bars in gas-richer discs at higher redshifts ($z \gtrsim 0.2$). They survive the galaxy quenching phase, undergoing secular deceleration and lengthening due to dynamical friction, ultimately appearing as slow, fossilized rotators in the $z=0$ red sequence. We conclude that the specific excess of bar-like structures in TNG50 ETGs likely reflects a combination of the imperfect baryonic physics of the simulation (over-producing these bar-like structures or their host ETGs) and a potential observational blind spot regarding long-lived, secularly evolved bars in hot stellar systems.

We develop an analytic framework for the evolution of feedback-driven bubbles expanding into a hot, volume-filling circumgalactic medium (CGM), where the ambient pressure and sound speed are non-negligible and radiative cooling is often inefficient. The evolution is organized into four stages -- free expansion, Sedov--Taylor expansion, pressure-modified/transonic transition, and post-transonic relaxation -- and we derive self-consistent scalings for the characteristic radii and timescales that delimit these stages. A central result is that, in hot halos, the end of the strong-shock evolution is frequently set by pressure confinement and transonicity rather than by the onset of catastrophic cooling, implying only a modest late-time overshoot beyond the pressure-balance/transonic point. We connect the dynamics to observable outcomes by estimating bubble sizes and lifetimes, order-of-magnitude band-limited X-ray luminosities, and high-ionization ion column densities, and we provide stitched numerical trajectories that contrast our pressure-modified model appropriate for hot CGM conditions with a classical Sedov--Taylor benchmark. We then discuss physically motivated extensions beyond the single-event baseline, including continuous or episodic energy injection relevant for AGN-driven bubbles and nuclear outflows, highlighting the much higher specific energy of AGN feedback compared to supernovae and the resulting dynamical differences in how bubbles are driven. We further outline how multiphase interaction, mass loading, anisotropic dissipation, intermittency, confinement, and non-thermal channels can increase the emergent X-ray radiation efficiency without requiring changes to the intrinsic feedback energy partition at the launching site. This framework provides a transparent bridge between idealized bubble theory and feedback signatures in hot galactic halos.

We identify an S-shaped morphological feature in the enigmatic supernova remnant (SNR) 3C 397, which we attribute to the shaping by a precessing pair of jets during the explosion. We identify an S-shaped, faint region composed of two bubbles, located to the north and south of the center, between two X-ray-bright sides. We attribute the S-shape to a pair of precessing jets that were part of the explosion process. The identification of a main jet axis in SNR 3C 397 increases its similarity to the enigmatic SNR W49B. We discuss two possible scenarios for SNR 3C 397 and W49B. (1) The thermonuclear common-envelope-jet supernova scenario, which was suggested before for W49B, where a neutron star destroys a white dwarf and accretes part of the white dwarf's material via an accretion disk that undergoes a thermonuclear outburst and launches the jets. (2) The collapse-induced thermonuclear jet-driven explosion, which is a core-collapse supernova driven by jets, as in the majority of, or even all, core-collapse supernovae, and in addition, there is a thermonuclear outburst of a rare helium-oxygen mixed layer in the core, which is triggered by the core collapse. Our study emphasizes the primary role of jets even in the enigmatic SNR 3C 397.

Understanding the origin of the Earth requires determining the original formation location of its building material. Based on the similar Fe isotopic composition of Earth's mantle and Ivuna-type (CI) chondrites, a prior study has argued that Earth formed by accretion of sunward-drifting pebbles from the outer Solar System. Here, using new high-precision Fe isotopic data, we show however that CI chondrites and Earth's mantle have distinct Fe isotopic composition when the neutron-rich 58Fe is also considered. This observation rules out that the Fe in Earth's mantle derives from CI chondrite-like material and demonstrates that Earth did not form by accretion of sunwards-drifting pebbles. We show that the Fe in Earth's mantle instead derives from the inner Solar System, and has been partly or wholly delivered by bodies from the innermost disk that remained unsampled among meteorites. This provenance of terrestrial Fe is consistent with the classical model of Earth's formation by hierarchical growth among inner Solar System planetesimals and planetary embryos.

Stellar activity remains one of the main limitations in the detection of Earth-like planets using radial velocity (RV) measurements. The Sun, as the only star for which surface features can be spatially resolved, offers a unique testbed for studying the impact of active regions on RV and photometric variability. Using SOAPv4, we modelled solar RV and photometric variability induced by spots and faculae over long timescales. Our goal is to verify whether present-day, state-of-the-art models of the cross-correlation function correctly reproduce the observed variability. Moreover, we aim to assess how the choice of input data and identification technique influences the agreement between simulated and observed signals. To simulate solar RV and photometric time series, we first identified active regions in SDO images. This was done using mathematical morphological (MM) transforms applied to SDO/HMI and AIA images. MM identification was validated against other state-of-the-art identification methods. Using these inputs, we ran SOAPv4 to simulate solar RVs and photometry, and we validated the results with HARPS-N RV observations, as well as with VIRGO/SPM photometric measurements. The simulations that use MM identification achieved the best match with the observed RV time series, yielding residuals with a measured standard deviation of ~0.91 m/s. Other state-of-the-art methods produced higher filling factors and, consequently, larger discrepancies. The photometric simulations reproduced the overall variability trends. We demonstrate that MM transforms accurately identify solar active regions. Using these inputs, SOAPv4 reproduces the observed solar RV variability with a measured standard deviation of the residuals of ~0.91 m/s. Photometric simulations capture the overall variability trends, confirming that SOAP can reliably model the impact of both spots and faculae on solar RVs and photometry.

Radio-loud magnetars are well known for exhibiting rare and unusual radiative properties that are seldom seen in the wider pulsar population. Yet one form of emissive behavior that remains elusive among pulsars and magnetars is narrowband bursts of radio waves. Such emission is a hallmark of repeating sources of fast radio bursts (FRBs), intense radio flashes that originate from distant galaxies. Here, we report the detection of 84 narrowband radio bursts during observations of the magnetar 1E 1547.0-5408 by the Murriyang telescope one month after its 2009 outburst. All but six bursts appear temporally unresolved at millisecond timescales. They were confined to a transient profile component that appeared between 2009 February 23 to 25. This coincided with both dramatic changes in the magnetar line-of-sight magnetic-field geometry, and an emergent pulsed hard X-ray component detected by the Rossi X-ray Timing Explorer. The leading edge of the hard X-ray emission was phase-aligned with the narrowband component, indicating the bursts likely originated from pair cascades along closed magnetic field lines. Such closed-field emission could contribute to the lack of second-scale periodicity in repeating FRBs. Our characterization of the bursts suggests they may represent a low-energy analogue of the repeating FRB mechanism, further linking FRB progenitors to young, highly magnetized neutron stars.

We report diffuse extended radio-continuum emission spatially coinciding with the IR source WISEA J094409.17-751012.8, and a semi-variable star, V687 Carinae. We use 944 MHz radio data from the large-scale Evolutionary Map of the Universe (EMU) survey to analyse this diffuse emission (EMU J094412-751016), which we nickname "Anglerfish". We investigate if the spatially correlated infrared (IR) source, WISEA J094409.17-751012.8, is physically related to Anglerfish. The IR colours of WISEA J094409.17-751012.8 are indicative of an elliptical galaxy, raising the possibility that Anglerfish may belong to the newly-discovered class of extragalactic radio sources known as Odd Radio Circles (ORCs) with WISEA J094409.17-751012.8 as the host galaxy. We also investigate the possibility that Anglerfish is physically related to the star, V687 Carinae, and whether it may be a remnant from a previous epoch of stellar mass-loss. We determine that a physical association between the radio emission and the star is unlikely due to the emission's non-thermal nature and the star's weak stellar winds compared to the theoretical expansion velocity of the 'shell'. It is possible that Anglerfish may be a Galactic high-latitude supernova remnant (SNR); however, we find that the observed size and luminosity are not consistent with this scenario. We also investigate the ORC scenario, which we deem the most likely scenario based on the Anglerfish's observed properties such as size, brightness, lack of other frequency detections, and spectral index. We therefore propose Anglerfish as an ORC candidate, but note that additional radio and optical observations are vital to further constrain the properties and confirm this classification.

Measuring star formation in quasar host galaxies is crucial for understanding the coevolution of supermassive black holes (SMBHs) and galaxies, yet remains observationally challenging due to severe contamination from active galactic nucleus (AGN) emission. In this work, we present a new method to robustly isolate the AGN contribution to the [O II] $\lambda$3727 emission line in quasars, based on a kinematically consistent decomposition of [O II] and the high-ionization [Ne V] $\lambda$3426 line. We find that the [O II] emission in quasars is primarily dominated by star formation, with only a weak AGN contribution, and thus can be reliably used as a tracer of star formation in quasar hosts. Applying this technique to a large sample of Sloan Digital Sky Survey quasars, we derive mean SFRs as a function of bolometric luminosity. We find a tight correlation between mean SFR and luminosity. Further analysis, assuming a constant dust extinction correction to [O II] emission, shows that luminosity is the primary parameter most strongly associated with star formation, rather than SMBH mass or Eddington ratio. This supports the scheme in which star formation and black hole accretion are closely linked through their common dependence on the cold gas supply.

The chromosphere is a complex solar atmosphere that hosts a variety of transients and transports significant free energy to heat the corona. However, due to the limited sensitivity of polarization measurement and the influence of spectral line broadening, the basic magnetic field configuration in the chromosphere has not yet been fully revealed to correspond to the observed phenomena. In this work, we investigated the validity and application of the magnetic field inversion method for the H$_{\beta}$~4861~Å spectral line with non-local thermodynamic equilibrium approximations. We generated synthetic spectra by incorporating magnetic fields into semi-empirical FAL models for quiet Sun and sunspots, and then performed inversions to obtain the magnetic fields, which were then compared with the magnetic fields in the models. In addition, we evaluated the accuracy of the magnetic fields obtained using the weak field approximations and the impact of using the WFA results as the initial guess model for non-LTE inversion on the final results. Our work validates the effectiveness of the inversion method for the measurement of line-of-sight magnetic field components, which significantly improved the accuracy in both weak field (0 -- 500~G) and strong field ($>$2000~G) regions, while maintaining accuracy in the intermediate field range of 500 -- 2000~G. This demonstrates that the inversion techniques we employed are capable of resolving Zeeman-sensitive spectral lines in the chromosphere, which can be applied to the H$_{\beta}$ observational data from the new generation Solar Full-disk Multi-layer Magnetograph at GanYu Solar Station to provide full disk chromospheric magnetic field information.

We report the detection of a molecular cloud, CO+40.05-2.40, positionally coincident with the "heartbeating" GeV source Fermi J1913+0515 at the northern boundary of the SS 433/W50 system. Millimeter and submillimeter spectroscopy with the Nobeyama 45 m telescope and the James Clerk Maxwell Telescope shows that the cloud has physical properties typical of quiescent dark clouds in the Galactic disk, with no evidence of shock heating or enhanced excitation. We examine possible high-energy emission mechanisms and find that the observed GeV luminosity cannot be accounted for by electron bremsstrahlung or hadronic interactions driven by relativistic particles originating from SS 433 under reasonable energetic assumptions. As an alternative, we propose that the gamma-rays may arise from a compact object embedded within the cloud and powered by Bondi-type accretion. In this framework, the reported heartbeat-like variability may reflect periodic modulation of the accretion flow by density waves induced by the precessing equatorial outflow of SS 433.

We present chemical abundance ratios of 8 nitrogen-rich ([N/O]$>0.3$) galaxies at $z\sim 6-12$ identified by the first 4 years of the JWST observations, and compare these ratios with chemical evolution models. We reanalyze the JWST/NIRSpec data of these galaxies in the self-consistent manner for line fluxes and upper limits including those previously unconstrained. We derive the abundance ratios and constraints of [N/O], [C/O], [Ne/O], [Ne/C], [Ar/O], [S/O] and [Fe/O], characterizing the nebulae in the galaxies with the electron temperatures and densities measured with {\sc[Oiii]}$\lambda4363$ and {\sc[Oii]}$\lambda\lambda3727, 3729$ lines, respectively. We develop the chemical evolution models for the three major scenarios, Wolf-Rayet stars, supermassive stars, and tidal disruption events (TDEs) with the AGB star contribution, integrating the ejecta of the stars and core-collapse supernovae (CCSNe) over the age with yields calculated by numerical simulations. We compare the models with the [N/O] measurements and stellar ages, and find that all of the scenarios reproduce [N/O] as high as those of our galaxies. However, the time-scales of the high [N/O] ratios are too short to explain our galaxies in any of the scenarios, suggestive of very frequent failed supernovae that do not increase oxygen against nitrogen. We find that the three scenarios are distinguished in the plane of [Ne/C] vs. [N/O] due to Ne production outside CNO cycle, and that the observed abundance ratios are explained by the Wolf-Rayet models better than supermassive-star and TDE models. We argue that abundance ratios of various elements and time scales are clues for understanding nitrogen-rich galaxies.

Quasars,asextremelyluminousanddistantspecialcelestialbodiesintheuniverse,aredrivenbyacomplexsystemcomposedof this http URL-domainobservationstrategyandcombines the analysis of light curves with the construction of structure functions to indirectly reveal the physical essence of the central this http URL SloanDigitalSkySurvey(SDSS).Throughextensivedatastatisticsandcorrelationanalysis,aseriesofimportantfindingshave been obtained: the characteristic parameters of the structure function of quasars show significant correlations with luminosity, black hole mass, and Eddington ratio. That is, quasars with higher luminosity, larger black hole mass, and larger Eddington this http URL,thelargertheEddingtonratio,thesmallerthestructure function. However, the correlation between the structure function and redshift or rest wavelength is not significant, indicating that the variabilitycharacteristicsofquasars aremainly determined bytheir own physical propertiesandareminimallyaffected by the cosmologicalredshifteffect.

The radius valley, a bimodal feature in the size distribution of close-in small exoplanets, is widely interpreted as a signature of atmospheric loss and therefore provides a key constraint on the formation and atmospheric evolution of these planets. We investigate its dependence on host-star properties using 769 planets orbiting 558 stars, for which we derive stellar ages, chromospheric activity, and Galactic birth radius, together with elemental abundances. We find that the radius valley is not fully established at ages $\sim 3$ Gyr and evolves over gigayear timescales, with its prominence strongly affected by stellar population mixing. The dependence on magnetic activity is non-monotonic: a clear valley is present even among magnetically quiet stars, while highly active systems do not show a systematically stronger depletion. The valley morphology also varies with stellar composition: the valley is strongest in metal-poor stars, weakens near solar metallicity, and partially strengthens again at the highest metallicities. In addition, the valley shows sensitivity to refractory element ratios such as [Mg/Si], while correlations with [C/O] are weaker, indicating a dependence on planetary interior structure. Our results are more consistent with a dominant role for core-powered atmospheric mass loss than with purely irradiation-driven photoevaporation. Finally, the radius valley also depends on the Galactic birth environment, with systems near the estimated solar birth radius $\sim 4.5$ kpc showing a high fraction of Earth-like planets and a well-defined bimodal structure, suggesting that the Solar System formed in a region with a well-developed Earth-sized planet population.

During solar flares, a considerable portion of the flare atmosphere becomes heated; however, the energy deposition process is still unclear, especially in the lower solar atmosphere. Here, we present spectroscopic and imaging observations of a small-scale transient of lifetime $<$1-min and further formation of a hot loop of lifetime $\approx$2-min in a solar active region. The observed transient shows the appearance of hot plasma $>$10 MK at the loop foot-point and the subsequent formation of a small-scale transient loop with a loop-top temperature $>$8 MK. The transient shows an enhancement in intensities in several AIA and IRIS passbands. Light curves obtained from several lower atmospheric passbands show consistent time lags in several peak intensities, which, to our knowledge, has never been reported before. Beneath the transient, associated HMI magnetogram shows evidence of flux emergence of both polarities. Using the IRIS \ion{O}{IV} line pair, we obtained the average electron number density of $10^{11.22}$ cm$^{-3}$ at the transient. IRIS transition region lines such as \ion{O}{IV} and \ion{Si}{IV} show a redshift of 10-15 km s$^{-1}$, whereas neutral lines such as \ion{C}{I} and \ion{S}{I} show a redshift of about 5 km s$^{-1}$. These Doppler shifts suggest a down-flowing warmer plasma in the lower atmosphere. The appearance of \ion{Mg}{II} triplets in emission is also observed. We interpret these enhancements in intensities in the lower atmosphere as a result of heating due to both non-thermal electrons and thermal conduction operating simultaneously.

The origin of the cosmic-ray (CR) knee remains one of the central open questions in particle astrophysics. Recent measurements by the Large High Altitude Air Shower Observatory revealed a pronounced feature in the proton spectrum at $\sim3-4$~PeV, while observations of diffuse gamma rays above $100$~TeV do not exhibit a corresponding spectral break. This apparent discrepancy challenges the standard interpretation, in which the local CR distribution is representative of the Galactic CR sea. Here, we investigate whether the CR knee can instead originate from the Cygnus region as a nearby PeVatron. By combining CR measurements at Earth with very-high-energy gamma-ray observations from LHAASO and the Tibet-AS$\gamma$ experiment, we identify an additional hard gamma-ray component in the inner Galaxy consistent with a source located in the Cygnus region. We show that our results provide a concordance multimessenger picture. The required properties are compatible with the PeVatron candidate detected by LHAASO in the Cygnus bubble and with the Galactic neutrino flux observed by the IceCube Neutrino Observatory.

We identify a sample of 83 spatially resolved hot molecular cores (HMCs) in the QUARKS survey, aiming at investigating thermal feedback from massive stars. Using CH$_3$CN\,(12--11) line emission together with 1.3\,mm continuum data we derive the radial temperature, volume density and \ch3cn{} abundance profiles for the 83 HMCs. Based on the envelope temperature and density profiles, we compute the luminosities of the embedded massive protostars with \radmc{} radiation transfer model. The derived luminosities are comparable (within $\sim1$ dex) to the bolometric luminosities of their natal clumps and show strong correlations with several core-scale properties, including the HMC mass ($Log[ M_\mathrm{env}] = 1.01\,Log [L_\star] - 4.80$), the inner core radius (the flat radius of Plummer-like volume density profile) ($Log[a] = 0.46\,Log[L_\star] + 0.52$) and the central density $ (Log[n_c] = -0.55 Log[L_\star] +10.47) $. These empirical relations provide useful observational constraints for physical models of protostellar objects. Importantly, we find a strong positive correlation between the massive protostellar luminosity and the local thermal Jeans mass. The derived Jeans masses, $M_\mathrm{Jeans}$, exceed the HMC masses $M_\mathrm{env}$, with the average $M_\mathrm{Jeans}$ being two times larger than the average $M_\mathrm{env}$. This provides observational evidence that thermal feedback from massive protostars can effectively suppress further fragmentation of HMCs, thereby promoting massive star formation. In addition, the positive correlation between massive protostellar luminosity and natal clump mass suggests that more massive clumps preferentially host more luminous protostars, leading to stronger thermal feedback.

We investigate the correspondence between unimodular diffusion cosmology and interacting dark sector models at the background and linear perturbation levels. In the diffusion framework, the effective cosmological constant becomes time dependent, $\Lambda(t)$, sourced by a diffusion current. We show that at background level this framework can be mapped onto interacting dark energy models with $w=-1$ and energy transfer $Q$. Using two common parameterizations, $Q = \xi H \rho_{\rm de}$ and $Q = \xi H \rho_{\rm dm}$, and data from supernovae, DESI BAO, cosmic chronometers, and CMB distance priors, we find $\xi = -0.0197 \pm 0.0076$ for the vacuum coupled case, while the matter coupled case gives a best fit $\xi = 0.0018$ with comparable fit. At linear perturbations, the diffusion framework is perturbatively equivalent only to interacting vacuum models with homogeneous energy transfer ($Q \propto \rho_{\rm de}$, $\delta Q=0$). Including redshift space distortion data, we obtain $\xi = -0.0147 \pm 0.0075$, consistent with $\Lambda$CDM ($\xi=0$) at $2\sigma$. The inferred clustering amplitude is $S_8 = 0.782 \pm 0.026$ for the diffusion model, compared to $S_8 = 0.77 \pm 0.025$ for $\Lambda$CDM under the same dataset, showing a modest impact on structure growth.

Neutrino telescopes provide a unique observational gateway to the high-energy universe, enabling the study of cosmic accelerators and extreme environments that remain inaccessible to the other high-energy messengers. Although they share core detection principles with neutrino experiments in particle physics, such as the observation of Cherenkov radiation, their scientific objectives and operational constraints diverge markedly. This paper reviews the motivations behind astrophysical neutrino detection, outlines key design strategies across various media and deployment environments, and highlights the critical role of neutrino telescopes in the context of multimessenger astronomy. In particular, we emphasize their potential to illuminate the origins of cosmic rays and to probe the mechanisms driving the most energetic phenomena in the universe.

