Papers for Wednesday, Mar 05 2025

We present atmospheric retrievals from Keck/KPIC phase II observations of the ultra-hot Jupiter KELT-20/MASCARA-2~b. Previous free retrievals of molecular abundances for ultra-hot Jupiters have been impacted by significant model biases due to variations in vertical abundance profiles, which we address by including molecular dissociation into our retrieval framework as an additional free parameter. We measure the abundance of CO ($\rm \log CO_{MMR} = -2.5^{+0.6}_{-0.5}$) and obtain a lower limit on the abundance of H$_2$O ($\rm \log H{_2}O_{MMR} = -1.5^{+0.8}_{-1.0}$, $>-3.0$ at 95\% confidence) in the atmosphere of \keltb. These abundances yield an atmospheric $\rm C/O = 0.1^{+0.4}_{-0.1}$ ($\rm C/O < 0.9$ at 95\% confidence) and suggest a metallicity approximately solar to $10\times$ solar. H$_2$O is dissociated at pressures below $\log P_{\rm H_2O} = -1.2^{+0.5}_{-0.7}$ bar, roughly consistent with predictions from chemical equilibrium models, and suggesting that the retrieved composition is not a result of assumptions about the vertical mixing profiles. We also constrain the rotational velocity of \keltb\ to $v\sin i = 7.5\pm0.7$ \kms, suggesting the presence of a jet comparable to the sound speed in the direction of the planet's rotation, assuming the actual rotation of the planet is tidally locked.

The Photometric Objects Around Cosmic Webs (PAC) method integrates cosmological photometric and spectroscopic surveys, offering valuable insights into galaxy formation. PAC measures the excess surface density of photometric objects, $\bar{n}_2w_{\rm{p}}$, with specific physical properties around spectroscopic tracers. In this study, we improve the PAC method to make it more rigorous and eliminate the need for redshift bins. We apply the enhanced PAC method to the DESI Y1 BGS Bright spectroscopic sample and the deep DECaLS photometric sample, obtaining $\bar{n}_2w_{\rm{p}}$ measurements across the complete stellar mass range, from $10^{5.3}{\rm M}_{\odot}$ to $10^{11.5}{\rm M}_{\odot}$ for blue galaxies, and from $10^{6.3}{\rm M}_{\odot}$ to $10^{11.9}{\rm M}_{\odot}$ for red galaxies. We combine $\bar{n}_2w_{\rm{p}}$ with $w_{\rm{p}}$ measurements from the BGS sample, which is not necessarily complete in stellar mass. Assuming that galaxy bias is primarily determined by stellar mass and colour, we derive the galaxy stellar mass functions (GSMFs) down to $10^{5.3}{\rm M}_{\odot}$ for blue galaxies and $10^{6.3}{\rm M}_{\odot}$ for red galaxies, while also setting lower limits for smaller masses. The blue and red GSMFs are well described by single and double Schechter functions, respectively, with low-mass end slopes of $\alpha_{\rm{blue}}=-1.54^{+0.02}_{-0.02}$ and $\alpha_{\rm{red}}=-2.50^{+0.08}_{-0.08}$, resulting in the dominance of red galaxies below $10^{7.6}{\rm M}_{\odot}$. Stage-IV cosmological photometric surveys, capable of reaching 2-3 magnitudes deeper than DECaLS, present an opportunity to explore the entire galaxy population in the local universe with PAC. This advancement allows us to address critical questions regarding the nature of dark matter, the physics of reionization, and the formation of dwarf galaxies.

Recent JWST observations hint at unexpectedly intense cosmic star-formation in the early Universe, often attributed to enhanced star-formation efficiencies (SFEs). Here, we analyze the SFE in THESAN-ZOOM, a novel zoom-in radiation-hydrodynamic simulation campaign of high-redshift ($z \gtrsim 3$) galaxies employing a state-of-the-art galaxy formation model resolving the multiphase interstellar medium (ISM). The halo-scale SFE ($\epsilon^{\ast}_{\rm halo}$) - the fraction of baryons accreted by a halo that are converted to stars - follows a double power-law dependence on halo mass, with a mild redshift evolution above $M_{\rm halo} \gtrsim 10^{9.5}\,{\rm M}_{\odot}$. The power-law slope is roughly $1/3$ at large halo masses, consistent with expectations when gas outflows are momentum-driven. At lower masses, the slope is roughly $2/3$ and is more aligned with the energy-driven outflow scenario. $\epsilon^{\ast}_{\rm halo}$ is a factor of $2-3$ larger than commonly assumed in empirical galaxy-formation models at $M_{\rm halo} \lesssim 10^{11}\,{\rm M}_{\odot}$. On galactic (kpc) scales, the Kennicutt-Schmidt (KS) relation of neutral gas is universal in THESAN-ZOOM, following $\Sigma_{\rm SFR} \propto \Sigma_{\rm gas}^2$, indicative of a turbulent energy balance in the ISM maintained by stellar feedback. The rise of $\epsilon^{\ast}_{\rm halo}$ with halo mass can be traced primarily to increasing gas surface densities in massive galaxies, while the underlying KS relation and neutral, star-forming gas fraction remain unchanged. Although the increase in $\epsilon^{\ast}_{\rm halo}$ with redshift is relatively modest, it is sufficient to explain the large observed number density of UV-bright galaxies at $z \gtrsim 12$. However, reproducing the brightest sources at $M_{\rm UV} \lesssim -21$ may require extrapolating the SFE beyond the halo mass range directly covered by THESAN-ZOOM.

Late infall events challenge the traditional view that planet formation occurs without external influence. Here we present deep ALMA $^{12}$CO $J=2-1$ and SO $J_{N}=5_6-4_5$ observations toward AB Aurigae, a Class II disk system with strong signs of gravitational instability and ongoing planet formation. By applying Keplerian and anti-Keplerian masks, we separate disk-like and non-disk-like motions of $^{12}$CO, considering the two outputs as the 'disk' and 'exo-disk' (out of disk) emission components, respectively. The disk component of $^{12}$CO extends to $\sim 1600$ au in radius and exhibits a stunningly rich architecture of global spiral structure. The exo-disk emission consists predominantly of three spiral structures -- S1, S2 and S3 -- whose projections are co-spatial with the disk. We successfully reproduce their trajectories with a ballistic accretion flow model, finding that S1 and S2 (both redshifted) are infalling toward the disk from in front, and S3 (blueshifted) is infalling from behind. Where the terminal ends of S1 and S2 become indistinguishable from the disk, we observe a brightness peak in SO emission $2.5\times$ the azimuthal average of a background SO ring. This merging zone lies within a relatively confined region $15-100$ degrees east of north, and between $\sim150-300$ au from the star, at scales relevant to where planet candidates have been previously identified. The AB Aur system provides a unified picture of late infall inducing replenishment of the disk, triggering gravitational instability, and modifying the conditions of forming planets.

In addition to the hot intracluster medium, massive galaxy clusters host complex, multi-phase gaseous halos. In this work, we quantify the abundance, spatial distribution, and origin of the cool T < 10^4.5 K gas within clusters. To do so, we combine the TNG-Cluster and TNG300 cosmological magnetohydrodynamical simulations, yielding a sample of 632 simulated galaxy clusters at z=0 with masses M_200c ~ 10^14-15.4 solar masses. We find that cool gas is present in every cluster at z=0, although it constitutes only a small fraction of the total gas mass within twice the virial radius, ranging from ~10^-4 to a few per cent. The majority of cool gas resides in the cluster outskirts in infalling satellites and other halos. More rarely, cool gas can also be present in the central regions of clusters. More massive halos contain larger amounts (but not fractions) of cool gas ~10^10-12 solar masses, and we identify correlations between cluster cool gas fraction and several global halo and galaxy properties at fixed halo mass. Using Monte-Carlo Lagrangian tracer particles, we then track the origin of cool gas in present-day clusters. We find that the primary source is recent accretion at z < 0.1, predominantly in the form of pre-cooled gas carried by infalling satellite galaxies and other halos. However, in-situ cooling of the hot intracluster medium gas accreted at earlier epochs also contributes, especially in present-day cool-core clusters.

Most of our knowledge regarding molecular clouds and the early stages of star formation stems from molecular spectral-line observations. However, the various chemical and radiative-transfer effects, in combination with projection effects, can lead to a distorted view of molecular clouds. Our objective is to simultaneously study all of these effects by creating synthetic spectral-line observations based on a chemo-dynamical simulation of a collapsing molecular cloud. We performed a 3D ideal MHD simulation of a supercritical turbulent collapsing molecular cloud where the dynamical evolution was coupled to a nonequilibrium gas-grain chemical network consisting of 115 species, the evolution of which was governed by >1600 chemical reactions. We post-processed this simulation with a multilevel non-LTE radiative-transfer code to produce synthetic PPV data cubes of the CO, HCO+, HCN, and N2H+ (J = 1-0) transitions under various projection angles with respect to the mean component of the magnetic field. We find that the chemical abundances of various species in our simulated cloud tend to be over-predicted in comparison to observationally derived abundances and attribute this discrepancy to the fact that the cloud collapses rapidly and therefore the various species do not have enough time to deplete onto dust grains. This suggests that our initial conditions may not correspond to the initial conditions of real molecular clouds and cores. We show that the projection angle has a notable effect on the moment maps of the species for which we produced synthetic observations. Specifically, the integrated emission and velocity dispersion of CO, HCO+, and HCN are higher when the cloud is observed "face on" compared to "edge on," whereas column density maps exhibit an opposite trend. Finally, we show that only N2H+ is an accurate tracer of the column density of the cloud across all projection angles.

The TNG-Cluster magnetohydrodynamic cosmological simulations, produce a diverse population of X-ray cavities in the intracluster medium (ICM) of simulated galaxy clusters. These arise from episodic, high velocity, kinetic energy injections from the central active supermassive black hole (AGN, SMBH). Here, we present the first comprehensive comparative analysis of X-ray cavities in TNG-Cluster with observational data. First, we select a volume-limited sample of 35 real clusters ($z \leq 0.071$, M$_\text{500c}$ = 10$^{14-14.8}$ M$_\odot$) observed with the Chandra X-ray Observatory, identify 3 analogs for each in TNG-Cluster (total of 105) and generate mock Chandra images using same exposure times as their observed counterparts. We identify X-ray cavities and measure their properties in both datasets using identical techniques, ensuring a direct, apples-to-apples comparison. Our analysis reveals that both samples have a similar fraction of X-ray cavities (35-43 per cent). They exhibit comparable sizes and morphologies, although the sizes of simulated X-ray cavities still attached to the SMBH are somewhat larger in TNG-Cluster -- a scarcity at $< 10$ kpc. The area of TNG X-ray cavities increases as they rise in the ICM, consistent with the trend seen in the observational sample. The cavity powers, estimated using observational techniques, show good agreement between the two samples (10$^{42-45}$ erg.s$^{-1}$), suggesting that X-ray cavities in the simulation are an important heating mechanism in cluster cores. Overall, the rather simple AGN feedback model of TNG, with no model choices made to reproduce X-ray morphological features, and without cosmic rays, creates a quantitatively realistic population of X-ray cavities at cluster scales.

Enceladus exhibits some remarkable phenomena, including water geysers spraying through surface cracks, a global ice shell that is librating atop an ocean, a large luminosity, and rapid outward orbital migration. Here we model the coupled evolution of Enceladus's orbit and interior structure. We find that Enceladus is driven into a periodic state: a limit cycle. Enceladus's observed phenomena emerge from the model, and the predicted values for the orbital eccentricity, libration amplitude, shell thickness, and luminosity agree with observations. A single limit cycle lasts around ten million years, and has three distinct stages: (1) freezing, (2) melting, and (3) resonant libration. Enceladus is currently in the freezing stage, meaning that its ice shell is getting thicker. That pressurizes the ocean, which in turn cracks the shell and pushes water up through the cracks. In this stage the orbital eccentricity increases, as Saturn pushes Enceladus deeper into resonance with Dione. Once the eccentricity is sufficiently high, tidal heating begins to melt the shell, which is the second stage of the cycle. In the third stage the shell remains close to 3km thick. At that thickness the shell's natural libration frequency is resonant with the orbital frequency. The shell's librations are consequently driven to large amplitude, for millions of years. Most of the tidal heating of Enceladus occurs during this stage, and the observed luminosity is a relic from the last episode of resonant libration.

