We outline theoretical predictions for extended emission from MgII, tracing cool ~10^4 K gas in the circumgalactic medium (CGM) of star-forming galaxies in the high-resolution TNG50 cosmological magnetohydrodynamical simulation. We synthesize surface brightness maps of this strong rest-frame ultraviolet metal emission doublet (2796, 2803), adopting the assumption that the resonant scattering of MgII can be neglected and connecting to recent and upcoming observations with the Keck/KCWI, VLT/MUSE, and BlueMUSE optical integral field unit spectrographs. Studying galaxies with stellar masses 7.5 < log(M*/M_sun) < 11 at redshifts z=0.3, 0.7, 1 and 2 we find that extended MgII halos in emission, similar to their Lyman-alpha counterparts, are ubiquitous across the galaxy population. Median surface brightness profiles exceed 10^-19 erg/s/cm^2/arcsec^2 in the central ~10s of kpc, and total halo MgII luminosity increases with mass for star-forming galaxies, reaching 10^40 erg/s for M* ~ 10^9.5 Msun. MgII halo sizes increase from a few kpc to > 20 kpc at the highest masses, and sizes are larger for halos in denser environments. MgII halos are highly structured, clumpy, and asymmetric, with isophotal axis ratio increasing with galaxy mass. Similarly, the amount and distribution of MgII emission depends on the star formation activity of the central galaxy. Kinematically, inflowing versus outflowing gas dominates the MgII luminosity at high and low galaxy masses, respectively, although the majority of MgII halo emission at z~0.7 traces near-equilibrium fountain flows and gas with non-negligible rotational support, rather than rapidly outflowing galactic winds.

WD 0145+234 is a white dwarf that is accreting metals from a circumstellar disc of planetary material. It has exhibited a substantial and sustained increase in 3-5 micron flux since 2018. Follow-up Spitzer photometry reveals that emission from the disc had begun to decrease by late 2019. Stochastic brightening events superimposed on the decline in brightness suggest the liberation of dust during collisional evolution of the circumstellar solids. A simple model is used to show that the observations are indeed consistent with ongoing collisions. Rare emission lines from circumstellar gas have been detected at this system, supporting the emerging picture of white dwarf debris discs as sites of collisional gas and dust production.

Bimetric gravity is a ghost-free and observationally viable extension of general relativity, exhibiting both a massless and a massive graviton. The observed abundances of light elements can be used to constrain the expansion history of the Universe at the period of Big Bang nucleosynthesis. Applied to bimetric gravity, we readily obtain constraints on the theory parameters which are complementary to other observational probes. For example, the mixing angle between the two gravitons must satisfy $\theta \lesssim 18^\circ$ in the graviton mass range $m_\mathrm{FP} \gtrsim 10^{-16} \, \mathrm{eV}/c^2$, representing a factor of two improvement compared with other cosmological probes.

Binaries play a critical role in the formation, evolution, and fundamental properties of planets, stars, and stellar associations. Observational studies in these areas often include a mix of observations aimed at detecting or ruling out the presence of stellar companions. Rarely can non-detections rule out all possible binary configurations. Here we present MOLUSC, our framework for constraining the range of properties of unseen companions using astrometric, imaging, and velocity information. We showcase the use of MOLUSC on a number of systems, ruling out stellar false positives in the signals of HIP67522b, and DS Tuc Ab. We also demonstrate how MOLUSC could be used to predict the number of missing companions in a stellar sample using the ZEIT sample of young planet hosts. Although our results are not significant, with a larger sample MOLUSC could be used to see if close-in planets are less common in young binary systems, as is seen for their older counterparts.

Orbital eccentricity is one of the most robust discriminators for distinguishing between dynamical and isolated formation scenarios of binary black holes mergers using gravitational-wave observatories such as LIGO and Virgo. Using state-of-the-art cluster models, we show how selection effects impact the detectable distribution of eccentric mergers from clusters. We show that the observation (or lack thereof) of eccentric binary black hole mergers can significantly constrain the fraction of detectable systems that originate from dynamical environments such as dense star clusters. After roughly 150 observations, observing no eccentric binary signals would indicate that clusters cannot make up the majority of the merging binary black hole population in the local Universe (95% credibility). However, if dense star clusters dominate the rate of eccentric mergers and a single system is confirmed to be measurably eccentric in the first and second gravitational-wave transient catalogues, clusters must account for at least 14% of detectable binary black hole mergers. The constraints on the fraction of detectable systems from dense star clusters become significantly tighter as the number of eccentric observations grows, and will be constrained to within 0.5 dex once 10 eccentric binary black holes are observed.

Twenty years ago, the mismatch between the observed number of Milky Way satellite galaxies and the predicted number of cold dark matter subhalos was dubbed the "missing satellites problem". Although mostly framed since in terms of satellite counts in luminosity space, the missing satellites problem was originally posed in velocity space. The stellar velocity dispersion function encodes information about the density profile of satellites as well as their abundance. We compare the completeness-corrected MW satellite velocity function down to its ultrafaint dwarfs (L > 340 L$_\odot$) against well-motivated, semi-empirical predictions based on galaxy-halo scaling relations. For our most conservative completeness correction, we find good agreement with a simple CDM model in which massive, classical satellites (M$_{\rm vir} \gtrsim 10^9~$M$_\odot$) have baryon-driven cores, while low-mass, ultrafaint satellites (M$_{\rm vir} \lesssim 10^9~$M$_\odot$) inhabit cuspy halos that are not strongly tidally stripped. This bifurication is required to explain a non-power-law feature in the velocity function at $\sigma_{\rm los}^* \approx 10$ km/s. Intriguingly, this feature could point to a flattening of the stellar-mass--halo-mass relation. Tidal destruction of satellites by the Milky Way's disk must be minimal, or the corrected velocity function exceeds any plausible prediction -- a "too many satellites" problem. We rule out non-core-collapsing self-interacting dark matter models with a constant cross section $\gtrsim$ 0.3 cm$^2$/g. Constraints on warm dark matter are stronger than those based on the luminosity function on account of the velocity function's additional sensitivity to the central densities of subhalos. Reducing uncertainties on stellar kinematics and the amount of tidal stripping experienced by the faintest dwarfs is key to determining the severity of the too many satellites problem.

We test the adequacy of ultraviolet (UV) spectra for characterizing the outer structure of Type Ia supernova (SN) ejecta. For this purpose, we perform spectroscopic analysis for ASASSN-14lp, a normal SN Ia showing low continuum in the mid-UV regime. To explain the strong UV suppression, two possible origins have been investigated by mapping the chemical profiles over a significant part of their ejecta. We fit the spectral time series with mid-UV coverage obtained before and around maximum light by HST, supplemented with ground-based optical observations for the earliest epochs. The synthetic spectra are calculated with the one dimensional MC radiative-transfer code TARDIS from self-consistent ejecta models. Among several physical parameters, we constrain the abundance profiles of nine chemical elements. We find that a distribution of $^{56}$Ni (and other iron-group elements) that extends toward the highest velocities reproduces the observed UV flux well. The presence of radioactive material in the outer layers of the ejecta, if confirmed, implies strong constraints on the possible explosion scenarios. We investigate the impact of the inferred $^{56}$Ni distribution on the early light curves with the radiative transfer code TURTLS, and confront the results with the observed light curves of ASASSN-14lp. The inferred abundances are not in conflict with the observed photometry. We also test whether the UV suppression can be reproduced if the radiation at the photosphere is significantly lower in the UV regime than the pure Planck function. In this case, solar metallicity might be sufficient enough at the highest velocities to reproduce the UV suppression.

We perform force-free simulations for a neutron star orbiting a black hole, aiming at clarifying the main magnetosphere properties of such binaries towards their innermost stable circular orbits. Several configurations are explored, varying the orbital separation, the individual spins and misalignment angle among the magnetic and orbital axes. We find significant electromagnetic luminosities, $L\sim 10^{42-46} \, [B_{\rm pole}/ 10^{12}{\rm G}]^2 \, {\rm erg/s}$ (depending on the specific setting), primarily powered by the orbital kinetic energy, being about one order of magnitude higher than those expected from unipolar induction. The systems typically develop current sheets that extend to long distances following a spiral arm structure. The intense curvature of the black hole produces extreme bending on a particular set of magnetic field lines as it moves along the orbit, leading to magnetic reconnections in the vicinity of the horizon. For the most symmetric scenario (aligned cases), these reconnection events can release large-scale plasmoids that carry the majority of the Poynting fluxes. On the other hand, for misaligned cases, a larger fraction of the luminosity is instead carried outwards by large-amplitude Alfv{\'e}n waves disturbances. We estimate possible precursor electromagnetic emissions based on our numerical solutions, finding radio signals as the most promising candidates to be detectable within distances of $\lesssim 200$\,Mpc by forthcoming facilities like the Square Kilometer Array.