To investigate the rest-frame optical emission of "Little Red Dots", we model the formation of and evolution of quasi-stars, i.e. stellar envelopes supported by the accretion luminosity onto a central black hole, originating from rapidly accreting proto-stars reaching the supermassive star regime ($>10^4$ M$_{\odot}$) and undergoing general relativistic instability. We compute stellar evolution models with net mass gain rates $=0.01$, 0.1, and 1 M$_{\odot}$/yr and metallicities $Z=0$-0.01. For the mass gain rates $\ge 0.1$ M$_{\odot}$/yr, stars remain nearly fully convective with $T_\mathrm{eff}\sim4000$-9000~K. The general relativistic instability leading to central BH formation occurs at $M_\star\sim3.5\times10^4$ M$_{\odot}$ ($6.6\times10^4$ M$_{\odot}$) for $\dot{M}_{\rm acc}=0.1$ M$_{\odot}$/yr (1 M$_{\odot}$/yr), at luminosities $L \sim 10^9$ L$_{\odot}$. The lifetime of quasi-stars is estimated to be $10^7$-$10^8$~yr, $\sim$100-1000 times longer than their progenitors. In an environment allowing for rapid accretion the formation, evolution, and properties of quasi-stars are found be essentially independent of metallicity. Comparing the luminosities of our models with those of Little Red Dots at $z<4.5$ ($L_\mathrm{bol}\sim10^{9.5}$-$10^{11.5}$ L$_{\odot}$) yields quasi-star masses $10^{4.5}$-$10^{6.5}$ M$_{\odot}$. The observed minimum luminosity of $\sim10^{9.5}$~\Lsun\ implies accretion rates $\gtrsim0.1$ M$_{\odot}$/yr for Little Red Dots progenitors. Our models offer a metallicity-independent framework supporting quasi-stars as the source of Little Red Dot optical emission, and provide insights into their lifetimes, composition, and progenitor environment.

We report the presence of a highly ionized absorber in the transient, eclipsing low-mass X-ray binary AX J1745.6-2901, observed from Feb. 26 to 29, 2024 with XRISM's Resolve and Xtend instruments. During a soft/high state without dips, Resolve's high spectral resolution (E/dE ~ 1000, full width at half maximum) revealed narrow velocity widths (sigma ~ 110 km/s) for Fe XXVI and Ni XXVIII lines, even with low photon statistics. These widths are consistent with binary orbital motion. The observed modest blueshift velocity (~160 km/s) indicates that the absorber is located sufficiently far from the neutron star (> 10^9 cm), so that gravitational redshift effects are not dominant. On the other hand, broad-band spectral analysis using a photoionized plasma model applied to the Xtend data constrains the absorber to lie within a radius of < 10^9.5 cm, as inferred from the upper limits of the best-fit ionization parameter (log xi ~ 4.4) and the large column density (~ 1.6 x 10^24 cm^-2). At this distance, the observed outward velocity of the absorber is about an order of magnitude smaller than the escape velocity from the neutron star.

Recent observational efforts using imaging atmospheric Cherenkov telescopes (IACTs) have led to firm detections of very-high-energy (VHE) signals from bright gamma-ray bursts (GRBs), often at moderate redshifts. This work presents 15 years of H.E.S.S. GRB observations and examines their implications through population comparisons and selected modelling cases. GRBs are a key science target of the High Energy Stereoscopic System (H.E.S.S.). With a low-energy threshold ($\lesssim$100 GeV) and rapid repointing capabilities, H.E.S.S. can begin follow-up observations within tens of seconds after a GRB trigger, covering the late prompt or early afterglow phases. We report GRB follow-up observations with H.E.S.S. from 2004 to 2019, which resulted in no significant VHE signals (aside from the detections of GRB~180720B and GRB~190829A). The resulting upper limits comprise the largest set available for GRBs at VHE. A subset of bursts with favourable conditions were selected for X-ray analysis and emission modelling. Population studies were performed to compare detected and non-detected GRBs. The results indicate that VHE-detected GRBs are not a distinct population, but tend to feature luminous X-ray emission and favourable redshift and observing conditions. This highlights the potential of next-generation IACTs such as the Cherenkov Telescope Array Observatory (CTAO), whose lower energy threshold will enhance the detection of fainter and more distant GRBs.

It is thought that, sometime after their formation, the solar system's giant planets experienced a dynamical instability that caused their orbits to excite, diverge, and ejected one or more objects with masses comparable to the ice giants. A key feature of this model is that the planets experience encounters with other planetary bodies, and these encounters facilitate the capture of nearby small bodies as irregular satellites. Instability simulations indicate that planet-planet encounter distances can typically fall below 0.1 au, which is only roughly an order of magnitude larger than the radial extent of the modern planets' regular satellite systems. In this paper we model the effects of these encounters on the dynamical stability of the regular moons of Jupiter and Uranus. We tested encounter histories from 122 plausible outer solar system dynamical histories. We find that the survival probability for the Jovian and Uranian moon systems are both less than 15%. Moreover, we only identify one case where both Uranus and Jupiter's large satellites consistently survive the same instability. Interestingly, Jupiter's moons are most likely to survive in instabilities initialized with two smaller extra ice giants, and cases with one larger additional planet provide more favorable conditions for Uranian system survival. In either case, if Uranus encounters another ice giant at D<0.02 au, or one of the gas giants at D<0.1 au, satellite system destruction is effectively guaranteed. Wider encounters can also affect the system, particularly when they occur successively. Since the Laplace resonance likely would not be in place today if Jupiter's moons experienced an instability that led to collisions, our results indicate that Uranus' moons were likely perturbed to the point of collisions at least twice: as a result of both the impact that tilted the planet and the giant planet instability.

Phase transitions during inflation can generate a stochastic gravitational-wave background that probes primordial physics. We study the detectability and parameter reconstruction of such a signal with a space-based gravitational-wave detector. Using a Taiji-like mission as a benchmark, we construct a realistic data-analysis framework that includes instrumental noise, astrophysical foregrounds and backgrounds, and the $A$, $E$, and $T$ time-delay interferometry channels. The target signal is described in a minimal, model-independent form and analyzed using both Fisher-matrix forecasts and Bayesian inference with nested sampling. We quantify detection significance and parameter-recovery thresholds, showing that while detection is achievable at moderate signal-to-noise ratios, stronger signals provide more reliable parameter reconstruction. These results offer a realistic assessment of the capability of future space-based missions to probe phase transitions during inflation through stochastic gravitational radiation.

The evolutionary role of the so-called ``changing-look'' (CL) active galactic nucleus (AGN), which is characterized by spectral-type transitions within $\sim10$ yr, has been suggested in the past few years. By focusing on CL-AGNs having spectra similar to those of broad-line Seyfert 1 galaxies, some authors have proposed that CL-AGNs tend to be at a special evolutionary stage associated with intermediate-to-old stellar populations. Here we attempt to verify this evolutionary role by extending the sample to CL narrow-line Seyfert 1 (NLS1) galaxies, which are believed to be ``young'' AGNs with a less massive supermassive black hole and high accretion rate. Combining the recent large NLS1 catalog provided by Paliya et al. (2024) and the SDSS-V DR19 spectral survey returns only three CL-NLS1s out of a parent sample of 884 objects, reinforcing the rarity of CL-NLS1s. Subsequent spectral analysis shows that the evolutionary role mentioned above still holds, although CL-NLS1s tend to occupy the young end of the intermediate-old population. Finally, we propose that off-center SDSS spectra caused by the ``fiber drop'' effect have great potential for determining the properties of the narrow-line region of NLS1s.

X-ray transients on sub-observation timescales represent a diverse and underexplored class of astrophysical phenomena, from stellar flares and magnetar bursts to extragalactic fast transients and supernova shock breakouts. We present a systematic search for such events across 20,212 Chandra ACIS observations using a new detection pipeline that combines source identification, light-curve analysis, catalogue cross-matching, and a novel statistical classifier, the cumulative distribution discriminator (CuDiDi). From 1420 initial candidates, we identified a high-confidence golden sample of 765 transients spanning a broad range of timescales, fluxes, and spectral shapes. The candidates are distributed across the whole sky and show a wide range of durations with a median of 10 ks. A subset of fast events lasting < 30 s displays very soft spectra and is likely due to flaring dwarf stars, although extragalactic phenomena cannot be ruled out for all of them. The comparison with previously published samples showed that CuDiDi identifies most known transients while imposing somewhat stricter variability criteria, and it also extends the total sample of Chandra transients to include shorter events. We deliver a comprehensive catalogue of sub-observation Chandra X-ray transients and establish a general method for exploiting archival datasets to uncover rare short-lived high-energy phenomena.

The sequence of eclipses of binary stars is subject to inequalities for various reasons. The presence of a third component in the system causes periodic motion of the binary's center of mass along the line of sight of an observer. The finite value of the light velocity implies that the epochs of eclipses periodically advance and delay with respect to the exact orbital period of the binary, a phenomenon termed the light-time effect (LITE). We aim to refine two aspects of the mathematical treatment of LITE. First, we provide both generalized and more accurate analytic formulation describing the light-travel time in the binary system itself presented in previous works. Second, we analytically estimate the so far neglected coupling of LITE with the dynamical interaction of the binary orbit with the motion of the third star. Our principal results are given in a simple analytical form, which is suitable for the analysis of photometric observations that require minimization over a multidimensional parameter space of the triple system. The leading correction to the traditional formulation of LITE due to the light-travel time in the binary system may be detectable for triple systems with a period ratio of $P_2/P_1\lesssim 20$, for which accurate photometric observations are available. On the other hand, the correction due to the dynamical coupling of the two orbits with $P_2$ periodicity is small, but may become relevant in the future.

Despite significant progress in cosmological simulations of galaxy formation, the role of subgrid physics in shaping the detailed properties of galaxies remains incompletely understood. In this work, we analyze two sets of zoom-in simulations that share identical initial conditions but adopt distinct implementations of baryonic physics, enabling a controlled comparison of their predictions. We examine the stellar properties, morphological structures, and satellite populations of the simulated galaxies at $z=0$. We find that AURIGA galaxies systematically exhibit higher stellar masses and surface densities than their APOSTLE counterparts. These differences are primarily driven by variations in the efficiency of gas cooling from the circumgalactic medium (CGM) into the star-forming gas. Both simulations form well-defined disk galaxies; however, AURIGA systems generally display higher disk-to-total mass ratios, earlier disk formation, and more prominent dynamical structures such as bars and spiral arms. Nevertheless, strongly disk-dominated systems are present in both simulations, although they do not arise in the same host haloes. The vertical disk structure in both simulations is well described by a sech density profile, with scale heights below ~ 1 kpc in the inner regions. The satellite populations also differ, with AURIGA producing systematically more massive satellites, including a ~ 0.3 dex increase in the most massive system, while the number of satellites above $10^6 M_{\odot}$ remains comparable in most halo pairs. Both simulations reproduce similar satellite stellar mass--metallicity relations, albeit ~ 0.25 dex higher than observation. This comparative study therefore provides useful benchmarks for future efforts to better constrain galaxy formation models.

Millisecond pulsars (MSPs) are powerful probes of globular clusters (GCs), tracing stellar evolution, cluster dynamics, and the local gravitational potential. We investigate the MSP population in GC Omega Centauri. We perform Fourier-domain acceleration and jerk searches on MeerKAT observations, and carry out pulsar timing using MeerKAT and Parkes Murriyang data spanning 2021-2025. We fold Fermi LAT and NICER photons using updated radio ephemerides to search for high-energy pulsations. We discover a new isolated MSP, PSR J1326-4728S (hereafter S), with a spin period of 4.538 ms and a dispersion measure of 96.24 cm$^3$pc. We update the orbital parameters of all known binary systems, with those of I, N, and Q differing significantly from previous estimates, and obtain new timing solutions for G, H, and K. Pulsars B, G, H, K, and L exhibit black widow-like properties, I, N and Q are found in wider binaries, with N and Q having >0.2 M$_\odot$ companions, and N showing a significant orbital eccentricity (e=0.093). Significant spin period derivatives are measured for eight pulsars and interpreted as arising from the cluster gravitational potential. No pulsed high-energy emission is detected from individual pulsars. The inferred line-of-sight accelerations are consistent with a King-model gravitational potential. While our measurements are insensitive to an intermediate-mass black hole with mass 10$^3$-10$^4$ M$_\odot$, they place an upper limit of <10$^5$ M$_\odot$ at 90% confidence. The high fraction of isolated MSPs and black widows systems, and possibly the eccentricity of N, are difficult to reconcile with MSP population predictions based solely on encounter rates. Instead, these properties likely reflect the complex evolutionary history of Omega Centauri, with part of its MSP population having formed in denser environments than the one observed today.

We use deep MUSE data from the MUDF survey to investigate the cool gas around galaxies at redshifts 0.5 < z < 2. We constructed two samples: one sample for a down-the-barrel analysis, probing outflows via MgII absorption against galaxy continua, and the other sample for projected galaxy pairs to examine the gas around the foreground galaxies in the transverse direction. From down-the-barrel stacked spectra, we detected blueshifted MgII absorption, indicative of outflows, in which the absorption strength increases with stellar mass and star formation rate. Lower-mass galaxies exhibit weaker absorption, but higher outflow velocities, whereas higher-mass systems retain more cool gas with slower outflows. In the transverse direction, the absorption of MgII decreases with the impact parameter, following a shallow profile. Comparing observations with radiative transfer models, we found that extrapolating an expanding halo model constrained with down-the-barrel measurements to halo scales overestimates the observed equivalent widths, likely due to the outflow geometry and the absence of the interstellar medium in the model. Our results highlight that mass, outflow geometry, and gas retention shape the cool circumgalactic medium, and that the combination of absorption and emission diagnostics provides powerful constraints on the properties of the cold halo gas.

Context. To better understand the observed brightness of low Earth orbit satellites, we must characterize their reflectivity, which in turn depends importantly on their bus designs. The reflectivity of a body can be described by Lambert's law, in terms of its albedo, cross-sectional area, range (distance), phase angles, and the mixing coefficient between diffuse and specular reflection components. Aims. We aim to analyze the reflectivity of more than 300 ONEWEB satellites using the diffuse Lambertian sphere, diffuse and specular Lambertian sphere, and the relative reflectance brightness models. Methods. Astrometric and photometric measurements, plus two-line elements (TLE) orbital information were used to compute the apparent and range-magnitude, as well as the relevant angles related to the orientation of the Sun, the satellites, and the observer. A differential evolution Monte Carlo algorithm was used to obtain each model's parameters that best fit the data. Results. All models can fit the mean observed brightness of the satellites but cannot describe the observed phase-angle-dependent brightness modulations. The residuals in all cases have a standard deviation of $\sim$0.6 magnitudes, while the observational photometric errors are on average $\sim$0.2 magnitudes. Conclusions. The studied brightness models, which depend on the relative Sun-body-observer position but are independent of the specific orientation of the reflecting body surface(s) with respect to the observer, cannot entirely explain the observed brightness of the ONEWEB constellation satellites. Accounting for the real shape and the changing attitude of the satellite, as well as the effect of Earth's albedo is needed to better explain satellite photometric observations

New Horizons RALPH/LEISA near-infrared spectra allow for regional mapping of Pluto's surface ices and their physical state; however, scan-to-scan artifacts and variable spatial resolution complicate quantitative interpretation. We extend previous LEISA compositional studies (Protopapa et al., 2017(arXiv:2110.00662); Schmitt et al., 2016; Emran et al., 2023(arXiv:2301.06027)) by combining five close-approach observations into co-registered equirectangular maps at 7 km/pixel and by jointly retrieving surface temperature, ice abundances, and grain sizes using a Hapke-based mixing model. We mitigate bad pixels and edge overexposure linked to flat-field uncertainties and correct for residual scan-to-scan spectral discrepancies using per-observation scale and offset terms. The resulting maps provide distributions of CH4-rich ice, N2-rich ice, H2O ice, and Titan tholins, alongside a corresponding temperature map.

Observations show that many solar eruptions remain confined within strong overlying magnetic fields, forming a so-called magnetic cage. While confinement by poloidal overlying fields has been widely investigated, the role of strong external toroidal fields remains unclear. Using three-dimensional magnetohydrodynamic simulations, we study confined eruptions in a toroidal magnetic cage, focusing on the interplay between the Lorentz force and magnetic reconnection, and their observational signatures. We further employ a guiding-center test-particle approach to synthesize hard X-ray emission for comparison between thermal and nonthermal responses. We find that overlying toroidal fields play a crucial role in confinement by generating strong return currents that produce a significant downward Lorentz force, suppressing flux rope ascent. At the same time, they induce large-angle rotation of the flux rope, leading to reconnection with overlying fields and eventual break-up. Synthetic EUV emission reveals multi-ribbon flares with highly sheared, globally cowboy-hat-like loop structures. Hard X-ray diagnostics show that thermal and nonthermal emissions are not co-spatial, with return currents acting as an efficient accelerator of energetic electrons. These results demonstrate that toroidal-field-induced forces govern both the confinement and rotation of erupting flux ropes, providing an explanation for failed eruptions even under torus-unstable conditions. These results suggest that the morphology and shearing angle of flare loops are the useful diagnostics for distinguishing confined from eruptive events.

Planets in binary-star systems exhibit demographic differences compared to planets in single-star systems. In particular, planets with binary-star hosts have a lower overall occurrence rate compared to their single-star counterparts, as well as a suppressed relative occurrence rate for sub-Neptunes ($R_p=2{-}4R_{\oplus}$) compared to super-Earths ($R_p=1.0{-}1.5R_{\oplus}$). These differences are most pronounced in close separation binaries ($\rho < 100$ au) which has been interpreted as a result of binary stars disrupting the protoplanetary disks of their stellar companions. The architectures of planetary systems -- i.e. the arrangements of planet sizes and orbits -- provide additional information about system formation and evolution. Architectures of single-star planetary systems are well studied, but architectures of binary-star planetary systems have not been investigated in detail. In this work, we analyzed a large sample of Kepler planetary systems (162 planets in 118 binary-star systems; 880 planets in 544 single-star systems) to compare their architectures as a function of stellar multiplicity. We found that planets with binary-star hosts follow a similar ``peas-in-a-pod'' tendency toward uniformity in planet radii and log-uniformity in period spacing as planets with single-star hosts. However, we also detected modest ($2.5-3\sigma$) differences in period spacing and planet multiplicity, with binary-star systems having higher typical gap complexities (indicating more uneven spacing) and a higher prevalence of single planets. We interpret these results as evidence that binary stars primarily influence the planetary architectures of their stellar companions by shaping the protoplanetary disk at formation, with subsequent dynamical processing more gently altering the system architectures over secular timescales.

Context: Composite galaxies that contain both Seyfert and starburst components may produce very high-energy (VHE; >100 GeV) gamma-ray emission at a wide range of spatial scales, from a few Schwarzschild radii of a supermassive black hole to dimensions of kiloparsec-size jet-driven outflows. In addition to supernova remnants, various sources have been suggested to explain data collected on composite galaxies, including multi-messenger neutrino and ultra-high-energy cosmic-ray data. Aims: The closest composite Seyfert-starburst galaxies (NGC 1068, the Circinus galaxy, and NGC 4945) are observed with the High Energy Stereoscopic System (H.E.S.S.) to provide constraints on cosmic-ray populations in these systems. Methods: Data obtained in H.E.S.S. observations have been analyzed to search for VHE gamma-ray counterparts to the GeV gamma-ray signals detected with Fermi-LAT and for potential spectral components in the VHE range. Results: No significant signals have been found in these H.E.S.S. data. Upper limits on the VHE gamma-ray fluxes were applied to constrain theoretical models involving different spectral components.

These notes are from three lectures given at the 54th Saas-Fee Advanced Course of the Swiss Society of Astrophysics and Astronomy in January 2025. This chapter reviews the dramatic evolution in our understanding of supermassive black holes in the first billion years, from ground-based discoveries to recent space-based infrared observations with JWST. Section 1 introduces AGN and quasars to contextualise observations at the highest redshifts. Section 2 reviews the pre-JWST understanding of early quasars, including personal accounts of how key discoveries were made. Section 3 examines how JWST is transforming the field, from black hole mass measurements and host galaxy characterisation to large-scale environmental studies, and identifies emerging directions.

Upcoming stage-IV surveys such as Euclid and Rubin will deliver vast amounts of high-precision data, opening new opportunities to constrain cosmological models with unprecedented accuracy. A key step in this process is the reconstruction of the dark matter distribution from noisy weak lensing shear measurements. Current deep learning-based mass mapping methods achieve high reconstruction accuracy, but either require retraining a model for each new observed sky region (limiting practicality) or rely on slow MCMC sampling. Efficient exploitation of future survey data therefore calls for a new method that is accurate, flexible, and fast at inference. In addition, uncertainty quantification with coverage guarantees is essential for reliable cosmological parameter estimation. We introduce PnPMass, a plug-and-play approach for weak lensing mass mapping. The algorithm produces point estimates by alternating between a gradient descent step with a carefully chosen data fidelity term, and a denoising step implemented with a single deep learning model trained on simulated data corrupted by Gaussian white noise. We also propose a fast, sampling-free uncertainty quantification scheme based on moment networks, with calibrated error bars obtained through conformal prediction to ensure coverage guarantees. Finally, we benchmark PnPMass against both model-driven and data-driven mass mapping techniques. PnPMass achieves performance close to that of state-of-the-art deep-learning methods while offering fast inference (converging in just a few iterations) and requiring only a single training phase, independently of the noise covariance of the observations. It therefore combines flexibility, efficiency, and reconstruction accuracy, while delivering tighter error bars than existing approaches, making it well suited for upcoming weak lensing surveys.

