Papers for Thursday, Sep 04 2025

Vision-Language Models (VLMs), such as recent Qwen and Gemini models, are positioned as general-purpose AI systems capable of reasoning across domains. Yet their capabilities in scientific imaging, especially on unfamiliar and potentially previously unseen data distributions, remain poorly understood. In this work, we assess whether generic VLMs, presumed to lack exposure to astronomical corpora, can perform morphology-based classification of radio galaxies using the MiraBest FR-I/FR-II dataset. We explore prompting strategies using natural language and schematic diagrams, and, to the best of our knowledge, we are the first to introduce visual in-context examples within prompts in astronomy. Additionally, we evaluate lightweight supervised adaptation via LoRA fine-tuning. Our findings reveal three trends: (i) even prompt-based approaches can achieve good performance, suggesting that VLMs encode useful priors for unfamiliar scientific domains; (ii) however, outputs are highly unstable, i.e. varying sharply with superficial prompt changes such as layout, ordering, or decoding temperature, even when semantic content is held constant; and (iii) with just 15M trainable parameters and no astronomy-specific pretraining, fine-tuned Qwen-VL achieves near state-of-the-art performance (3% Error rate), rivaling domain-specific models. These results suggest that the apparent "reasoning" of VLMs often reflects prompt sensitivity rather than genuine inference, raising caution for their use in scientific domains. At the same time, with minimal adaptation, generic VLMs can rival specialized models, offering a promising but fragile tool for scientific discovery.

Intensity Mapping (IM) of the 21-cm line of the neutral hydrogen (\textsc{Hi}) has become a compelling new technique to map the large-scale structure of the Universe. One of the main challenges is the presence of strong foreground emissions of several orders of magnitude larger than the \textsc{Hi}~signal. Here, we implement a version of the Principal Component Analysis, a blind component-separation technique, based on a kind of spherical wavelets called needlets. These functions exploit double localization both in real and in harmonic space. We test Need-PCA performances on a set of maps that simulates the SKA MID radio telescope in the AA4 configuration. We compare our results with other component separation methods such as Generalised Morphological Component Analysis (GMCA) and Generalized Needlet Internal Linear Combination (GNILC). All the methods have comparable results, recovering the \textsc{Hi}~signal within 10\% accuracy across the frequency channels, in the multipole range 30 $\lesssim \ell \lesssim$ 136. We also test our pipeline in the presence of systematics such as polarization leakage. We find that the cleaning methods are insensitive to the presence of such systematic, yielding the same results as in the leakage-free case.

Fast radio bursts (FRBs) are short-duration and energetic radio transients of unknown origin. Observationally, they are commonly categorized into repeaters and non-repeaters. However, this binary classification may be influenced by observational limitations such as sensitivity and time coverage of telescopes. In this work, we employ unsupervised machine learning techniques to re-examine the CHIME/FRB catalog, with the goal of identifying intrinsic groupings in the FRB population without relying on preassigned labels. Using t-distributed stochastic neighbor embedding (t-SNE) for dimensionality reduction and hierarchical density-based spatial clustering of applications with noise (HDBSCAN) for clustering, we find that the FRB sample separates naturally into two major clusters. One cluster contains nearly all known repeaters but is contaminated by some apparently non-repeaters, while the other cluster is dominated by non-repeaters. This suggests that certain FRBs previously labeled as non-repeaters may share intrinsic similarities with repeaters. The mutual information analysis reveals that rest-frame frequency width and peak frequency are the most informative features governing the clustering structure. Even when reducing the input space to just these two features, the classification remains robust.

This white paper explores the potential for strategic synergies between the JWST and the Ariel telescopes, two flagship observatories poised to revolutionise the study of exoplanet atmospheres. Both telescopes have the potential to address common fundamental questions about exoplanets-especially concerning their nature and origins-and serve a growing scientific community. With their operations now anticipated to overlap, starting from 2030, there is a unique opportunity to enhance the scientific outputs of both observatories through coordinated efforts. In this report, authored by the Ariel-JWST Synergy Working Group, part of the Ariel Consortium Science Team, we summarise the capabilities of JWST and Ariel; we highlight their key differences, similarities, synergies, and distinctive strengths. Ariel is designed to conduct a broad survey of exoplanet atmospheres but remains highly flexible, allowing the mission to integrate insights from JWST's discoveries. Findings from JWST, including data from initiatives shaped by NASA's decadal survey priorities and community-driven research themes, will inform the development of Ariel's core survey strategy. Conversely, Ariel's ability to perform broad-wavelength coverage observations for bright targets provides complementary avenues for exoplanet researchers, particularly those interested in time-domain observations and large-scale atmospheric studies. This paper identifies key pathways for fostering JWST-Ariel synergies, many of which can be initiated even before Ariel's launch. Leveraging their complementary designs and scopes, JWST and Ariel can jointly address fundamental questions about the nature, formation, and evolution of exoplanets. Such strategic collaboration has the potential to maximise the scientific returns of both observatories and lay the foundation for future facilities in the roadmap to exoplanet exploration.