JWST is detecting an excess of high-redshift ($z\gtrsim 10$), bright galaxies challenging most theoretical predictions. To address this issue, we investigate the impact of Primordial Black Holes (PBHs) on the halo mass function and UV luminosity function (LF) of super-early galaxies. We explore two key effects: (i) the enhancement of massive halos abundance due to the compact nature and spatial distribution of PBHs, and (ii) the luminosity boost, characterized by the Eddington ratio $\lambda_E$, due to Active Galactic Nuclei (AGN) powered by matter accretion onto PBHs. We build an effective model, calibrated using data at lower redshifts ($z\approx 4-9$), to derive the evolution of the LF including the additional PBH contribution. Via Bayesian analysis, we find that: (a) Although a small fraction ($\log f_{\rm PBH} \approx -5.42$) of massive ($\log M_{\rm PBH} / {\rm M_{\odot}} \approx 8.37$), non-emitting ($\lambda_E=0$) PBHs can explain the galaxy excess via the halo abundance enhancement, this solution is excluded by CMB $\mu$-distortion constraints on monochromatic PBHs. (b) If PBHs power an AGN emitting at super-Eddington luminosity ($\lambda_E \approx 10$), the observed LF can be reproduced by a PBH population with characteristic mass $\log M_{\rm PBH} / {\rm M_{\odot}} \approx 3.69$ constituting a tiny ($\log f_{\rm PBH} \approx -8.16$) fraction of the cosmic dark matter content. In the AGN scenario, about 75% of the observed galaxies with ${\rm M_{UV}}=-21$ at $z=11$ should host a PBH-powered AGN and typically reside in low mass halos, $M_h = 10^{8-9} {\rm M_{\odot}}$. These predictions can be tested with available and forthcoming JWST spectroscopic data. We note that our analysis considers a lognormal PBH mass function and compares its parameters with monochromatic limits on PBH abundance. Further work is required to relax such limitations.

In this study, we examine the frequency and physical drivers of transformations from cool-core (CC) to non-cool-core (NCC) clusters, and vice versa, in a sample of 352 massive galaxy clusters (M_vir = 10^14-15.3 M_sun) from the TNG-Cluster magnetohydrodynamical cosmological simulation of galaxies. By identifying transformations based on the evolution of central entropy and focusing on z<2.5, we find that clusters frequently undergo such events, depending on their assembly and supermassive black hole histories. On average, clusters experience 2 to 3 transformations. Transformations can occur in both directions and can be temporary, but those to higher entropy cores, i.e. in the direction from CC to NCC states, are the vast majority. CC phases are shorter than NCC phases, and thus overall the TNG-Cluster population forms with low-entropy cores and moves towards NCC states with time. We study the role that mergers play in driving transformations, and find that mergers within ~1Gyr prior to a transformation toward higher (but not lower) entropy cores occur statistically more often than in a random control sample. Most importantly, we find examples of mergers associated with CC disruption regardless of their mass ratio or angular momentum. However, past merger activity is not a good predictor for z=0 CC status, at least based on core entropy, even though clusters undergoing more mergers eventually have the highest core entropy values at z=0. We consider the interplay between AGN feedback and evolving cluster core thermodynamics. We find that core transformations are accompanied by an increase in AGN activity, whereby frequent and repeated (kinetic) energy injections from the central SMBHs can produce a collective, long-term impact on central entropy, ultimately heating cluster cores. Whether such fast-paced periods of AGN activity are triggered by mergers is plausible, but not necessary.

The formation of the most massive quasars observed at high redshifts requires extreme accretion rates ($>1$ M$_\odot$ yr$^{-1}$). Inflows of $10-1000$ M$_\odot$ yr$^{-1}$ are found in hydrodynamical simulations of galaxy mergers, leading to the formation of supermassive discs (SMDs) with high metallicities ($>$ Z$_\odot$). Supermassive stars (SMSs) born in these SMDs could be the progenitors of the most extreme quasars. Here, we study the properties of non-rotating SMSs forming in high metallicity SMDs. Using the stellar evolution code GENEC, we compute numerically the hydrostatic structures of non-rotating SMSs with metallicities $Z=1-10$ Z$_\odot$ by following their evolution under constant accretion at rates $10-1000$ M$_\odot$ yr$^{-1}$. We determine the final mass of the SMSs, set by the general-relativistic (GR) instability, by applying the relativistic equation of adiabatic pulsations to the hydrostatic structures. We find that non-rotating SMSs with metallicities $Z=1-10$ Z$_\odot$ accreting at rates $10-1000$ M$_\odot$ yr$^{-1}$ evolve as red supergiant protostars until their final collapse. All the models reach the GR instability during H-burning. The final mass is $\sim10^6$ M$_\odot$, nearly independently of the metallicity and the accretion rate.

Interstellar magnetic fields are thought to play a fundamental role in the evolution of star-forming regions. Polarized thermal dust emission serves as a key probe for understanding the structure of the POS component of the magnetic field. However, inclination effects can significantly influence the apparent morphology of the magnetic field and lead to erroneous conclusions regarding its dynamical importance. Our aim is to investigate how projection-angle effects impact dust polarization maps and to explore new ways for accessing the inclination angle of the mean component of the magnetic field with respect to the POS. We post-processed a 3D ideal MHD simulation of a turbulent collapsing molecular cloud and produced synthetic dust polarization measurements under various projection angles, ranging from "face-on" (i.e., viewed along the mean magnetic field direction) to "edge-on" (perpendicular to the mean magnetic field direction). Additionally, we used synthetic PPV data cubes from the CO (J = 1-0) transition, presented in a companion paper. The projected magnetic-field morphology is found to be highly affected by the projection angle with the hourglass morphology being clearly visible only for projection angles close to edge-on. We find that the direction of the apparent "flow" between successive velocity channels in the simulated PPV data cubes shows an increasing correlation with the synthetic dust polarization observations, as the cloud is observed closer to an edge-on orientation. Based on this property, we developed a new method to probe the inclination angle of the magnetic field relative to the POS. We validated our approach by generating additional synthetic data (PPV cubes and polarization maps) at an earlier stage of the cloud's evolution and demonstrated an excellent quantitative agreement between the derived inclination angle and the true observational angle.

Saturn raises a time-dependent tide on its small moon Enceladus, due to the eccentricity of the orbit. As shown in a companion paper (Goldreich et al.), the resulting tidal heating drives Enceladus into a limit cycle, in which its eccentricity and shell thickness vary in tandem, on a timescale of ~ 10 Myr. The limit cycle explains a variety of observed phenomena on Enceladus, including its large luminosity and cracked ice shell. Here we derive the tidal heating rate needed for that study, starting from a simple first-principles derivation of Enceladus's tidal response. Enceladus is comprised of three layers: a rocky core, an outer ice shell, and an ocean sandwiched in between. Tides force the shell to librate and distort, which generates heat. We calculate the libration amplitude and tidal heating rate by minimizing the sum of elastic and gravitational energies. The final expressions are analytic, and account for the finite hardness of the shell, and for resonant libration. Although we specialize to Enceladus, our approach may be extended to other bodies that have a similar three layer structure, such as Europa and Titan.

We present a detailed analysis of the nature of migration of protoplanetary clumps formed via disc instability in self-consistent 3D hydrodynamical (HD) and magneto-hydrodynamical (MHD) simulations of self-gravitating discs. Motivated by the complex structure of protoplanetary clumps we do not introduce sink particles. We find that the orbital evolution of the clumps has a stochastic character but also exhibits recurrent properties over many orbits. Clump migration is governed by two sources of gravitational torques: a torque originating from a region about twice the Hill sphere around each clump's orbit, and the torque resulting from clump-clump interactions. Compared to non-magnetized companion runs, the latter are more frequent in MHD simulations, which give rise to more numerous clumps starting off at smaller masses, often below a Neptune mass. Clump-clump interactions can lead to temporary strong accelerations of migration in both directions, but integrated over time provide a lesser impact than disc-driven torques. They can also lead to clump mergers but do not cause ejections; a difference to previous works which adopted sink particles. The local "Hill torque" is responsible for the fast migration, inward or outward. Estimating the characteristic timescales of conventional migration in our regime, we find that the disc-driven migration timescales are in agreement with Type III migration. However, the dominant local torque is rapidly fluctuating, which reflects the turbulent nature of the flow. The resulting stochastic migration pattern is markedly different from Type III runaway migration and appears to be a distinctive feature of orbital dynamics in a fragmenting disc.

Haro 11 is the closest known Lyman continuum leaking galaxy and serves as an important laboratory for studying the escape of Lyman continuum radiation. The galaxy is a metal-poor, starburst galaxy believed to be undergoing a merger that might help facilitate the escape of radiation. In this study, we carry out a large suite of numerical simulations of a merger between two disc galaxies, to study possible origins of Haro 11 and understand under which conditions various features of the galaxy are formed. By varying galaxy parameters describing the orbital configurations, masses, and their inclination, we perform a total of ~500 simulations. We demonstrate that a two-disc galaxy merger is able to reproduce key, observed features of Haro 11, including its morphology, gas kinematics, star formation history, and stellar population ages and masses. We also find that small parameter variations have minimal impact on the orbits and resulting galaxy properties. In particular, we present a fiducial Haro 11 model that produces the single observed tidal tail, the presence of three stellar knots, and inner gas morphology and kinematics. By performing mock observations, we compare with the results of observational data and discuss possible origins for various features. Furthermore, we present newly gathered observational data that confirms the presence of a stellar tidal tail with similar length and direction as our simulations.

The new era of high-resolution X-ray spectroscopy will significantly improve our understanding of the intra-cluster medium (ICM) by providing precise constraints on its underlying physical properties. However, spectral fitting requires reasonable assumptions on the thermal and chemical distributions of the gas. We use the output of TNG-Cluster, the newest addition to the IllustrisTNG suite of cosmological magnetohydrodynamical simulations, to provide theoretical expectations for the multi-phase nature of the ICM across hundreds of z=0 clusters (M$_{500c}$ = 10$^{14.0-15.3}$ M$_\odot$) based upon a realistic model for galaxy formation and evolution. We create and analyse, in an observer-like manner, end-to-end XRISM/Resolve mock observations towards cluster centres. We then systematically compare the intrinsic properties of the simulated gas with the inferred ones from spectral fitting via a variety of commonly used spectral-emission models. Our analysis suggests that models with a distribution of temperatures, such as bvlognorm and bvgadem, better describe the complex thermal structure of the ICM, as predicted by TNG-Cluster, but incur biases of 0.5-2 keV (16th-84th percentiles). The 1T bvapec is too simplistic for the predicted broad temperature distributions, while a 2T double bvapec model systematically fails to capture the input temperature structure. However, all spectral emission models systematically underestimate the Fe abundance of the central ICM by ~0.1 Solar (~ 20 per cent) primarily due to projection effects. Selecting only strong cool core clusters leads to minor improvements on inference quality, removing the majority of outliers but maintaining similar overall biases and cluster-to-cluster scatter.

The majority of core-collapse supernova (CCSN) progenitors are massive stars in multiple systems, and their evolution and final fate are affected by interactions with their companions. These interactions can explain the presence of circumstellar material in many CCSNe, and the inferred low mass in stripped-envelope supernova progenitors. Through binary interactions, stars can gain mass, lose mass, or merge, impacting their final properties. Specific sub-types of binary interaction products have been investigated but few detailed full population models exist. Using {thousands of} detailed simulations with updated prescriptions for binary interactions and winds at Milky Way and Magellanic Clouds metallicities, we follow the evolution of single massive stars, primaries in interacting binaries and coalescence products following common envelope evolution. We also follow the evolution of the surviving secondary star, with a compact companion formed from the evolutionary end of the primary star or alone if the system was disrupted in the first supernova. The endpoints of our simulations map the rich landscape of CCSN progenitors, and provide detailed mass-loss history and progenitor structures. We identify an important evolutionary phase for stripped-envelope supernova progenitors, in which the wind mass-loss rate of stars stripped by binary interaction rapidly increases in their final evolutionary stages, after core helium burning. These strong winds would give rise to a Wolf-Rayet (WR) spectral appearance, though only for a few millennia, in contrast to hundreds of millennia for their more massive WR counterparts. Such lightweight WR stars in binaries can account for observed properties of type Ib/c supernovae.

The red hypergiant VY CMa is remarkable for its very visible record of high mass loss events observed over the range of wavelengths from the optical and infrared to the submillimeter region with ALMA. The SW Clump or SW knots are unique in the ejecta of VY CMa. Except for the central star, they are the brightest sources of dusty infrared emission in its complex ejecta. In this paper we combine the proper motions from the HST images, and infrared fluxes from 2 to 12 microns with the 12CO images from ALMA to determine their ages and mass estimates. The SW knots were ejected more than 200 years ago with an active period lasting about 30 years, and with a total mass in the Clump more than 0.02 Solar masses.

Gravitational waves from individually resolved compact object mergers can be used as standard sirens, offering a novel self-calibrating precision probe of cosmology. While the standard siren method has been well-explored, the gravitational-wave background arising from unresolved mergers offers a novel alternative to probing cosmology. We demonstrate that the combination of resolved binary black hole mergers with the unresolved signals composing the stochastic gravitational-wave background can be used to measure cosmological parameters, including the Hubble constant, $H_0$. We apply this ``stochastic siren'' method to existing gravitational-wave data and find that including the current non-detection of the background increases the accuracy at which $H_0$ can be measured, relative to using resolved mergers alone. We also provide projections for upcoming detectors to highlight their ability to probe cosmology with the background. With the anticipated detection of the astrophysical gravitational-wave background, the stochastic siren approach can be expected to improve future standard siren cosmological measurements.