Context. The formation and destruction of molecules in the interstellar medium is a complex interplay between gas-phase reactions as well as processes on grain surfaces and within icy mantles. For many decades, the gas-phase composition of the cold material towards star-forming regions could be well characterized using (sub)mm facilities. Prior to the launch of the James Webb Space Telescope (JWST), ice species other than the main constituents (H2O, CO, CO2, NH3, CH4, CH3OH) were challenging to detect due to insufficient sensitivity as well as angular and/or spectral resolution. Aims. We determine molecular ice and gas-phase column densities towards the young and embedded high-mass hot core IRAS 18089-1732 within a region of 5000 au. Methods. We use spectroscopic data from 5-28 micron obtained with JWST to derive ice column densities of H2O, SO2, OCN-, CH4, HCOO-, HCOOH, CH3CHO, CH3COOH, C2H5OH, CH3OCH3, and CH3COCH3. Gas-phase column densities of a total of 38 molecules, including, O-, N-, S-, and Si-bearing species as well as less abundant isotopologues, are inferred from sensitive molecular line observations taken with the Atacama Large Millimeter/submillimeter Array (ALMA) at 3 mm wavelengths. Results. We find comparable abundances (relative to C2H5OH or CH3OH) in both phases for C2H5OH, CH3OH, and CH3OCH3. The abundances of SO2 and CH3COCH3 are higher in the gas-phase suggesting additional gas-phase formation routes. The abundance of CH3CHO is one order of magnitude higher in the ices compared to the gas-phase. The ice abundances (relative to H2O ice) towards the IRAS 18089 hot core are similar to previously studied Galactic low- and high-mass protostars. There are hints of a decreasing abundance with Galactocentric distance for OCN-, CH3OH, and CH3CHO ice. (abridged)

Massive He stars are potential candidates of type Ib/c supernova (SN) progenitors. Understanding their final fates remains a key issue in astrophysics. In this work, we investigate the evolution of He stars with initial masses from 5 $M_\odot$ to 65 $M_\odot$, focusing on the presupernova (pre-SN) core structures to assess their explodability. Our simulations indicate that the final core structure is determined by the CO core mass and the central 12C mass fraction at the end of core He burning, affecting the properties of central C-burning and the locations of convective shells. The location of the last convective C-burning shell sets the mass of the C-free core, constraining the iron core mass and compactness. We found that the final compactness and iron core mass exhibit non-monotonic behavior with initial mass, suggesting that the boundary between neutron star and black hole formation is not a simple mass threshold. This is due to core C/Ne burning becoming neutrino dominated. This process drives stronger core contraction, ultimately increasing the iron core mass and the final compactness. In contrast, earlier core Ne/O/Si ignition and shell mergers inhibit core contraction, reducing both the iron core mass and final compactness. We also discuss the effects of metallicity and overshooting on the pre-SN core structure. These factors potentially affect the explodability of progenitors.

Accreting neutron stars exhibit pulsed X-rays and complex temporal variability across multi-wavelengths and different timescales. This variability could be driven by various physical processes including instability or inhomogeneous motions within the accretion flow, thermonuclear bursts on the neutron star surface. In this review, we present a concise overview of the observational features for millihertz (mHz) quasi-periodic oscillations (QPOs) at a frequency range of $\sim 1- 1000$ mHz observed in light curves of X-ray pulsars for both low-mass X-ray binaries and high-mass X-ray binaries, based on recent X-ray missions, e.g., NICER, Insight-HXMT and NuSTAR. We further summarize current theoretical interpretations, discuss remaining challenges and propose potential directions for future studies to advance the understanding of the nature and physical origin of these QPOs.

Recent observations by the JIRAM instrument onboard NASA's Juno mission have confirmed that many of Io's volcanic hot spots are active lava lakes, characterized by a colder central crust surrounded by a hotter peripheral ring. In this study, we investigate the thermal properties of thirty such lava lakes, providing new constraints on their structure and energy budget. We find that most of the total power from Io's lava lakes comes from their low-temperature crusts rather than the hotter peripheral rings, suggesting previous estimates underestimated lava lake power by up to a factor of 10. Io's paterae undergo stochastic resurfacing on timescales of roughly a decade, with each lake possibly following its own characteristic cycle. We also explore the relationship between the average temperature of the crust and the evolutionary state of each lake, offering insights into the frequency of resurfacing processes. Finally, we propose an improved assessment of Io's global thermal output, emphasizing that only full-surface observation of Io with sufficient spatial and spectral resolution can yield realistic values for the moon's volcanic total heat flux.

WISPIT 2 is a nearby young star with a multi-ringed disk which was recently confirmed to host a ~4.9 MJup gas giant planet embedded in a large (60 au) gap at a radial separation of 57 au from the host star. We confirm and characterise a second, close-in planet in the WISPIT 2 system using a combination of new VLT/SPHERE H-band dual-polarisation imaging and VLTI/GRAVITY K-band interferometric observations of the WISPIT 2 system. The GRAVITY detection is consistent with a point-like source while its extracted K-band spectrum shows CO band-head absorption at 2.3 microns and a continuum shape consistent with a young giant planet. From the GRAVITY data we extract a medium resolution K-band spectrum of the companion and fit atmospheric model grids using the species tool with nested sampling to constrain its effective temperature, radius, and luminosity. We infer Teff of 1500-2600 K, a radius of 0.91-2.2 RJup, and a luminosity of (-3.47)-(-3.63). Comparison with evolutionary tracks implies a mass range of 8-12 MJup, approximately twice as massive as the previously confirmed WISPIT 2b. The astrometry rules out a background source and marginally detects orbital motion of WISPIT 2c, which needs further follow-up observations for confirmation. WISPIT 2 now becomes an analogue to PDS 70, offering a second laboratory for studying the formation and early evolution of a multi-planet system within its natal disk.

Solar radio bursts (SRBs) are intense emissions observed in radio wavelengths most frequently during solar transients, such as coronal mass ejections (CMEs) and flares. SRBs are direct signatures of accelerated electrons in the solar atmosphere. These solar transients have a direct impact on the near-Earth atmosphere. SRBs serve as key diagnostic tools for plasma processes, particle accelerations, magnetic field dynamics in the solar corona and the heliosphere, which are the root cause of these solar transients. There are several key science question which solar radio observations can answer, such as: When $\&$ where is the bulk of the energy released in flares?, what are the physical properties of the energy release site?, what are the properties of heated plasma $\&$ accelerated particles?, how does the transport of heated plasma $\&$ accelerated particles?, what bearing do flares have on the question of coronal heating? The Square Kilometre Array (SKA), with its unprecedented sensitivity, temporal, spectral, and spatial resolution, as well as dynamic range, is expected to provide an enhanced understanding of the physics behind solar transients with unprecedented detail.

Type-C quasi-periodic oscillations (QPOs) in black hole X-ray binaries are sensitive probes of accretion geometry. Using Insight-HXMT observations of MAXI J1348-630, we study the evolution of type-C QPOs during its 2019 main outburst and later mini outbursts. We carry out timing and spectral analysis, tracking QPO frequency, fractional rms, energy dependence and their correlations with flux and spectral shape. The QPO frequency increased from 0.24 Hz to 7.28 Hz during the rise and remained near 7 Hz when reappearing in different states. The rms spectrum hardened after the transition from hard to hard-intermediate state. The frequency-flux relation shows strong hysteresis between rise and decay, with the loop reversed between main and mini outbursts. In contrast, frequency and hardness follow a tight single-track anti-correlation. Our results support that the Compton region can reform at a characteristic scale. The QPO frequency is mainly driven by spectral shape rather than luminosity. The reversed hysteresis suggests differences between main and mini outbursts related to initial conditions.

Microquasars such as SS 433 are considered potential contributors to cosmic rays up to the knee of the cosmic ray energy spectrum ($\sim4\,\mathrm{PeV}$), where a transition in the dominant acceleration processes is expected. The SS 433 system, located within the W50 supernova remnant, is a Galactic microquasar with relativistic jets interacting with the surrounding medium over parsec scales, providing an example for studying jet-driven particle acceleration. A deep morphological and spectral study of SS 433 is performed using more than 150 hours of observations with VERITAS, sensitive to $\gamma$-ray energies $>100\,\mathrm{GeV}$. With an angular resolution better than $0.1^°$, extended TeV $\gamma$-ray emission is resolved from both the eastern and western jet lobes, located tens of parsecs from the central binary. The emission appears elongated along the jet axis and coincides with regions where the jets interact with the surrounding supernova remnant. No TeV emission is detected from the central binary, nor is significant emission observed between the central binary and the jet lobes. Phase-resolved analyses show no evidence for variability with orbital or precessional phase, supporting a steady emission scenario. The observed morphology and spectra are consistent with scenarios where particles are accelerated in the lobes of the jets, possibly through shocks or alternative processes such as magnetic reconnection. The extended TeV emission from the jet lobes of SS 433 favors a leptonic origin in the VERITAS energy range, suggesting any hadronic acceleration is subdominant. The results offer valuable constraints on how microquasar jets may contribute to the Galactic cosmic-ray population toward the knee.

We study the formation of multiphase gas in the post-accretion-shock regions of cosmic sheets, filaments, and the circumgalactic medium (CGM) of haloes, i.e., cosmic web objects (CWOs). Local instabilities in the hot medium result in fragmentation and cooling, eventually forming small-scale overdensities with temperatures of $\sim 10^{4}{\,\rm K}$ in pressure equilibrium with the hot environment. Such dense, ionised inhomogeneities can affect the propagation of radio waves from fast radio bursts (FRBs), thereby offering us a way to probe their presence and properties in CWOs through scattering signatures in the observed FRB flux. We find that high-$z$ filaments \& sheets have a negligible contribution to the total observed scattering. The high rates of FRBs expected even at high redshifts may still allow detection from high-temperature filaments along rare sightlines, and we suggest other methods for such systems in a companion paper. Our model further predicts that if turbulent cloudlets exist in the CGM of intervening massive haloes with a volume-filling fraction of $f_{\rm v}\gtrsim 10^{-3}$, they are expected to cause considerable cumulative scattering along an average sightline, resulting in a significant correlation between the total scattering time and source redshifts. The lack of such a correlation in current observations may imply that the cool gas in the CGM has substantial non-thermal pressure, reducing its density, or significant damping of small-scale density fluctuations. Forthcoming localised FRB samples can map these constraints into bounds on volume-filling fractions, densities, cloud sizes, and the strength of turbulence.

SPHEREx is a NASA mission designed to perform an all-sky spectroscopic survey in the 0.75 - 5 $\mu$m wavelength range. Its primary science objectives are to investigate: (1) inflationary cosmology, (2) the history of galaxy formation, and (3) the abundance of molecular ices - critical for prebiotic chemistry - found on the surfaces of interstellar dust grains within planet-forming regions. This paper focuses on the third theme, the SPHEREx Ices investigation, for which SPHEREx is conducting a spectroscopic survey of nearly ten million preselected sources throughout the Milky Way and Magellanic Clouds to characterize their ice absorption features. By selecting targets based on infrared color, spatial isolation, and brightness, the Ices Investigation secures high-signal-to-noise spectra across a broad range of astrophysical environments that are relatively free of spectral contamination. Rather than attempting to decompose each spectrum into its individual ice components, the Ices Investigation prioritizes accurate measurements of the integrated optical depths of key molecular ice absorption features. This approach enables statistically powerful correlation studies between ice abundances and environmental parameters - including extinction, temperature, gas composition, radiation field strength, cosmic ray flux, and star formation activity. The data pipeline developed for this purpose incorporates machine learning for continuum estimation, drawing on both SPHEREx and ancillary datasets. Ultimately, the expansive spectral archive produced by SPHEREx, combined with targeted follow-up from facilities like JWST, will transform our understanding of Galactic ice formation, evolution, abundance and their inheritance into planetary systems and prebiotic inventories.

We propose a new marked two-point correlation function weighted by the global gravitational potential as a probe for testing gravity models. Using the LCDM model based on general relativity (GR) as a reference, we investigate two representative modified gravity (MG) scenarios: f(R) gravity and nDGP. The mark used in this work, the global gravitational potential that is reconstructed from the galaxy distribution via the Poisson equation, is in contrast to the local property based mark (e.g., local galaxy number density or gravitational potential of host halo) used in previous studies. By applying two weighting schemes to quantify environment-dependent clustering, we find that this statistic is able to distinguish MG models from GR, with the signal being enhanced in regions corresponding to particular ranges of gravitational potential. These results indicate that the proposed statistic can serve as a useful complement to conventional clustering probes in future surveys, once observational effects and modeling uncertainties are properly taken into account.

We expand upon our paper (Rice and Yeates, 2021) which introduced `Outflow Fields': alternatives to the widely-used potential field source surface (PFSS) extrapolations of the Sun's coronal magnetic field which take into account the effect of the solar Wind. We showed that our fields have several advantages over PFSS, namely more accurate measurements of the Open Solar Flux (OSF) relative to observations, more realistic streamer shapes and less dependence on the arbitrary source-surface height. In this paper we seek to quantify these improvements. This includes comparison of magnetic field line angles with eclipse photography, an improved solar wind solution model and the introduction of data from a wider range of observations. We use these comparisons to determine the optimum parameters for our model using an evolutionary algorithm, in addition to the creation of synthetic eclipse images. We find that our Outflow Fields can accurately capture the overall topology of the magnetic field, and reduce the well-known discrepancy with in-situ magnetic field measurements by a significant margin relative to PFSS. Specifically, over the period between 2000 and 2022 for a typical source-surface height we find that optimized Outflow fields reduce this discrepancy from around 45% to 24% while also matching the field line topology seen during eclipse photography. Our model is presented for wider use by the community as a new python package "outflowpy".

Galaxies frequently interact with nearby systems, a process that can significantly alter their morphology and star formation activity. However, spectroscopic studies of their faint and diffuse remnants require very long exposure times and often exceed the limited field of view of integral field units (IFUs). On the other hand, broad-band imaging can have a much wider field of view, but lacks the spectral resolution to identify key spectral features, restricting accurate constraints on stellar population properties. With its 54 narrow-band filters in the optical and wide coverage (planned 8000 square degrees), J-PAS fills this gap. In this case study, we examine PGC 3087775, a massive galaxy at z = 0.046179 (~ 201 Mpc) in the later stages of a major merger in the J-PAS early data release. Photometry was validated with MaNGA IFU data (for the central part). Stellar population properties was derived using both J-PAS and SDSS photometry. SDSS indicates a metal-rich population with an extended star formation history (SFH) and elevated star formation rates. J-PAS instead points to a less metal-rich population with moderate extinction and a more rapid SFH, consistent with a quenched stellar population. The average Dn(4000) index of the tidal features is 1.24, suggesting that it was a non-dry merger and a fourfold improvement in the precision of stellar mass and Dn (4000) was found with J-PAS. We also assessed two heuristic methods for estimating the mass-to-light ratio from SDSS filters and found that they overestimate the stellar mass in this galaxy by 0.5 dex and 0.4 dex relative to SED fitting results from J-PAS and SDSS, respectively. Future work will extend this analysis to a larger sample of merging galaxies and evolution of the stellar populations of such structures across the nearby Universe to unprecedented detail. This project is fully reproducible, through Maneage (commit 0f0d7e2).

Mass loss from massive stars located in the part of the Hertzsprung-Russell diagram (HRD) where we find luminous blue variables (LBVs) is profoundly important for stellar evolution yet poorly understood. We use time-dependent radiation-hydrodynamic (RHD) simulations to examine the atmosphere and wind properties of such massive stars, computing 2D and 1D RHD models of the coupled envelopes, atmospheres, and wind outflows, tuned to this region in the HRD. Our unified simulations start deep in the stellar envelope (well below T ~ 200 kK) and include the outflowing wind, accounting for line-driving, radiative enthalpy, and photon tiring. Mass-loss rates, wind speeds, and the radiative luminosity at the photosphere are emergent properties in the simulations. A grid of models is created by slightly increasing the stellar energy at the lower boundary. This results in a natural transition from very turbulent atmospheres with line-driven winds to effectively stationary super-Eddington massive outflows. Our sub-Eddington models are essentially blue hypergiant stars with very variable surfaces, effective mass-loss rates $\dot{M} \sim 2 - 5 \times 10^{-5}$ $M_{\odot}$/year, and wind speeds $v_{\infty} \sim 200 - 300$ km/s, resembling quiescent LBVs like P Cygni. The super-Eddington models have optically thick wind envelopes and extremely inflated yellow surfaces (Teff ~ 5000 K), $\dot{M} \sim 0.1 - 1$ $M_{\odot}$/year, and $v_{\infty} \sim 400 - 500$ km/s, resembling a massive star during a great eruption like eta Carinae's. Our models naturally reproduce the overall characteristic stellar and wind parameters inferred for massive stars in their quiescent LBV and yellow giant eruptive phases. It remains an open question whether the energy increase needed to trigger a giant eruption can be obtained solely by the internal evolution of the star itself or if it requires an external energy source.

We present a systematic analysis of high-cadence optical light curves of the non-blazar AGN PKS~0521$-$36 obtained with \textit{TESS} across three sectors: Sectors~5 and~6 (Cycle~1, 30~min cadence) and Sector~32 (Cycle~3, 10~min cadence). The source exhibits moderate variability with $F_\mathrm{var} \approx 0.69$--$1.19\%$, consistent with a mildly beamed jet. The power spectral density (PSD) in all sectors is better described by a bending power-law than a simple power law, with high-frequency slopes $\alpha_1 \approx 2.1$--2.9, indicating red-noise dominated variability. Flux distributions require two-component models, with a double log-normal providing the best description, suggesting the presence of two distinct optical flux states associated with quiescent jet emission and episodic flaring activity. A significant QPO at $P = 2.838 \pm 0.078$~d is detected in Sector~5 at $>99.99\%$ confidence in the Lomb--Scargle periodogram, independently confirmed by WWZ ($2.839 \pm 0.110$~d) and supported at the $3\sigma$ level by DRW analysis. The signal spans $\sim$9 cycles within the 26.1-day baseline in Sector~5 and is absent in Sectors~6 and~32, indicating a transient feature. The PSD bending frequency ($\nu_b \approx 0.308$~d$^{-1}$; $\sim$3.2~d) is consistent with the QPO period, suggesting a common origin. We interpret the oscillation as magnetohydrodynamic kink instabilities in the relativistic jet, consistent with the observed helicoidal structure. A moderate Doppler factor ($\delta \approx 5$--10) naturally explains the day-scale periodicity. Together with previously reported $\gamma$-ray QPOs on longer timescales, this suggests a hierarchical variability structure, and, to the best of our knowledge, provides the first evidence for an optical QPO in a non-blazar AGN with a directly imaged helical jet.

We examine solutions of the hydrodynamic equations for dark matter (DM) modeled as a Bose-Einstein condensate (BEC) with axionlike interaction, forming a spherically symmetric halo in dwarf galaxies. Small perturbations and decoherence of the BEC DM arise from changes in the gravitational background induced by subgalactic baryonic processes. Focusing on the events in the central region of a galaxy, overlapping with the solitonic DM core, we consider three scenarios: (i) expansion of a gaseous shell mimicking stellar explosions, (ii) collapse of a shell modeling star formation, and (iii) contraction of a stellar cluster toward the galactic center, driven by dynamical friction within a gaseous shell. Numerical parameters are extracted from observational data for NGC 2366. Our results show central DM density increases of 0.01 percent and DM wind velocities of only a few meters per second. A greater increase in density is observed at lower wind speeds and vice versa. These results raise the question of whether minor DM variations significantly affect star formation. In analyzing the fate of the cumulative impact of baryonic processes, we turn to the quantum excitation model with a discrete spectrum in finite volume. In the inhomogeneous DM halo, including unstable phase, metastable excitations associated with false vacuum states decay on a timescale of 32 Myr. This induces the decay of the system's evolutionary operator. Meanwhile, the Beliaev damping, originating from the decay of stable quasiparticles, emerges in the next order of perturbation.

The Quick-Look Pipeline (QLP; Huang et al. 2020, Kunimoto et al. 2021 and references therein) generates light curves for up to 2 million stars every 27.4 days observed by TESS as part of its planet search. As machine learning methods enable deeper searches and scientific priorities shift toward fainter stars, there is a motivation for QLP to perform better at fainter magnitudes. We have adopted the photometry methods employed by the TESS-Gaia Light Curve package (Han & Brandt 2023), which has been shown to have better noise characteristics than the original QLP photometry from 10.5 $<$ $T$ $<$ 13.5. We still perform aperture photometry and deliver 3 apertures, and 3 levels of detrending for all stars brighter than $T$ = 13.5, so the changes should be seamless for external users. This method is implemented as of Sector 94 in QLP light curves and is providing users with higher precision light curves and allows detection of fainter signals in our planet searches.

Galaxy size provides key insights into the physical processes driving galaxy formation and evolution. Using deep JWST/NIRCam and MIRI imaging from the PRIMER survey, we investigate the rest-frame optical size-stellar mass relation of galaxies at $0.5 < z < 6.0$. We find that star-forming galaxies (SFGs) exhibit a broken power-law size-mass relation at all redshifts, with a nearly constant pivot mass ($M_{\rm p}$) of $\sim 10^{10} M_\odot$, and a slope flattening above $M_{\rm p}$. This highlights the prevalence of a population of compact, massive SFGs, likely underrepresented in previous studies. The size distribution of quiescent galaxies (QGs) is well described by a mixture power-law model, with the pivot mass increasing with redshift, from $M_{\rm p} \sim 10^{10.0} M_\odot$ at $z =0.75$ to $M_{\rm p} \sim 10^{10.5} M_\odot$ at $z = 2.6$, suggesting the minimum halo mass required to quench a high-mass QG increases with redshifts. The bending in the size-mass relation of SFGs supports two distinct size growth modes. At $M_{\star} < M_{\rm p}$, galaxy size growth is closely coupled to halo growth, while at $M_{\star} > M_{\rm p}$, an increasing fraction of SFGs decouple from halo growth and become more compact, likely associated with rapid bulge (and black hole) growth in $M_{\rm h} \gtrsim 10^{12} M_{\odot}$ halos. These compact SFGs are promising progenitors of massive QGs, as evidenced by their similar masses, surface brightness profiles, morphologies and number densities. These results suggests that the compaction pathway, rather than major mergers of extended SFGs, dominates the formation of massive QGs at $z \gtrsim 2$.