Atmospheric compositions offer valuable clues to planetary formation and evolution. Jupiter has been the most well-studied giant planet in terms of its atmosphere; however, the origin of the Jovian atmospheric composition remains a puzzle as the abundances of nitrogen and noble gases as high as those of other elements could only originate from extremely cold environments. We propose a novel idea for explaining the Jovian atmospheric composition: Dust pileup at the H$_2$O snow line casts a shadow and cools the Jupiter orbit so that N$_2$ and noble gases can freeze. Planetesimals or a core formed in the shadowed region can enrich nitrogen and noble gases as much as other elements through their dissolution in the envelope. We compute the temperature structure of a shadowed protosolar disk with radiative transfer calculations. Then, we investigate the radial volatile distributions and predict the atmospheric composition of Jupiter with condensation calculations. We find that the vicinity of the current Jupiter orbit, approximately $3$--$7~{\rm AU}$, could be as cold as $30~{\rm K}$ if the small-dust surface density varies by a factor of $\gtrsim30$ across the H$_2$O snow line. According to previous grain growth simulations, this condition could be achieved by weak disk turbulence if silicate grains are more fragile than icy grains. The shadow can cause the condensation of most volatile substances, namely N$_2$ and Ar. We demonstrate that the dissolution of shadowed solids can explain the elemental abundance patterns of the Jovian atmosphere even if proto-Jupiter was formed near Jupiter's current orbit. The disk shadow may play a vital role in controlling atmospheric compositions. The effect of the shadow also impacts the interpretation of upcoming observations of exoplanetary atmospheres by JWST.

The properties of galaxies at redshift $z>6$ hold the key to our understanding of the early stages of galaxy evolution and can potentially identify the sources of the ultraviolet radiation that give rise to the epoch of reionisation. The far-infrared cooling line of [CII] at 158$\mu$m is known to be bright and correlate with the star formation rate (SFR) of low-redshift galaxies, and hence is also suggested to be an important tracer of star formation and interstellar medium properties for very high-redshift galaxies. With the aim to study the interstellar medium properties of gravitationally lensed galaxies at $z>6$, we search for [CII] and thermal dust emission in a sample of 52 $z\sim6$ galaxies observed by the ALMA Lensing Cluster Survey (ALCS). We perform our analysis using \textsc{LineStacker}, stacking both [CII] and continuum emission. The target sample is selected from multiple catalogues, and the sample galaxies have spectroscopic redshift or low-uncertainty photometric redshifts ($\sigma_z < 0.02$) in nine galaxy clusters. Source properties of the target galaxies are either extracted from the literature or computed using spectral energy distribution (SED) fitting. Both weighted-average and median stacking are used, on both the full sample and three sub-samples. Our analyses find no detection of either [CII] or continuum. An upper limit on $L_{\rm [CII]}$ is derived, implying that [CII] remains marginally consistent for low-SFR $z>6$ galaxies but likely is under-luminous compared to the local $L_{\rm [CII]}$-SFR relationship. We discuss potential biases and possible physical effects that may be the cause of the non-detection. Further, the upper limit on the dust continuum implies that less than half of the star formation is obscured.

Due to the chaotic nature of planetary dynamics, there is a non-zero probability that Mercury's orbit will become unstable in the future. Previous efforts have estimated the probability of this happening between 3 and 5 billion years in the future using a large number of direct numerical simulations with an N-body code, but were not able to obtain accurate estimates before 3 billion years in the future because Mercury instability events are too rare. In this paper we use a new rare event sampling technique, Quantile Diffusion Monte Carlo (QDMC), to obtain accurate estimates of the probability of a Mercury instability event between 2 and 3 billion years in the future in the REBOUND N-body code. We show that QDMC provides unbiased probability estimates at a computational cost of up to 100 times less than direct numerical simulation. QDMC is easy to implement and could be applied to many problems in planetary dynamics in which it is necessary to estimate the probability of a rare event.

Globular clusters (GCs) in the Milky Way (MW) bulge are very difficult to study because: i) they suffer from the severe crowding and galactic extinction; which are characteristic of these inner Galactic regions ii) they are more prone to be affected by dynamical processes. Therefore, they are relatively faint and difficult to map. However, deep near-infrared photometry like that provided by the VISTA Variables in the Via L\'actea Extended Survey (VVVX) is allowing us to map GCs in this crucial yet relatively uncharted region. Our results confirm with high confidence that both FSR 19 and FSR 25 are genuine MW bulge GCs. Each of the performed tests and resulting parameters provides clear evidence for the GC nature of these targets. We derive distances of 7.2$\pm$0.7 kpc and D=7.0$\pm$0.6 (corresponding to distance moduli of 14.29$\pm$0.08 and 14.23$\pm$0.07) for FSR 19 and FSR 25, respectively. Their ages and metallicities are 11 Gyr and [Fe/H]= -0.5 dex for both clusters, which were determined from Dartmouth and PARSEC isochrone fitting. The integrated luminosities are M$_{Ks}$(FSR 19) = -7.72 mag and M$_{Ks}$(FSR 25) = -7.31 mag which places them in the faint tail of the GC Luminosity Function. By adopting a King profile for their number distribution, we determine their core and tidal radii ($r_c$, $r_t$). For FSR 19, r$_{c}$= 2.76$\pm$0.36 pc and r$_{t}$=5.31$\pm$0.49 pc, while FSR 25 appears more extended with r$_{c}$= 1.92$\pm$0.59 pc and r$_{t}$=6.85$\pm$1.78 pc. Finally their mean GC PMs (from Gaia EDR3) are $\mu_{\alpha^\ast}$= -2.50 $\pm$0.76 mas $yr^{-1}$, $\mu_{\delta}$= -5.02 $\pm$0.47 mas $yr^{-1}$ and $\mu_{\alpha^\ast}$= -2.61 $\pm$ 1.27 mas $yr^{-1}$ , $\mu_{\delta}$= -5.23 $\pm$0.74 mas $yr^{-1}$ for FSR 19 and FSR 25, respectively. }

End-to-end simulation of the influence of the optical train on the observed scene is important across optics and is particularly important for predicting the science yield of astronomical telescopes. As a consequence of their goal of suppressing starlight, coronagraphic instruments for high-contrast imaging have particularly complex field-dependent point-spread-functions (PSFs). The Roman Coronagraph Instrument (CGI), Hybrid Lyot Coronagraph (HLC) is one example. The purpose of the HLC is to image exoplanets and exozodiacal dust in order to understand dynamics of solar systems. This paper details how images of exoplanets and exozodiacal dust are simulated using some of the most recent PSFs generated for the CGI HLC imaging mode. First, PSFs are generated using physical optics propagation techniques. Then, the angular offset of pixels in image scenes, such as exozodiacal dust models, are used to create a library of interpolated PSFs using interpolation and rotation techniques, such that the interpolated PSFs correspond to angular offsets of the pixels. This means interpolation needs only be done once and an image can then be simulated by multiplying the vector array of the model astrophysical scene by the matrix array of the interpolated PSF data. This substantially reduces the time required to generate image simulations by reducing the process to matrix multiplication, allowing for faster scene analysis. We will detail the steps required to generate coronagraphic scenes, quantify the speed-up of our matrix approach versus other implementations, and provide example code for users who wish to simulate their own scenes using publicly available HLC PSFs.