Young associations provide a record that traces the star formation process, and the youngest populations connect progenitor gas dynamics to the resulting stellar populations. We therefore conduct the first comprehensive overview of the Circinus Complex, an under-studied and massive ($\sim$1500 M$_{\odot}$) region consisting of approximately 3100 recently formed stars alongside the Circinus Molecular Cloud (CMC). We find a clear age pattern in the contiguous central region (CirCe), where younger stars are found further from the massive central cluster, and where the velocities are consistent with uniform expansion. By comparing this structure to an analogous STARFORGE simulation, we find that the age structure and dynamics of the association are consistent with star formation in two stages: the global collapse of the parent cloud that builds the $500 M_{\odot}$ central cluster ASCC 79, followed by triggered star formation in a shell swept up after the first massive stars form. We also find that filaments with a range of distances from the central cluster can naturally produce multi-generational age sequences due to differences in feedback strength and exposure. Outlying populations show velocities consistent with formation independent from the CirCe region, but with similar enough velocities that they may be difficult to distinguish from one another later in their expansion. We therefore provide a new alternative view of sequential star formation that relies on feedback from a single central cluster rather than the multiple sequential generations that are traditionally invoked, while also providing insight into the star formation history of older populations.

Be stars are rapidly rotating, with angular frequency around $0.7-0.8$ of their Keplerian break up frequency, as a result of significant accretion during the earlier stellar evolution of a companion star. Material from the equator of the Be star is ejected and forms a decretion disc, although the mechanism for the disc formation has remained elusive. We find one-dimensional steady state decretion disc solutions that smoothly transition from a rapidly rotating star that is in hydrostatic balance. Boundary layer effects in a geometrically thick disc which connects to a rotationally flattened star enable the formation of a decretion disc at stellar spin rates below the break up rate. For a disc with an aspect ratio $H/R\approx 0.1$ at the inner edge, the torque from the disc on the star slows the stellar spin to the observed range and mass ejection continues at a rate consistent with observed decretion rates. The critical rotation rate, to which the star slows down to, decreases as the disc aspect ratio increases. More generally, steady state accretion and decretion disc solutions can be found for all stellar spin rates. The outcome for a particular system depends upon the balance between the decretion rate and any external infall accretion rate.

Numerous stellar surveys have been or will provide photometric, astrometric, and spectroscopic data for a large number of stars in the Milky Way and neighbouring galaxies. Modern data processing tools and analysis methods are needed to deal with these data sets and obtain accurate and precise results. In this context, we are developing a new spectroscopic analysis pipeline based on the differential analysis method. The CHEmical Survey analysis System (CHESS) aims to automate the steps needed to obtain high-quality stellar parameters and abundances from large samples of spectra. To automatically identify the spectra of similar stars that are suitable for a differential analysis, CHESS first performs what we call a similarity analysis by directly using the observed spectra. This step of analysis uses unsupervised machine learning algorithms (such as dimensionality reduction methods). To validate the findings, we used atmospheric parameters from several catalogues (in particular those available in Gaia DR3). Alternatively, such a similarity analysis also serves as a consistency check of the atmospheric parameters in these catalogues. Here, we present our method for finding similar stars in globular clusters and the first preliminary results of their atmospheric parameters.

This paper presents the gamma-ray spectral and timing results from the long-term regular observations of Mrk 421 with the Large Area Telescope (LAT) onboard Fermi during 2008 August - 2023 August. We discerned six periods the relatively stronger 0.3-300 GeV activity compared to other time intervals. The baseline brightness level varied on timescales from several months to years during these periods, which was superimposed by shorter-term flares of the different asymmetry associated with various interplay between the light-crossing, particle acceleration and cooling timescales. The source also frequently exhibited two-peak flares, to be triggered by the propagation of forward and reverse shocks after collision between the shells of high-energy plasma, moving with different speeds down the jet. The strongest long-term flaring activity was recorded during 2012 June - 2013 October and 2017 October - 2018 March, when the source was robustly detectable even on intraday timescales. We detected 25 instances of intraday variability and a large number of the flux doubling or halving instances. The source generally showed a lognormal variability in the LAT energy range, explained as an imprinting of the disc nonstationary processes on the jet, proton-initiated hadronic cascades or random fluctuations in the particle acceleration rate. Most of the 0.3-300 GeV spectra were well-fit with a simple power-law model and showed a very broad range of the photon-index from 2.8 down to 1.2, with the mean values of 1.75-1.84 and distribution peaks at 1.73-1.82 during the periods of strong activity. Our spectral study also revealed the features of inverse-Compton upscatter of X-ray photons in the Klein-Nishina regime, relativistic magnetic reconnection, first-order Fermi mechanism within the magnetic field of different confinement efficiencies and stochastic acceleration

We present the first brown dwarf spectral binary characterized with JWST: WISE J014656.66+423410.0, the coldest blended-light brown dwarf binary straddling the T/Y transition. We obtained a moderate resolution (R$\sim$2700) G395H spectrum of this unresolved binary with JWST/NIRSpec and we fit it to late-T and Y dwarf spectra from JWST/NIRSpec, and model spectra of comparable temperatures, both as individual spectra and pairs mimicking an unresolved binary system. We find that this tightly-separated binary is likely composed of two unequal-brightness sources with a magnitude difference of $0.50\pm0.08$ mag in IRAC [4.5] and a secondary $1.01\pm0.13$ mag redder than the primary in [3.6]-[4.5]. Despite the large color difference between the best fit primary and secondary, their temperature difference is only $92\pm23$\,K, a feature reminiscing of the L/T transition. Carbon disequilibrium chemistry strongly shapes the mid-infrared spectra of these sources, as a complex function of metallicity and surface gravity. While a larger library of JWST/NIRSpec spectra is needed to conclusively examine the peculiarities of blended-light sources, this spectral binary is a crucial pathfinder to both understand the spectral features of planetary-mass atmospheres and detect binarity in unresolved, moderate-resolution spectra of the coldest brown dwarfs.

The maintenance of primary mirror segment co-phasing is a critical aspect to the operation of segmented telescopes. However, speckle-based measurements of the phasing of the Keck primary have estimated semi-static surface aberrations of approximately 65 nm rms, which were not sensed by the current phasing control system. We propose directly sensing and controlling the primary via the adaptive optics (AO) system, as a Controllable Segmented Primary (CSP), to actively correct its phasing. We develop a methodology for separating the independent controllable signal of the CSP from the rest of the AO system and show estimations of the achievable measurement precision from models of the Keck-II AO system.

There are scientific and technological needs to improve the co-phasing of the primary mirrors of segmented telescopes. We have developed a methodology for using the wavefront sensor of an adaptive optics (AO) system to disentangle the phase of a Controllable Segmented Primary mirror (CSP) from the residual phase aberrations to be corrected by the rest of the AO system. We show simulations of the Keck-II AO system where we simultaneously control the CSP surface and a single-conjugate AO system using a pyramid wavefront sensor in a low-bandwidth closed loop, resulting in significantly decreased aberrations on the primary and improvements in the performance of the AO system. Analysis of on-sky telemetry data from the Keck-II AO system validates these simulations and shows that accurate measurements of the primary phase can be made in the presence of real atmospheric turbulence. Ultimately, this work suggests that it is feasible to simultaneously monitor and control the CSP with an AO wavefront sensor while in closed-loop operation and that doing so may significantly improve the performance of the AO system.

Modern X-ray and gamma-ray observatories time-tag detected photons. The distribution of intervals between successive photons may reveal variations of the flux on time scales too short for direct flux measurement of the mean count rate, provided a sufficient number of photons have been detected cumulatively. We demonstrate this with synthetic data and apply to RXTE data from Cyg X-1.

Context. Transition disks (TDs) are a type of protoplanetary disk characterized by a central dust and gas cavity. The processes behind how these cavities are formed and maintained, along with their observed high accretion rates of $10^{-8} -10^{-7} \, M_{\odot} \, \mathrm{yr}^{-1}$, continue to be subjects of active research. Aims. This work aims to investigate how the inclusion of the Hall effect (HE) alongside Ohmic resistivity (OR) and ambipolar diffusion (AD) affects the structure of the TD. Of key interest is the dynamical evolution of the cavity and whether it can indeed produce transonic accretion, as predicted by theoretical models in order to account for the observed high accretion rates despite the inner disk's low density. Methods. We present our results of 2D axisymmetric global radiation magnetohydrodynamic (MHD) simulations of TDs for which all three non-ideal MHD effects are accounted. We used the NIRVANA-III fluid code and initialized our model with a disk cavity reaching up to $R=8~\mathrm{au}$ with a density contrast of $10^5$. We performed three runs, one with only OR and AD, and one for each of the two configurations that arise when additionally including the HE, that is, with the field aligned (anti-aligned) with respect to the rotation axis. Results. For all three runs, our models maintain an intact inner cavity and an outer standard disk. MHD winds are launched both from the cavity and from the disk. Notably, when the HE is included, ring-like structures develop within the cavity. We moreover obtain accretion rates of $3 - 8 \times 10^{-8} \, M_{\odot} \, \mathrm{yr}^{-1}$, comparable to typical values seen in full disks. Importantly, we clearly observe transonic accretion ($v_{\mathrm{acc}} \gtrsim c_{s}$) in the cavity. Additionally, outward magnetic flux transport occurs in all three runs.

The Convective Overstability (COS) is a hydrodynamic instability occurring in protoplanetary disk (PPD) regions with an adverse radial entropy gradient. It is a potential driver of turbulence and may influence planetesimal formation. In this second paper of our series, we study the effects of the COS on dust dynamics in radially global PPD simulations, focusing on the mid-plane region, where vertical gravity on the dust is included. Axisymmetric 2D simulations show susceptibility to both the COS and the Vertically Shearing Streaming Instability. For a Stokes number tau = 0.1, strong dust clumping occurs only for highly super-solar initial metallicities Z greater than 0.05. In 3D non-axisymmetric simulations, the COS generates large-scale, long-lived vortices that have the potential to efficiently concentrate dust, with dust accumulation strengthening as tau increases. For tau = 0.01, no strong clumping occurs even at metallicities as high as Z = 0.1, and vortices remain robust and long-lived. At tau = 0.04, strong dust clumping is observed for solar metallicity (Z = 0.01) and higher. For tau = 0.1, clumping occurs even at strongly sub-solar metallicities (Z greater or equal to 0.004), peaking at Z approximately 0.01 to 0.03, including solar values. Under these conditions, vortices weaken significantly and become more spatially extended. At higher metallicities (Z greater or equal to 0.04) with tau = 0.1, large-scale vortex formation is suppressed, leading to nearly axisymmetric dust rings, which can still undergo clumping via the classical Streaming Instability.

Given recent X-ray observations of high-redshift active galactic nuclei (AGNs), we consider whether the extreme luminosities of these AGNs are consistent with current semi-analytical models. In particular, we apply extreme-value statistics (EVS) to obtain predictions of extreme X-ray luminosities of AGNs in the redshift range $3\lesssim z\lesssim 6$. We apply this formalism using different X-ray luminosity functions and compare the predicted extreme luminosities to AGNs in the Stripe-82 X-ray catalogue. We find a general consistency between data and the EVS predictions although there is some tension with certain luminosity functions. In addition, the extreme X-ray luminosities are found to be at least an order of magnitude below the Eddington luminosity limit. We discuss possible extensions to this model, including extrapolating our results to even higher redshifts ($z\gtrsim10$) where AGNs have recently been observed.

In 1962, Yoshihide Kozai reported his findings on the secular dynamics of asteroids moving in orbits with high inclination and eccentricity. In contrast to the classic understanding of the stability of planetary motion in the solar system, Kozai showed that asteroids can significantly change their orbital shape over a long timescale in an oscillatory manner between nearly circular orbits and highly elliptic orbits. An anti-correlated variation between orbital inclination and eccentricity characterizes this oscillation. The importance of Kozai's work in understanding the dynamical evolution of various systems was recognized decades later, including the fields of irregular satellites of planets, Oort Cloud, extrasolar planets, binary star systems, type Ia supernovae, planet climate, merging black hole systems, and so on.

This report presents the findings of a NIAC Phase I feasibility study for the Artemis-enabled Stellar Imager (AeSI), a proposed high-resolution, UV/Optical interferometer designed for deployment on the lunar surface. Its primary science goal is to image the surfaces and interiors of stars with unprecedented detail, revealing new details about their magnetic processes and dynamic evolution and enabling the creation of a truly predictive solar/stellar dynamo model. This capability will transform our understanding of stellar physics and has broad applicability across astrophysics, from resolving the cores of Active Galactic Nuclei (AGN) to studying supernovae, planetary nebulae, and the late stages of stellar evolution. By leveraging the stable vacuum environment of the Moon and the infrastructure being established for the Artemis Program, AeSI presents a compelling case for a lunar-based interferometer. In this study, the AeSI Team, working with the NASA Goddard Space Flight Center's Integrated Design Center (IDC), has firmly established the feasibility of building and operating a reconfigurable, dispersed aperture telescope (i.e., an interferometer) on the lunar surface. The collaboration produced a credible Baseline design featuring 15 primary mirrors arranged in an elliptical array with a 1 km major axis, with the potential to expand to 30 mirrors and larger array sizes through staged deployments. Additionally, this study identified numerous opportunities for optimization and the necessary trade studies to refine the design further. These will be pursued in follow-up investigations, such as a NIAC Phase II study, to advance the concept toward implementation.