Close binary central stars of PNe offer a unique window for investigating the conditions immediately following the ejection of a common envelope (CE). Double eclipsing and double-lined double systems are particularly valuable as they provide minimally model-dependent constraints on fundamental binary parameters. We report that the nucleus of Pa13 (P=0.3988d) belongs to this rare class of systems and present a comprehensive analysis of its double-degenerate binary. We performed a two-component NLTE spectral analysis based on phase-resolved X-Shooter spectroscopy, multi-band light-curve modeling, SED fitting, as well as a kinematic analysis. Both stars are found to be hot pre-white dwarfs, with Star1 being cooler but larger (Teff=50kK, R=0.40Rsol) than Star2 (Teff=75kK, R=0.16Rsol). The weakness of spectral lines of Star2 made both the atmospheric and RV analyses challenging, and we uncovered a strong sensitivity of the assumed surface ratio to its derived RV curve. Yet, the RV curve and Kiel mass of Star1 (M1=0.41+/-0.02Msol) could be determined precisely, allowing for a dynamical mass determination of Star2 (M2=0.39+/-0.04Msol). We uncovered that Pa13 exhibits a small but significant orbital eccentricity (e=0.02+/-0.01), making it only the second post-CE binary nucleus with a measured eccentricity. We conclude that Pa13 provides hitherto the strongest evidence that PNe can be observed around post-RGB stars. Immediately after the CE-ejection, Star1 likely still filled its Roche lobe, suggesting that Pa13 is a more evolved, detached descendant of over-contact double-degenerate systems such as Hen2-428. Since the mass ratio of Pa13 is close to unity the system may have formed through double-core CE evolution. Alternatively, there must exist an efficient CE-induced rejuvenation mechanism capable of reheating the cool white dwarf in the binary, as already indicated by Hen2-428. (abbreviated)

This paper explores the extent to which the circumgalactic medium (CGM) of Milky Way-like galaxies is located in an extended, ionized, disklike structure. To test this hypothesis, we analyze the spatial and kinematic distributions of different ion species within a sample of MW-like systems in IllustrisTNG. We model commonly observed ions (HI, MgII, SiIV, CIV and OVI) and calculate (1) their angular momentum misalignment from the star-forming disk ($\theta$) and (2) the fraction of absorption consistent with galaxy rotation ($f_\mathrm{EWcorot}$). We find that 63% of MgII, 45% of SiIV, 38% of CIV, and 35% of OVI mass along the major axis have kinematics aligned with the galaxy angular momentum axis. We extend this to a mock absorption line survey and quantify $f_\mathrm{EWcorot}$. We find that $f_\mathrm{EWcorot}$(MgII) $\sim80\%$ and $f_\mathrm{EWcorot}$(OVI) $\sim60\%$ at $\sim0.5\ \mathrm{R_{200c}}$, in agreement with recent observational work. We find that in the typical MW analog, there is evidence of cool-warm material in an extended, corotating structure, regardless of whether the angular momentum or observational definition is used. Hence, we expect that the typical MW CGM, especially in the low ions, should be mainly on the plane.

It has been claimed that a fraction of the so-called Little Red Dots (LRDs) are characterised by exponential broad line profiles, which have been ascribed to broadening from electron scattering by an ionised cocoon. In this work, we investigate the H$\alpha$ broad line profiles of 32 AGN, including Little Red Dots (LRDs), Little Blue Dots (LBDs), and X-ray detected sources, using high SNR and resolution spectroscopy. We find that while single Gaussian models are statistically rejected, the exponential model is not universally preferred. Lorentzian and multi-Gaussian profiles provide equally good or superior fits for the majority of the sample, with no statistical preference for exponential profiles in $\sim$60% of cases across all AGN subtypes. There are indications that exponential profiles are preferred more frequently among LBDs, indicating that exponential profiles are not a prerogative of LRDs, which actually seem to more often favour Lorentzian profiles. Furthermore, we demonstrate that exponential wings can emerge naturally from the stratification of BLR clouds in virial motion, without invoking any scattering process. More generally, we also show that stacking multiple broad lines (either from multiple objects, as done in previous works, or from different BLR components within the same object) generally yields an exponential profile, even if none of the individual profiles are exponential. Explaining the exponential profiles in terms of BLR stratification solves various observational tensions with the electron scattering interpretation. While electron scattering may play a role, there is no evidence that it dominates the line profiles and that it significantly affects the inferred black hole masses.

Ion sputtering from loose powders remains poorly understood despite its relevance to planetary science and industry. We developed a multiscale Monte Carlo model to simulate sputtering from powders, using a higher-fidelity approach for the target geometry compared to voxel-based methods. Simulating Kr+ ions impacting Cu powders and flat slabs, we show that sputtering from loose powders differs markedly from that of flat slabs or rough surfaces. The main differences are: (1) for incident angles a > 0 degree relative to the bulk normal, the escaping sputtering yield is dominated by backward-directed ejecta for all ion energies; (2) for a < 60 degrees, the yield peaks toward the ion-beam origin, similar to the opposition effect seen in optical observations of airless bodies; (3) the angular distribution peak is half or less than that of a flat slab; (4) as ion energy increases, no evolution occurs from primary to secondary knock-on sputtering in the ejecta angular distribution. We attribute these behaviors to the powders interconnected voids. Ions penetrate these voids and sputter underlying grains; the ejecta then preferentially escape toward the ion-beam origin, where shadowing is minimal. We derive two fitting functions: 1) relating the escaping sputtering yield of a powder to that of a flat surface, depending only on porosity, incident angle, mean local incidence angle, and the corresponding flat slab yield; 2) providing the double-differential angular distribution of the escaping ejecta for porosities > 0.49. These provide a potentially universal fitting function of the absolute doubly-differential escaping sputtering yield from loose powders.

In this work, we investigate the equilibrium structure of white dwarfs within the covariant formulation of symmetric teleparallel $f(Q)$ gravity, in which gravity is described by the nonmetricity scalar $Q$ instead of spacetime curvature. We consider static and spherically symmetric stellar configurations composed of cold, fully degenerate electron matter and adopt a quadratic form of the gravitational Lagrangian, $f(Q)=Q+\alpha Q^{2}$, where $\alpha$ quantifies deviations from general relativity. The corresponding modified stellar structure equations are solved numerically in conjunction with the Chandrasekhar equation of state. We examine the impact of the parameter $\alpha$ on the internal structure and global properties of white dwarfs, including the radial profiles of the metric potentials, pressure, density, nonmetricity scalar, and enclosed mass, as well as the mass--radius relation. While negative values of $\alpha$ were explored, they lead to unstable or nonphysical configurations at high densities; therefore, the analysis is restricted to non-negative values of $\alpha$. Our results show that nonmetricity corrections produce significant deviations from the general relativistic predictions in the high-density regime. In particular, increasing $\alpha$ modifies the equilibrium configurations and leads to a reduction in the maximum mass relative to the Chandrasekhar limit, accompanied by corresponding changes in the stellar radius and interior profiles. For $\alpha = 5\times10^{18}\,\mathrm{cm^2}$, we obtain a maximum mass $M_{\max}=1.3519\,M_{\odot}$ and radius $R=2228.85\,\mathrm{km}$, which are consistent with the observational constraints of the ultra-massive white dwarf ZTF J1901+1458. These findings suggest that white dwarfs can provide a complementary astrophysical probe for testing the viability of $f(Q)$ gravity in the strong-field regime.

Power law tails induced by nonlinearities of General Relativity (``sourced'' or ``nonlinear'' tails) were recently shown to dominate the late time waveform of Schwarzschild black hole ringdowns. We extend the analytical results regarding such nonlinear tails from Schwarzschild to Kerr black holes by studying the Teukolsky equation. Using a far field approximation to the radial Green's function, we analytically derived the tail power law to be $t^{-\ell-\beta-s}$ for spin-weight $s \neq 0$, harmonic mode $(\ell m)$ and source decay $r^{-\beta}$. We numerically confirmed these results for $\beta = 0, 1$. We also demonstrate the dynamical formation of such nonlinear tails for a massless scalar by numerically solving the Teukolsky equation. In all numerical results, Kerr black hole nonlinear tails have the same power laws as that for Schwarzschild black holes, as expected from the Minkowski nature of the spacetime in the far field region.

We propose a mechanism for baryogenesis in which the baryon asymmetry is generated as an \emph{equilibrium response} of weak sphalerons in a region where electroweak sphaleron transitions remain unsuppressed, $h/T\lesssim 1$. A nonzero equilibrium baryon density arises in the presence of an approximately conserved global charge $X$, carried by states with nonzero hypercharge and, after electroweak symmetry breaking, electric charge. Plasma screening enforces gauge-charge neutrality, so an $X$ asymmetry induces compensating gauge-charge densities in the Standard Model plasma, which in turn bias weak sphaleron transitions toward a state with nonvanishing baryon number. The required $X$ asymmetry is generated during a phase transition that changes the strength of electroweak symmetry breaking, but need not coincide with the final electroweak phase transition. In particular, the mechanism can operate during an inverse electroweak phase transition, where baryon number is produced behind the advancing wall, in contrast to conventional electroweak baryogenesis. Because baryon production is decoupled from a direct first-order electroweak phase transition, the scenario can be realized at parametrically higher temperatures than standard electroweak baryogenesis, thereby weakening current experimental constraints. This framework provides a qualitatively distinct route to electroweak baryogenesis, with different parametric dependence, phase-transition dynamics, and phenomenological signatures.

We study two singular spectral components of the Green's function of a Schwarzschild black hole and their interpretation in the frequency domain: (i) the low-frequency branch cut, which yields corrections to Price's law tails in the form of inverse power laws weighted by logarithmic terms; and (ii) the quasinormal-mode spectrum, which generates a redshifted response for sources extended toward the horizon. We show that the frequency-domain Green's function can be naturally interpreted in terms of greybody factors, providing the first analytical justification for recent phenomenological ringdown models based on these quantities. For sources localized outside the peak of the potential barrier, we identify two tail contributions activated with a time delay, arising from backscattering of the prompt response and of the ringdown signal. We show that corrections to Price's law can be relevant at intermediate times, when the ringdown still dominates the waveform. For sources localized inside the potential barrier peak, the tail is suppressed and the signal is instead dominated by quasinormal frequencies. In this regime, these spectral components produce both the ordinary quasinormal-mode ringdown and an infinite tower of exponentially decaying terms governed by the horizon surface gravity, the so-called redshift terms. We demonstrate that this component is not screened by geometric features of the background spacetime and persists up to late times, as supported by numerical investigations of perturbative waveforms. Our results provide a mathematical foundation for phenomenological modeling of the branch-cut contribution at intermediate times, which is relevant for prospective observations of tails, and strong evidence for the presence of redshifted components from intermediate to late times.

We examine parameter degeneracies in Culetu, Bardeen and Hayward regular black holes across lensing, shadow and quasinormal mode regimes. Our analysis reveals that while Einstein ring data yield extremely loose constraints, with the regularization parameter $q$ exceeding $\mathcal{O}(10^3)$, they fail to improve the parameter estimation when combined with strong lensing observables. In contrast, the Event Horizon Telescope observations provide remarkably tight limits: $0 \leq q < 0.0466 <0.0847$ for Culetu, $0 \leq q < 0.5115 <0.6682$ for Bardeen and $0 \leq q < 1.0258 <1.1881$ for Hayward, which shows that the strong field regime alone dominates the available parameter space. Despite these bounds, leading order geometric observables remain highly degenerate, which masks the microscopic details of non-singular cores. To break this ``macroscopic universality,'' we identify high order signatures, such as the Lyapunov exponent and subleading time delays, as sensitive probes of near horizon curvature. Crucially, we discover that the brightness hierarchy of accretion induced intensity profiles undergoes a fundamental inversion when transitioning from lensing dominated static flows to dynamics dominated infalling flows. These results demonstrate that high resolution temporal and intensity profiles are essential for distinguishing between regular black hole geometries.

We construct a generalized class of Joshi-Malafarina-Narayan (JMN) naked singularity spacetimes that arise as equilibrium end states of gravitational collapse with non-vanishing tangential pressure. The generalization introduces density inhomogeneity through a radially dependent mass function $F(r)=(M_0+M_n r^n)r^3$, leading to a two-parameter family of solutions matched smoothly to an exterior Schwarzschild spacetime. The observational properties of the spacetime are then examined through shadow formation and thin accretion disk emission. We find that when the photon sphere lies in the exterior Schwarzschild region, the shadow is identical to that of a Schwarzschild black hole. Accretion disk spectra show enhanced high-frequency emission compared to Schwarzschild, while deviations from the original JMN model remain small due to strong constraints on the inhomogeneity parameter. These results indicate that the generalized model effectively serves as a small perturbation of the JMN spacetime, demonstrating the robustness of JMN-type naked-singularity geometries.

Non-local gravity terms have a relevant role in determining the cosmological dynamics. Here we consider curvature- and torsion-based cosmological models where non-local terms can be ``scalarised'' and then reduced under the standard of scalar-tensor gravity. In this context, we study the role of non-local cosmology with regards to the recent results reported by the IceCube/KM3NeT experiments, which revealed high-energy astrophysical neutrino fluxes up to energies of $220$\,PeV. Specifically, we consider the four-dimensional operator $y_{\alpha\chi}\bar L_\alpha H\chi$ in order to explain both the neutrino rate result and the abundance of dark matter in the Universe, provided that the cosmological background evolves according to non-local gravitational field equations. We show that different dynamical systems representing the evolution of the Universe can be highly sensitive to the parameters of non-local gravity at energies probed by IceCube/KM3NeT. In particular, we adopt power law solutions inferred by the existence of Noether symmetries in non-local cosmological models.

We analyze the causal structure of horizonless compact objects via the light-cone geometry and conformal compactification of the Joshi-Malafarina-Narayan (JMN-1) and Janis-Newman-Winicour (JNW) spacetimes. Penrose diagrams reveal that JMN-1 undergoes a transition from timelike $(0<M_0<2/3)$ to null $(2/3<M_0<4/5)$ singularities, while JNW remains timelike throughout, in contrast to the spacelike singularity of the Schwarzschild spacetime. We show that photon spheres exist in Schwarzschild and JNW, but arise in JMN-1 only in the null singularity phase, establishing a direct link between causal character and null geodesic trapping. We further demonstrate that radial timelike geodesics develop turning points for certain parameter regimes in both JMN-1 and JNW spacetimes, indicating the emergence of effective repulsive behavior in the strong field region. These features lead to distinct strong field lensing and shadow signatures, potentially testable by very long baseline interferometric observations such as those of the Event Horizon Telescope.

We discuss the connection between logotropes and polytropes in astrophysics and cosmology. The logotropic equation of state $P=A\ln(\rho/\rho_P)$ may be seen as a degenerate form of the polytropic equation of state $P=K\rho^{\gamma}$ in the limit $\gamma\rightarrow 0$, $K\rightarrow\infty$ with $A=K\gamma$ fixed. The logotropic distribution function corresponds to the polytropic distribution function of index $\gamma=0$ for which the density is finite but the pressure diverges logarithmically. We show that the polytropic and logotropic distribution functions can be obtained in the nondegenerate limit of the Lynden-Bell theory of violent relaxation for a particular distribution of phase levels given by the $\chi$-squared distribution. This provides a justification of the Tsallis entropy from the Lynden-Bell entropy. The logotropic distribution function presents a power-law energy tail decreasing as $\epsilon^{-5/2}$. Interestingly, this ``universal'' power-law tail is predicted by recent kinetic theories of collisionless relaxation based on the coarse-grained Vlasov equation and on the secular dressed diffusion equation. When coupled to gravity, the associated density profile decreases as $r^{-1}$. This may explain the universal surface density of dark matter halos, or account for an effective NFW density cusp. This also accounts for the universal gravitational acceleration felt by a test particle and for the Tully-Fisher relation. The logotropic model can thus provide an alternative to the modification of Newtonian dynamics (MOND) theory. We recall how the logotropic model leads to a very accurate expression of the cosmological constant $\Lambda={G^2m_e^6}/{\alpha^6\hbar^4}=1.36\times 10^{-52}\, {\rm m^{-2}}$ in terms of the mass of the electron and the fundamental constants of physics.

We investigate the influence of boundary terms in gravitational field theories, by considering that in the Einstein-Hilbert action the boundary can be described by a non-metric Weyl-type geometry. The gravitational action and the the field equations, are thus generalized to include new geometrical terms, coming from the non-metric nature of the boundary, and depending on the Weyl vector, and its covariant derivatives. The field equations obtained within this framework generalize the standard Einstein equations by including in their mathematical structure the Weyl vector, and its covariant derivatives. As an applications of the general formalism we investigate the cosmological evolution in a flat FLRW geometry. We obtain the generalized Friedmann equations, which contain extra terms depending on the Weyl vector and its derivatives, arising due to the presence of the Weylian boundary, and which describe an effective, time dependent dark energy. By imposing to the dark energy an equation of state parameter of the Barboza-Alcaniz type, the Friedmann equations can be solved numerically. We compare the predictions of the Weylian boundary gravitational theory with late-time observational data and the predictions of the $\Lambda$CDM paradigm. Our results show that the Weylian boundary cosmological models give a good description of the observational data, and they can reproduce almost exactly the predictions of the $\Lambda$CDM paradigm. Hence, the extension of gravitational theories through the addition of Weylian boundary terms, in which dark energy has a purely geometric origin, emerges as a viable alternative to standard general relativity.

We investigate $f\left( Q\right) $-gravity with a matter-gravity coupling as a geometric dark energy candidate for the description of the late-time cosmic acceleration within a spatially flat Friedmann--Lema\^ıtre-Robertson-Walker geometry. We select a noncoincident connection that naturally follows from the general framework of cosmological models with nonzero spatial curvature. We present observational constraints for the simplest $f\left( Q\right) =f_{0}Q^{n}$ model using data from Supernovae, Baryon Acoustic Oscillations and Cosmic Chronometers. For different data combinations we found consistent constraints, with a best-fit value for the power-law index $n\simeq2$. A comparison with the $\Lambda$CDM model shows that the $f\left( Q\right) $-gravity leads to larger values for the likelihood, while Akaike's Information Criterion suggests statistical equivalence between the two models for most data combinations.

We construct and analyse two-dimensional, current-carrying ring solutions, known as kinky vortons, in the $\mathbb{Z}_2$-symmetric global two-Higgs-doublet model (2HDM). We demonstrate the existence of multiple dynamically stable configurations that persist under non-axially symmetric perturbations. These solutions are described with high accuracy by the thin string approximation and elastic string formalism, which correctly capture both their equilibrium radii and dynamical oscillation frequencies. Kinky vortons in the $\mathbb{Z}_2$-symmetric theory establish the viability of vorton solutions in a phenomenologically motivated extension of the Standard Model, and should provide a computationally tractable proxy for vortons in the $U(1)$-symmetric 2HDM. In addition, we identify a composite domain wall configuration in which localized condensates are supported on secondary domain walls existing on a $\mathbb{Z}_2$ wall, suggesting a mechanism by which kinky-vorton-like defects could arise in a three dimensional setting.

We investigate s-wave kaon condensation in dense matter and neutron stars within the updated Chiral Mean Field model with an improved meson description (mCMF), which incorporates dynamically generated in-medium meson masses arising from explicit chiral symmetry breaking and vector-meson self-interactions. In contrast to conventional relativistic mean-field descriptions with constant meson masses, the mCMF framework introduces a self-consistent feedback between the meson sector and the dense-matter equations of motion. The kaon dispersion relation is derived from the nonlinear SU(3) Lagrangian, including the Weinberg-Tomozawa interaction and additional baryon-pseudoscalar couplings, and the onset of condensation is determined under conditions of charge neutrality and $\beta$ equilibrium. Our calculations include the full baryon octet together with electrons and muons at zero temperature. We analyze the impact of hyperons, muons, and kaon condensation on the equation of state, on neutron-star mass--radius relations, and neutron-star thermal evolution, and examine the sensitivity of the onset density and stellar properties to variations in the nucleon--kaon scattering length and to different model vector parameters and vector self-interactions. We find that $K^{-}$ condensation sets in between $n \sim (2-8)\, n_0$ (in units of nuclear saturation density) and leads to a moderate to strong softening (in one case, a slight stiffening of the equation of state), depending on the interplay of kaons and hyperons, while remaining compatible with current $2\,M_\odot$ and small-radius neutron-star observational constraints and producing distinguishable behavior in the neutron-star cooling. This work provides an improved and thermodynamically consistent framework for studying exotic degrees of freedom in neutron-star matter.