We have conducted an Arecibo 327 MHz search of two dwarf irregular galaxies in the Local Group, Leo A and T, for radio pulsars and single pulses from fast radio bursts and other giant pulse emitters. We detected no astrophysical signals in this search, and we estimate flux density limits on both periodic and burst emission. Our derived luminosity limits indicate that only the most luminous radio pulsars known in our Galaxy and in the Magellanic Clouds (MCs) would have been detectable in our search if they were at the distances of Leo A and T. Given the much smaller stellar mass content and star formation rates of Leo A and T compared to the Milky Way and the MCs, there are likely to be few (if any) extremely luminous pulsars in these galaxies. It is therefore not surprising that we detected no pulsars in our search.

In the pursuit of directly imaging exoplanets, the high-contrast imaging community has developed a multitude of tools to simulate the performance of coronagraphs on segmented-aperture telescopes. As the scale of the telescope increases and science cases move toward shorter wavelengths, the required physical optics propagation to optimize high-contrast imaging instruments becomes computationally prohibitive. Gaussian Beamlet Decomposition (GBD) is an alternative method of physical optics propagation that decomposes an arbitrary wavefront into paraxial rays. These rays can be propagated expeditiously using ABCD matrices, and converted into their corresponding Gaussian beamlets to accurately model physical optics phenomena without the need of diffraction integrals. The GBD technique has seen recent development and implementation in commercial software (e.g. FRED, CODE V, ASAP) but appears to lack an open-source platform. We present a new GBD tool developed in Python to model physical optics phenomena, with the goal of alleviating the computational burden for modeling complex apertures, many-element systems, and introducing the capacity to model misalignment errors. This study demonstrates the synergy of the geometrical and physical regimes of optics utilized by the GBD technique, and is motivated by the need for advancing open-source physical optics propagators for segmented-aperture telescope coronagraph design and analysis. This work illustrates GBD with Poisson's spot calculations and show significant runtime advantage of GBD over Fresnel propagators for many-element systems.

The Geostationary Lightning Mapper (GLM) instrument onboard the GOES 16 and 17 satellites has been shown to be capable of detecting bolides (bright meteors) in Earth's atmosphere. Due to its large, continuous field of view and immediate public data availability, GLM provides a unique opportunity to detect a large variety of bolides, including those in the 0.1 to 3 m diameter range and complements current ground-based bolide detection systems, which are typically sensitive to smaller events. We present a machine learning-based bolide detection and light curve generation pipeline being developed at NASA Ames Research Center as part of NASA's Asteroid Threat Assessment Project (ATAP). The ultimate goal is to generate a large catalog of calibrated bolide lightcurves to provide an unprecedented data set which will be used to inform meteor entry models on how incoming bodies interact with the Earth's atmosphere and to infer the pre-entry properties of the impacting bodies. The data set will also be useful for other asteroidal studies. This paper reports on the progress of the first part of this ultimate goal, namely, the automated bolide detection pipeline. Development of the training set, ML model training and iterative improvements in detection performance are presented. The pipeline runs in an automated fashion and bolide lightcurves along with other measured properties are promptly published on a NASA hosted publicly accessible website, https://neo-bolide.ndc.nasa.gov.

We describe a numerical scheme for magnetohydrodynamics simulations of dust-gas mixture by extending smoothed particle magnetohydrodynamics. We employ the single-species particle approach to describe dust-gas mixture with several modifications from the previous studies. We assume that the charged and neutral dusts can be treated as single-fluid and the electro-magnetic force acts on the gas and that on the charged dust is negligible. The validity of these assumption in the context of protostar formation is not obvious and is extensively evaluated. By investigating the electromagnetic force and electric current with terminal velocity approximation, it is found that as the dust size increases, the contribution of dust to them becomes smaller and negligible. We conclude that our assumptions of the electro-magnetic force on the dusts is negligible are valid for the dust size with a d & 10{\mu}m. On the other hand, they do not produce the numerical artifact for the dust a d . 10{\mu}m in envelope and disk where the perfect coupling between gas and dusts realizes. However, we also found that our assumptions may break down in outflow (or under environment with very strong magnetic field and low density) for the dust a d . 10{\mu}m. We conclude that our assumptions are valid in almost all cases where macroscopic dust dynamics is important in the context of protostar formation. We conduct numerical tests of dusty wave, dusty magnetohydrodynamics shock, and gravitational collapse of magnetized cloud core with our simulation code. The results show that our numerical scheme well reproduces the dust dynamics in the magnetized medium.

Methyl formate, HCOOCH$_3$, and many of its isotopologues have been detected in astrophysical regions with considerable abundances. However, the recipe for the formation of this molecule and its isotopologues is not yet known. In this work, we attempt to investigate, theoretically, the successful recipe for the formation of interstellar HCOOCH$_3$ and its deuterated isotopologues. We used the gas-grain chemical model, UCLCHEM, to examine the possible routes of formation of methyl formate on grain surfaces and in the gas-phase in low-mass star-forming regions. Our models show that radical-radical association on grains are necessary to explain the observed abundance of DCOOCH$_3$ in the protostar IRAS~16293--2422. H-D substitution reactions on grains significantly enhance the abundances of HCOOCHD$_2$, DCOOCHD$_2$, and HCOOCD$_3$. The observed abundance of HCOOCHD$_2$ in IRAS 16293--2422 can only be reproduced if H-D substitution reactions are taken into account. However, HCOOCH$_2$D remain underestimated in all of our models. The deuteration of methyl formate appears to be more complex than initially thought. Additional studies, both experimentally and theoretically, are needed for a better understanding of the interstellar formation of these species.

Galactic and extra-galactic sources produce X-rays that are often absorbed by molecules and atoms in giant molecular clouds (GMCs), which provides valuable information about their composition and physical state. We mimic this phenomenon with a laboratory Z-pinch X-ray source, which is impinged on neutral molecular gas. The novel technique produces a soft X-ray pseudo continuum using a pulsed-current generator. The absorbing gas is injected from a 1 cm long planar gas-puff without any window or vessel along the line of sight. An X-ray spectrometer with a resolving power of $\lambda/\Delta\lambda\sim$420, comparable to that of astrophysical space instruments, records the absorbed spectra. This resolution clearly resolves the molecular lines from the atomic lines; therefore, motivating the search of molecular signature in astrophysical X-ray spectra. The experimental setup enables different gas compositions and column densities. K-shell spectra of CO$_2$, N$_2$ and O$_2$ reveal a plethora of absorption lines and photo-electric edges measured at molecular column densities between $\sim$10$^{16}$ cm$^{-2}$ -- 10$^{18}$ cm$^{-2}$ typical of GMCs. We find that the population of excited-states, contributing to the edge, increases with gas density.

The Event Horizon Telescope (EHT) collaboration, an Earth-size sub-millimetre radio interferometer, recently captured the first images of the central supermassive black hole in M87. These images were interpreted as gravitationally-lensed synchrotron emission from hot plasma orbiting around the black hole. In the accretion flows around low-luminosity active galactic nuclei such as M87, electrons and ions are not in thermal equilibrium. Therefore, the electron temperature, which is important for the thermal synchrotron radiation at EHT frequencies of 230 GHz, is not independently determined. In this work, we investigate the commonly used parameterised ion-to-electron temperature ratio prescription, the so-called R-$\beta$ model, considering images at 230 GHz by comparing with electron-heating prescriptions obtained from general-relativistic magnetohydrodynamical (GRMHD) simulations of magnetised accretion flows in a Magnetically Arrested Disc (MAD) regime with different recipes for the electron thermodynamics. When comparing images at 230 GHz, we find a very good match between images produced with the R-$\beta$ prescription and those produced with the turbulent- and magnetic reconnection- heating prescriptions. Indeed, this match is on average even better than that obtained when comparing the set of images built with the R-$\beta$ prescription with either a randomly chosen image or with a time-averaged one. From this comparative study of different physical aspects, which include the image, visibilities, broadband spectra, and light curves, we conclude that, within the context of images at 230 GHz relative to MAD accretion flows around supermassive black holes, the commonly-used and simple R-$\beta$ model is able to reproduce well the various and more complex electron-heating prescriptions considered here.