The end points of massive star evolution are poorly known, especially those in interacting binary systems containing compact objects, such as neutron stars or black holes. Such systems are bright in X-rays, and the most luminous among them are called ultra-luminous X-ray sources (ULXs). In this paper, we address the enigmatic NGC 300 ULX-1. It's X-ray activity started in 2010 with the supernova impostor-like event SN 2010da. In the following few years the ULX was powered by persistent super-Eddington accretion but then it dimmed in X-rays. We present the most recent X-ray and optical observations. The Chandra and Swift telescopes confirm that SN 2010da/NGC 300 ULX-1 is not accreting at super-Eddington level anymore. We attribute this switch in accretion regime to the donor star variability and its fast evolution. In order to gain a better understanding of the donor star's nature, we consider its optical light curve on a decade-long time scale and show that the optical counterpart of SN 2010da/NGC 300 ULX-1 dimmed significantly over recent years. The most recent detection in optical by the Gemini telescope reveals that the source is now > 2.5 mag fainter in the r' band compared to the epoch when it was spectroscopically classified as a red supergiant. We discuss the nature of the abrupt changes in the donor star properties, and consider among other possibilities the silent collapse of the donor star into a black hole.

Type-I X-ray bursts are thermonuclear explosions caused by the unstable burning of accreted material on the surface of neutron stars. We report the detection of seven type-I X-ray bursts from the ultracompact X-ray binary M15 X-2 observed by the Neutron Star Interior Composition Explorer (NICER) during its 2022 outburst. We found all the bursts occurred in the soft state and exhibited similar light curve profiles, with no cases of photospheric radius expansion. Time-resolved spectroscopy showed clear deviations from the blackbody model during the first ten seconds of all the bursts. The fits were improved by using the enhanced persistent emission method, which we interpret as evidence of burst-disk interaction. We compared the performance of these models against a neutron star atmosphere model and found it made no significant improvements. After analyzing the burst rise times and fuel composition, we propose that these bursts were powered by the burning of pure helium, confirming the ultracompact nature of the source.

Observations of Galactic supernova remnants (SNRs) are crucial to understanding supernova explosion mechanisms and their impact on our Galaxy's evolution. SNRs are usually identified by searching for extended, circular structures in all-sky surveys. However, the resolution and sensitivity of any given survey results in selection biases related to the brightness and angular scale of a subset of the total SNR population. As a result, we have only identified 1/3 of the expected number of SNRs in our Galaxy. We used data collected by the Murchison Widefield Array (MWA) to perform a visual search for SNR candidates over 285deg < l < 70deg and |b| < 16deg. We then used the Widefield Infrared Survey Explorer to eliminate likely HII regions from our SNR candidate sample. By exploiting the resolution and sensitivity of MWA data, we have successfully detected 10 new candidates using our proposed method. In addition, our method has also enabled us to detect and verify 10 previously known but unconfirmed candidates. The 20 SNR candidates described in the paper will increase the known SNR population in the Galaxy by 7{\%}.

Gas-phase metallicity in interacting and merging galaxies offers key insights into their star formation processes and evolutionary histories. This study investigates the spatial evolution of gas-phase metallicity (i.e, oxygen abundance, 12 $+$ log(O/H)) in these galaxies using integral field unit (IFU) data from the SDSS-IV MaNGA survey, focusing on changes in metallicity gradients across different stages of interactions -- from early encounters to final coalescence. By comparing interacting and merging galaxies with isolated counterparts, we identify characteristic trends in how interactions influence metallicity gradients over time. Our analysis reveals that metallicity gradients typically flatten shortly after the first pericenter passage, likely due to radial gas mixing, with later stages showing either metallicity enrichment or dilution depending on the intensity of the interaction and star formation activity. These changes can result in gradients that are either flatter or steeper than the initial profiles. Notably, we observe steeper metallicity gradients in interacting galaxies at certain merger stages, which is inconsistent with predictions from some galaxy simulations. This discrepancy emphasizes the complexity of galaxy interactions. Overall, our findings provide valuable insights into how galaxy interactions reshape metallicity distribution, enhancing our understanding of the processes driving galaxy evolution during mergers.

This paper extends the creep tide theory to exoplanetary systems with significant obliquities. The extended theory allows us to obtain the stellar and planetary hydrodynamic equilibrium tides and the evolution of the rotational state of the bodies. The dynamic ellipsoidal figure of equilibrium of the body is calculated taking into account that its reaction to external forces is delayed by its viscosity. The derived equations are used to determine the motion of the tidal bulge of the planetary companion CoRoT-3b (a brown dwarf) and its host star. We show how the tides deform the figure of the companion and how its tidal bulge moves close to the substellar meridian from one hemisphere to another. The stellar lag is mostly positive and is braking the star's rotation.

The gas-phase abundances of deuterium (D) in the local interstellar medium (ISM) exhibit considerable regional variations. Particularly, in some regions the gas-phase D abundances are substantially lower than the primordial D abundance generated in the Big Bang, after subtracting the astration reduction caused by the Galactic chemical evolution. Deuterated polycyclic aromatic hydrocarbon (PAH) molecules have been suggested as a potential reservoir of the D atoms missing from the gas-phase. Recent observations from the James Webb Space Telescope's Near Infrared Spectrograph have revealed the widespread of deuterated PAHs in the Orion Bar through their aliphatic C--D emission at 4.65${\,{\rm \mu m}}$ and possibly aromatic C--D emission at 4.4${\,{\rm \mu m}}$ as well. To examine the viability of deuterated PAHs as the D reservoir, we model the infrared (IR) emission spectra of small PAH molecules containing various aromatic and aliphatic D atoms in the Orion Bar. We find that small deuterated PAHs exhibit a noticeable emission band at 4.4 or 4.65${\,{\rm \mu m}}$ even if they contain only one aromatic or aliphatic D atom. We derive ${N_{\rm D,ali}}/{N_{\rm H}}\approx3.4\%$, the deuteration degree of PAHs measured as the number of aliphatic D atoms (relative to H), from the observed intensity ratios of the 4.65${\,{\rm \mu m}}$ band to the 3.3${\,{\rm \mu m}}$ aromatic C--H band. The deuteration degree for aromatically-deuterated PAHs is less certain as C--N stretch also contributes to the observed emission around 4.4${\,{\rm \mu m}}$. If we attribute it exclusively to aromatic C--D, we derive an upper limit of $\approx14\%$ on the deuteration degree, which is capable of accounting for an appreciable fraction of the missing D budget.

Using the integral field unit data from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey, we build a sample of gas-star misaligned galaxies. The large-scale environment of misaligned galaxies is dominated by filaments and clusters, while is less dense relative to the gas-star aligned control galaxies. The direction of the large-scale structure (LSS) is defined by its minor axis ($\vec{e_{3}}$), which indicates the slowest collapsing direction. For the aligned controls, the gas and stellar spins are preferentially perpendicular to $\vec{e_{3}}$, since these galaxies reside in high-mass host haloes. For the misaligned galaxies, the gas spins also tend to be perpendicular to $\vec{e_{3}}$, suggesting that misaligned gas is recently accreted from the LSS. Meanwhile, there is no correlation between their stellar spins and $\vec{e_{3}}$. There are two possible explanations for this observational phenomenon: (1) the large-scale environments of misaligned galaxies evolve as they grow, with stellar angular momenta acquiring in different environments having different orientations; (2) the correlation between stellar spins and the LSS is smeared out since a relatively higher portion of misaligned galaxies in sheet environments are statistically analysed together with those in filament environments.

Point spread functions (PSFs) describe the distribution of light for a pure point source in an astronomical image due to the instrument optics. For deconvolution, as for point source photometry and for source removal, it is key to have an accurate PSF for a particular image. Space-based telescopes can then pose a challenge as their PSFs are informed by their complex construction, and the myriad of pointings and rotations used to capture deep images. These telescopes also capture the highest resolution images of astronomical sources, resolving stars around even relatively distant galaxies. Proper co-addition of PSFs at a specific source position for space-based imaging is then both critical and challenging. This code, spike, generates model PSFs and runs them through the same processing pipeline used to derive deep, co-added images, providing correctly co-added and resampled PSFs for images from the Hubble Space Telescope, the James Webb Space Telescope, and the Nancy Grace Roman Space Telescope.

We present the SpecDis value added stellar distance catalogue accompanying DESI DR1. SpecDis trains a feed-forward Neural Network (NN) on a large sample of stars with Gaia parallaxes, but without applying selections on parallax error or signal-to-noise (S/N) of the stellar spectra. We incorporate parallax error into the loss function for training. This approach ensures the training sample not suffering from biases. Moreover, SpecDis predicts the reciprocal of the square root of luminosity, which is linearly proportional to parallax and helps to avoid excluding negative parallaxes. To enhance the precision of distance predictions, we employ Principal Component Analysis (PCA) to reduce the noise and dimensionality of stellar spectra. Validated by independent external samples of member stars with precise distances from globular clusters, dwarf galaxies, and stellar streams, combined with BHB stars, we demonstrate that our distance measurements show no significant bias up to 100 kpc, and are much more precise than Gaia parallax beyond 7 kpc. The median distance uncertainties are 23 %, 19 %, 11 % and 7 % for S/N$<$20, 20$\leq$S/N$<$ 60, 60$\leq$ S/N $<$ 100 and S/N$\geq$100. Selecting stars with $\log g<3.8$ and distance uncertainties smaller than 25 %, we have more than 74,000 giant candidates within 50 kpc to the Galactic center and 1,500 candidates beyond this distance. Additionally, we develop a Gaussian mixture model to identify binaries and identify 120,000 possible binaries, and discover that the binary fraction increases with [Fe/H] and $\log g$ and declines with [$\alpha$/Fe] and $T_\mathrm{eff}$, indicating stars with low Fe and high $\alpha$, which form early, may have experienced more encounters and tidal effects to disrupt binaries. Our final catalogue provides distances and distance uncertainties for $>$4 million stars, offering a valuable resource for Galactic astronomy.

Accretion supermassive black holes in the center of active galaxies usually produce ``jets''-collimated bipolar outflows of relativistic particles. Magnetic fields near the black hole event horizon may play a crucial role in the formation of jets/outflows. Both theory and observation indicate that jets/outflows driven by centrally active supermassive black holes (SMBHs) have a feedback effect on the overall properties of the host galaxies. Therefore, the magnetic field is a key ingredient for the formation and evolution of galaxies. Here we report a clear correlation between the magnetic field of jets and star formation rate (SFR) for a large sample of 96 galaxies hosting supermassive black holes, which suggests that the star formation of active galactic nuclei (AGN) host galaxies may be powered by the jets.

The circumgalactic medium (CGM) is poorly constrained at the sub-parsec scales relevant to turbulent energy dissipation and regulation of multi-phase structure. Fast radio bursts (FRBs) are sensitive to small-scale plasma density fluctuations, which can induce multipath propagation (scattering). The amount of scattering depends on the density fluctuation spectrum, including its amplitude $C_{\rm n}^2$, spectral index $\beta$, and dissipation scale $l_{\rm i}$. We use quasar observations of CGM turbulence at $\gtrsim$ pc scales to infer $C_{\rm n}^2$, finding it to be $10^{-16}\lesssim C_{\rm n}^2\lesssim 10^{-9}$ m$^{-20/3}$ for hot ($T>10^6$ K) gas and $10^{-9}\lesssim C_{\rm n}^2\lesssim 10^{-5}$ m$^{-20/3}$ for cool ($10^4\lesssim T\lesssim 10^5$ K) gas, depending on the gas sound speed and density. These values of $C_{\rm n}^2$ are much smaller than those inferred in the interstellar medium at similar physical scales. For most FRB sightline geometries, the scattering delays from the CGM are negligible ($\ll10$ $\mu$s at 1 GHz), but are more detectable from the cool gas as radio scintillation. Joint quasar-FRB observations of individual galaxies can yield lower limits on $l_{\rm i}$, even if the CGM is not a significant scattering site. An initial comparison between quasar and FRB observations (albeit for different systems) suggests $l_{\rm i}\gtrsim200$ km in $\sim10^4$ K gas in order for the quasar and FRB constraints to be consistent. If a foreground CGM is completely ruled out as a source of scattering along an FRB sightline then $l_{\rm i}$ may be comparable to the smallest cloud sizes ($\lesssim$ pc) inferred from photoionization modeling of quasar absorption lines.