Dense neutrino media in core-collapse supernovae and neutron star mergers can experience collective flavor transformations in the form of neutrino oscillation waves. It was recently reported that the stable fast modes of collective oscillations can be damped through a mechanism similar to the Landau damping of plasma waves. In this work, we show that the actual damping rates of fast oscillation waves are usually very small and vanishes in the pure fast limit. This result does not affect the unstable modes that eventually drive collective neutrino flavor conversions in supernovae and neutron star mergers.

One of the key limitations of large-scale structure surveys of the current and future generation, such as Euclid, LSST-Rubin or Roman, is the influence of feedback processes on the distribution of matter in the Universe. This effect, called baryonic feedback, modifies the matter power spectrum on non-linear scales much stronger than any cosmological parameter of interest. Constraining these modifications is therefore key to unlocking the full potential of the upcoming surveys, and we propose to do so with the help of Fast Radio Bursts (FRBs). FRBs are short, astrophysical radio transients of extragalactic origin. Their burst signal is dispersed by the free electrons in the large-scale structure, leading to delayed arrival times at different frequencies characterised by the dispersion measure (DM). Since the dispersion measure is sensitive to the integrated line-of-sight electron density, it is a direct probe of the baryonic content of the Universe. We investigate how FRBs can break the degeneracies between cosmological and feedback parameters by correlating the observed Dispersion Measure with the weak gravitational lensing signal of a Euclid-like survey. In particular, we use a simple one-parameter model controlling baryonic feedback, but we expect similar findings for more complex models. Within this model, we find that $\sim 5\times 10^4$ FRBs are sufficient to constrain the baryonic feedback significantly better than cosmic shear alone, tightening the constraints considerably (roughly by a factor of five). We also expect a 1.5-fold improvement in the sum of neutrino masses.

We show scenarios in which primordial black hole accretion under the magnetorotational instability (MRI) uniquely relates the density of the early Universe to the abundance of present day dark matter. We demonstrate via long duration general relativistic magnetohydrodynamic (GRMHD) simulations that MRI-dominated accretion at least hundreds of gravitational radii from black holes can occur under conditions expected in the Positronium Era. We thereby identify that the positronium plasma that existed 0.01 s to 14 s into the Big Bang can serve as the primary source of mass that augmented primordial black hole seeds to 10^16-10^17g black holes contributing to dark matter today. This population of black holes, in turn, radiates in a manner consistent with the observed gamma ray background. At a time of uncertainty about the role of new kinds of particles, the better understood primordial black hole MRI accretion process may be the best way to pin down how much dark matter mass lies behind horizons versus new dark sector particles.

We quantify the stellar rotation of galaxies by computing the $\lambda_{R}$ parameter, a proxy for the stellar angular momentum in a sample of 106 galaxies with redshift 0.1 $<$ z $<$ 0.8 and stellar masses from $\sim$10$^{7.5}$ to 10$^{11.8}$ M$_{\odot}$. The sample is located in the CANDELS/GOODS-S and COSMOS fields, and it was observed by various MUSE surveys. We create stellar velocity and velocity dispersion maps using a full-spectrum fitting technique, covering spatially $\sim$2$R_{e}$ for the galaxies. We study the impact of the atmospheric seeing on the spin parameter and apply corrections when pertinent. Through the analysis of the $\lambda_{R}-\epsilon$ diagram, we notice that the fraction of round and massive galaxies increases with redshift. We lack galaxies with $\lambda_{R}$ < 0.1 in the sample and we find only one potential, but uncertain, low-mass slow rotator at z $\sim0.3$. Moreover, we do not see an evident evolution or trend in the stellar angular momentum with redshift. We characterize the sample environment using two indicators: a local estimator based on the Voronoi tesselation method, and a global estimator derived by the use of the Friends-of-Friends algorithm. We find no correlation between the environment and $\lambda_{R}$ given that we are not probing dense regions or massive galaxy structures. We also analyze the kinematic maps of the sample finding that about 40$\%$ of galaxies are consistent with being regular rotators, having rotating stellar discs with flat velocity dispersion maps, while $\sim20\%$ of galaxies have complex velocity maps and can be identified as non-regular rotators in spite of their $\lambda_{R}$ values. For the remaining galaxies the classification is uncertain. As we lack galaxies with $\lambda_{R}$< 0.1, we are not able to identify when galaxies become slow rotators within the surveyed environments, area and redshift range.

Neutron stars (NSs) are conventionally discovered through radio, X-ray, or gamma-ray observations. Unlike these methods, optical time-domain surveys can unveil the important yet underexplored population of non-accreting NS in wide binaries. Here we report the discovery of a NS candidate using asteroseismology, spectroscopic surveys, and pulsation timing. The candidate, SZ~Lyncis, resides in a single-lined spectroscopic binary containing an optically visible $\delta$ Scuti star. Through asteroseismic modeling, we precisely determined the visible star's mass as $M_1 = 1.83^{+0.06}_{-0.01}$~M$_{\odot}$. We derived the companion masses using dynamical methods. We obtained $M_2 = 1.76_{-0.042}^{+0.042}$~M$_{\odot}$ from a radial velocity analysis, and $M_2 = 2.07_{-0.045}^{+0.045}$~M$_{\odot}$ from timing variations based on an astrometric inclination of 38.67 ($\pm$0.29) degrees, as obtained from Gaia and Hipparcos astrometric data. These masses rule out main-sequence stars and massive white dwarfs (WDs), leaving NS as the only possible companions. While a binary system comprising two WDs cannot be entirely ruled out, the absence of spectroscopic signatures of a WD from the companion and the consistency with single light-travel time effects suggest the presence of a NS. However, precise determination of the companion's mass requires future Gaia astrometry, and detection of potential radio emission necessitates FAST observations. SZ~Lyncis demonstrates the potential of optical time-domain surveys combined with asteroseismology and precise timing to unveil quiescent NSs in wide binaries.

The continuing exploration of neighboring planetary systems is providing deeper insights into the relative prevalence of various system architectures, particularly with respect to the solar system. However, a full assessment of the dynamical feasibility of possible terrestrial planets within the Habitable Zones (HZ) of nearby stars requires detailed knowledge of the masses and orbital solutions of any known planets within these systems. Moreover, the presence of as yet undetected planets in or near the HZ will be crucial for providing a robust target list for future direct imaging surveys. In this work, we quantify the distribution of uncertainties on planetary masses and semi-major axes for 1062 confirmed planets, finding median uncertainties of 11.1% and 2.2%, respectively. We show the dependence of these uncertainties on stellar mass and orbital period, and discuss the effects of these uncertainties on dynamical analyses and the locations of mean motion resonance. We also calculate the expected radial velocity (RV) semi-amplitude for a Neptune-mass planet in the middle of the HZ for each of the proposed Habitable Worlds Observatory target stars. We find that for more than half of these stars, the RV semi-amplitude is less than 1.5 m/s, rendering them unlikely to be detected in archival RV data sets and highlighting the need for further observations to understand the dynamical viability of the HZ for these systems. We provide specific recommendations regarding stellar characterization and RV survey strategies that work toward the detection of presently unseen perturbers within the HZ.

We present an analysis of very metal-poor (VMP) and metal-poor stars ($-3.0 < \mathrm{Fe/H]} < -1.5$) in the Gaia BP/RP or XP catalog, which reveals two distinct metallicity distribution functions (MDFs) in regions of the Galactic disk above and below $|z| = 1.0$ kpc. The low-$|z|$ regions display a metallicity peak around [Fe/H] = -2.0 with a sharp transition in Galactocentric azimuthal velocity ($v_\phi$), a feature notably absent in high-$|z|$ regions. Using a galactic chemical evolution (GCE) model, we found that the proto-Milky Way underwent two distinct formation scenarios: a rapid star formation burst followed by quenching near the Galactic center and an extended period of steady star formation. This starburst could have been triggered by a gas-rich accretion event in the first Gyr of our Galaxy's history. Comparison with Milky Way-analog galaxies in Auriga simulations shows strong agreement in the characteristics of this starburst population. During the accretion event, gas rapidly sinks into the inner regions of these analog galaxies, producing the observed MDF peak and the low $v_\phi$ values. The simulations further indicate that most stars at the metallicity peak formed in situ, rather than through accretion. These findings identify this starburst population as the long-sought in situ component of the proto-Galaxy.

We perform a comprehensive thermodynamic analysis of three sign-switching dark energy models in a flat FLRW cosmology: graduated dark energy (gDE), sign-switching cosmological constant ($\Lambda_s$), and smoothed sign-switching cosmological constant ($\Lambda_t$). We systematically derive key cosmological thermodynamic quantities -- horizon temperature, horizon entropy, internal entropy, total entropy, and their first and second derivatives -- using the Generalised Second Law (GSL) as the fundamental evaluation criterion. We first confirm the compliance of the $\Lambda$CDM model with the GSL, establishing a baseline for comparison. We find that despite their unconventional negative-to-positive energy density transitions, both $\Lambda_s$ and $\Lambda_t$ remain thermodynamically consistent. In contrast, gDE exhibits significant issues: divergences in its equation-of-state lead to infinite horizon temperature and entropy derivatives; and asymptotically, the horizon temperature diverges while entropy approaches zero, causing entropy reduction and violating the GSL. We highlight a key insight: models with divergences in the product of the dark energy equation-of-state parameter and its energy density ($w_x \Omega_x$) inevitably produce thermodynamic inconsistencies in standard cosmology. This thermodynamic approach provides a complementary criterion alongside observational constraints for evaluating the physical viability of cosmological models.

Rapid uniformly-rotating neutron stars are expected to be formed for instance in the collapse of some massive stars, the accretion of compact object binaries, and double neutron star mergers. The huge amount of the rotational energy has been widely believed to be the source of some cosmic gamma-ray bursts and superluminous supernovae. Benefited from the constraints on the equation of state of the neutron star matter set by the latest multi-messenger data, the chiral effective field theory and perturbative quantum chromodynamics, here we present the maximum gravitational mass as well as the rotational energy for a neutron star at a given spin period. Our nonparametric equation of state analysis reveals that the critical Keplerian configurations ($\Omega_{\rm kep}^{\rm crit}=1.02_{-0.07}^{+0.06}\times 10^{4}~{\rm rad/s}$) can sustain maximum gravitational masses of $M_{\rm kep}^{\rm crit}=2.73 \pm 0.09 M_\odot$ with corresponding rotational energy reaching $E_{\rm rot,kep}^{\rm crit}=2.36^{+0.24}_{-0.22}\times 10^{53}$ erg. However, the maximum rotational energy that can be feasibly extracted from a neutron star is limited to $1.40^{+0.14}_{-0.13}\times 10^{53}$ erg, which holds for a baryon mass of $2.66^{+0.10}_{-0.09}M_\odot$. All these parameters, obtained via the nonparametric reconstruction of the equation of state, are at the $68.3\%$ confidence level and the adoption of a quarkonic model yields rather similar results. These findings are found to have already set some intriguing constraints on the millisecond magnetar interpretation of some exciting data.

Accurate measurements of fundamental cosmological parameters, especially the Hubble constant (H_0) and present-day matter density (\Omega_{m0}), are crucial for constraining dark energy (DE) evolution. We analyze the sensitivities of cosmological observables (H(z), D_L(z), E_{G}) to \Omega_{m0}, w_0, and w_an under different parametrizations. Our results show observables are far more sensitive to \Omega_{m0} than to DE equation of state parameters (e.g., at z \sim 0.5, H(z)'s \Omega_{m0} sensitivity is \sim 0.7 vs. w_a's \sim 0.04). This hierarchy mandates high-precision \Omega_{m0} measurements to accurately constrain time-varying DE. We also find DE parameter sensitivity highly depends on parametrization; the standard CPL form shows low sensitivity to w_a, but \omega(z) = w_0 + w_a \ln(1+z) significantly enhances it. Our analysis of DESI DR1/DR2 data confirms these theoretical limits: standalone DESI data primarily provides only upper limits for w_a, underscoring insufficient constraining power for a definitive time-varying DE detection. While combined datasets offer tighter constraints, interpretation requires caution due to parametrization influence. We further confirm this point using simulated Supernovae MCMC data. In conclusion, improving \Omega_{m0} precision and adopting optimized parametrizations are imperative for future surveys like DESI to fully probe dark energy's nature.

We consider a general dark energy (DE) model parametrized by its equation-of-state (EoS), featuring three free parameters: $w_0$ (the present-day value of the DE EoS), $w_{\beta}$ (quantifying the dynamical nature of the DE EoS), and $\beta$ (governing various dynamical forms of the DE EoS). The key controlling parameter $\beta$ can recover several existing DE models in the literature, such as the Chevallier-Polarski-Linder (CPL) parametrization ($\beta = 1$), the logarithmic parametrization (in the limit $\beta \rightarrow 0$), and the linear parametrization ($\beta = -1$), alongside generate a class of new DE parametrizations for other values of $\beta$. The resulting DE scenario is constrained using a suite of the latest cosmological probes, including Cosmic Microwave Background (CMB) temperature and polarization anisotropies from three different experiments (Planck 2018 and Atacama Cosmology Telescope combined with WMAP), CMB lensing, Baryon Acoustic Oscillations from DESI Year 2, and PantheonPlus from Type Ia supernovae. Our analyses reveal that stringent constraints on the DE parameters are obtained only when all cosmological probes are combined; otherwise, some parameters remain unconstrained. The present-day value of the DE EoS remains in the quintessence regime according to our results, and no significant evidence for a dynamical DE EoS is found. However, based on the $\Delta \chi^2$ and Bayesian evidence analyses, we observe a mild preference for the present three-parameter DE parametrization over the CPL parametrization when all cosmological probes are taken into account. Nonetheless, the Bayesian evidence difference remains below the threshold for statistical significance according to the revised Jeffreys scale, indicating that both models are effectively equally preferred by the data.

We present early results from a high-resolution analysis ($\sim$100-200pc) of the CO(2-1)/CO(1-0) line ratio in twelve nearby galaxies. We use new ALMA CO(1-0) observations from the Fundamental CO(1-0) Transition Survey (FACTS), and re-imaged CO(2-1) data from PHANGS. We make empirical classifications based on the optical and molecular gas morphologies, which show clear systematic trends in the variation of $R_{21}$ as a function of galactic structure. The sample includes barred and unbarred, and flocculent galaxies. The barred spiral galaxies follow a general trend when the gas exists significantly: $R_{21}$ is high in the center, low along the bar, increases at the bar ends, and then lowers beyond the bar end or flattens in the outer parts of the disk. The structure dependence suggests the importance of galactic dynamics on molecular gas evolution, and consequently on star formation, in galaxies. $R_{21}$ fluctuates in the spiral arms for both barred and unbarred galaxies. Areas around HII regions in some cases appear to show more high-ratio gas. Together, $R_{21}$ varies systematically as a function of galactic structure, dynamics, and star formation activity.

The stochastic-$\delta \mathcal{N}$ formalism is widely used to study inflation models in which the quantum diffusion of inflatons dominates the background dynamics, leading to interesting phenomena such as the production of primordial black holes. Among numerical approaches to calculate the curvature perturbation spectrum $\mathcal{P}_\zeta(k)$ in this formalism, the Monte Carlo simulation-based approach has been proposed as a promising choice, especially in multifield cases. In this approach, we generate many paths of inflatons from the initial points to the end of inflation, obtain statistics of $\delta N$ from the paths, and then estimate $\mathcal{P}_\zeta(k)$. However, this method involves a nested Monte Carlo simulation, which requires generating many branch paths from each trunk path at the point corresponding to the scale $k$ of interest, resulting in a high computational cost. In this paper, we propose a new Monte Carlo-based approach that utilizes least squares fitting, introducing two novel features for reducing computational cost. First, we devise a simple estimator of a key statistic $\langle \delta\mathcal{N}_{\mathbf{X}}^2\rangle$, the variance of $\delta \mathcal{N}$ conditioned on the branching point, to avoid nesting path generation. Second, via least squares fitting of a parametric function to the sampled values of the estimator, we obtain not just an estimate of $\mathcal{P}_\zeta(k)$ for a single value of $k$ but an approximating function of $\mathcal{P}_\zeta(k)$ over a range of $k$ of interest. We also conduct numerical demonstrations for concrete inflation models, which show the usefulness of our method.

Infrared-blocking, aerogel-based scattering filters have a broad range of potential applications in astrophysics and planetary science instruments in the far-infrared, sub-millimeter, and microwave regimes. This paper demonstrates the ability of conductively-loaded, polyimide aerogel filters to meet the mechanical and science instrument requirements for several experiments, including the Cosmology Large Angular Scale Surveyor (CLASS), the Experiment for Cryogenic Large-Aperture Intensity Mapping (EXCLAIM), and the Sub-millimeter Solar Observation Lunar Volatiles Experiment (SSOLVE). Thermal multi-physics simulations of the filters predict their performance when integrated into a cryogenic receiver. Prototype filters have survived cryogenic cycling to 4\,K with no degradation in mechanical properties. Measurement of total hemispherical reflectance and transmittance, as well as cryogenic tests of the aerogel filters in a full receiver context, allow estimates of the integrated infrared emissivity of the filters. Knowledge of the emissivity will help instrument designers incorporate the filters into future experiments in planetary science, astrophysics, and cosmology.

Primordial non-Gaussianities (PNGs) are features in the initial density field that provide a window into the nonlinear dynamics of particles during the inflationary epoch. Among them, a distinctive set of signatures from "cosmological collider physics" originates through interactions of the inflaton with heavy particles active at high energies. The amplitude and form of these signatures depend on the strength and nature of the interactions. The corresponding features in large-scale structure have been studied predominantly through the use of perturbation theory, restricted to the linear regime of the density field. In this work, we implement a method for running cosmological simulations with arbitrary bispectra signals in their initial density field, and produce a simulation suite of over thirty PNG-generating templates, resolving the corresponding collider signatures in the strongly nonlinear regime of the density field. We detail the signals in a variety of late-time measurements -- the matter power spectra, matter bispectra, the halo abundance, and halo bias. We then forecast the potential constraints on the signal amplitudes using weak lensing measurements from the Year-10 dataset of the Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST). The second and third moments of the lensing convergence field produce constraints that are competitive and complementary to those from the Cosmic Microwave Background. The data products are publicly released as part of the Ulagam simulation suite. Our initial conditions generator is also publicly available at this https URL.

Primordial non-Gaussianities (PNGs) are imprints in the initial density field sourced by the dynamics of inflation. These dynamics can induce scale dependence, oscillations, and other features in the primordial bispectrum. We analyze a suite of over thirty PNG templates, including those used in the _Planck_ analyses of the Cosmic Microwave Background (CMB), and resolve their signatures in the deeply nonlinear regime of the late-time density field. Using simulations, we forecast results from a lensing analysis of the Year-10 data from the Rubin Observatory Legacy Survey of Space and Time (LSST). We find that lensing achieves sensitivity comparable to the CMB for many models, and even surpasses it for templates whose features peak on smaller scales, $k \gtrsim 0.2 h/{\rm Mpc}$. Many templates generate non-monotonic behaviors in mass and length scales, providing a distinct phenomenology in the resulting late-time structure. We simulate, for the first time, resonant signatures consistently in both the primordial power spectrum and bispectrum. The constraints on their amplitudes $(A_{\rm pk}, f_{\rm NL})$ are essentially independent, as each affects structure formation in distinct ways. Overall, we find that lensing data can provide competitive and complementary constraints on these models, and can deliver leading constraints when the primordial features are predominantly on smaller scales. The data products are publicly released as part of the Ulagam simulation suite. Our initial conditions generator is publicly available at this https URL.

We present a comprehensive Bayesian statistical analysis of brown dwarf companions to investigate the physical mechanisms responsible for the observed ``brown dwarf desert'' -- the notable paucity of brown dwarf companions at orbital separations $<$5~AU. Using a carefully vetted sample of 88 confirmed brown dwarf companions from the \texttt{this http URL} catalog with masses 13--80~$\mjup$ and semi-major axes 0.1--5.0~AU, we employ Markov Chain Monte Carlo (MCMC) optimization and two-dimensional Kolmogorov-Smirnov tests to compare observed orbital and mass distributions with three theoretical formation scenarios: (A) Type II disk-driven migration, (B) core accretion with mass-dependent survival, and (C) dynamical scattering from wide orbits. Our analysis spans 4-parameter models for each scenario, with proper posterior distributions quantifying parameter uncertainties and correlations. The disk migration model provides statistically superior fits (2D KS $p = 0.18$), with optimal parameters $\log_{10}\nu = -6.47^{+0.42}_{-0.31}$, $\sigma_\nu = 0.34^{+0.23}_{-0.17}$, $t_{\rm disk} = 1.66^{+1.24}_{-0.84}$~Myr, and $M_{\rm gap} = 12.0^{+4.7}_{-8.3}~\mjup$, consistent with Type II migration theory. The dynamical scattering model achieves intermediate performance ($p = 0.08$), while core accretion scenarios show poor agreement ($p < 0.001$) despite theoretical sophistication. Occurrence rate analysis reveals the desert region (0.1--5~AU) is depleted by a factor of $\approx$1.6 relative to wide separations ($>$5~AU), a constraint successfully reproduced only by the migration model. Our results provide quantitative evidence that brown dwarfs form at wide separations (10--30~AU) through disk fragmentation and undergo limited Type II migration to reach observed close-in locations, with migration naturally halting near 1~AU through gap-opening processes.