A generic prediction of particle dark matter theories is that a large population of dark matter substructures should reside inside the host haloes of galaxies. In gravitational imaging, strong gravitational lens observations are used to detect individual objects from this population, if they are large enough to perturb the strongly lensed images. We show here that low-mass haloes, below the individually detectable mass limit, have a detectable effect on the lensed images when in large numbers, which is the case in cold dark matter (CDM). We find that, in CDM, this population causes an excess of 40 per cent in the number of detected subhaloes for HST-like strong lens observations. We propose a pseudo-mass function to describe this population, and fit for its parameters from the detection data. We find that it mostly consists of objects two orders of magnitude in mass below the detection limit of individual objects. We show that including this modification, so that the effect of the population is correctly predicted, can dramatically improve the available constraints on dark matter from strong lens observations. We repeat our experiments using models that contain varying amounts of angular structure in the lens galaxy. We find that these multipole perturbations are strongly degenerate with the population signal, to an even greater extent than with individual subhaloes. This further highlights the need for better understanding of the angular mass structure of lens galaxies, so that the maximum information can be extracted from strong lens observations for dark matter inference.

The James Webb Space Telescope (JWST) has revealed a previously unknown population of compact, red galaxies at $z \sim 5$, known as "Little Red Dots" (LRDs). With effective radii of $\sim 100$ pc and stellar masses of $10^9-10^{11} \, \rm M_\odot$, a purely stellar interpretation implies extreme central densities, $\rho_\star\sim10^4-10^5 \, \rm M_\odot \, pc^{-3}$ and in some cases up to $\sim 10^9 \, \rm M_\odot \, pc^{-3}$, far exceeding those of globular clusters. At such densities, the dynamical friction time for $10 \, \rm M_\odot$ stars in the central $0.1$ pc is $< 0.1$ Myr, driving rapid mass segregation. We investigate the dynamical consequences of such an environment using: (i) a Fokker-Planck analysis of long-term core evolution, (ii) an analytical model for the collisional growth of a very massive star (VMS), and (iii) direct $N$-body simulations. All approaches show that runaway collisions produce a VMS with mass $9\times10^3 < M_{\rm VMS} \, [\rm M_\odot] < 5\times10^4$ within $<1$ Myr. Once the supply of massive stars is depleted, the VMS contracts on a $\sim 8000$ yr Kelvin-Helmholtz timescale and undergoes a general relativistic collapse, leaving a massive black hole of mass $M_\bullet \sim 10^4 \, \rm M_\odot$. We conclude that LRDs are natural nurseries for the formation of heavy black hole seeds via stellar-dynamical processes. This pathway produces seed number densities that far exceed those expected from direct collapse models, and, owing to the dense residual stellar core, can sustain high rates of tidal disruption events.

We present and analyze follow-up, higher resolution ($R$ $\sim$ 70) $H$ and $K$ band integral field spectroscopy of the superjovian exoplanet HIP 99770 b with SCExAO/CHARIS. Our new data recover the companion at a high signal-to-noise ratio in both bandpasses and more than double the astrometric baseline for its orbital motion. Jointly modeling HIP 99770 b's position and the star's astrometry from \textit{Hipparcos} and \textit{Gaia} yields orbital parameters consistent with those from the discovery paper, albeit with smaller errors, and a slight preference for a smaller semimajor axis ($\sim$15.7--15.8 au)and a larger eccentricity ($\sim$0.28--0.29), disfavoring a circular orbit. We revise its dynamical mass slightly downwards to 15.0$_{-4.4}^{+4.5}$ $M_{\rm Jup}$ for a flat prior and 13.1$_{-5.2}^{+4.8}$ $M_{\rm Jup}$ for a more standard log-uniform mass prior, where the inclusion of its relative radial-velocity measurement is primarily responsible for these changes. \textcolor{red}{We find consistent results for HIP 99770 b's dynamical mass including recent VLTI/GRAVITY astrometry, albeit with a slightly smaller, better constrained eccentricity of $e$ $\sim$ 0.22$^{+0.10}_{-0.13}$}. HIP 99770 b is a $\sim$ 1300 K object at the L/T transition with a gravity intermediate between that of the HR 8799 planets and older, more massive field brown dwarfs with similar temperatures but with hints of equilibrium chemistry. HIP 99770 b is particularly well suited for spectroscopic follow up with Roman CGI during the technology demonstration phase at 730 nm to further constrain its metallicity and chemistry; JWST thermal infrared observations could likewise explore the planet's carbon chemistry, metallicity, and clouds.