Quasi-periodic oscillations (QPOs) are very common in black hole accretion systems that are seen from the modulations in luminosity. Many supermassive black hole sources (e.g., RE J1034+396, 1H~0707-495, MCG-6-30-15, 1ES~1927+654, Sgr~A$^*$) have been observed to exhibit QPO-like variability in the range of mHz in different energy bands (e.g., radio, NIR, X-ray). Due to the shorter infalling time, low-angular momentum accretion flows can have resonance close to the black hole, which will raise variability centiHz (cHz) or beyond QPOs for supermassive black holes. In this study, we for the first time show that such resonance conditions can be achieved in simulations of low angular momentum accretion flows onto a black hole. The QPOs could have values beyond $\nu_{\rm QPO}\gtrsim0.1-1\times 10^7M_\odot/M_{\rm BH}\,$cHz and the harmonics have a ratio of 2:1. Hunting down of these cHz QPOs will provide a smoking gun signature for the presence of low-angular momentum accretion flows around black holes (e.g., Sgr~A$^*$, 1ES~1927+654).

LOFAR is a low-frequency array distributed across several European countries. Each LOFAR station contains thousands of antennas and associated electronics, making monitoring and thorough testing of those components essential to ensuring station reliability. This paper discusses various anomalies that may arise in LOFAR antennas, tile elements, modems, and summators. We also introduce two diagnostic pipelines designed to detect these anomalies: a real-time station monitoring system and an offline stationtest system. These pipelines provide valuable insights into the operational status of each antenna, issuing alerts to minimize observational disruptions while maximizing station uptime, reliability, and sensitivity. By enhancing the efficiency and stability of LOFAR stations, they also serve as a foundation for future large-scale arrays like SKA-Low. The experience gained from their development and deployment will contribute to the construction and maintenance of SKA-Low, improving monitoring and diagnostic capabilities for large-scale antenna networks. Ultimately, these systems play a crucial role in ensuring continuous observations and maintaining data integrity.

We obtained high spectral resolution spectra ($\Delta v$ $\sim$ 2.5 km s$^{-1}$) for DG Tau A from 4800 Å to 7500 Å using Subaru High Dispersion Spectrograph (HDS) for the first time. The low-velocity components (LVCs, |$v$| < 100 km s$^{-1}$) were observed in the [O I] 5577, 6300, 6364 Å, [S II] 6716, 6731 Å lines. The offset position spectra observed in the LVCs show a "negative velocity gradient", supporting the presence of a wide-angled wind associated with the LVC emission. The offset position spectra observed in a component within the LVC velocity range between -16 km s$^{-1}$ to -41 km s$^{-1}$, namely, LVC-M, show a "negative velocity gradient'', supporting the presence of a wide-angled wind. With 12-70 au wind lengths measured using spectroastrometry, we estimate a lower limit to the wind mass-loss rate of $\sim$10$^{-8}$ M$_\odot$ yr$^{-1}$. In addition to the LVCs, we identify two high-velocity components (HVCs, |$v$| > 100 km s$^{-1}$) associated with the collimated jet in 26 lines ([N I], [N II], [O I], [O II], [O III], [S II], [Ca II], [Fe II], H$\alpha$, H$\beta$, He I). The one with a clear spatial offset from the star ($n_e$ $\sim$10$^4$ cm$^{-3}$, HVC1) is associated with an internal shock surface of the jet, while the other at the base ($n_e$ $\sim$10$^6$ cm$^{-3}$, HVC2) may be a stationary shock component. We find that the observed line profiles and the spatial scales of the LVC emission do not agree with the existing predictions for photoevaporative or magnetohydrodynamical (MHD) disk winds. These could be explained by the X-wind model, but synthetic observations are required for detailed comparisons.

Comet 7P/Pons-Winnecke was observed from the Calar Alto Observatory (Spain) for four months during the 2021 inbound apparition. Broad-band visible images were taken between 1.71 and 1.25 AU pre-perihelion, while long-slit spectrophotometric data were taken at $\sim$ 1.25 AU pre-perihelion. This dataset has been complemented with three $r$-Sloan images observed from Zwicky Transient Facility (ZTF) to model the physical properties and loss rate of the dust with a forward Monte Carlo dust tail code. The model fits the observed isophotes well for most observations. The peak dust production rate was measured at 83 kg s$^{-1}$, 15 days after perihelion. The particle terminal speed ranges from 3 m s$^{-1}$ for 0.1 m particles to 23 m s$^{-1}$ for 5 $\mu$m particles. Regarding the gas production from spectra, CN and C$_2$ show asymmetric emission between the sunward and antisunward directions beyond the data uncertainties and error propagation, while a clear asymmetry for C$_3$ cannot be definitively claimed. Average production rates for CN, C$_2$, and C$_3$ near 2021 perihelion are 1.15 $\times 10^{24}$, 2.32$\times 10^{24}$, and 1.69$\times 10^{23}$ s$^{-1}$, respectively. The dust-to-gas mass ratio value is estimated to be around 2, suggesting a dust-rich composition. Based on the gas composition and the $Af\rho$ value, we classify 7P/Pons-Winnecke as having a typical composition for Jupiter Family comets, with some C$_3$ depletion. Given the limited previous knowledge, our work contributes to expanding the understanding of the activity and characteristics of 7P/Pons-Winnecke.

The study of exoplanets has led to many surprises, one of which is the discovery of planets larger than Earth yet smaller than Neptune, super Earths and gas dwarfs. No such planet is a member of the Solar System, yet they appear to be abundant in the local neighbourhood. Their internal structure is not well understood. Super Earths presumably are rocky planets with a thin secondary atmosphere, whereas gas dwarfs have a substantial (by volume) primary H/He atmosphere. However, conflicting evidence exists regarding the presence of a third class of planets, so-called water worlds, which are hypothesised to contain a significant mass fraction of water in condensed or steam form. This study examines the evidence for water worlds and presents a sample of 60 precisely measured small exoplanets (less than 4 Earth radii) orbiting M dwarf stars. We combine observational data and unsupervised machine-learning techniques to classify these planets based on their mass, radius, and density. We individually model the interior of each planet using the ExoMDN code and classify them into populations based on these models. Our findings indicate that the sample divides into two distinct planet populations, with no clear evidence supporting the existence of water worlds in the current dataset.

Galactic chemical abundances provide crucial insights into fundamental galactic parameters, such as the high-mass slope of the initial mass function (IMF) and the normalization of Type Ia supernova (SN Ia) rates. Constraining these parameters is essential for advancing our understanding of stellar feedback, metal enrichment, and galaxy formation processes. However, traditional Bayesian inference techniques, such as Hamiltonian Monte Carlo (HMC), are computationally prohibitive when applied to large datasets of modern stellar surveys. We leverage simulation-based-inference (SBI) as a scalable, robust, and efficient method for constraining galactic parameters from stellar chemical abundances and demonstrate its the advantages over HMC in terms of speed, scalability, and robustness against model misspecifications. We combine a Galactic Chemical Evolution (GCE) model, CHEMPY, with a neural network emulator and a Neural Posterior Estimator (NPE) to train our SBI pipeline. Mock datasets are generated using CHEMPY, including scenarios with mismatched nucleosynthetic yields, with additional tests conducted on data from a simulated Milky Way-like galaxy. SBI results are benchmarked against HMC-based inference, focusing on computational performance, accuracy, and resilience to systematic discrepancies. SBI achieves a $\sim75,600\times$ speed-up compared to HMC, reducing inference runtime from $\gtrsim42$ hours to mere seconds for thousands of stars. Inference on $1,000$ stars yields precise estimates for the IMF slope ($\alpha_{\rm IMF} = -2.298 \pm 0.002$) and SN Ia normalization ($\log_{10}(N_{\rm Ia}) = -2.885 \pm 0.003$), deviating less than 0.05% from the ground truth. SBI also demonstrates similar robustness to model misspecification than HMC, recovering accurate parameters even with alternate yield tables or data from a cosmological simulation. (shortened...)

Measurements of the number count dipole with large surveys have shown amplitudes in tension with kinematic predictions based on the observed Doppler dipole of the cosmic microwave background (CMB). These observations seem to be in direct conflict with a homogeneous and isotropic Universe as asserted by the cosmological principle, demanding further investigation into the origin of the tension. Here, we investigate whether the observed number count dipoles are consistent with being fully kinematic or if there is any residual anisotropy contributing to the total observed dipole. To disentangle these contributions, we aim to leverage the fact that the kinematic matter dipole expected in a given galaxy catalogue scales with observed properties of the sample, and different catalogues used in the literature therefore have different kinematic dipole expectations. We here perform joint dipole fits using the NRAO VLA Sky Survey (NVSS), the Rapid ASKAP Continuum Survey (RACS), and the AGN catalogue derived from the Wide-field Infrared Survey Explorer (CatWISE). Assuming a common kinematic and non-kinematic dipole component between all catalogues, we find that a large residual, non-kinematic dipole anisotropy is detected, though a common direction between the two components is disfavoured by model selection. Freeing up both amplitude and direction for this residual dipole while fixing the kinematic dipole to the CMB dipole expectation, we recover a significant residual dipole with $\mathcal{D}_{resid} = (0.81\pm0.14)\times10^{-2}$, that is offset from the CMB dipole direction by $39\pm8$ degrees. While the present work provides a valuable first test of this concept, its scrutinising power is limited by the currently employed catalogues. Larger catalogues, especially in radio, will be needed to further lift the degeneracy between the kinematic and residual dipole components.

The Compton Spectrometer and Imager (COSI) is a Compton telescope designed to survey the 0.2-5 MeV sky, consisting of a compact array of cross-strip germanium detectors. As part of its development, in 2016 COSI had a successful 46 day flight on board NASA's Super Pressure Balloon platform. This was a precursor to the COSI Small Explorer (COSI-SMEX) satellite mission that will launch in 2027 into a equatorial low Earth (530 km) orbit. The observation of MeV gamma-rays is dominated by background radiation, especially due to the activation of the detector materials induced by cosmic-ray interactions. Thus, background simulation and identification are crucial for the data analysis. Because the COSI-SMEX detectors will be similar to the ones used for the balloon flight, the balloon measurements provide an important tool for testing and cross-checking our background simulations for the upcoming space mission. In this work we perform Monte Carlo simulations of the background emission from the 2016 COSI balloon flight. Including a phenomenological shape correction, we obtain an agreement with the data at the 10-20% level for energies between 0.1-1.6 MeV, and we successfully reproduce most of the activation lines induced by cosmic ray interactions.

X-rays provide a robust method in identifying AGN. However, in the high-redshift Universe, their space density is relatively low, and, in combination with the small areas covered by X-ray surveys, the selected AGN are poorly sampled. Deep optical/infrared data are essential for locating counterparts and determining redshifts. In this work, we leverage the XMM-Newton 4XMM-DR11 serendipitous catalogue alongside the extensive optical Dark Energy Survey and the near-infrared VISTA Hemisphere Survey (VHS) to select one of the largest high-z X-ray AGN samples to date. Our analysis focuses on the overlapping area of these surveys, covering about 185 $deg^2$. In addition, we aspire to compare the properties of the X-ray AGN with the optically-selected QSOs. For sources without spectroscopic data (80%), we estimated the photometric redshifts using both SED fitting and machine-learning algorithms. Among the 65,000 X-ray sources in the 4XMM-DES-VHS area, we ended up with 833 z>3.5 AGN (11% having spec-z information) with high reliability and a fraction of outliers {\eta}<10%. The sample completeness is 90%, driven by the depth of DES data. Only 10% of the X-ray selected AGN are also optical QSOs and vice versa. Our findings indicate an observed absorbed fraction ($\log N_H~[cm^{-2}] \geq 23$) of 20-40% for the X-ray AGN, significantly higher than that of optical QSOs. X-ray AGN exhibit fainter observed optical magnitudes and brighter mid-IR magnitudes than optical QSOs. Their median rest-frame SED shapes differ notably with optical QSOs being dominated by AGN emission in the UV-optical wavelengths. While the median SEDs of X-ray AGN suggest extinction in the UV-optical range, individual sources exhibit a wide range of spectral shapes, indicating significant diversity within the population. This analysis supports that X-ray and optically-selected AGN represent distinct and complementary populations.

The R2D2 Deep Neural Network (DNN) series was recently introduced for image formation in radio interferometry. It can be understood as a learned version of CLEAN, whose minor cycles are substituted with DNNs. We revisit R2D2 on the grounds of series convergence, training methodology, and DNN architecture, improving its robustness in terms of generalisability beyond training conditions, capability to deliver high data fidelity, and epistemic uncertainty. Firstly, while still focusing on telescope-specific training, we enhance the learning process by randomising Fourier sampling integration times, incorporating multi-scan multi-noise configurations, and varying imaging settings, including pixel resolution and visibility-weighting scheme. Secondly, we introduce a convergence criterion whereby the reconstruction process stops when the data residual is compatible with noise, rather than simply using all available DNNs. This not only increases the reconstruction efficiency by reducing its computational cost, but also refines training by pruning out the data/image pairs for which optimal data fidelity is reached before training the next DNN. Thirdly, we substitute R2D2's early U-Net DNN with a novel architecture (U-WDSR) combining U-Net and WDSR, which leverages wide activation, dense connections, weight normalisation, and low-rank convolution to improve feature reuse and reconstruction precision. As previously, R2D2 was trained for monochromatic intensity imaging with the Very Large Array (VLA) at fixed $512 \times 512$ image size. Simulations on a wide range of inverse problems and a case study on real data reveal that the new R2D2 model consistently outperforms its earlier version in image reconstruction quality, data fidelity, and epistemic uncertainty.