The 21-cm line of hydrogen is the most promising probe of the Dark Ages and Cosmic Dawn. We combine hydrodynamical simulations with a large-scale grid in order to calculate the effect of non-linear structure formation on the large-scale 21-cm power spectrum, focusing on redshifts $z=20-40$. As the clumping effect arises from small-scale density fluctuations, it offers a unique opportunity to probe the standard cold dark matter model in a new regime and thus potentially investigate the properties of dark matter. To this end, we also study a warm dark matter $-$ like model with a Gaussian cutoff on a scale of 50 kpc. We find that clumping has a significant impact on the large-scale 21-cm power spectrum. For example, for the Dark Ages case at $z=30$ and wavenumber $k=0.05$ Mpc$^{-1}$, small-scale clustering enhances the 21-cm power spectrum by $13\%$. Once Lyman-$\alpha$ coupling kicks in due to the first stars, the 21-cm signal strengthens, and the effect of clumping grows; it suppresses the observable power spectrum at $z=20$ by a factor of two, while the cutoff model has less than half the clumping impact. The clumping effect is significantly higher than the sensitivity of the planned Square Kilometre Array (SKA) AA$^\star$ configuration, by up to a factor of 20 for standard cold dark matter, though detection will require separation from foregrounds and from astrophysical contributions to the 21-cm power spectrum.

Scalar-induced gravitational waves (SIGWs) open a unique window into early-universe physics. While their generation from adiabatic perturbations has been extensively studied, the contribution from isocurvature perturbations remains largely unexplored. In this work, we develop a lattice simulation framework to compute the stochastic gravitational wave background from both pure isocurvature and mixed initial conditions. Our numerical results show excellent agreement with semi-analytical predictions in the pure isocurvature case. We further analyze multi-peak structures under general initial conditions and find that they closely match those produced in purely adiabatic scenarios. Additionally, we examine SIGWs in early matter-dominated eras, revealing that the peak amplitude and spectral slope are sensitive to the microphysical properties of the dominant field, such as the primordial black hole mass, abundance, or soliton decay rate. This study establishes lattice simulations as a robust tool for predicting SIGW spectra from complex primordial perturbations, with important implications for interpreting current and future gravitational wave observations.

We present a rigorous identification of candidates for dormant black holes (BHs) and neutron stars (NSs) in binaries using summary statistics from Gaia DR3, rather than full orbital solutions. Although Gaia astrometric orbits have already revealed a small sample of compact object binaries, many systems remain undetected due to stringent quality cuts imposed on the published orbits. Using a forward-modelling framework that simulates Gaia observables, in particular the re-normalised unit weight error (ruwe) and radial velocity (RV) scatter, we infer posterior distributions for companion mass and orbital period via MCMC sampling, marginalising over nuisance orbital parameters. We validate our approach by comparing the predicted masses and periods against full orbit solutions from DR3, and by successfully recovering known compact object binaries as promising candidates. The method is best suited for systems with red giant primaries, which have more reliable Gaia RV scatter and a light centroid more likely dominated by one component, compared to main-sequence stars, and they are less likely to be triples with short-period inner binaries, which produce confounding signatures. We applied the method to three million giants and identify 389 systems with best-fit companion masses $\gtrsim 3\,M_\odot$. Recovery simulations suggest our selection method is substantially more sensitive than the DR3 non-single-star catalogue, particularly for binaries with periods below 1 year and above $\sim 6$ years. These candidates represent promising targets for spectroscopic follow-up and Gaia DR4 analysis to confirm the presence of compact objects. Candidate main-sequence stars with massive companions face a larger set of confounding effects. Therefore, we present an analogous catalogue of 279 additional main-sequence candidates only as an appendix.

We present a comprehensive timing analysis of the black hole X-ray binary Cygnus X-1 using 26 NuSTAR observations spanning 2012-2024, providing the most detailed characterization to date of its accretion flow variability across spectral states. Our analysis reveals fundamental insights into the physics governing state transitions in stellar-mass black holes. We discover distinct bimodal flux distributions in the 8-79 keV band with well-separated peaks, contrasting with overlapping distributions in the 3-8 keV band. This energy-dependent bimodality establishes hard X-rays as the optimal diagnostic for state classification, directly tracing the geometric transformation between corona-dominated and disk-dominated configurations. Power spectral analysis uncovers state-dependent characteristic frequencies shifting from 0.050 Hz (hard) to 0.074 Hz (intermediate), with featureless red noise in soft states. These frequencies correspond to disk truncation radii evolving from $\sim$5.5 $R_g$ to $\sim$2 $R_g$, providing direct observational evidence for the inward progression of the accretion disk during state transitions. Frequency-dependent time lags evolve systematically from $\sim$50 ms hard lags at 0.1 Hz in hard states to near-zero in soft states, quantifying the collapse of the Comptonizing corona. Linear rms-flux relations persist across all states with parameters that precisely track the relative contributions of thermal versus non-thermal emission components. Most remarkably, we identify a failed state transition (observation 30302019006) exhibiting anticorrelated band behavior, suppressed variability ($F_{var}$ < 1.38\%), and apparent sub-ISCO truncation. This discovery challenges standard transition models and suggests new pathways for accretion flow evolution in wind-fed systems.

We show that core-collapsed self-interacting dark matter halos of mass $\sim 10^6\,{M_\odot}$, originally simulated to explain the dense perturber of the GD-1 stellar stream, also reproduce the structural properties inferred for the dense perturber detected in the strong lensing system JVAS B1938+666 from radio observations. Furthermore, these halos are sufficiently compact and dense to gravitationally capture field stars in satellite galaxies of the Milky Way, providing a natural explanation for the origin of Fornax 6, a stellar cluster in the Fornax dwarf spheroidal galaxy. Our results demonstrate that observations of halos with similar masses but residing in different cosmic environments offer a powerful and complementary probe of self-interacting dark matter.

Wideband timing of the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) datasets, where a single time-of-arrival (TOA) and a single dispersion measure (DM) are measured using the entire bandwidth of each observation, was first done for the 12.5-year dataset, and proved to be invaluable for characterizing the time-varying dispersion measure, reducing the data volume, and for improving the overall timing precision. The Canadian Hydrogen Intensity Mapping Experiment (CHIME) Telescope has been observing most NANOGrav millisecond pulsars (MSPs) at nearly daily cadence (compared to roughly monthly cadence for other NANOGrav observations) since 2019 with the objective of integration into future pulsar timing array (PTA) datasets. In this paper, we show the results of integration of high-cadence, low-observing-frequency CHIME data with data from the NANOGrav experiment for an isolated MSP PSR J0645$+$5158 and three binary MSPs PSR J1012$+$5307, PSR J2145$-$0750, and PSR J2302$+$4442. Using a wideband timing pipeline which we also describe, we present updated timing results for all four sources, including improvements in measurements of relativistic post-Keplerian parameters for the three binary pulsars in this analysis. For PSR J2302$+$4442, we report an updated strong detection of Shapiro delay from which we measured a companion mass of $0.35^{+0.05}_{-0.04}\ M_{\odot}$, a pulsar mass of $1.8^{+0.3}_{-0.3}\ M_{\odot}$, and an orbital inclination of ${80^{\circ}}^{+1}_{-2}$. We also report updated constraints on the reflex motion for PSR J2145$-$0750 using a combination of Very Long Baseline Array astrometry and our updated measurement of the time derivative of the projected semi-major axis of the pulsar orbit as a prior.

To understand the physical mechanisms underlying the prompt emission of gamma-ray bursts (GRB), single FRED (Fast-Rise-Exponential-Decay) profile GRBs serve as an ideal sample, as they origin from single epoch central engine activity. These GRBs have been found to exhibit a peculiar morphology-including the elegant cross-energy-similarity across energy bands and the recently discovered composite nature-challenging nearly all existing radiation mechanisms, sparking widespread curiosity about their origins. Here we propose a physical model which includes radiation locations sequentially triggered by propagating magnetic perturbations. It naturally explains all observed properties of these GRBs, including the self-similar FRED profile, multi-band aligned subpulses, hard-to-soft spectral evolution, local intensity tracking, and increasing subpulse durations. Furthermore, our results demonstrate that the duration of these GRBs is not reflecting the activity timescale of the central engine, reconciling recent challenges to the traditional merger-short/collapsar-long dichotomy of GRBs.

When a supernova remnant (SNR) interacts with the dense material of an interstellar cloud, its shock wave decelerates rapidly, and the post-shock temperature drops to levels that permit efficient cooling of the shocked plasma. At this stage, the shock enters the post-adiabatic phase of its evolution. During this phase, the internal structure of the SNR undergoes significant changes, particularly in the immediate post-shock region, at spatial scales relevant to cosmic ray acceleration. Once the shock enters the post-adiabatic regime, the efficiency of diffusive shock acceleration increases due to a higher plasma compression, to a change in the direction of the advection velocity, and to an increased rate of momentum gain. As a result, the momentum spectrum of relativistic particles hardens, deviating from a pure power law at high energies. Particles could reach higher maximum values compared to classical predictions. We highlight the dynamics of post-adiabatic flows in SNRs, study their impact on particle acceleration, and present supporting observational evidence in the radio band.

Upcoming measurements of the kinetic Sunyaev-Zel'dovich (kSZ) effect, which results from Cosmic Microwave Background (CMB) photons scattering off moving electrons, offer a powerful probe of the Epoch of Reionization (EoR). The kSZ signal contains key information about the timing, duration, and spatial structure of the EoR. A precise measurement of the CMB optical depth $\tau$, a key parameter that characterizes the universe's integrated electron density, would significantly constrain models of early structure formation. However, the weak kSZ signal is difficult to extract from CMB observations due to significant contamination from astrophysical foregrounds. We present a machine learning approach to extract $\tau$ from simulated kSZ maps. We train advanced machine learning models, including swin transformers, on high-resolution seminumeric simulations of the kSZ signal. To robustly quantify prediction uncertainties of $\tau$, we employ the Laplace Approximation (LA). This approach provides an efficient and principled Gaussian approximation to the posterior distribution over the model's weights, allowing for reliable error estimation. We investigate and compare two distinct application modes: a post-hoc LA applied to a pre-trained model, and an online LA where model weights and hyperparameters are optimized jointly by maximizing the marginal likelihood. This approach provides a framework for robustly constraining $\tau$ and its associated uncertainty, which can enhance the analysis of upcoming CMB surveys like the Simons Observatory and CMB-S4.

Inertial modes have been recently detected in the Sun via helioseismology, yet their origin, evolution, and role in the dynamics of the solar plasma and magnetic field remain poorly understood. In this study, we employ global numerical simulations to investigate the excitation mechanisms and dynamical consequences of inertial modes in the Sun and stellar interiors. We validate first our numerical setup by analyzing the evolution of sectoral and tesseral perturbations imposed on a rigidly rotating sphere. The results confirm that a perturbation of a given mode can excite neighboring modes with both smaller and larger wavenumbers along the dispersion relation of Rossby waves. Subsequently, we use a physically motivated forcing to impose differential rotation with varying shear amplitudes, and examine the spontaneous onset and nonlinear evolution of inertial modes. The simulations reveal that the growth of velocity perturbations is primarily driven by baroclinic instability. It gives rise to high-latitude inertial modes in the form of retrograde polar vortices whose properties depend on the imposed shear. Equatorial Rossby modes are also excited, albeit with lower intensity than their high-latitude counterpart. Perturbations with arbitrary azimuthal wavenumbers lead to the excitation of Rossby modes for all available wave numbers, sustained by both direct and inverse energy cascades. In simulations with stronger shear, the high latitude modes produce Reynolds stresses able to modify the imposed differential rotation and accelerate the rotation of the poles.

We present JWST observations of the radio galaxy TGSSJ1530+1049, spectroscopically confirmed at $z=4.0$. NIRCam images and NIRSpec/IFU spectroscopy (R=2700) show that TGSSJ1530+1049 is part of one of the densest-known structures of continuum and line-emitting objects found at these redshifts. NIRCam images show a number of distinct continuum objects and evidence of interactions traced by diffuse emission, and the NIRSpec IFU cube reveals further strong line emitting regions. We identify six continuum and four additional strong H$\alpha$ emitting sources with weaker or no underlying continuum within the 3x3 arcsec IFU field. From spatial alignment with high-resolution radio data and emission line profiles, the radio AGN host galaxy is clearly identified. The bright H$\alpha$ emission (but not the optical components) is distributed remarkably linearly along the radio axis, suggestive of a biconical illumination zone by a central obscured AGN. The emission line kinematics indicate jet-gas interactions on scales of a few kpc. However, due to large relative velocities and presence of underlying continuum, the alignment with the radio structure appears to be, at least partly, caused by a particular configuration of interacting galaxies. At least four objects within a 10x10 (projected) kpc$^2$ area which includes the radio source have high stellar masses ($\log(M_\star/M_\odot)>10.3$) and star formation rates in the range $70-163\,M_\odot$ yr$^{-1}$. Using a stellar mass-based analysis, we predict a total dark matter halo mass of $\approx10^{13} M_\odot$. Based on the physical separations and velocity differences between the galaxies, it is expected that these galaxies will merge to form a massive galaxy within a few Gyr. The system qualitatively resembles the forming brightest cluster galaxies in cosmological simulations that form early through a rapid succession of mergers.

We discuss the properties of a sample of z>6 bright (bolometric luminosity L$_{\rm bolo}$>10$^{46.25}$ erg/s) Quasars drawn from a realisation of the GAlaxy Evolution and Assembly (GAEA) model coupled with the Planck Millennium Simulation. We focus on the properties and environment of host galaxies on a physical scale of 10 cMpc, and their evolution down to z=0, with the aim of assessing how well the bright high redshift QSOs population traces the progenitors of the most massive haloes in the local Universe. GAEA predicts that z>6 bright QSOs live in a variety of environments, and that secular processes like disc instability are responsible for triggering roughly the same number of QSOs as galaxy mergers. We consider mock fields built around these high-z QSOs, and we show that roughly half of them include other active galaxies (with L$_{\rm bolo}$>10$^{44}$ erg/s). The predicted large field-to-field variance in the number of companions is qualitatively consistent with recent results from JWST observations. Descendants of host galaxies at z=0 cover a wide range of physical properties and environments with only a small fraction of them belonging to massive galaxy clusters (M$_{\rm DM}$>10$^{14.5}$ M$_\odot$). Viceversa, GAEA predicts that only a small fraction of Bright Central Galaxies have a bright z>6 QSOs among their progenitors. Our results suggest that luminous high-z QSO loosely trace the progenitors of low-z galaxy clusters, but that additional information about their environment (like the number of active galaxy companions) are required to identify the most promising proto-cluster candidates.

It is usually taken for granted that mutual synchronisation of a tidal two-body system is attained through tidal recession, assuming the reduced Hill sphere is not reached. However, synchronisation can be achieved also via tidal approach, provided the Roche limit is not crossed. For each of the two scenarios, we derive the condition under which the evolving synchronicity radius catches up with the tidally evolving orbit. We consider the two scenarios for the Pluto-Charon system and examine the impact-origin hypothesis of Charon's formation against capture. Based on geophysical evidence, we propose that capture appears more likely. Motivated by this conclusion, we investigate the capture scenario, wherein the orbital evolution of Charon starts at a higher altitude than present and undergoes tidal descent, both analytically and numerically. We also consider the possibility that Pluto's initial prograde spin underwent a reversal by a tidally approaching retrograde Charon. Depending on the initial conditions, we observe temporary locking of Charon into higher spin-orbit resonances (3:2 to 7:2) during the first 0.5 Myr of the system's evolution. Owing to a greater initial separation between the partners, the power dissipated in each of them turns out to be much lower than in the case of tidal recession of bodies of the same internal structure. The greater initial separation also results in lower tidal stress, which may explain the absence of tidally generated fracture patterns.

The earliest phase of the Milky Way's evolution involved a transition from a dispersion-supported proto-galaxy to a rotationally supported disk. A key chemical signature of this transition is the moderate rise in [$\alpha$/Fe] near $\mathrm{[Fe/H]}\approx-1.3$, which we previously interpreted as evidence for $\alpha$-enhanced gas accretion fueling early disk formation. However, this trend alone does not uniquely constrain the trade-off between initial gas mass, inflow rate, and star formation efficiency (SFE), leaving the physical condition of the proto-Milky Way uncertain. To break this degeneracy, we analyze the metal-poor tail ($-3<\mathrm{[Fe/H]}<-2$) of the Milky Way's metallicity distribution function (MDF) using Gaia DR3 BP/RP (XP) metallicities from ten catalogs. After applying recommended quality cuts, all catalogs exhibit a single-slope exponential tail with slopes $k\simeq0.6$--$2.0$. Comparison with one-zone galactic chemical-evolution (GCE) models that replicated the [$\alpha$/Fe]-rise from Paper I shows that shallow tails ($k\simeq0.6$) require a massive initial cold gas reservoir ($\gtrsim10^9\, \mathrm{M_\odot}$), while steeper tails ($k\gtrsim1$) arise from small reservoirs that built up over time with weak inflow. MDFs with $k \simeq 1.0$ are best reproduced under our GCE framework, which favor a proto-Galaxy with a moderate gas reservoir ($10^{8}$--$10^{9}\, \mathrm{M_\odot}$) sustained through weak continuous inflow ($\sim 2 \ \mathrm{M_\odot \ yr^{-1}}$) and SFE comparable to today's value (a few $\times 10^{-10}\,\mathrm{yr^{-1}}$) during the first Gyr. This scenario is reinforced by MDFs of 30 Milky Way analogs in the Auriga simulations, which exhibit similar slopes ($k\approx1.25$). The metal-poor MDF tail thus provides a quantitative constraint on the Milky Way's early gas accretion and star formation history.

$E_G$ is a summary statistic that combines cosmological observables to achieve a test of gravity that is relatively model-independent. Here, we consider the power of a measurement of $E_G$ using galaxy-galaxy lensing and galaxy clustering with sources from the Rubin Observatory's Legacy Survey of Space and Time (LSST), and lenses from the Dark Energy Spectroscopic Instrument (DESI). We first update the theoretical framework for the covariance of $E_G$ to accommodate this Stage IV scenario. We then demonstrate that $E_G$ offers in principle a model-agnostic test of gravity using only linear-scale information, with the caveat that a careful treatment of galaxy bias is required. We finally address the persistent issue of $E_G$'s theoretical dependence on the measured value of $\Omega_{\rm M}^0$. We propose a framework that takes advantage of the posterior predictive test to consistently incorporate uncertainty on $\Omega_{\rm M}^0$ in tests of gravity with $E_G$, which should be of general use beyond the LSST+DESI scenario. Our forecasting study using this method shows that the prior information available for $\Omega_{\rm M}^0$ is instrumental in determining the power of $E_G$ in the LSST+DESI context. For the full survey dataset, with priors on $\Omega_{\rm M}^0$ from existing CMB data, we find that for some modified gravity scenarios considered, we are likely to be able to reject the GR null hypothesis.

The nature of the compact objects within the supposed "lower mass gap" remains uncertain. Observations of GW190814 and GW230529 highlight the challenges gravitational waves face in distinguishing neutron stars from black holes. Interpreting these systems is especially difficult because classifications depend simultaneously on measurement noise, compact binary population models, and equation of state (EOS) constraints on the maximum neutron star mass. We analyze 66 confident events from GWTC-3 to quantify how the probability of a component being a neutron star, P(NS), varies across the population. The effects are substantial, the dominant drivers of classification are the pairing preferences of neutron stars with other compact objects, and the neutron star spin distributions. The data reveals that P(NS) varies between 1% - 67% for GW230529's primary and between 51% - 100% for GW190425's primary. By contrast, P(NS) for GW190814's secondary varies by <10%, demonstrating robustness from its high signal-to-noise ratio and small mass ratio. Analysis using EOS information tends to affect P(NS) through the inferred maximum neutron star mass rather than the maximum spin. As it stands, P(NS) remains sensitive to numerous population parameters, limiting its reliability and potentially leading to ambiguous classifications of future GW events.

We present the characterization of macrolensing properties of the gravitationally lensed system PKS 1830-211, utilizing data from the Fermi Large Area Telescope. While at gamma-rays we can not spatially resolve the lensed images, a macrolensing-induced time pattern is expected in the blazar's lightcurve, resulting from the delay between variable gamma-ray components originating from its two brightest lensed images. Compared to our previous study, here we employ high-quality lightcurves coupled with prolonged outburst activity, and improved time-series techniques. Analyzing six independent data segments, we identified a delay of 20.26 +/- 0.62 days (statistical and stochastic uncertainty), with a chance detection probability at the 2.5 x $10^{-5}$ level (post-trial). We also present a novel approach to the magnification ratio estimate based on a comparison with simulated data. Our work suggests that the gamma-ray flux ratio between the two main lens components is $\mu_{\gamma} \lesssim$ 1.8. We do not observe convincing evidence of microlensing effects, as previously claimed. The measured gamma-ray time delay is in 2-sigma tension with radio-based estimates, suggesting either distinct emission sites, underestimated radio uncertainties, or gamma-ray production in a region opaque to radio. Our study highlights the potential of well sampled lightcurves and advanced time-series techniques to distinguish true lensing-induced delays from stochastic variability. When combined with improved radio constraints and refined lens models, PKS 1830-211 and similar sources constitute promising systems for time-delay cosmography, offering new insights into both jet structure and cosmological parameters.