We develop a nonperturbative method through the Hartree factorization to examine the quantum fluctuation effects on the single-field inflationary models in a spatially flat FRW cosmological space-time. Apart from the background field equation as well as the Friedmann equation with the corrections of quantum field fluctuations, the modified Mukhanov-Sasaki equations for the mode functions of the quantum scalar field are also derived by introducing the nonzero $\Delta_B$ term. We consider the Universe undergoing the slow roll (SR)-ultra slow roll (USR) -slow roll (SR) inflation where in particular the presence of the USR inflation triggers the huge growth of $\Delta_B$ that in turn gives the boost effects to the curvature perturbations for the modes that leave horizon in the early times of the inflation. However, the cosmic friction term in the mode equation given by the Hubble parameter presumably prohibits the boost effects. Here we propose two representative models to illustrate these two competing terms.

Double-peaked emission line AGN (DPAGN) have been regarded as binary black hole candidates. We present here results from parsec-scale radio observations with the Very Long Baseline Array (VLBA) of five DPAGN belonging to the KISSR sample of emission-line galaxies. This work concludes our pilot study of nine type 2 Seyfert and LINER DPAGN from the KISSR sample. In the nine sources, dual compact cores are only detected in the "offset AGN", KISSR 102. The overall incidence of jets however, in the eight sources detected with the VLBA, is $\ge$60%. We find a difference in the "missing flux density" going from the Very Large Array (VLA) to VLBA scales between Seyferts and LINERs, with LINERs showing less missing flux density on parsec-scales. Using the emission-line modeling code, MAPPINGS III, we find that the emission lines are likely to be influenced by jets in 5/9 sources. Jet-medium interaction is the likely cause of the emission-line splitting observed in the SDSS spectra of these sources. Jets in radio-quiet AGN are therefore energetically capable of influencing their parsec- and kpc-scale environments, making them agents of "radio AGN feedback", similar to radio-loud AGN.

Solar radio type II bursts serve as early indicators of incoming geo-effective space weather events such as coronal mass ejections (CMEs). In order to investigate the origin of high-frequency type II bursts (HF type II bursts), we have identified 51 of them (among 180 type II bursts from SWPC reports) that are observed by ground-based Compound Astronomical Low-cost Low-frequency Instrument for Spectroscopy and Transportable Observatory (CALLISTO) spectrometers and whose upper-frequency cutoff (of either fundamental or harmonic emission) lies in between 150 MHz-450 MHz during 2010-2019. We found that 60% of HF type II bursts, whose upper-frequency cutoff $\geq$ 300 MHz originate from the western longitudes. Further, our study finds a good correlation $\sim $ 0.73 between the average shock speed derived from the radio dynamic spectra and the corresponding speed from CME data. Also, we found that analyzed HF type II bursts are associated with wide and fast CMEs located near the solar disk. In addition, we have analyzed the spatio-temporal characteristics of two of these high-frequency type II bursts and compared the derived from radio observations with those derived from multi-spacecraft CME observations from SOHO/LASCO and STEREO coronagraphs.

We study the inflationary consequences of Degenerate Higher Order Scalar Tensor (DHOST) theories in a de Sitter background. We perturb the de Sitter background by operators breaking either the degeneracy condition, i.e scordatura DHOST, or the shift symmetry in the scalar field. We first consider derivative scodurata and find that in all cases the power spectra of curvature perturbations are scale-invariant. We then investigate small perturbations by an axion-like potential, and show that in this scenario the power spectrum becomes scale-dependent. The modifications to the spectral index and its first two derivatives are compatible with the latest inflationary constraints. Moreover the tensor to scalar ratio and the non-Gaussianities of these models could be within reach of future experiments.

Context. Far-side helioseismology is a technique used to infer the presence of active regions in the far hemisphere of the Sun based on the interpretation of oscillations measured in the near hemisphere. A neural network has been recently developed to improve the sensitivity of the seismic maps to the presence of far-side active regions. Aims. Our aim is to evaluate the performance of the new neural network approach and to thoroughly compare it with the standard method commonly applied to predict far-side active regions from seismic measurements. Methods. We have computed the predictions of active regions using the neural network and the standard approach from five years of far-side seismic maps as a function of the selected threshold in the signatures of the detections. The results have been compared with direct extreme ultraviolet observations of the far hemisphere acquired with the Solar Terrestrial Relations Observatory (STEREO). Results. We have confirmed the improved sensitivity of the neural network to the presence of far-side active regions. Approximately 96% of the active regions identified by the standard method with a strength above the threshold commonly employed by previous analyses are related to locations with enhanced extreme ultraviolet emission. For this threshold, the false positive ratio is 3.75%. For an equivalent false positive ratio, the neural network produces 47% more true detections. Weaker active regions can be detected by relaxing the threshold in their seismic signature. Conclusions. The neural network is a promising approach to improve the interpretation of the seismic maps provided by local helioseismic techniques.

We report the discovery of an extended very-high-energy (VHE) gamma-ray source around the location of the middle-aged (207.8 kyr) pulsar PSR J0622+3749 with the Large High Altitude Air Shower Observatory (LHAASO). The source is detected with a significance of $8.2\sigma$ for $E>25$~TeV assuming a Gaussian template. The best-fit location is (R.A., Dec.)$=(95^{\circ}\!.47\pm0^{\circ}\!.11,\,37^{\circ}\!.92 \pm0^{\circ}\!.09)$, and the extension is $0^{\circ}\!.40\pm0^{\circ}\!.07$. The energy spectrum can be described by a power-law spectrum with an index of ${-2.92 \pm 0.17_{\rm stat} \pm 0.02_{\rm sys} }$. No clear extended multi-wavelength counterpart of the LHAASO source has been found from the radio to sub-TeV bands. The LHAASO observations are consistent with the scenario that VHE electrons escaped from the pulsar, diffused in the interstellar medium, and scattered the interstellar radiation field. If interpreted as the pulsar halo scenario, the diffusion coefficient, inferred for electrons with median energies of $\sim160$~TeV, is consistent with those obtained from the extended halos around Geminga and Monogem and much smaller than that derived from cosmic ray secondaries. The LHAASO discovery of this source thus likely enriches the class of so-called pulsar halos and confirms that high-energy particles generally diffuse very slowly in the disturbed medium around pulsars.

In a recent paper, we argued that systematic uncertainties related to the choice of Cepheid color-luminosity calibration may have a large influence on the tension between the Hubble constant as inferred from distances to Type Ia supernovae and the cosmic microwave background as measured with the Planck satellite. Here, we investigate the impact of other sources of uncertainty in the supernova distance ladder, including Cepheid temperature and metallicity variations, supernova magnitudes and GAIA parallax distances. Excluding Milky Way Cepheids based on parallax calibration uncertainties, for the color excess calibration we obtain $H_0 = 70.8\pm 2.1$ km/s/Mpc, in $1.6\,\sigma$ tension with the Planck value.

In order to further develop and implement novel drift scan imaging experiments to undertake wide field, high time resolution surveys for millisecond optical transients, an appropriate telescope drive system is required. This paper describes the development of a simple and inexpensive hardware and software system to monitor, characterise, and correct the primary category of telescope drive errors, periodic errors due to imperfections in the drive and gear chain. A model for the periodic errors is generated from direct measurements of the telescope drive shaft rotation, verified by comparison to astronomical measurements of the periodic errors. The predictive model is generated and applied in real-time in the form of corrections to the drive rate. A demonstration of the system shows that that inherent periodic errors of peak-to-peak amplitude ~100'' are reduced to below the seeing limit of ~3''. This demonstration allowed an estimate of the uncertainties on the transient sensitivity timescales of the prototype survey of Tingay & Joubert (2021), with the nominal timescale sensitivity of 21 ms revised to be in the range of 20 - 22 ms, which does not significantly affect the results of the experiment. The correction system will be adopted into the final version of high cadence imaging experiment, which is currently under construction. The correction system is inexpensive (<$A100) and composed of readily available hardware, and is readily adaptable to other applications. Design details and codes are therefore made publicly available.

A coming resurgence of super heavy-lift launch vehicles has precipitated an immense interest in the future of crewed spaceflight and even future colonisation efforts. While it is true that a bright future awaits this sector, driven by commercial ventures and the reignited interest of old space-faring nations, and the joining of new ones, little of this attention has been reserved for the science-centric applications of these launchers. The Arcanum mission is a proposal to use these vehicles to deliver an L-class observatory into a highly eccentric orbit around Neptune, with a wide-ranging suite of science goals and instrumentation tackling Solar System science, planetary science, Kuiper Belt Objects and exoplanet systems.