The Solar Ultraviolet Imaging Telescope (SUIT) is one of the seven payloads on board Aditya-L1 mission of the Indian Space Research Organization (ISRO). SUIT provides full and partial disk images of the Sun in the 200-400 nm wavelength range. This would help us probe the solar atmosphere at different heights and understand the mass and energy transfer process between its layers. For the first time, SUIT will also help us measure spatially resolved solar spectral irradiance at this wavelength band, which is significant for studying the sun-climate relationships. To perform these studies, it is necessary to photometrically calibrate the payload and validate the spectral coverage of the various bandpasses. We perform the photometric calibration and spectral validation of 8 bandpasses using light of known intensity and spectral coverage. For photometric calibration, the telescope throughput is modeled using sun-as-a-star spectrum from SOLSTICE and SOLSPEC. The modeled throughput is compared with in-lab measurements taken with light of known intensity. The ratio of measured photoelectrons gathered with the modeled prediction agree within 20%. For spectral validation, readings are taken across the transmission spectrum of each filter, keeping adjacent readings independent of each other. The relative intensity measured at each wavelength is seen to trace the modeled telescope bandpass for that filter. These tests could not be performed for filters with bandpasses operating below 250 nm (NB01, BB01 and BB02), primarily due to heavy atmospheric attenuation in these wavelengths leading to decreased SNR of the data. The experimentally measured results agree closely with the modeled values, validating SUIT's optical performance and presenting the reliability of the developed throughput model.

The distribution of dark matter at the galactic center, crucial for indirect searches, remains uncertain. In particular, in the vicinity of the massive black hole in the center of a galaxy where indirect signals may be stronger, the density of a dark matter spike may undergo redistribution. Here we calculate the density surrounding Schwarzschild black holes that originate from diverse initial dark halos and estimate the velocity distribution of dark matter particles. By employing a series of Hernquist and power-law initial dark halos, we obtain a fitting formula between dark matter spikes and black hole masses. The Maxwell-Boltzmann distribution is utilized to approximate the velocity distribution of dark matter particles. As an application, taking into account dark matter self-annihilation, we assess the relic densities of dark matter spikes around black holes. We find that the relic spikes for s-wave annihilation are higher than p-wave annihilation, and the relic densities obtained for p-wave annihilation depend on the velocity distribution, varying significantly with distance. The findings shall further provide useful insights for multi-messenger dark matter detections in the future.

We report on multiwavelength observations of FRB 20240114A, a nearby (z=0.13), hyperactive, repeating fast radio burst that was discovered in January 2024. We performed simultaneous observations of the source with the Effelsberg 100-m radio telescope, the Thai National Radio Telescope, the Astropeiler Stockert, and the X-ray satellite XMM-Newton in May 2024. On May 23, 2024, we detected 459 bursts from the source using the Ultra-Broad-Band (UBB) receiver of the Effelsberg telescope, covering a frequency range from 1.3 GHz to 6 GHz. All bursts have simultaneous X-ray coverage, which allows us to put stringent constraints on the X-ray-to-radio fluence ratio, $\eta_{x/r}$, of FRB 20240114A. In this work, we focus on the three brightest radio bursts detected during the campaign. The brightest burst exhibits a radio fluence of $1.4\times 10^{-17}$ erg cm$^{-2}$, while the $3\sigma$ upper limit of the 0.2$-$12 keV absorption-corrected X-ray burst fluence lies in the range of $3.4\times 10^{-11}$ erg cm$^{-2}$ to $1.7\times 10^{-10}$ erg cm$^{-2}$, depending on the spectral model. Assuming a 10 keV black-body spectrum, the X-ray-to-radio fluence ratio can be constrained to $\eta_{x/r}<1.2\times10^{7}$. A cutoff power law ($\Gamma=1.56$, cutoff at 84 keV) is also considered, physically motivated by the Galactic magnetar SGR 1935+2154, which has previously shown X-ray bursts associated with FRB-like radio bursts at a measured X-ray-to-radio fluence ratio of $\eta_{x/r}\sim2.5\times 10^{5}$ (1$-$250 keV). In this scenario, we find that $\eta_{x/r}<2.4\times 10^6$. Our results are consistent with FRB 20240114A being powered by a mechanism similar to that of SGR 1935+2154. We show that future multiwavelength campaigns will be able to improve this limit if sufficiently bright radio bursts are observed with simultaneous X-ray coverage.

There is evidence that stars and browns dwarfs grow through episodic rather than continuous gas accretion. However, the role of episodic accretion in the formation of brown dwarfs remains mostly unexplored. We investigate the role of episodic accretion, triggered by the magnetorotational instability in the inner disk regions, resulting in episodic outbursts during the formation of brown dwarfs, and its implications for their early formation stages. We use hydrodynamical simulations coupled with a sub-grid accretion model to investigate the formation of young proto-brown dwarfs and protostars, taking into account the effects of episodic accretion resulting in episodic radiative feedback, i.e. in luminosity outbursts. The formation timescale for proto brown dwarfs is at least one order of magnitude shorter than that of protostars. Episodic accretion leads to a shorter main accretion phase compared to continuous accretion in brown dwarfs, whereas the opposite is true for low-mass stars. Episodic accretion can accelerate early mass accretion in proto-brown dwarfs and protostars, but it results in less massive objects by the end of the main phase compared to continuous accretion. We find an approximately linear correlation between an object's mass at the end of the main accretion phase and the timing of the last episodic outburst: later events result in more massive brown dwarfs but less massive low-mass stars. Episodic outbursts have a stronger effect on brown dwarf-forming cloud cores, with the last outburst essentially splitting the brown dwarf evolution into a short high-accretion and a much longer low-accretion phase.

Various theories of dark matter predict distinctive astrophysical signatures in gravitational-wave sources that could be observed by ground- and space-based laser interferometers. Different candidates-including axions, dark photons, macroscopic dark matter, WIMPs, and dark-matter spikes-may appear in interferometer data via their coupling to gravity or the Standard Model, altering the measured gravitational-wave strain in distinct ways. Despite their differences, these candidates share two key features: (1) they can be probed through their effects on gravitational waves from inspiraling compact objects, isolated black holes, and neutron stars, or via direct interactions with detectors, and (2) their signatures likely persist far longer than the seconds-long mergers detected today, necessitating new data analysis methods beyond matched filtering. This review outlines these dark matter candidates, their observational signatures, and approaches for their detection.

Distinguishing galaxies as either fast or slow rotators plays a vital role in understanding the processes behind galaxy formation and evolution. Standard techniques, which are based on the $\lambda_R$-spin parameter obtained from stellar kinematics, frequently face difficulties to classify fast and slow rotators accurately. These challenges arise particularly in cases where galaxies have complex interaction histories or exhibit significant morphological diversity. In this paper, we evaluate the performance of a Convolutional Neural Network (CNN) on classifying galaxy rotation kinematics based on stellar kinematic maps from the SAMI survey. Our results show that the optimal CNN architecture achieves an accuracy and precision of approximately 91% and 95% on the test dataset, respectively. Subsequently, we apply our trained model to classify previously unknown rotator galaxies for which traditional statistical tools have been unable to determine whether they exhibit fast or slow rotation, such as certain irregular galaxies or those in dense clusters. We also used Integrated Gradients (IG) to reveal the crucial kinematic features that influenced the CNN's classifications. This research highlights the power of CNNs to improve our comprehension of galaxy dynamics and emphasizes their potential to contribute to upcoming large-scale Integral Field Spectrograph (IFS) surveys.

Multiple active galactic nuclei (multi-AGN) are a known result of galaxy mergers. Therefore, they are an important tool for studying the formation and dynamical evolution of galaxies and supermassive black holes (SMBHs). A novel method for the selection of multi-AGN leverages the exquisite positional accuracy of Gaia to detect astrometrically-variable quasars. Previous work has paired this method with radio interferometry on sub-arcsecond scales. In this paper, we present a follow-up study of seven astrometrically-variable quasars from the pilot sample using the Very Long Baseline Array (VLBA). We targeted these seven quasars with the VLBA at 2.0-2.4 GHz (S-band) and 8.0-8.4 GHz (X-band), reaching milliarcsecond resolutions, in order to study the radio properties at smaller scales and to constrain the origin of the astrometric variability. The new observations are also used to identify significant radio-optical offsets in all seven objects, suggesting that many astrometrically-variable quasars also exhibit significant radio-optical offsets. We find that four of the seven sources are possible candidate multi-AGN based on their radio properties and radio-optical offsets. Overall, we use this follow-up study to constrain the smaller-scale radio properties of this sample of astrometrically-variable quasars, and continue to explore the use of this method in the field of multi-AGN.

In order to reduce light pollution we have to reduce the overall amount of artificial light emissions. This is a consequence of the basic rules governing the propagation of light in the terrestrial environment. In this work I revisit the physical laws causing that (i) "all" artificial light emitted outdoors is lost or pollutant, (ii) the negative effects of light pollution depend monotonically on the local concentration of photons of anthropogenic origin, and (iii) this concentration depends linearly on the total artificial light emissions, weighted by the light pollution propagation functions. Setting total emission limits becomes necessary in order to ensure that the negative effects of light pollution do not surpass red-lines of unacceptable degradation of the natural night. Once these red-lines are socially agreed, monitoring compliance becomes a relevant task. Several complementary methods for assessing total light emissions are being used nowadays, including public inventories of installed lights, direct radiance measurements from ground or low Earth orbit satellites, and scattered radiance measurements using ground based detectors (night sky brightness monitoring). While updated administrative inventories could in principle be trusted, independent verification is a must. The required measurements pose in turn significant challenges: we discuss here how the variability of the terrestrial atmosphere sets a lower limit on the minimum emission changes that can be reliably detected by measurements, and propose some ways to improve this performance.

Early-type galaxies (ETGs) show a bimodal distribution in key structural properties like stellar specific angular momentum, kinematic morphology, and nuclear surface brightness profiles. Slow rotator ETGs, mostly found in the densest regions of galaxy clusters, become common when the stellar mass exceeds a critical value of around $M_*^\mathrm{crit}\approx2\times 10^{11}\,M_\odot$, or more precisely when $\lg(R_\mathrm{e}/\mathrm{kpc}) \gtrsim 12.4 - \lg(M_*/M_\odot)$. These galaxies have low specific angular momentum, spheroidal shapes, and stellar populations that are old, metal-rich, and $\alpha$-enhanced. In contrast, fast rotator ETGs form a continuous sequence of properties with spiral galaxies. In these galaxies, the age, metallicity, and $\alpha$-enhancement of the stellar population correlate best with the effective stellar velocity dispersion $\sigma_\mathrm{e} \propto \sqrt{M_*/R_\mathrm{e}}$ (i.e., properties are similar for $R_\mathrm{e}\propto M_*$), or with proxies approximating their bulge mass fraction. This sequence spans from star-forming spiral disks to quenched, passive, spheroid-dominated fast rotator ETGs. Notably, at a fixed $\sigma_\mathrm{e}$, younger galaxies show lower metallicity. The structural differences and environmental distributions of ETGs suggest two distinct formation pathways: slow rotators undergo early intense star formation followed by rapid quenching via their dark halos and supermassive black holes, and later evolve through dry mergers during hierarchical cluster assembly; fast rotators, on the other hand, develop more gradually through gas accretion and minor mergers, becoming quenched by internal feedback above a characteristic $\lg(\mathrm{\sigma_e^{crit}}/\text{ km s}^{-1})\gtrsim2.3$ (in the local Universe) or due to environmental effects.

We introduce and apply a methodology based on dynamic time warping (DTW) to compare the whole set of gamma-ray light curves reported in the Third Fermi-Large Area Telescope Pulsar Catalogue. Our method allows us to quantitatively measure the degree of global similarity between two light curves beyond comparing indicators such as how many peaks there are, which is their separation, width, and height. Once the morphology of the light curve is showcased via background subtraction, min-max scaler normalization, and rotations are considered to take into account that phase 0 is arbitrary, the level of detail with which light curves of different pulsars appear is revealed. In many cases their similarity is striking and occurs disregarding any other timing, physical, or spectral property. In particular, some MSPs and young pulsars share detailed light curve morphology.