Time-delay cosmography leverages strongly lensed quasars to measure the Universe's current expansion rate, H_0, independently from other methods. While the latest TDCOSMO results relied mainly on quadruply lensed quasars, doubly lensed systems are far more common and offer precise time delays, potentially enlarging the usable sample by a factor of five and enabling percent-level constraints on H_0. We present the first TDCOSMO analysis of a doubly imaged source, HE1104-1805, including the measurement of the four necessary ingredients. First, by combining 17 years of data from the SMARTS, Euler and WFI telescopes, we measure a time delay of 176.3\pm 10.8 days. Second, using MUSE data, we extract stellar velocity dispersion measurements in three radial bins with up to 5% precision. Third, employing F160W HST imaging for lens modelling and marginalising over various modelling choices, we measure the Fermat potential difference between the images. Fourth, using wide-field imaging, we measure the convergence added by objects not included in the lens modelling. Hence, we measure the time delay distance and the angular diameter distance to the deflector, favouring a power-law mass model over a baryonic and dark matter composite model. The measurement was performed blindly and yielded H_0 = 64.2^{+5.8}_{-5.0} x $\lambda_{int} km s^{-1} Mpc^{-1}, where \lambda_{int} is the internal mass sheet degeneracy parameter. This is in agreement with the TDCOSMO-2025 milestone and its precision for \lambda_{int}=1 is comparable to that obtained with the best-observed quadruply lensed quasars (4-6%). This work is a stepping stone towards a precise measurement of H_0 using a large sample of doubly lensed quasars, supplementing the current sample. The next TDCOSMO milestone paper will include this system in its hierarchical analysis, constraining \lambda_{int} and H_0 jointly with multiple lenses.

In this work we derive analytic expressions and numerical recipes for finding the effective observed position of sources close enough on sky that their Point Spread Functions (PSF), modelled as Gaussian profiles, overlap. In particularly we derive these for an elongated PSF, with a long and short axis, such as we would see from an instrument with a rectangular or elliptical mirror (relevant, for example, for the Gaia mission). We show that in this case the problem can be reduced to a one dimensional brightness profile with extrema along the line connecting the two sources, with an effective PSF width that depends on the relative orientation of the PSF and its degree of elongation. The problem can then be expressed in units of this effective width to be a function of the relative separation and light ratio alone (thus reducing to a rescaling of the un-elongated case). We derive the minimum light ratio, for a given separation and effective width, above which two sources will be resolved. We map out numerical procedures for finding the positions of these extrema across all possible cases. Finally we derive the positional offset and deviance associated with observing a fixed pair of blended sources from a variety of orientations, showing that this can be a significant source of excess noise.

We present an all-sky map of the synchrotron spectral index and curvature between 45 and 2300 MHz at a resolution of 1 degree calculated from a combination of numerous partial sky empirical measurements. We employ a least-squares parametric fit which relies on removing a free-free emission template and a component separation technique which fits for both synchrotron and free-free emission. We compare our diffuse sky model estimates against those derived from the models widely used in the community (e.g. pysm3 and GSM) employing external datasets that were not included in the estimation process. Our evaluation focuses on identifying the enhanced consistency at both the map level and in pixel-to-pixel correlations, allowing for a more robust verification of our model's performance. We find our parametric, least-squares synchrotron estimate to be the most reliable across radio frequencies as it consistently provides sky models with average accuracies (when compared to empirical data) of around 20 per cent, whilst other model performances range on average between 10 and 70 per cent accurate. The results obtained have been made publicly accessible online and can be utilized to further develop and refine models of Galactic synchrotron emission.

Interacting Dark Energy (IDE) models offer a promising avenue to explore possible exchanges of energy and momentum between dark matter and dark energy, providing a dynamical extension of the standard $\Lambda$CDM paradigm. Such interactions modify the growth of cosmic structures, imprinting distinctive signatures on the matter power spectrum that can be tested through large-scale structure (LSS) observations. In this work, we compute the one-loop corrections to the matter power spectrum in IDE models. We then reinterpret these results within the standard framework of the Effective Field Theory of Large-Scale Structure (EFTofLSS), which provides a consistent description of mildly non-linear scales and allows for reliable comparisons with observational data. We investigate two commonly studied forms of the coupling function, $Q$, namely $Q = \xi \mathcal{H} \rho_{\rm m}$ and $Q = \xi \mathcal{H} \rho_{\rm DE}$, and introduce a novel interaction term, $Q = \Gamma \, \rho_{\rm m} \, \rho_{\rm DE} \, \theta_{\rm m}$, characterized by the non-linear coupling constant $\Gamma$, which links the interaction strength to the velocity divergence of dark matter. This coupling function is proposed to isolate the effects solely of the IDE model on mildly non-linear scales. Using Full-Shape (FS) measurements of the galaxy power spectrum from BOSS DR12, we constrain the interaction rate $\Gamma$, the cosmological parameters, and the bias parameters. We find $\Gamma = 0.0039 \pm 0.0082$, which is highly consistent with the $\Lambda$CDM model. This work opens the possibility of testing IDE models at mildly non-linear scales, potentially providing new insights for this class of models beyond the standard $\Lambda$CDM framework.

In this paper, we present a comprehensive catalog of short bursts from magnetars based on eight years of NICER observations. A total of 1130 bursts were identified from 14 sources, with the sample dominated by SGR 1935+2154, which accounts for 76% of all detected bursts. We analyzed burst durations, spectral properties, and their correlations across multiple sources. Bursts from SGR 1935+2154 exhibit significantly longer durations, with a distribution peak at 316 ms, compared to a peak of 23 ms for bursts from other magnetars. Two {\mu}s-scale bursts were detected for the first time, originating from 1E 1048.1-5937 and CXOU J010043.1-721134. Spectral analysis in the 0.5-8 keV range using both blackbody and power-law models shows that bursts with higher fluences have harder spectra. In contrast, correlations between burst duration and spectral parameters are weak or absent. This catalog provides a valuable dataset for studying magnetar short bursts, enabling future modeling efforts and improving our understanding of the diversity and physical mechanisms of magnetar bursts.

LISA can observe cosmological millihertz (mHz) gravitational wave (GW) backgrounds that may offer a decisive test for asteroid-mass primordial black hole (PBH) dark matter (DM). In standard scenarios, failing to detect a scalar-induced gravitational wave (SIGW) background would exclude the last viable window for PBH DM formed through critical collapse. We show that this conclusion becomes much weaker in the presence of astrophysical foregrounds and strongly non-Gaussian primordial density perturbations, by studying how these phenomena affect the link between SIGWs and PBHs, and reevaluate LISA's sensitivity to asteroid-mass PBHs. In addition, we analyse the interplay between PBHs and SIGWs to gain further insights into the nature of primordial non-Gaussianity. We find that uncertainties in $f_{\rm NL}$ can induce substantial uncertainties in the PBH abundance, which ultimately limits LISA's capacity to fully probe the asteroid-mass PBH DM window.

A substantial fraction of metal-poor stars in the local Milky Way halo exhibit large overabundances of carbon. These stars, dubbed Carbon-Enhanced Metal-Poor (CEMP) stars, provide crucial constraints on the nature of the early universe including the earliest nucleosynthetic events. Whether these stars exist at similar rates in nearby galaxies is a major open question with implications for the environmental dependence of early chemical evolution. Here, we present the discovery of the first five CEMP stars in the Milky Way's largest dwarf companion, the LMC, using SDSS-V spectra from the BOSS instrument. We measure metallicities ranging from [Fe/H] = -2.1 to -3.2 and evolutionary state corrected carbon enhancements of [C/Fe] = +1.2 to +2.4, placing these stars among the most metal-poor and carbon-rich ever identified in the LMC. Their absolute carbon abundances and metallicities classify them as Group I CEMP stars, suggesting binary mass-transfer origins, though neutron-capture abundance measurements are required to confirm whether this classification scheme applies beyond the Milky Way. Although these stars were selected as the most promising CEMP candidates from the SDSS-V sample, likely biasing this initial sample toward higher absolute carbon abundances, their discovery suggests that previous null detections of CEMP stars in the LMC were caused by metallicity-sensitive photometric targeting biases against high [C/H] stars. A forthcoming analysis of the full spectroscopic sample will push to lower carbon abundances, providing a more complete census and enabling critical tests of whether environmental differences shape the formation channels and frequencies of CEMP stars in this system.

Near-infrared (NIR) detectors -- which use non-destructive readouts to measure time-series counts-per-pixel -- play a crucial role in modern astrophysics. Standard NIR flux extraction techniques were developed for space-based observations and assume that source fluxes are constant over an observation. However, ground-based telescopes often see short-timescale atmospheric variations that can dramatically change the number of photons arriving at a pixel. This work presents a new statistical model that shares information between neighboring spectral pixels to characterize time-variable observations and extract unbiased fluxes with optimal uncertainties. We generate realistic synthetic data using a variety of flux and amplitude-of-time-variability conditions to confirm that our model recovers unbiased and optimal estimates of both the true flux and the time-variable signal. We find that the time-variable model should be favored over a constant-flux model when the observed count rates change by more than 3.5%. Ignoring time variability in the data can result in flux-dependent, unknown-sign biases that are as large as ~120% of the flux uncertainty. Using real APOGEE spectra, we find empirical evidence for approximately wavelength-independent, time-dependent variations in count rates with amplitudes much greater than the 3.5% threshold. Our model can robustly measure and remove the time-dependence in real data, improving the quality of data-model comparison. We show several examples where the observed time-dependence quantitatively agrees with independent measurements of observing conditions, such as variable cloud cover and seeing.

We have used Auriga --a set of state-of-the-art cosmological hydrodynamical simulations of Milky Way-size systems-- to study the impact of baryons on the Galactic subhalo population. A DM-only run counterpart of Auriga allows us to compare results with and without baryons. We repopulate the original suites with low-mass subhalos orders of magnitude lighter than the mass resolution limit, starting from a detailed characterization of Auriga data in the well-resolved subhalo mass range. The survival of low-mass subhalos to tidal forces is unclear and under debate nowadays, thus in our study we stay agnostic and consider two different levels of subhalo resilience to tidal stripping ('fragile' and 'resilient' subhalos). We find baryons to alter the Galactic substructure significantly, by decreasing its overall abundance by a factor $\sim2.4$ (fragile) and $\sim1.9$ (resilient) and subhalo concentration --here defined in terms of maximum circular velocity-- by $\sim1.5$ with respect to the DM-only scenario. This has important consequences for indirect searches of DM. As an example, we investigated the case of using unidentified gamma-ray sources to set constraints on the DM particle properties, assuming some of them may be dark satellites. Our results show the importance of including baryons to properly characterize the Galactic subhalo population, as well as to propose the most optimal subhalo search strategies, not only via its potential DM annihilation products but also through their gravitational signatures (e.g.~stellar streams, strong lensing).

Waves launched from the neutron star surface or inner magnetosphere propagate through the magnetosphere as small perturbations, but can grow relative to the background magnetic field and steepen into ``monster shocks'' -- ultra-relativistic magnetized shocks which can power high-energy emission from magnetars, neutron star mergers and collapse. They occur in magnetically dominated plasma and are described by relativistic magnetohydrodynamics (MHD). We present global relativistic MHD simulations of monster shocks in unperturbed and perturbed (``wrinkled'') backgrounds with a global dipolar geometry. Our simulations confirm analytical predictions for equatorial shocks and provide new insight into the behavior of oblique shocks off the equator. Simulations where the shock is formed through Alfvén mode to fast mode conversion are also presented, demonstrating the generic nature of the monster shock mechanism. We explore how the presence of additional modes in the magnetosphere modifies the shock behavior. Modes of comparable amplitude can fragment the shock front, substantially reduce the magnetization, produce localized enhancements in the Lorentz factor relative to an unperturbed dipole background, and intermittently generate additional shocks along a line of sight.

We present a Monte Carlo study of galactic cosmic-ray (GCR) energy deposition and its implications for stratospheric chemistry, performed with the Geant4 toolkit. Primary nuclei (protons, $\alpha$, CNO, and Si) were propagated through an atmosphere modeled from 0 to 120~g~cm$^{-2}$, considering both Polar ($R_{\mathrm{c}}=0.1$~GV) and Equatorial ($R_{\mathrm{c}}=15$~GV) geomagnetic cutoff conditions. The simulations resolve the variation of energy deposition with altitude for primary and secondary particles, revealing that $\sim$~96\% of the stratospheric energy budget arises from cascade secondaries within the 15--35~km domain. By converting layer-resolved energy deposition into ion pair production rates, we quantify the resulting formation of odd nitrogen (NO$_{\rm x}$) and odd hydrogen (HO$_{\rm x}$) radicals, which catalyze the destruction of ozone. The modeled production rates peak between 18 and 22~km altitude, leading to an estimated fractional ozone decrease of order $10^{-3}$--$10^{-2}$ under average GCR fluxes, consistent with observed background modulation over the solar cycle. These results establish a physically consistent link between cosmic-ray induced energy deposition and ozone chemistry, providing a benchmark framework for coupling high-energy particle transport to atmospheric photochemical models.

Terraforming Mars can be evaluated with a small set of system-level feasibility constraints linking (i) target pressures and compositions to required atmospheric inventories, (ii) target surface temperatures to required radiative control authority, (iii) inventories and radiative agents to sustained industrial throughput and power over a build time, and (iv) persistence against collapse, escape, and geochemical sinks. We use transparent order-of-magnitude scalings to map proposed levers (endogenous CO$_2$ release, synthetic super-greenhouse gases, CO$_2$-H$_2$ CIA, engineered aerosols/nanoparticles, orbital mirrors/albedo modification, and regional solid-state greenhouse ``paraterraforming'') onto common metrics $\{M,\ \tau_{\rm IR}/\Delta F_{\rm TOA} \dot M,\ P\}$. We find: (1) human-relevant pressures imply exaton-class inventories, $M_{\rm atm}\simeq 4\pi R_{\rm Mars}^2 P_s/g_{\rm Mars}\sim 10^{17}$-$10^{18}$ kg; (2) accessible CO$_2$ plausibly provides $\lesssim 20$ mbar, yielding $\lesssim 10$ K warming under present insolation; (3) achieving $T_s$ ~ 250-273 K at current insolation requires an effective IR opacity target $\tau_{\rm IR,eff}\sim 2$-4 (uncertain at the ~30-50% level but not altering mass-scale conclusions); (4) breathable endpoints are dominated by O$_2$ and buffer-gas mass and by a minimum oxygenation work $\gtrsim 10^{25}$ J, implying $\dot M\sim 10^{7}$-$10^{8}$ kg s$^{-1}$ and multi-$10^2$ TW to PW-class average power for century-to-millennial build times. We conclude that regional habitability gains via paraterraforming are plausible on near-term industrial scales, whereas global transformation of Mars requires multi-century planetary industry and becomes credible only under conditions of (a) massive exogenous volatile supply or much larger discovered inventories, and (b) sustained high-authority climate control and retention against sinks and loss.

Understanding the connection between galaxy properties and their central massive black holes (MBHs) is key to unveiling their co-evolution. We use the ${\tt L{-}Galaxies{-} \it BH}$ semi-analytical model and the ${\tt Millennium}$ suite of simulations to investigate the physical origin of galaxies hosting overmassive and undermassive MBHs with respect to the $M_{\rm BH}-M_*$ relation, across stellar mass and cosmic time. We find that distinct evolutionary pathways drive different offsets from the scaling relation. Overmassive MBHs are primarily associated with galaxies that experienced enhanced merger history and secular activity. At $z\,{>}\,4$, this activity often leads to early, rapid MBH growth, frequently involving super-Eddington accretion episodes. At low redshift, a minority of overmassive systems ($20\%$) instead arise from environmental effects that reduce the stellar mass of the host, shifting galaxies above the relation without requiring additional MBH growth. Undermassive MBHs originate from two main channels. In massive galaxies, gravitational recoil following MBH mergers can eject the central MBH, temporarily leaving the galaxy without a nucleus. During this phase, MBHs coming from previous galaxy mergers can become the new central MBHs, but their masses remain below the expected ones from the scaling relation, as they never co-evolved with their new host galaxy. In low-mass galaxies ($M_*<10^9 M_\odot$), undermassive MBHs are more commonly linked to a quiescent evolutionary history, with limited mergers and weak secular processes that suppress an efficient MBH growth. We therefore conclude that outliers of the $M_{\rm BH}-M_*$ do not arise from a single mechanism, but from the interplay between environmental effects, gravitational recoils, and diverse MBH fueling histories, whose relative importance varies with galaxy mass and redshift.

We investigate how diversity in the core-halo mass relation affects constraints on the fuzzy dark matter particle mass $m_\psi$ inferred from the internal kinematics of dwarf galaxies, and how these constraints are impacted by the inclusion of higher-order stellar velocity moments. Using stellar line-of-sight velocities and projected positions for eight Milky Way dwarf spheroidal galaxies, we model their dark matter halos as solitonic cores embedded within outer NFW envelopes. We apply both second- and fourth-order Jeans analyses to derive the posterior distribution of $m_\psi$. Our results show that there are two ranges of $m_\psi$ consistent with the observed kinematics: $\log_{10}(m_\psi/\mathrm{eV}) = -19.79^{+0.60}_{-0.53}$, and a narrower small-mass window $\log_{10}(m_\psi/\mathrm{eV}) = -21.82^{+0.35}_{-0.26}$, both within the 68% credible intervals. The latter becomes prominent only when core-halo diversity is taken into account, which highlights the sensitivity of the inferred fuzzy dark matter particle mass constraints to our understanding of the core-halo relation. Future observations, providing larger stellar samples and more precise kinematic measurements, will be essential for clarifying the allowed parameter space of fuzzy dark matter.

A quantitative understanding of cometary outbursts requires robust constraints on the size distribution of ejected particles, which governs outburst dynamics and underpins estimates of released gas and dust. In the absence of direct measurements of particle sizes, assumptions about the size distribution play a central role in modelling dust-trail formation, their dynamical evolution and observability, and the potential production of meteor showers following encounters with Earth. We analyse brightness amplitude variations associated with outbursts of comet 17P/Holmes from 1892 to 2021, with particular emphasis on the exceptional 2007 mega-outburst. During this event the comet underwent a rapid and substantial brightening: at its peak, the expanding coma reached a diameter exceeding that of the Sun and briefly became the largest object in the Solar System visible to the naked eye. We constrain the size distribution and total mass of porous agglomerates composed of ice, organics, and dust ejected during the outburst. The inferred particle size distribution is consistent with a power law of index q, yielding effective particle sizes between 10^-6 m for q = 4 and 5 x 10^-3 m for q = 2. Accounting for effective particle size, sublimation flux, and bulk density, we find that the total number of ejected particles increases with both q and sublimation flux. These results place constraints on the physical properties of outburst ejecta and provide physically motivated initial conditions for long-term dust-trail evolution modelling. They further indicate that cometary outburst brightness is determined primarily by the number of particles and their size distribution, rather than by the total ejected mass alone, with direct implications for the origin and evolution of meteoroid streams and the interplanetary dust population.

Magnetic fields play a crucial role throughout stellar evolution, regulating angular momentum, channelling accretion, and launching jets and outflows. While the magnetic properties of Classical T Tauri Stars (CTTS) are well characterised, those of their progenitors, Class I and Flat-Spectrum (FS) protostars, remain poorly constrained due to observational challenges linked to their embedded nature. We aim to detect and characterise large-scale magnetic fields in a sample of Class I and FS protostars, which are expected to host strong dynamo-generated fields. Using SPIRou, a high-resolution near-infrared spectropolarimeter, we analysed polarised spectra and applied the Least Squares Deconvolution (LSD) technique to extract magnetic signatures and measure longitudinal fields from Stokes V profiles. We report new detections of large-scale magnetic fields in 5 FS protostars. Including the previously known magnetic FS protostar V347 Aur, 40% of our sample (15 objects) is confirmed to be magnetic. These stars exhibit clear Zeeman signatures, with longitudinal field strengths ranging from ~80 to ~200 G. The remaining targets show no detectable Stokes V signature, with upper limits on dipolar fields between 500 G and >5 kG. These results indicate that Class I and FS protostars can host large-scale magnetic fields, possibly weaker than in CTTS, supporting the idea that magnetic processes are already active during the main accretion phase and may influence star-disk interactions from the earliest stages.

The emergence of habitable conditions on the early Earth and on rocky exoplanets requires persistent energy sources that can drive both prebiotic chemistry and climate warming under magnetically active young G to M stars. To quantify the contribution of stellar energetic particle (StEP) events associated with superflares to the atmospheric chemistry of young planets with primitive atmospheres, we carried out a suite of laboratory proton irradiation experiments on mildly reduced gas mixtures. We present first proton irradiation experiments of $N_{\mathrm{2}}$/$CO_{\mathrm{2}}$ rich gas mixtures that yield abundant nitrous oxide ($N_{\mathrm{2}}O$) at mixing ratios up to 1000 ppmv, together with amino acid precursors including glycine, corresponding to global production rates of order $2\times10^{10}$ kg/yr on the early Earth. Our photochemical modeling of StEP driven proton irradiation reproduces the experimentally inferred $N_{\mathrm{2}}O$ production rates and provides self-consistent atmospheric $N_{\mathrm{2}}O$ profiles. We then use these profiles of $N_{\mathrm{2}}O$ as input to a 3D global climate model to evaluate the radiative and climatic impact of StEP generated $N_{\mathrm{2}}O$ in primitive atmospheres representative of the early Earth and young rocky exoplanets. Our results show that frequent StEP events can help alleviate the faint young Sun paradox on the early Earth and can maintain temperate surface conditions on young rocky exoplanets beyond the outer edges of habitable zone, while simultaneously enhancing the buildup of prebiotic molecules. Together, these processes may constitute a robust pathway toward early planetary habitability.