Titan, Saturn's largest moon, supports a dense atmosphere, numerous bodies of liquid on its surface, and as a richly organic world is a primary focus for understanding the processes that support the development of life. In-situ exploration to follow that of the Huygens probe is intended in the form of the coming NASA Dragonfly mission, acting as a demonstrator for powered flight on the moon and aiming to answer some key questions about the atmosphere, surface, and potential for habitability. While a quadcopter presents one of the most ambitious outer Solar System mission profiles to date, this paper aims to present the case for an aerial vehicle also capable of in-situ liquid sampling and show some of the attempts currently being made to model the behaviour of this spacecraft.

In order to find the possible progenitors of Milky Way globular clusters, we perform orbit integrations to track the orbits of 151 Galactic globular clusters and the eleven classical Milky Way satellite galaxies backward in time for 11 Gyr in a Milky-Way-plus-satellites potential including the effect of dynamical friction on the satellites. To evaluate possible past associations, we devise a globular-cluster--satellite binding criterion based on the satellite's tidal radius and escape velocity and we test it on globular clusters and satellites associated with the Sagittarius dwarf and with the Large Magellanic Cloud. For these, we successfully recover the dynamical associations highlighted by previous studies and we derive their time of accretion by the Galaxy. Assuming that Milky Way globular clusters are and have been free of dark matter and thus consist of stars alone, we demonstrate that none of the globular clusters show any clear association with the eleven classical Milky Way satellites even though a large fraction of them are believed to be accreted. This means that accreted globular clusters either came in as part of now-disrupted satellite galaxies or that globular clusters may have had dark matter halos in the past -- as suggested by the similar metallicity between globular clusters and dwarf galaxies.

The low mass protostar IRAS 16293$-$2422 is a well-known young stellar system that is observed in the L1689N molecular cloud in the constellation of Ophiuchus. In the interstellar medium and solar system bodies, water is a necessary species for the formation of life. We present the spectroscopic detection of the rotational emission line of water (H$_{2}$O) vapour from the low mass protostar IRAS 16293$-$2422 using the Atacama Large Millimeter/submillimeter Array (ALMA) band 5 observation. The emission line of H$_{2}$O is detected at frequency $\nu$ = 183.310 GHz with transition J=3$_{1,3}$$-$2$_{2,2}$. The statistical column density of the emission line of water vapour is $N$(H$_{2}$O) = 4.2$\times$10$^{16}$ cm$^{-2}$ with excitation temperature ($T_{ex}$) = 124$\pm$10 K. The fractional abundance of H$_{2}$O with respect to H$_{2}$ is 1.44$\times$10$^{-7}$ where $N$(H$_{2}$) = 2.9$\times$10$^{23}$ cm$^{-2}$.

Similar to the case of solar system planets, reflected starlight from exoplanets is expected to be polarized due to atmospheric scattering and the net disk integrated polarization should be non-zero owing to the asymmetrical illumination of the planetary disk. The computation of the disk-integrated reflected flux and its state of polarization involves techniques for the calculation of the local reflection matrices as well as the numerical recipes for integration over the planetary disks. In this paper, we present a novel approach to calculate the azimuth-dependent reflected intensity vectors at each location on the planetary disk divided into grids. We achieve this by solving the vector radiative transfer equations that describe linear polarization. Our calculations incorporate self-consistent atmospheric models of exoplanets over a wide range of equilibrium temperature, surface gravity, atmospheric composition, and cloud structure. A comparison of the flux and the amount of polarization calculated by considering both single and multiple scattering exhibits the effect of depolarization due to multiple scattering of light depending on the scattering albedo of the atmosphere. We have benchmarked our basic calculations against some of the existing models. We have also presented our models for the hot Jupiter HD 189733 b, indicating the level of precision required by future observations to detect the polarization of this planet in the optical and near-infrared wavelength region. The generic nature and the accuracy offered by our models make them an effective tool for modeling the future observations of the polarized light reflected from exoplanets.

The GALANTE optical photometric survey is observing the northern Galactic plane and some adjacent regions using seven narrow- and intermediate-filters, covering a total of 1618 square degrees. The survey has been designed with multiple exposure times and at least two different air masses per field to maximize its photometric dynamic range, comparable to that of Gaia, and ensure the accuracy of its photometric calibration. The goal is to reach at least 1% accuracy and precision in the seven bands for all stars brighter than AB magnitude 17 while detecting fainter stars with lower values of the signal-to-noise ratio.The main purposes of GALANTE are the identification and study of extinguished O+B+WR stars, the derivation of their extinction characteristics, and the cataloguing of F and G stars in the solar neighbourhood. Its data will be also used for a variety of other stellar studies and to generate a high-resolution continuum-free map of the H{\alpha} emission in the Galactic plane. We describe the techniques and the pipeline that are being used to process the data, including the basis of an innovative calibration system based on Gaia DR2 and 2MASS photometry.

We report a discovery of a new X-ray-selected supernova remnant (SNR) candidate SGRe~J0023-3633 = G116.6-26.1 found in the data of \textit{SRG}/eROSITA all-sky survey. The source features a large angular extent ($\sim 4$ deg in diameter), nearly circular shape, and soft spectrum of the X-ray emission, dominated by emission lines of helium- and hydrogen-like oxygen, with the estimated absorption column density consistent with the line-of-sight integral in that direction. It lacks bright counterparts of similar extent at other wavelengths which could be unequivocally associated with it. Given the relatively high Galactic latitude of the source, $b\approx-26$ deg, we interpret these observational properties as an indication of the off-disk location of this SNR candidate. Namely, we propose that this object originated from a Type Ia supernova which exploded some 40 000 yr ago in the low density ($\sim 10^{-3}\,{\rm cm^{-3}}$) and hot ($\sim (1-2)\times10^6\,{\rm K}$) gas of the Milky Way halo at a distance of $\sim 3\,{\rm kpc}$ from the Sun. The low density of the halo gas implies that various collisional time scales, in particular, the cooling time and the collisional ionization equilibrium (CEI) time for the gas downstream of the forward shock are much longer than the age of the SNR. This should result in a specific combination of the relatively soft spectrum, reflecting the pre-shock ionization state of the gas, and a strong boost in the plasma emissivity (compared to CEI) due to enhanced collisional excitation through the increased electron temperature. If confirmed, such a rare object would provide us with a unique "in situ" probe of physical conditions (density, temperature, and metallicity) near the interface between the Milky Way's disk and the halo.

Stripped-envelope supernovae (SE-SNe) show a wide variety of photometric and spectroscopic properties. This is due to the different potential formation channels and the stripping mechanism that allows for a large diversity within the progenitors outer envelop compositions. Here, the photometric and spectroscopic observations of SN 2020cpg covering $\sim 130$ days from the explosion date are presented. SN 2020cpg ($z = 0.037$) is a bright SE-SNe with the $B$-band peaking at $M_{B} = -17.75 \pm 0.39$ mag and a maximum pseudo-bolometric luminosity of $L_\mathrm{max} = 6.03 \pm 0.01 \times 10^{42} \mathrm{ergs^{-1}}$. Spectroscopically, SN 2020cpg displays a weak high and low velocity H$\alpha$ feature during the photospheric phase of its evolution, suggesting that it contained a detached hydrogen envelope prior to explosion. From comparisons with spectral models, the mass of hydrogen within the outer envelope was constrained to be $\sim 0.1 \mathrm{M}_{\odot}$. From the pseudo-bolometric light curve of SN 2020cpg a $^{56}$Ni mass of $M_\mathrm{Ni} \sim 0.27 \pm 0.08$ $\mathrm{M}_{\odot}$ was determined using an Arnett-like model. The ejecta mass and kinetic energy of SN 2020cpg were determined using an alternative method that compares the light curve of SN 2020cpg and several modelled SE-SNe, resulting in an ejecta mass of $M_\mathrm{ejc} \sim 5.5 \pm 2.0$ $\mathrm{M}_{\odot}$ and a kinetic energy of $E_\mathrm{K} \sim 9.0 \pm 3.0 \times 10^{51} \mathrm{erg}$. The ejected mass indicates a progenitor mass of $18 - 25 \mathrm{M}_{\odot}$. The use of the comparative light curve method provides an alternative process to the commonly used Arnett-like model to determine the physical properties of SE-SNe.