SS433 is an exotic Galactic microquasar in which there is a supercritical inflow of matter into a compact object of likely black hole nature. Here I report on an SS433 flare that occurred during a TESS observation of Sector 54 in June of 2022. The flare lasted for about 10 days and culminated in a flux increase by a factor of three relative to quiescence. The unprecedented continuous photometric coverage of the flare afforded by TESS shows that the flux can rise and fall by up to a factor of two within 4 to 7 hours. Furthermore, there is evidence that the flare peaks occur with a quasi-period $P_{\mathrm{QPO}} = 13.3$ hours. The flare can be most naturally explained by accretion rate ($\dot{M}$) variations due to oscillations in the donor star mass loss rate. We estimate $\dot{M}$ variations up to a factor of two with an increase in the photospheric radius of the accretion disk by about the same factor, implying that a transient ``common envelope'' enshrouds the binary system during the flares. If the flares are due to radial pulsations in the donor star envelope then their quasi-period $P_{\mathrm{QPO}}$ could imply a mean density $\left < \rho \right > \sim 18 \text{ kg} \text{ m}^{-3}$ for the donor star, compared to $\left < \rho_{\mathrm{RL}} \right > = 0.7-1 \text{ kg} \text{ m}^{-3}$ for a synchronized Roche-lobe filling donor star. Another SS433 lightcurve from a Sector 80 TESS observation in 2024 hints that there may be an outflow from behind the the donor star.

Context: Compared to Class 0 protostars, the higher densities and lower temperatures of the disk midplanes of Class I young stellar objects (YSOs) limit the detectability of complex organic molecules (COMs). The elevated luminosities of eruptive YSOs increase disk temperatures sublimating frozen molecules and easing their detection. Aims: Our aim is to investigate the chemical composition of four FUor-like Class I YSOs: L1551 IRS 5, Haro 5a IRS, V346 Nor, and OO Ser, and to compare their abundances of COMs with other YSOs in the literature. Methods: We search for COMs line emission in ALMA Band 6 observations. We use the CASSIS software to determine their column densities (N) and excitation temperatures (T_ex) assuming local thermodynamical equilibrium. Results: We detect 249 transitions from 12 COMs. In L1551 IRS 5 we identified CH3OH, 13CH3OH, CH318OH, CH2DOH, CH3CHO, CH3OCH3, CH3OCHO, CH3COCH3, C2H5OH, C2H5CN, 13CH3CN, and CH3C15)N. Haro 5a IRS and OO Ser have emission from CH3OH, CH3CHO, CH3OCH3, and CH3OCHO. CH3COCH3 is also detected in OO Ser. In V346 Nor we found CH3OH, CH2DOH, CH3CHO, CH3OCH3, CH3OCHO, and C2H5CN. The emission of COMs is compact in all targets. The analysis indicates their temperatures are above 100K. The abundance ratios of COMs derived for these eruptive YSOs, as well as for other protostars in the literature, span several orders of magnitude without any clear differentiation between the eruptive and quiescent YSOs. The column density of the main isotopologue of CH3OH should not be used as a reference, as most of the lines are optically thick. Conclusions: The hot and compact emission of COMs indicates that the four FUor-like targets are hot corino-like. Spectral studies of such objects can be useful to investigate the complex organic chemistry at later evolutionary stages than the usual Class 0 stage.

Context. Radiation plays a significant role in solar and astrophysical environments as it may constitute a sizeable fraction of the energy density, momentum flux, and the total pressure. Modelling the dynamic interaction between radiation and magnetized plasmas in such environments is an intricate and computationally costly task. Aims. The goal of this work is to demonstrate the capabilities of the open-source parallel, block-adaptive computational framework MPI-AMRVAC, in solving equations of radiation-magnetohydrodynamics (RMHD), and to present benchmark test cases relevant for radiation-dominated magnetized plasmas. Methods. The existing magnetohydrodynamics (MHD) and flux-limited diffusion (FLD) radiative-hydrodynamics physics modules are combined to solve the equations of radiation-magnetohydrodynamics (RMHD) on block-adaptive finite volume Cartesian meshes in any dimensionality. Results. We introduce and validate several benchmark test cases such as steady radiative MHD shocks, radiation-damped linear MHD waves, radiation-modified Riemann problems and a multi-dimensional radiative magnetoconvection case. We recall the basic governing Rankine-Hugoniot relations for shocks and the dispersion relation for linear MHD waves in the presence of optically thick radiation fields where the diffusion limit is reached. The RMHD system allows for 8 linear wave types, where the classical 7-wave MHD picture (entropy and three wave pairs for slow, Alfven and fast) is augmented with a radiative diffusion mode. Conclusions. The MPI-AMRVAC code now has the capability to perform multidimensional RMHD simulations with mesh adaptation making it well-suited for larger scientific applications to study magnetized matter-radiation interactions in solar and stellar interiors and atmospheres.

A proposed Vera C. Rubin Observatory Deep Drilling micro-survey of the Kuiper Belt will investigate key properties of the distant solar system. Utilizing 30 hours of Rubin time across six 5-hour visits over one year starting in summer 2026, the survey aims to discover and determine orbits for up to 730 Kuiper Belt Objects (KBOs) to an $r$-magnitude of 27.5. These discoveries will enable precise characterization of the KBO size distribution, which is critical for understanding planetesimal formation. By aligning the survey field with NASA's {\it New Horizons} spacecraft trajectory, the micro-survey will facilitate discoveries for the mission operating in the Kuiper Belt. Modeling based on the Outer Solar System Origin Survey (OSSOS) predicts at least 12 distant KBOs observable with the {\it New Horizons} LOng Range Reconnaissance Imager (LORRI) and approximately three objects within 1~au of the spacecraft, allowing higher-resolution observations than Earth-based facilities. LORRI's high solar phase angle monitoring will reveal these objects' surface properties and shapes, potentially identifying contact binaries and orbit-class surface correlations. The survey could identify a KBO suitable for a future spacecraft flyby. The survey's size, depth, and cadence design will deliver transformative measurements of the Kuiper Belt's size distribution and rotational properties across distance, size, and orbital class. Additionally, the high stellar density in the survey field also offers synergies with transiting exoplanet studies.

Interactions play a significant role in the formation and evolution of galaxies in the Universe. The galaxy systems, NGC 7252 and NGC 5291 are two nearby interacting systems that are hosting Tidal Dwarf Galaxies (TDGs) and star-forming knots. The present work aims (a) To determine the attenuation-corrected star formation rate (SFR) of the interacting system NGC 7252 (b) To compare the star formation in the NGC 7252 system with that of the NGC 5291 system (c) To explore the relation between surface densities of gas and SFR in these two systems. The study utilises high-resolution FUV and NUV imaging data from the Ultraviolet Imaging Telescope (UVIT) on board AstroSat. Six star-forming regions, including the merger remnant, were identified in the NGC 7252 system. The SFR corrected for attenuation of the knots in the NGC 7252 system is determined using the continuum slope (\beta) calculated from the FUV-NUV colour. It has been observed that the attenuation-corrected SFR values of the knots in this system fall within the range of SFR values determined for the NGC 5291 knots. The TDGs in both systems adhere to the same Kennicutt-Schmidt (KS) relation as regular spiral galaxies.

The origin of Mercury still remains poorly understood compared to the other rocky planets of the Solar System. One of the most relevant constraints that any formation model has to fulfill refers to its internal structure, with a predominant iron core covered by a thin silicate layer. This led to the idea that it could be the product of a mantle stripping caused by a giant impact. Previous studies in this line focused on binary collisions involving bodies of very different masses. However, such collisions are actually rare in N-body simulations of terrestrial planet formation, whereas collisions involving similar mass bodies appear to be more frequent. Here, we perform smooth particle hydrodynamics simulations to investigate the conditions under which collisions of similar mass bodies are able to form a Mercury-like planet. Our results show that such collisions can fulfill the necessary constraints in terms of mass (0.055 $M_\oplus$) and composition (30/70 silicate-to-iron mass ratio) within less than 5%, as long as the impact angles and velocities are properly adjusted according to well established scaling laws.

We describe the basic instrument detrending software for the NIRWALS spectrograph on the SALT telescope. Its basic purpose is to process multiple non-destructive reads of increasing exposure time into a final image reflecting the observed source intensity as expressed in counts (or electrons) per second, including its uncertainty. The output products of this pipeline can then be used to as input for follow-up data processing to apply wavelength solutions and extract fluxes for individual fibers. All pipeline code is implemented in python and can be obtained via common portals such as PyPI and GitHub. Additional information on how to use the code is available online at this http URL

We perform a model-independent reconstruction of the angular diameter distance ($D_{A}$) using the Multi-Task Gaussian Process (MTGP) framework with DESI-DR1 BAO and DES-SN5YR datasets. We calibrate the comoving sound horizon at the baryon drag epoch $r_d$ to the Planck best-fit value, ensuring consistency with early-universe physics. With the reconstructed $D_A$ at two key redshifts, $z\sim 1.63$ (where $D_{A}^{\prime} =0$) and at $z\sim 0.512$ (where $D_{A}^{\prime} = D_{A}$), we derive the expansion rate of the Universe $H(z)$ at these redshifts. Our findings reveal that at $z\sim 1.63$, the $H(z)$ is fully consistent with the Planck-2018 $\Lambda$CDM prediction, confirming no new physics at that redshift. However, at $z \sim 0.512$, the derived $H(z)$ shows a more than $5\sigma$ discrepancy with the Planck-2018 $\Lambda$CDM prediction, suggesting a possible breakdown of the $\Lambda$CDM model as constrained by Planck-2018 at this lower redshift. This emerging $\sim 5\sigma$ tension at $z\sim 0.512$, distinct from the existing ``Hubble Tension'', may signal the first strong evidence for new physics at low redshifts.

The Fornax cluster is one of the most nearby X-ray bright galaxy clusters. Previous observations of the intracluster medium were limited to less than R500. We aim to significantly extend the X-ray coverage. We use data from five SRG/eROSITA all-sky surveys and perform a detailed one- and two-dimensional X-ray surface brightness analysis, allowing us to trace hot gas emission from kpc to Mpc scales with a single instrument. We compare the results to those from a recent numerical simulation of the local Universe (SLOW) and correlate the X-ray emission distribution with that of other tracers, including cluster member galaxies, ultra compact dwarf galaxies, intracluster globular clusters, and HI-tail galaxies. We detect X-ray emission out to well beyond the virial radius, R100=2.2 deg. We do not find obvious evidence for the bow shock several hundred kpc south of the cluster center predicted by previous numerical simulations of the Fornax cluster. Instead, we discover finger-like structures beyond R500 to the west and south-east that stretch out far beyond the virial radius. They might be due to gas being pushed outward by the previous merger with NGC 1404 or due to warm-hot gas infall along large-scale filaments. Intriguingly, we find the distributions of the other tracers -- galaxies and globular clusters -- to be correlated with the X-ray excess regions, favoring the latter infall scenario. Interestingly, we also discover an apparent Bridge of low surface brightness emission beyond the virial radius connecting to the Fornax A galaxy group, which is also traced by the member galaxy and globular cluster distribution. This X-ray Bridge furthermore approximately coincides with a region of enhanced Faraday depth detected previously. The gas distribution in the SLOW simulation shows similar features as those we have discovered with SRG/eROSITA.

With the aim of testing massive gravity in the context of black hole physics, we investigate the gravitational radiation emitted by a massive particle plunging into a Schwarzschild black hole from slightly below the innermost stable circular orbit. To do so, we first construct the quasinormal and quasibound resonance spectra of the spin-2 massive field for odd and even parity. Then, we compute the waveforms produced by the plunging particle and study their spectral content. This allows us to highlight and interpret important phenomena in the plunge regime, including (i) the excitation of quasibound states, with particular emphasis on the amplification and slow decay of the post-ringdown phase of the even-parity dipolar mode due to harmonic resonance; (ii) during the adiabatic phase, the waveform emitted by the plunging particle is very well described by the waveform emitted by the particle living on the innermost stable circular orbit, and (iii) the regularized waveforms and their unregularized counterparts constructed from the quasinormal mode spectrum are in excellent agreement. Finally, we construct, for arbitrary directions of observation and, in particular, outside the orbital plane of the plunging particle, the regularized multipolar waveforms, i.e., the waveforms constructed by summing over partial waveforms.

Building upon the recent findings regarding inverse phase transitions in the early universe, we present the first natural realisation of this phenomenon within a supersymmetry-breaking sector. We demonstrate that inverse hydrodynamics, which is characterized by the fluid being aspired by the bubble wall rather than being pushed or dragged, is actually not limited to a phase of (re)heating but can also occur within the standard cooling cosmology. Through a numerical analysis of the phase transition, we establish a simple and generic criterion to determine its hydrodynamics based on the generalised pseudo-trace. Our results provide a proof of principle highlighting the need to account for these new fluid solutions when considering cosmological phase transitions and their phenomenological implications.

We employ a covariant formalism to study the evolution of cosmological perturbations during a first-order phase transition, addressing in particular their gauge dependence that have been overlooked so far. Our results reveal that non-covariant treatments employed in previous studies can substantially overestimate the production of primordial black holes and scalar-induced gravitational waves. Once gauge dependencies are properly accounted for, we find that both effects occur at significantly lower levels than previously estimated.