We consider gravitational collapse of a spherically symmetric sphere of a fluid with spin and torsion into a black hole. We use the Tolman metric and the Einstein$-$Cartan field equations with a relativistic spin fluid as a source. We show that gravitational repulsion of torsion prevents a singularity and replaces it with a nonsingular bounce. Quantum particle production during contraction helps torsion to dominate over shear. Particle production during expansion can generate a finite period of inflation and produce enormous amounts of matter. The resulting closed universe on the other side of the event horizon may have several bounces. Such a universe is oscillatory, with each cycle larger in size than the previous cycle, until it reaches the cosmological size and expands indefinitely. Our universe might have therefore originated from a black hole.

The fusion of $\alpha$ and $^8$Be to produce a $^{12}$C nucleus is a crucial process in nucleosynthesis. In the laboratory, this process can only be studied theoretically as a $^8$Be target or projectile cannot be prepared experimentally. We use the potential scattering theory in the coupled-channel formalism to study such a process in terms of the collision between the $\alpha$ particle on a deformed $^8$Be nucleus, both on resonance and off resonance in the Hoyle resonance and associated resonances region. The experimental $^{12}$C energy levels and widths constrain the nuclear potential to suggest the need to include a parity-dependent surface potential component that is more attractive for even-$L$ positive-parity partial waves than for odd-$L$ negative-parity partial waves. As a consequence, the radial dependence of the total potentials for the set of \{0$^+$, 2$^+$, 4$^+$\} resonances of ${}^{12}$C exhibit a double-hump behavior, possessing two local energy minima and a doublet of each of the ${}^{12}$C \{0$^+$, 2$^+$, 4$^+$\} resonances in the Hoyle and associated resonances region. We examine the approximate agreement of the theoretical results with experiment and suggest the search for the as-yet unobserved lower-energy 2${}^+_2$ and 4${}_1^+$ resonances to test the double-hump potential description. In addition, for practical astrophysical applications, we evaluate and estimate the astrophysical $S(E_{\rm c.m.})$-factor for the $\alpha$+$^8$Be $\to$ $^{12}$C$(0^{+*})$ $\to$ $^{12}$C$(2_1^+)$ + $\gamma$ reaction for $E_{\rm c.m.}$ $<$ 1.0 MeV.

We explore the $511$~keV emission associated to sub-GeV dark matter (DM) particles that can produce electron-positron pairs and form positronium after thermalizing. We use $\sim16$~yr of SPI data from INTEGRAL to constrain DM properties, considering the full positron propagation and losses, and the free electron density drop away from the Galactic plane. We show that the predicted longitude and latitude profiles vary significantly for different DM masses, unlike previous assumptions, and obtain the strongest limits on sub-GeV DM (from the MeV to a few GeV) so far, excluding cross-sections down to $\langle \sigma v \rangle \lesssim10^{-32}$ cm$^3$ s$^{-1}$ for $m_{\chi}\sim1\,\text{MeV}$ and $\langle \sigma v \rangle \lesssim10^{-26}$ cm$^3$ s$^{-1} $ for $m_{\chi}\sim5\,\text{GeV}$ and lifetimes up to $\tau \gtrsim 10^{29}\, \textrm{s} \, (m_{\chi}\sim1\,\text{MeV}) $ and $\tau \gtrsim 10^{27}\,\textrm{s}$ ($m_{\chi}\sim5$~GeV) for the typical Navarro-Frenk-White DM profile. Our derived limits are robust within a factor of a few due to systematic uncertainties.

We propose a direct axion dark matter (DM) search using superconducting transmon qubits as quantum sensors. With an external magnetic field applied, axion DM generates an oscillating electric field which causes the excitation of the qubit; such an excitation can be regarded as a signal of the axion DM. We provide a theoretical consideration of the excitation process of the qubits taking into account the effects of the shielding cavity surrounding the qubits and estimate the signal rate for the axion DM detection. We also discuss the enhancement of the DM signal by using cavity resonance and entangled quantum sensors realized by a quantum circuit. Combining these two effects, we can reach the parameter region suggested by QCD axion models.

We study the evolution of matter composition from nuclear to quark densities in the confining regime, by extending an ideal model of Quarkyonic matter, IdylliQ model, to multi-flavor systems including strangeness. The model provides a dual description of quark and baryon occupation probabilities which are determined by minimizing the energy of the system. Saturation of low-momentum quark states drives the formation of quark matter and constrains baryon distributions, inducing statistical repulsion among baryon species. Applying the model to charge-neutral matter composed of neutrons, $\Lambda_0$, and $\Sigma_0$ hyperons, we find that, for typical size of baryons, $d$-quark saturation occurs before hyperons appear, delaying their onset and shifting the threshold density from $\sim 2$--$3n_{\rm sat}$ to $\sim 5$--$6n_{\rm sat}$ ($n_{\rm sat} \approx 0.16\,{\rm fm^{-3}}$: nuclear saturation density). After hyperons emerge, low-momentum hyperon states remain only sparsely occupied due to the quark saturation. These features mitigate the hyperon puzzle, in which the appearance of hyperons softens neutron star equations of state significantly by increasing energy density with little pressure increase. Our results highlight the key role of quark saturation in dense baryonic matter and provide new insights into the interplay between quark dynamics and hyperon physics in neutron stars.

Super-resolution imaging has revolutionized the study of systems ranging from molecular structures to distant galaxies. However, existing super-resolution methods require extensive calibration and retraining for each imaging setup, limiting their practical deployment. We introduce a device-agnostic deep-learning framework for super-resolution imaging of point-like emitters that eliminates the need for calibration data or explicit knowledge of optical system parameters. Our device-agnostic modeling utilizes diverse, numerically simulated dataset encompassing a broad range of imaging conditions, enabling generalization across different optical setups. Once trained, the model reconstructs super-resolved images directly from a single resolution-limited camera frame with superior accuracy and computational efficiency compared to state-of-the-art methods. We experimentally validate our approach using a custom microscopy setup with controllable ground-truth emitter positions. We also demonstrate its versatility on astronomy and single-molecule localization microscopy datasets, achieving unprecedented resolution without prior information. Our findings establish a pathway toward universal, calibration-free super-resolution imaging, expanding its applicability across scientific disciplines.

We investigate the production of primordial black holes and gravitational waves in composite hybrid inflation. Starting from an effective chiral Lagrangian with a dilaton and pions, we identify inflation occurring due to the walking dynamics of the theory. A $\mathbb{Z}_2$ symmetry-breaking term in the pion sector induces a shift in the inflaton's trajectory, which leads to a tachyonic instability phase. Curvature perturbations grow exponentially, producing copious primordial black holes and a stochastic gravitational wave background. We show that the primordial black hole mass and the gravitational wave frequency are strongly restricted by the anomalous dimensions of the pion operators, with larger anomalous dimensions giving lighter primordial black holes and higher frequency gravitational waves. In both cases, the associated signatures lie within reach of future gravitational wave observatories.

We show that the ionization of dense molecular clouds can be used to set strong constraints on dark matter models producing UV/X-ray photons in their annihilation or decay. We place robust and competitive constraints on various dark matter models, such as axion-like particles, scalars and sterile neutrinos, for masses between $\sim30$~eV and $10$~keV, and project forecasts to illustrate the potential of this target. We discuss how these constraints can be significantly improved by considering a more refined sample of molecular clouds near the Galactic Center and above the Galactic plane, a detailed modeling of the cosmic-ray ionization contribution and, potentially, a more refined analysis of the gas density in clouds through dust extinction maps. Thus, ionization of molecular clouds emerges as one of the most powerful tools for probing sub-keV dark matter.

Interferometric observations of the low-frequency radio sky (< 1 GHz) are largely limited by systematic effects introduced by the ionosphere. Here, we analyse a ten-hour nighttime uGMRT Band-4 observation of 3C48 to characterise ionospheric phase fluctuations across baselines up to 25 km. We compute spatial phase structure functions across three sub-bands (575-725~MHz), revealing power-law behaviour consistent with turbulence and a diffractive scale r_diff ~ 6.7 - 8.3 km useful for assessing calibration requirements. The turbulence exhibits anisotropy with smallest scales perpendicular to Earth's magnetic field - consistent with wave-like structures such as MSTIDs rather than field-aligned irregularities. These findings from a single case study demonstrate uGMRT's sensitivity for ionospheric characterisation at low-latitudes (~ 19 deg N) and inform direction-dependent calibration strategies for similar conditions.

We study first order phase transitions that occur when the temperature of the system increases and we identify the conditions that lead to super-heating, a phase where the system can heat up arbitrarily. First order phase transitions with super-heating behave as inverse transitions. We quantify these claims by studying a prototypical example of a dark sector with a large number of interacting light bosons at finite temperature. Depending upon thermalisation, a super-heated phase transition in cosmology is often associated with another transition when the system is eventually cooling down, enriching the spectrum of gravitational waves from bubble collisions.

We investigate the thermal evolution of quark stars with and without a hadronic crust using an equation of state derived from perturbative QCD that incorporates the running of the strong coupling and the strange quark mass. Our analysis reveals that bare quark stars cool too rapidly to match the luminosity data, including those of the coldest observed isolated neutron stars, even when the uncertainty from the renormalization scale is taken into account. In contrast, configurations featuring a hadronic crust exhibit slower cooling and improved agreement with observational data. We also observe that the cooling band for bare quark stars narrows significantly after $t \sim 1$ year, whereas the configurations with a crust exhibit a larger uncertainty throughout their time evolution.

We investigate black hole superradiance evolution of the interacting multiple fields. We consider a model of two scalar fields interacting with a cubic coupling, and study the superradiant evolution of the cloud. We demonstrate that superradiance is typically suppressed when the superradiant field couples to another field, even with a very weak coupling strength. This implies that the constraints on dark particles derived from single-field analyses can be revised in the presence of interactions. Moreover, we find that the multi-field superradiant evolution and its corresponding observational signatures can be different across parameter spaces, which makes black hole superradiance an even more powerful probe of the dark sector in particle physics.

Axions and axion-like particles (ALPs) have gained immense attention in searches for beyond Standard Model (BSM) physics. Experiments searching for axions leverage their predicted couplings to Standard Model (SM) particles to look for observable signals. Though weak, these couplings allow axions to be produced abundantly in the interiors of stars such as the Sun. Once created, axions can escape the Sun and while passing through the solar atmosphere, oscillate into photons in the magnetic field producing x-rays. For the first time, we used data from the observation of soft x-rays from the quiet Sun during the 2019-20 solar minimum by the solar x-ray monitor (XSM), onboard India's Chandrayaan-2 lunar exploration mission, to constrain the coupling of axions to photons ($g_{a \gamma \gamma}$). Using the latest models of the solar atmosphere to calculate the magnetic field and plasma frequency, we constrain $g_{a \gamma \gamma} \lesssim (0.50 - 2.26) \times 10^{-10}$ GeV$^{-1}$ at $95\%$ confidence level for axion masses $m_a \lesssim 5 \times 10^{-4}$eV.

We investigate the influence of ideal Fermi gas dark matter on the observable properties of neutron stars (NSs). Our analysis considers dark matter (DM) particle masses ($\mu$) ranging from $0.2$ GeV to $1$ GeV and various DM mass fractions ($f$). By examining the coexistence of DM and baryonic matter (BM), we explore the formation of either a dense DM core or an extended dark halo within NSs. Our findings indicate that the resulting DM distribution depends critically on both $\mu$ and $f$. We systematically explore the parameter space of the fermionic DM model using two representative BM equations of state (EoSs) by applying constraints from NS radius measurements by the Neutron Star Interior Composition Explorer (NICER), observations of $2M_{\odot}$ NSs, and tidal deformability limits from the LIGO/Virgo Collaboration. This comprehensive analysis enables us to exclude specific ranges of $\mu$ and $f$, demonstrating that the amount of accumulated DM must be relatively small to satisfy current astrophysical constraints.

We analyze a generalized framework of smooth F-term hybrid inflation (smFHI) consistent with gauge coupling unification within the Minimal Supersymmetric Standard Model (MSSM). The embedding of the model in two specific Supergravity settings addresses at the same time the $\eta$ problem and the compatibility with the recent ACT or SPT data. The one relies on the choice of a shift-symmetric Kähler potential for the inflaton which revitalizes the SUSY predictions of smFHI, whereas the other employs a Kähler potential associated with an hyperbolic Kähler manifold. An essential role in both our constructions is played by a decoupled superheavy field without superpotential and Kaehler potential inspired by string- and D-brane--based models. Our proposal can be realized for a variety of representations for the Higgs fields involved in smFHI and assures monotonic inflationary potential.

Cosmological phase transitions are a frequent phenomenon in particle physics models beyond the Standard Model, and the corresponding gravitational wave signal offers a key probe of new physics in the early Universe. Depending on the underlying microphysics, the transition can exhibit either direct or inverse hydrodynamics, leading to a different phenomenology. Most studies to date have focused on direct transitions, where the cosmic fluid is pushed or dragged by the expanding vacuum bubbles. In contrast, inverse phase transitions are characterized by fluid profiles where the plasma is sucked in by the expanding bubbles. Using the sound shell model, we derive and compare the gravitational wave spectra from sound waves for direct and inverse phase transitions, providing new insights into the potential observable features and the possibility of discriminating among the various fluid solutions in gravitational wave experiments.

Compact binary systems emitting gravitational waves (GWs) can exhibit orbital eccentricity, along with generic spin orientations, leading to the precession of the orbital angular momentum, individual spins, and the orbital plane. While eccentric binaries with aligned spins are well studied, closed form post Newtonian (PN) expressions that simultaneously include eccentricity and precessing spin effects have remained unavailable. Eccentricity complicates orbital evolution because solving the coupled differential equations typically requires numerical integration, which slows down the generation of waveforms. We exploit the separation of timescales between orbital motion, spin precession, and radiation reaction, applying the precession averaging method of Morras et al. (2025) to remove explicit time dependence from the spin orbit and spin spin dynamics through the second PN order. Using this framework, we derive analytic phasing formulae from the evolution equations for orbital frequency and eccentricity, treating eccentricity as a small parameter. Closed form solutions for the eccentricity evolution and GW phase are obtained up to eighth order in the initial eccentricity. We also generalize the TaylorT2 approximant to include spin precession effects and compute the orbital phase in both time and frequency domains. To improve accuracy for moderate to high initial eccentricities, we perform a resummation of the TaylorT2 phasing. These results offer efficient, closed form phasing expressions that capture the coupled dynamics of eccentricity and precession, enabling more accurate and computationally tractable GW waveform modeling for data analysis.

Black hole binaries with small mass ratios will be important sources for the forthcoming Laser Interferometer Space Antenna (LISA) mission. Models of such binaries also serve as useful tools for understanding the dynamics of compact binary systems and the gravitational waves they emit. Using an eccentric Ori-Thorne procedure developed in previous work, we build worldlines that describe the full inspiral and plunge of a small body on an initially eccentric orbit of a Kerr black hole. We now calculate the gravitational waves associated with these trajectories using a code that solves the Teukolsky equation in the time domain. The final cycles of these waveforms, the ringdown, contain a superposition of Kerr quasinormal modes followed by a power-law tail. In this paper, we study how a binary's eccentricity and orbital anomaly angle affect the excitation of both quasinormal modes and late-time tails. We find that the relative excitation of quasinormal modes varies in an important and interesting way with these parameters. For some anomaly angles, the relative excitations of quasinormal modes are essentially indistinguishable from those excited in quasi-circular coalescences. Consistent with other recent studies, we find that eccentricity tends to amplify the late-time power-law tail, though the amount of this amplification varies significantly with orbital anomaly. We thus find that eccentricity has an important impact on the late-time coalescence waveform, but the interplay of eccentricity and orbit anomaly complicates this impact.

Recent work has highlighted the importance of a fully relativistic treatment of the dephasing of gravitational waves induced by dark-matter overdensities in extreme mass-ratio inspirals (EMRIs). However, a general-relativistic description of the dark matter phase-space distribution is currently available only for the case of a dark matter "spike" arising from adiabatic black hole growth. Here we develop a fully general-relativistic formalism for the more realistic scenario in which a supermassive stellar progenitor collapses to a black hole and produces a shallower dark matter overdensity, or "mound". We follow self-consistently the evolution of the supermassive star, its collapse, and the subsequent growth of the resulting black hole, together with the collisionless dark matter orbits. We find that in the regime where the collapse becomes non-adiabatic, the dark matter distribution function is significantly reshaped, with a clear depletion in the low-binding-energy region of phase space. Our results provide a more realistic prediction for the dark matter phase-space distribution around supermassive black holes, which is an essential step in our programme to use future EMRI observations to extract information about both the nature of dark matter and the formation history of the black hole.

A random number generator for the Kappa velocity distribution in particle simulations is proposed. Approximating the cumulative distribution function with the q-exponential function, an inverse transform procedure is constructed. The proposed method provides practically accurate results, in particular for k<4. It runs fast on graphics processing units (GPUs). The derivation, numerical validation, and relevance to GPU execution models are discussed.

We construct a gravastar configuration within the Shtanov-Sahni (SS) braneworld scenario, characterized by a timelike extra dimension and negative brane tension. Unlike classical black holes, which inevitably culminate in central curvature singularities, our model demonstrates that the SS braneworld dynamics naturally regularize the interior geometry and prevent singularity formation. By solving the modified Einstein field equations induced on the brane, we obtain explicit interior, shell, and exterior solutions without invoking the idealized thin-shell approximation. The gravastar core is modeled as a Bose--Einstein condensate, while the intermediate shell consists of ultra-dense stiff matter. Bulk Weyl corrections induce anisotropic effective pressures on the brane, a feature that emerges intrinsically in this scenario and supports stability. We analyze the active gravitational mass, energy, entropy, and proper thickness of the shell, and establish the junction conditions at the interfaces. Our analysis reveals that the SS gravastar exhibits suppressed or even negative effective mass, reflecting the repulsive nature of the interior condensate, and admits stable equilibrium solutions consistent with energy conditions. This highlights the SS braneworld gravastar as a physically viable compact object and a compelling alternative to black holes. A key novelty of our construction is that the stabilizing pressure anisotropy and suppressed effective gravitational mass arise dynamically from higher-dimensional Weyl corrections, rather than being imposed through ad hoc matter sources or thin-shell idealizations. This provides the first fully analytic realization of a finite-thickness, stable gravastar in the Shtanov-Sahni braneworld, highlighting a genuinely geometric mechanism for singularity avoidance in compact objects.

We present theoretical and experimental evidence for a new phase of matter in neutron-rich systems that we call multimodal superfluidity. Using ab initio lattice calculations, we show that the condensate consists of coexisting s-wave pairs, p-wave pairs in entangled double pair combinations, and quartets composed of bound states of two s-wave pairs. We identify multimodal superfluidity as a general feature of single-flavor spin-1/2 fermionic systems with attractive s-wave and p-wave interactions, provided the system is stable against collapse into a dense droplet. Beyond neutrons at sub-saturation densities, we demonstrate that this phase appears in generalized attractive extended Hubbard models in one, two, and three dimensions. We elucidate the mechanism for this coexistence using self-consistent few-body Cooper models and compare with Bardeen-Cooper-Schrieffer theory. We also derive the form of the effective action and show that spin, rotational, and parity symmetries remain unbroken. Finally, we analyze experimental data to show that p-wave pair gaps and quartet gaps are present in atomic nuclei, and we discuss the consequences of this new phase for the structure and dynamics of neutron star crusts.

Observations of supermassive black holes by the Event Horizon Telescope reveal significant inhomogeneities, most likely related to density and magnetic field perturbations. To model these features, we conduct high-resolution 2D general-relativistic magnetohydrodynamics (GRMHD) simulations of a Fishbone-Moncrief torus around a Kerr black hole using the Black Hole Accretion Code $\texttt{BHAC}$. We compare unperturbed accretion with a case featuring plasma density bubbles with pressure balanced magnetic islands of different amplitudes. Power spectrum analysis of accretion time series, performed via the Blackman-Tukey method, shows that the perturbed case exhibits (1) steeper spectral indices compared to the unperturbed case, deviating from the characteristic $1/\omega$ noise spectrum, and (2) increased correlation times, providing evidence for absorption of macro-structures at the event horizon. Spatial auto-correlation analysis of near-horizon turbulence confirms larger energy-containing coherent structures in the perturbed case altering the accretion rate. These results provide new insights for interpreting observations of supermassive black hole environments, where near-horizon turbulence may play a key role in the accretion process.

Atom interferometer (AI) experiments offer interesting prospects for searches for the interactions of ultralight bosonic dark matter with Standard Model particles as well as detection of gravitational waves in a frequency band inaccessible to experiments that are operating or under construction. Ideal locations for the next generation of such experiments are provided by long vertical shafts, such as that providing access to the Gotthard base railway tunnel from the Sedrun locality in the Canton Grisons of Switzerland. We present the results of an exploratory environmental measurement campaign at this location to evaluate the ground motion activity and the background electromagnetic field quality. We find that the backgrounds due to both ground motion and electromagnetic fields, including those due to passing trains, are low enough for successful operation of a 800-m AI experiment.