The X9.3 flare SOL20170906T11:55 was observed by the CsI detector aboard the first Chinese X-ray observatory Hard X-ray Modulation telescope (Insight-HXMT). By using wavelets method, we report about 22 s quasiperiodic pulsations(QPPs) during the impulsive phase. And the spectra from 100 keV to 800 keV showed the evolution with the gamma-ray flux, of a power-law photon index from $\sim 1.8$ before the peak, $\sim 2.0$ around the flare peak, to $\sim 1.8$ again. The gyrosynchrotron microwave spectral analysis reveals a $36.6 \pm 0.6 \arcsec$ radius gyrosynchrotron source with mean transverse magnetic field around 608.2 Gauss, and the penetrated $\ge$ 10 keV non-thermal electron density is about $10^{6.7} \mathrm{cm}^{-3}$ at peak time. The magnetic field strength followed the evolution of high-frequency radio flux. Further gyrosynchrotron source modeling analysis implies that there exists a quite steady gyrosynchrotron source, the non-thermal electron density and transverse magnetic field evolution are similar to higher-frequency light curves. The temporally spectral analysis reveals that those non-thermal electrons are accelerated by repeated magnetic reconnection, likely from a lower corona source.

We report on observations of the Be/X-ray binary system SwiftJ1626.6-5156 performed with NuSTAR during a short outburst in March 2021, following its detection of by the MAXI monitor and Spektrum-Roentgen-Gamma (SRG) observatory. Our analysis of the broadband X-ray spectrum of the source confirms the presence of two absorption-like features at energies ~9 and ~17 keV previously reported in literature and interpreted as the fundamental cyclotron resonance scattering feature (CRSF) and its first harmonic (based on RXTE data). The better sensitivity and energy resolution of NuSTAR, combined with the low energy coverage of NICER, allowed us to detect two additional absorption-like features at ~4.9 keV and ~13 keV. We conclude, therefore, that in total four cyclotron lines are observed in the spectrum of SwiftJ1626.6-5156: the fundamental CRSF at ~4.9 keV and three higher spaced harmonics. This discovery makes SwiftJ1626.6-5156 the second accreting pulsar, after 4U0115+63, whose spectrum is characterized by more than three lines of a cyclotronic origin, and implies the source has the weakest confirmed magnetic field among all X-ray pulsars B~4E11 G. This discovery makes SwiftJ1626.6-5156 one of prime targets for the upcoming X-ray polarimetry missions covering soft X-ray band such as IXPE and eXTP.

A neutron star was first detected as a pulsar in 1967. It is one of the most mysterious compact objects in the universe, with a radius of the order of 10 km and masses that can reach two solar masses. In fact, neutron stars are star remnants, a kind of stellar zombies (they die, but do not disappear). In the last decades, astronomical observations yielded various contraints for the neutron star masses and finally, in 2017, a gravitational wave was detected (GW170817). Its source was identified as the merger of two neutron stars coming from NGC 4993, a galaxy 140 million light years away from us. The very same event was detected in $\gamma$-ray, x-ray, UV, IR, radio frequency and even in the optical region of the electromagnetic spectrum, starting the new era of multi-messenger astronomy. To understand and describe neutron stars, an appropriate equation of state that satisfies bulk nuclear matter properties is necessary. GW170817 detection contributed with extra constraints to determine it. On the other hand, magnetars are the same sort of compact objects, but bearing much stronger magnetic fields that can reach up to 10$^{15}$ G on the surface as compared with the usual 10$^{12}$ G present in ordinary pulsars. While the description of ordinary pulsars is not completely established, describing magnetars poses extra challenges. In this paper, I give an overview on the history of neutron stars and on the development of nuclear models and show how the description of the tiny world of the nuclear physics can help the understanding of the cosmos, especially of the neutron stars.

Turbulence is the dominant source of collisional velocities for grains with a wide range of sizes in protoplanetary disks. So far, only Kolmogorov turbulence has been considered for calculating grain collisional velocities, despite the evidence that turbulence in protoplanetary disks may be non-Kolmogorov. In this work, we present calculations of grain collisional velocities for arbitrary turbulence models characterized by power-law spectra and determined by three dimensionless parameters: the slope of the kinetic energy spectrum, the slope of the auto-correlation time, and the Reynolds number. The implications of our results are illustrated by numerical simulations of the grain size evolution for different turbulence models. We find that for the modeled cases of the Iroshnikov-Kraichnan turbulence and the turbulence induced by the magneto-rotational instabilities, collisional velocities of small grains are much larger than those for the standard Kolmogorov turbulence. This leads to faster grain coagulation in the outer regions of protoplanetary disks, resulting in rapid increase of dust opacity in mm-wavelength and possibly promoting planet formation in very young disks.

The LIGO and Virgo gravitational-wave detectors carried out the first half of their third observing run from April through October 2019. During this period, they detected 39 new signals from the coalescence of black holes or neutron stars, more than quadrupling the total number of detected events. These detections included some unprecedented sources, like a pair of black holes with unequal masses (GW190412), a massive pair of neutron stars (GW190425), a black hole potentially in the supernova pair-instability mass gap (GW190521), and either the lightest black hole or the heaviest neutron star known to date (GW190814). Collectively, the full set of signals provided astrophysically valuable information about the distributions of compact objects and their evolution throughout cosmic history. It also enabled more constraining and diverse tests of general relativity, including new probes of the fundamental nature of black holes. This review summarizes the highlights of these results and their implications.

A model of the Galaxy with the outer ring R1R2 can explain the observed distribution of the radial, VR, and azimuthal, VT, velocity components along the Galactocentric distance, R, derived from the Gaia EDR3 data. We selected stars from the Gaia EDR3 catalogue with reliable parallaxes, proper motions and line-of-sight velocities lying near the Galactic plane, |z|<200 pc, and in the sector of the Galactocentic angles |theta|<15 degrees and calculated the median velocities VR and VT in small bins along the distance R. The distribution of observed velocities appears to have some specific features: the radial velocity VR demonstrates a smooth fall from +5 km s-1 at the distance of R=R0-1.5 kpc to -3 km s-1 at R=R0+1.0 kpc while the azimuthal velocity VT shows a sharp drop by 7 km s-1 in the distance interval R0<R<R0+1.0 kpc, where R0 is the solar Galactocentric distance. We build a model of the Galaxy including bulge, bar, disc and halo components, which reproduces the observed specific features of the velocity distribution in the Galactocentric distance interval |R-R0|< 1.5 kpc. The best agreement corresponds to the time 1.8+/-0.5 Gyr after the start of the simulation. A model of the Galaxy with the bar rotating at the angular velocity of Omega_b=55+/-3 km s-1 kpc-1, which sets the OLR of the bar at the distance of R0-0.5+/-0.4 kpc, provides the best agreement between the model and observed velocities. The position angle of the bar, theta_b, corresponding to the best agreement between the model and observed velocities is theta_b=45+/-15 degrees.

The main FRB event may leave behind a clump of relativistic plasma with high ``free energy'' density. As the plasma undergoes collisionless relaxation, it emits coherent electromagnetic waves. These electromagnetic waves may be observable as a fast radio afterglow, with decreasing frequency and intensity. We demonstrate the fast coherent afterglow in a numerical experiment. We tentatively predict the peak afterglow frequency decreasing with time as $\nu \propto t^{-3/2}$.

While dark energy has dominated cosmic dynamics only since $z\approx0.7$, its energy density was still $\gtrsim5\%$ of the total out to $z\approx2.5$. We calculate model independent constraints on its fraction from future galaxy surveys, finding that the rise of dark energy could be detected at $3\sigma$ nearly out to $z\approx2.5$.