In the framework of Einstein-scalar-Gauss-Bonnet (EsGB) gravity, we systematically study gravitational waves (GWs), first produced by remote compact astrophysical sources and then propagating through the flat homogeneous and isotropic Universe at cosmic distances before arriving at detectors. Assuming that the speed $c_T$ of the spin-2 graviton is the same as that of photons, we find explicitly the stability conditions of the theory and then obtain the severest observational constraint found so far. In particular, all these conditions and constraints are satisfied, provided that $0 \leq \alpha\dot{f}(\phi_0) \lesssim 8.97 \times 10^{-24}$ (km), where $\alpha{f}(\phi)$ denotes the coupling strength between the scalar field $\phi$ and the Gauss-Bonnet term, an over-dot represents the derivative with respect to the cosmic time, and $\phi_0$ is the present value of $\phi$. The trajectories for both spin-2 and spin-0 gravitons and the amplitudes of GWs along the trajectories are explicitly obtained. The amplitude of a spin-2 GW is practically indistinguishable from that of GR, while the spin-0 GWs remain almost constant during radiation- and matter-dominated epochs, and in the dark energy-dominated epoch it is proportional to the physical distance between the source and the observer. A careful analysis shows that the latter is due to the assumption $c_T = 1$. When $c_T \not= 1$ to the extent that is consistent with the stability conditions and observational constraints, the above behavior disappears.

We study classical background electric fields and the Schwinger effect in de Sitter space. We show that having a constant electric field in de Sitter requires the photon to have a tachyonic mass proportional to the Hubble scale. This has physical implications for the induced Schwinger current which affect its IR behaviour. To study this we recompute the Schwinger current in de Sitter space for charged fermions and minimally coupled scalars imposing a physically consistent renormalization condition. We find a finite and positive Schwinger current even in the massless limit. This is in contrast to previous calculations in the literature which found a negative IR divergence. We also obtain the first result of the Schwinger current for a non-minimally coupled scalar, including for a conformally coupled scalar which we find has very similar behaviour to the fermion current. Our results may have physical implications for both magnetogenesis and inflationary dark matter production.

Cuscuton Gravity is characterized as a scalar field that can be added to general relativity without introducing any new dynamical degrees of freedom on a cosmological background. Yet, it modifies gravity such that spacetime singularities can be avoided. This has led to the Cuscuton bounce, a nonsingular cosmology that has been shown to be linearly stable, which is a rare feat. Upon introducing mechanisms known to generate a near-scale-invariant power spectrum of isocurvature perturbations in the prebounce contracting phase, we perform an extensive linear analysis of all scalar perturbations as they evolve through the Cuscuton bounce, both analytically and numerically. Then, after deriving the third-order perturbed action for our theory, we compare the magnitude of its terms (on shell) to those in the second-order action. We show that perturbativity is maintained in the infrared throughout the evolution, including through the bounce. In the ultraviolet, we show that a hierarchy of scales is maintained, with the strong coupling scale well above the relevant background energy scale at all times. We reconfirm these results by computing the three-point functions in various limits and demonstrate that the models do not have any strong coupling problems and furthermore that there is negligible non-Gaussianities on observable scales. Consequently, the primary potential source of observable non-Gaussianities may only arise from the conversion of isocurvature perturbations to curvature perturbations. The whole scenario is thus a robust, stable, weakly coupled nonsingular cosmological model, consistent with observations.

Scientific discoveries are often made by finding a pattern or object that was not predicted by the known rules of science. Oftentimes, these anomalous events or objects that do not conform to the norms are an indication that the rules of science governing the data are incomplete, and something new needs to be present to explain these unexpected outliers. The challenge of finding anomalies can be confounding since it requires codifying a complete knowledge of the known scientific behaviors and then projecting these known behaviors on the data to look for deviations. When utilizing machine learning, this presents a particular challenge since we require that the model not only understands scientific data perfectly but also recognizes when the data is inconsistent and out of the scope of its trained behavior. In this paper, we present three datasets aimed at developing machine learning-based anomaly detection for disparate scientific domains covering astrophysics, genomics, and polar science. We present the different datasets along with a scheme to make machine learning challenges around the three datasets findable, accessible, interoperable, and reusable (FAIR). Furthermore, we present an approach that generalizes to future machine learning challenges, enabling the possibility of large, more compute-intensive challenges that can ultimately lead to scientific discovery.

We present an evaluation of how site dependent noise can affect the signal to noise ratio (SNR) of compact binary coalescence (CBC) signals in the future 3rd generation gravitational wave (GW) detector Einstein Telescope (ET). The design of ET is currently pushing the scientific community to study its scientific potential with respect to known, and possibly unexpected, GW signals using its design sensitivity curves. However, local ambient noise may have an impact on the ET sensitivity at low frequency and therefore affect the SNR of CBC signals at low frequency. Therefore, we study the impact of ambient noise on the ET sensitivity curve at the two sites candidate to host ET - Sardinia, in Italy, and the Euregio Meuse-Rhine (EMR) at the Netherlands-Belgium border - and infer the impact on the ET sensitivity curve and how the SNR of CBC signals at low frequencies is affected. We find that Sardinia shows results which are on par, if not better, than the design case. On the other hand, ambient noise for the current EMR sensitivity curve in Terziet causes a higher degradation of the SNR performances.

Recent observations of the supermassive black holes M87* and Sgr A* by the Event Horizon Telescope (EHT) have opened new avenues for testing gravity theories through black hole shadow observables. These observations offer a means to distinguish between general relativity and modified gravity theories while providing insights into the astrophysical properties of the observed black holes. In this work, we investigate photon orbits and shadow characteristics of rotating black holes within the Einstein-$\mathrm{SU(N)}$ nonlinear sigma model. We first analyze the static, spherically symmetric black hole solution, focusing on its asymptotically Anti-de Sitter behavior and causal structure. The Modified Newman-Janis Algorithm is then applied to obtain the rotating counterpart, followed by an examination of its geometric properties, ergoregions, and causal structure. Utilizing the Lagrangian formalism, we derive the equations of motion for photons and study the resulting black hole shadow on the celestial plane. We explore the dependence of the shadow's size and shape on the black hole parameters $K$ and $N$, imposing constraints using EHT observational data for M87* and Sgr A*. Finally, we analyze the black hole's evaporation rate under different scenarios.

When a gravitational wave signal encounters a massive object, such as a galaxy or galaxy cluster, it undergoes strong gravitational lensing, producing multiple copies of the original signal. These strongly lensed signals exhibit identical waveform morphology in the frequency domain, allowing analysis without the need for complex lens models. However, stellar fields and dark matter substructures within the galactic lens introduce microlensing effects that alter individual signal morphologies. Identifying these microlensing signatures is computationally challenging within Bayesian frameworks. In this study, we propose a novel residual test to efficiently search for microlensing signatures by leveraging the fact that current Bayesian inference pipelines are optimized solely for the strong lensing hypothesis. Using cross-correlation techniques, we investigate the microlensing-induced deviations from the strong hypothesis, which are imprinted in the residuals. Our simulated signals from realistic microlensing populations reveal that while most events exhibit small mismatches, a fraction exhibit significant deviations. We find that 31% (55%) and 45% (65%) of microlensed events with mismatch > 0.03 and > 0.1, respectively, can be discerned with O4 (O5) detector sensitivities, which demonstrates that high-mismatch events are more likely to be identified as microlensed. Including all events from a realistic population, 12% (21.5%) are identifiable with O4 (O5) sensitivity using our approach.

In this paper, we investigate the logarithmic divergence of the deflection angle in the strong deflection limit in static, spherically symmetric spacetimes. We propose a novel analytical framework that connects its physical origin to local, coordinate-invariant geometric quantities and properties of the matter distributions. Conventional approaches describe the divergence rate, characterized by the coefficient $\bar{a}$, in terms of coordinate-dependent metric functions. In contrast, our method relates $\bar{a}$ to the components of the Einstein tensor in an orthonormal tetrad adapted to the spacetime symmetry. By employing the Einstein equations, we express $\bar{a}$ in terms of the local values of energy density $\rho_{\mathrm{m}}$ and tangential pressure $\Pi_{\mathrm{m}}$ at the photon sphere with an areal radius $R_{\mathrm{m}}$: \begin{align*} \bar{a}=\frac{1}{\sqrt{1-8\pi R_{\mathrm{m}}^2\left(\rho_{\mathrm{m}}+\Pi_{\mathrm{m}}\right)}}. \end{align*} This formula clearly shows that, through the combination $\rho_{\mathrm{m}}+\Pi_{\mathrm{m}}$, the strong field limit coefficient $\bar{a}$ depends on the local matter distribution. In particular, if the matter fields satisfy $\rho+\Pi=0$, the universal result $\bar{a}=1$ emerges. This finding not only accounts for the behavior observed in the Schwarzschild spacetime but also provides a unified description applicable to a variety of spacetimes, including certain naked singularities and wormholes supported by a massless scalar field. Furthermore, these local properties are reflected in the frequencies of quasinormal modes, suggesting a profound connection between strong gravitational lensing and the dynamical response of gravitational wave signals. Our framework, independent of any specific gravitational theory, serves as a universal tool for testing gravitational theories and interpreting astrophysical observations.

We demonstrate that if the universe started as a vacuum fluctuation rather than from a singular Big Bang state, the universe must have a late-time cosmic acceleration. This is required by a ``cosmological sum rule'' derived using the Schwarzian form of the Friedmann equations. We discuss possible connections to conformal and Möbius transformations, and also compute that the best fit present cosmic data is consistent with the necessary crossing of the Schwarzian through zero having occurred (while it would not yet have happened in a $\Lambda$CDM cosmology).

We develop a quantum theory of inflaton and its decay product of various gauge boson pairs to investigate the preheating towards thermalized universe. The inflaton decay into gauge-boson pairs is shown to be inevitably accompanied by tachyon-mass-like correction to inflation potential that ultimately leads to an inflaton escape out of trapped local potential minimum towards the field infinity. This gives rise to a conversion mechanism of early inflationary acceleration to a quintessence dark energy acceleration at late stages of cosmic evolution. The success of the escape depends on how standard particles are incorporated into a scheme of extended Jordan-Brans-Dicke gravity. New types of super-radiance mechanism that enhance the ending of preheating are identified and compared with the Dicke model.

For space-borne gravitational wave detectors,such as LISA and TianQin ,the disturbance caused by the coupling of test masses and the external magnetic fields is one of the main sources of the residual acceleration noise. Although the detection frequency band is from 0.1 mHz to 1 Hz, magnetic fields with frequencies higher than 1 Hz can still contribute to the noise through down conversion effect. Therefore, it is necessary to measure the AC magnetic susceptibility or magnetic response of the test mass at higher frequency for the evaluation of the magnetic noise. In this work, we propose a magnetic field response measurement method by directly probing the induced magnetic field of the test mass placed in a spatially uniform magnetic field. The frequency can be measured up to 1500 Hz, satisfying the requirement of space-borne gravitational wave detection.

We present a minimal setup within the framework of Horndeski gravity that can describe a nonpathological Genesis scenario. Our setup allows for a fully stable transition to the kination epoch, during which General Relativity (GR) is restored. This Genesis scenario circumvents the no-go theorem at the cost of encountering the risk of strong coupling in the past. Interestingly, our scenario admits two different regimes for the background solution for Hubble parameter at the Genesis stage: power-law behavior and manifestly non-power-law behavior. We explicitly show that, in both regimes, our model remains within unitarity bounds. In most cases, the tensor spectrum is blue-tilted. Then, we adopt a mechanism with a spectator field that allows for a red-tilted scalar power spectrum. We also suggest a deformation of the model that enables us to achieve sufficiently small values for the r ratio. Finally, we discuss the geodesic (in)completeness of the current model.

String-inspired models are often believed to provide an interesting framework for quantum gravity and force unification with promising prospects to resolve issues like dark matter and dark energy which cannot be satisfactorily incorporated within the framework of general relativity (GR). The goal of the present work is to investigate the role of the Einstein-Maxwell dilaton-axion (EMDA) gravity arising in the low energy effective action of the heterotic string theory in explaining astrophysical observations, in particular, the high-frequency quasi-periodic oscillations (HFQPOs) observed in the power spectrum of black holes. EMDA gravity has interesting cosmological implications and hence it is worthwhile to explore the footprints of such a theory in available astrophysical observations. This requires one to study the stationary, axi-symmetric black hole solution in EMDA gravity, which corresponds to the Kerr-Sen spacetime. Such black holes are endowed with a dilatonic charge while the rotation is sourced from the axionic field. We investigate the orbital and epicyclic frequencies of matter rotating in the Kerr-Sen spacetime and consider eleven well-studied QPO models in this work. We compare the model dependent QPO frequencies with the available observations of five BH sources, namely, XTE J1550-564, GRS 1915+105, H 143+322, GRO J1655-40 and Sgr A*. Our analysis provides constrains on the spins of the aforesaid black holes which when compared with previous estimates enables us to understand the observationally favored QPO models for each of these sources. Further, from the current data the EMDA scenario cannot be ruled out in favor of general relativity. We comment on the implications and limitations of our finding and how the present constrains compare with the existing literature.