We investigate the Minimal Theory of Massive Gravity (MTMG) in the light of different observational data sets which are in tension within the $\Lambda$CDM cosmology. In particular, we analyze MTMG model, for the first time, with the Planck-CMB data, and how these precise measurements affect the free parameters of the theory. The MTMG model can affect the CMB power spectrum at large angular scales and cause a suppression on the amplitude of the matter power spectrum. We find that on adding Planck-CMB data, the graviton has a small, positive, but non-zero mass at 68\% confidence level, and from this perspective, we show that the tension between redshift space distortions measurements and Planck-CMB data in the parametric space $S_8 - \Omega_m$ can be resolved within the MTMG scenario. Through a robust and accurate analysis, we find that the $H_0$ tension between the CMB and the local distance ladder measurements still remains but can be reduced to $\sim3.5\sigma$ within the MTMG theory. The MTMG is very well consistent with the CMB observations, and undoubtedly, it can serve as a viable candidate amongst other modified gravity theories.

We study the tachyon inflation in the presence of the superpotential as an inflationary potential. We study the primordial perturbations and their non-gaussian feature in the equilateral configuration. We use the Planck2018 TT, TE, EE+lowE+lensing+BK14+BAO joint data at $68\%$ CL and $95\%$ CL, to perform numerical analysis on the scalar perturbations and seek for the observational viability of the tachyon inflation with superpotential. We also check the observational viability of the model by studying the tensor part of the perturbations and comparing the results with Planck2018 TT, TE, EE+lowE+lensing+BK14+BAO+ LIGO$\&$Virgo2016 joint data at $68\%$ CL and $95\%$ CL. By studying the phase space of the model's parameters, we predict the amplitude of the equilateral non-gaussianity in this model. The reheating phase after inflation is another issue that is explored in this paper. We show that, in some ranges of the model's parameters, it is possible to have an observationally viable tachyon model with superpotential.

We report the discovery of a very dense jet-like fast molecular outflow surrounded by a wide-angle wind in a massive young stellar object (MYSO) G18.88MME (stellar mass $\sim$8 M$_{\odot}$) powering an Extended Green Object G18.89$-$0.47. Four cores MM1-4 are identified in the Atacama Large Millimeter/submillimeter Array (ALMA) 1.3 mm continuum map (resolution $\sim$0.$"$8) toward G18.88MME, and are seen at the center of the emission structure (extent $\sim$0.3 pc $\times$ 0.2 pc) detected in the ALMA map. G18.88MME is embedded in the core MM1 (mass $\sim$13-18 M$_{\odot}$), where no radio continuum emission is detected. The molecular outflow centered at MM1 is investigated in the SiO(5-4), HC$_{3}$N(24-23) and $^{13}$CO(2-1) lines. The detection of HC$_{3}$N in the outflow is rare in MYSOs and indicates its very high density. The position-velocity diagrams display a fast narrow outflow (extent $\sim$28000 AU) and a slower wide-angle more extended outflow toward MM1, and both of these components show a transverse velocity gradient indicative of a possible rotation. All these observed features together make G18.88MME as a unique object for studying the unification of the jet-driven and wind-driven scenarios of molecular outflows in MYSOs.

We report here the first detection in the interstellar medium of the cyanomidyl radical (HNCN). Using the Yebes 40m and the IRAM 30m telescopes, we have targeted the doublets of the $N$=2$-$1, 4$-$3, 5$-$4, 6$-$5, and 7$-$6 transitions of HNCN toward the molecular cloud G+0.693-0.027. We have detected three unblended lines of HNCN, these are the $N$=6$-$5 doublet and one line of the $N$=4$-$3 transition. Additionally we present one line of the $N$=5$-$4 transition partially blended with emission from other species. The Local Thermodynamic Equilibrium best fit to the data gives a molecular abundance of (0.91$\pm$0.05)$\times$10$^{-10}$ with respect to H$_2$. The relatively low abundance of this species in G+0.693-0.027, and its high reactivity, suggest that HNCN is possibly produced by gas-phase chemistry. Our work shows that this highly reactive molecule is present in interstellar space, and thus it represents a plausible precursor of larger prebiotic molecules with the NCN backbone such as cyanamide (NH$_2$CN), carbodiimide (HNCNH) and formamidine (NH$_2$CHNH).

In the $Gaia$ era stellar kinematics are extensively used to study Galactic halo stellar populations, to search for halo structures, and to characterize the interface between the halo and hot disc populations. We use distribution function-based models of modern datasets with 6D phase space data to qualitatively describe a variety of kinematic spaces commonly used in the study of the Galactic halo. Furthermore, we quantitatively assess how well each kinematic space can separate radially anisotropic from isotropic halo populations. We find that scaled action space (the ``action diamond'') is superior to other commonly used kinematic spaces at this task. We present a new, easy to implement selection criterion for members of the radially-anisotropic $Gaia$-Enceladus merger remnant, which we find achieves a sample purity of 82 per cent in our models with respect to contamination from the more isotropic halo. We compare this criterion to literature criteria, finding that it produces the highest purity in the resulting samples, at the expense of a modest reduction in completeness. We also show that selection biases that underlie nearly all contemporary spectroscopic datasets can noticeably impact the $E-L_{z}$ distribution of samples in a manner that may be confused for real substructure. We conclude by providing recommendations for how authors should use stellar kinematics in the future to study the Galactic stellar halo.

Quasi-conformal models are an appealing scenario that can offer naturally a strongly supercooled phase transition and a period of thermal inflation in the early Universe. A crucial aspect for the viability of these models is how the Universe escapes from the supercooled state. One possibility is that thermal inflation phase ends by nucleation and percolation of true vacuum bubbles. This route is not, however, always efficient. In such case another escape mechanism, based on the growth of quantum fluctuations of the scalar field that eventually destabilize the false vacuum, becomes relevant. We study both of these cases in detail in a simple yet representative model. We determine the duration of the thermal inflation, the curvature power spectrum generated for the scales that exit horizon during the thermal inflation, and the stochastic gravitational wave background from the phase transition. We show that these gravitational waves provide an observable signal from the thermal inflation in almost the entire parameter space of interest. Furthermore, the shape of the gravitational wave spectrum can be used to ascertain how the Universe escaped from supercooling.

The physical properties of fast radio burst (FRB) host galaxies provide important clues towards the nature of FRB sources. The 16 FRB hosts identified thus far span three orders of magnitude in mass and specific star-formation rate, implicating a ubiquitously occurring progenitor object. FRBs localised with ~arcsecond accuracy also enable effective searches for associated multi-wavelength and multi-timescale counterparts, such as the persistent radio source associated with FRB 20121102A. Here we present a localisation of the repeating source FRB 20201124A, and its association with a host galaxy (SDSS J050803.48+260338.0, z=0.098) and persistent radio source. The galaxy is massive ($\sim3\times10^{10} M_{\odot}$), star-forming (few solar masses per year), and dusty. Very Large Array and Very Long Baseline Array observations of the persistent radio source measure a luminosity of $1.2\times10^{29}$ erg s$^{-1}$ Hz$^{-1}$, and show that is extended on scales $\gtrsim50$ mas. We associate this radio emission with the ongoing star-formation activity in SDSS J050803.48+260338.0. Deeper, more detailed observations are required to better utilise the milliarcsecond-scale localisation of FRB 20201124A reported from the European VLBI Network, and determine the origin of the large dispersion measure ($150-220$ pc cm$^{-3}$) contributed by the host. SDSS J050803.48+260338.0 is an order of magnitude more massive than any galaxy or stellar system previously associated with a repeating FRB source, but is comparable to the hosts of so far non-repeating FRBs, further building the link between the two apparent populations.

An observational program focused on the high redshift ($2<z<6$) Universe has the opportunity to dramatically improve over upcoming LSS and CMB surveys on measurements of both the standard cosmological model and its extensions. Using a Fisher matrix formalism that builds upon recent advances in Lagrangian perturbation theory, we forecast constraints for future spectroscopic and 21-cm surveys on the standard cosmological model, curvature, neutrino mass, relativistic species, primordial features, primordial non-Gaussianity, dynamical dark energy, and gravitational slip. We compare these constraints with those achievable by current or near-future surveys such as DESI and Euclid, all under the same forecasting formalism, and compare our formalism with traditional linear methods. Our Python code FishLSS $-$ used to calculate the Fisher information of the full shape power spectrum, CMB lensing, the cross-correlation of CMB lensing with galaxies, and combinations thereof $-$ is publicly available.

We investigate the impact of spiral structure on global star formation using a sample of 2226 nearby bright disk galaxies. Examining the relationship between spiral arms, star formation rate (SFR), and stellar mass, we find that arm strength correlates well with the variation of SFR as a function of stellar mass. Arms are stronger above the star-forming galaxy main sequence (MS) and weaker below it: arm strength increases with higher $\log\,({\rm SFR}/{\rm SFR}_{\rm MS})$, where ${\rm SFR}_{\rm MS}$ is the SFR along the MS. Likewise, stronger arms are associated with higher specific SFR. We confirm this trend using the optical colors of a larger sample of 4378 disk galaxies, whose position on the blue cloud also depends systematically on spiral arm strength. This link is independent of other galaxy structural parameters. For the subset of galaxies with cold gas measurements, arm strength positively correlates with HI and H$_2$ mass fraction, even after removing the mutual dependence on $\log\,({\rm SFR}/{\rm SFR}_{\rm MS})$, consistent with the notion that spiral arms are maintained by dynamical cooling provided by gas damping. For a given gas fraction, stronger arms lead to higher $\log\,({\rm SFR}/{\rm SFR}_{\rm MS})$, resulting in a trend of increasing arm strength with shorter gas depletion time. We suggest a physical picture in which the dissipation process provided by gas damping maintains spiral structure, which, in turn, boosts the star formation efficiency of the gas reservoir.

We present results of time-series data simulation. We aimed at estimating the threshold used for detecting signals in amplitude spectra, calculated from simulating TESS photometry of up to one year duration. We selected the threshold at a false alarm probability FAP=0.1% and derived S/N ratios between 4.6 and 5.7 depending on the data cadence and coverage. We also provide a formula to estimate the threshold for any FAP adopted and a given number of data points. Our result confirms that, to avoid spurious detection, space-based photometry may require substantially higher S/N than that typically being employed for ground-based data.

Macroscopic dark matter is almost unconstrained over a wide "asteroid-like" mass range, where it could scatter on baryonic matter with geometric cross section. We show that when such an object travels through a star, it produces shock waves which reach the stellar surface, leading to a distinctive transient optical, UV and X-ray emission. This signature can be searched for on a variety of stellar types and locations. In a dense globular cluster, such events occur far more often than flare backgrounds, and an existing UV telescope could probe orders of magnitude in dark matter mass in one week of dedicated observation.

The early universe may have contained internally thermalized dark sectors that were decoupled from the Standard Model. In such scenarios, the relic dark thermal bath, composed of the lightest particle in the dark sector, can give rise to an epoch of early matter domination prior to Big Bang Nucleosynthesis, which has a potentially observable impact on the smallest dark matter structures. This lightest dark particle can easily and generically have number-changing self-interactions that give rise to "cannibal'' behavior. We consider cosmologies where an initially sub-dominant cannibal species comes to temporarily drive the expansion of the universe, and we provide a simple map between the particle properties of the cannibal species and the key features of the enhanced dark matter perturbation growth in such cosmologies. We further demonstrate that cannibal self-interactions can determine the small-scale cutoff in the matter power spectrum even when the cannibal self-interactions freeze out prior to cannibal domination.

We study spherically symmetric spacetimes in Einstein-aether theory in three different coordinate systems, the isotropic, Painlev\`e-Gullstrand, and Schwarzschild coordinates, and present both time-dependent and time-independent exact vacuum solutions. In particular, in the isotropic coordinates we find a class of exact static solutions characterized by a single parameter $c_{14}$ in closed forms, which satisfies all the current observational constraints of the theory, and reduces to the Schwarzschild vacuum black hole solution in the decoupling limit ($c_{14} = 0$). However, as long as $c_{14} \not= 0$, a marginally trapped throat with a finite non-zero radius always exists, and in one side of it the spacetime is asymptotically flat, while in the other side the spacetime becomes singular within a finite proper distance from the throat, although the geometric area is infinitely large at the singularity. Moreover, the singularity is a strong and spacetime curvature singularity, at which both of the Ricci and Kretschmann scalars become infinitely large.

Using sophisticated string theory calculations, Maldacena and Susskind have intriguingly shown that near-extremal black holes are characterized by a {\it finite} mass gap above the corresponding zero-temperature (extremal) black-hole configuration. In the present compact paper we explicitly prove that the minimum energy gap ${\cal E}_{\text{gap}}=\hbar^2/M^3$, which characterizes the mass spectra of near-extremal charged Reissner-Nordstr\"om black holes, can be inferred from a simple semi-classical analysis.

Gravitational waves from compact binary coalescences provide a unique laboratory to test properties of compact objects. As alternatives to the ordinary black holes in general relativity, various exotic compact objects have been proposed. Some of them have largely different values of the tidal deformability and spin-induced quadrupole moment from those of black holes, and their binaries could be distinguished from binary black hole by using gravitational waves emitted during their inspiral regime, excluding the highly model-dependent merger and ring-down regimes. We reanalyze gravitational waves from low-mass merger events in the GWTC-2, detected by the Advanced LIGO and Advanced Virgo. Focusing on the influence of tidal deformability and spin-induced quadrupole moment in the inspiral waveform, we provide model-independent constraints on deviations from the standard binary black hole case. We find that all events that we have analyzed are consistent with the waveform of binary black hole in general relativity. Bayesian model selection shows that the hypothesis that the binary is composed of exotic compact objects is disfavored by all events.

The Maximum Entropy Spectral Analysis (MESA) method, developed by Burg, provides a powerful tool to perform spectral estimation of a time-series. The method relies on a Jaynes' maximum entropy principle and provides the means of inferring the spectrum of a stochastic process in terms of the coefficients of some autoregressive process AR($p$) of order $p$. A closed form recursive solution provides an estimate of the autoregressive coefficients as well as of the order $p$ of the process. We provide a ready-to-use implementation of the algorithm in the form of a python package \texttt{memspectrum}. We characterize our implementation by performing a power spectral density analysis on synthetic data (with known power spectral density) and we compare different criteria for stopping the recursion. Furthermore, we compare the performance of our code with the ubiquitous Welch algorithm, using synthetic data generated from the released spectrum by the LIGO-Virgo collaboration. We find that, when compared to Welch's method, Burg's method provides a power spectral density (PSD) estimation with a systematically lower variance and bias. This is particularly manifest in the case of a little number of data points, making Burg's method most suitable to work in this regime.

With the increasing sensitivities of the gravitational wave detectors and more detectors joining the international network, the chances of detection of a stochastic GW background (SGWB) is progressively increasing. Different astrophysical and cosmological processes are likely to give rise to backgrounds with distinct spectral signatures and distributions on the sky. The observed background will therefore be a superposition of these components. Hence, one of the first questions that will come up after the first detection of a SGWB will likely be about identifying the dominant components and their distributions on the sky. Both these questions were addressed separately in the literature, namely, how to separate components of isotropic backgrounds and how to probe the anisotropy of a single component. Here, we address the question of how to separate distinct anisotropic backgrounds with (sufficiently) different spectral shapes. We first obtain the combined Fisher information matrix from folded data using an efficient analysis pipeline PyStoch, which incorporates covariances between pixels and spectral indices. This is necessary for estimating the detection statistic and setting upper limits. However, based on a recent study, we ignore the pixel-to-pixel noise covariance that does not have a significant effect on the results at the present sensitivity levels of the detectors. We establish the validity of our formalism using injection studies. We show that the joint analysis accurately separates and estimates backgrounds with different spectral shapes and different sky distributions with no major bias. This does come at the cost of increased variance. Thus making the joint upper limits safer, though less strict than the individual analysis. We finally set joint upper limits on the multi-component anisotropic background using aLIGO data taken up to the first half of the third observing run.

The diffraction patterns of lensed gravitational waves encode information about their propagation speeds. If gravitons have mass, the dispersion relation and speed of gravitational waves will be affected in a frequency-dependent manner, which would leave potentially detectable traces in the diffraction pattern if the waves are lensed. In this paper, we study how the alternative dispersion relation induced by massive gravitons affects gravitational waves lensed by point-mass lenses, such as intermediate-mass black holes. By detecting a single lensed gravitational-wave signal, we can measure the graviton mass with an accuracy better than the combined measurement across $\mathcal{O}(10^2)$ unlensed signals. Our method can be generalised to other lens types, gravitational-wave sources, and detector networks, opening up new ways to measure the graviton mass through gravitational-wave detection.