Although hot Jupiters were the first exoplanets discovered orbiting main sequence stars, the dominant mechanisms through which they form and evolve are not known. To address the questions surrounding their origins, the Migration and Evolution of giant ExoPlanets (MEEP) survey aims to create a complete, magnitude-limited ($G<$12.5) sample of hot Jupiters that can be used to constrain the frequency of different migration pathways. NASA's Transiting Exoplanet Survey Satellite provides the unique combination of sky-coverage and photometric precision to achieve this goal, which will likely be a key result of the mission. In this second installment of the MEEP survey, we reanalyze one benchmark hot Jupiter system, TOI-4138, and discover four additional super-Jupiters which are each more than five times as massive as Jupiter: TOI-4773 b, TOI-5261 b, TOI-5350 b, and TOI-6420 b. One of these planets, TOI-5261 b, is 11.49 times the mass of Jupiter, nearly massive enough to ignite deuterium fusion, and has an eccentric ($e = 0.1585$) orbit. TOI-4138, TOI-4773, TOI-5350, and TOI-6420 each have lithium absorption features in their spectra. TOI-4138 is an F-type subgiant with a lithium equivalent width of $120. \pm 13$ mÅ, which is $\sim 4.5\sigma$ larger than the median lithium equivalent width of a control sample of 1381 similar stars, making TOI-4138 a compelling candidate for planetary engulfment.

Mass loss is a key physical process in the evolution of massive stars, the impact of which propagates into galactic evolution, population synthesis models, the interpretation of high-redshift galaxies, and explosive events such as supernovae. However, there are currently substantial uncertainties in the low-metallicity, low-luminosity thin wind regime where classical diagnostics (H-alpha and ultraviolet, UV, P Cygni profiles) yield wind momenta that are 1 to 2 orders of magnitude below prescriptions implemented by default in most evolutionary models. Here, we present spectra of the mass-loss diagnostic line Br-alpha in 15 OB-type stars in the Small Magellanic Cloud obtained using the Near Infrared Spectrograph on the James Webb Space Telescope. The line profile morphology, recovered by virtue of the outstanding signal-to-noise ratio of the data and the avoidance of regions with nebular emission, is consistent with predictions based on previous mass-loss rate estimates from optical and UV spectroscopy. Moreover, an initial spectroscopic analysis of sources covering the thin wind regime confirms the low mass-loss rates, indicates a change of slope in the wind-momentum-luminosity relation in this regime with respect to high-luminosity objects, and strengthens the abovementioned discrepancies with commonly used wind-momentum prescriptions.

About one in five white dwarfs undergoes spectral evolution from a helium atmosphere to hydrogen and then back to helium. These short-lived hydrogen envelopes - the result of residual hydrogen diffusion - are eventually destroyed by either hydrogen or helium convection. An emerging class of double-faced white dwarfs seems to catch this process in the act, with varying amounts of hydrogen across regions of the stellar surface. Here, we quantitatively test the hypothesis that these inhomogeneities are the result of the magnetic inhibition of convection. We compute the critical magnetic field $B_{\rm crit}(M,T_{\rm eff})\sim\sqrt{8\pi P}$ required to inhibit convection in both hydrogen and helium for $0.6-1.2\,M_\odot$ white dwarfs, where $P$ is the pressure at the base of the convection zone. When incorporating the magnetic field consistently into the stellar structure even at high pressures $P>B^2/(8\pi)$, we find that most of the measured magnetic fields $B$ of observed double-faced white dwarfs satisfy $B_{\rm crit}^{\rm H}\lesssim B\lesssim B_{\rm crit}^{\rm He}$, such that the magnetic inhibition of either hydrogen or helium convection could potentially explain the observations. Specifically, order of unity variations in the magnetic field's strength or orientation across the surface could account for the double-faced nature of these stars.

We investigate the origin of intervening cool MgII absorption detected in the spectra of background quasars and the nature of associated galaxies across a broad redshift range of $0.3 \le z \le 1.6$. Using nebular [O II] $\lambda\lambda$3727,3729 emission lines identified in DESI fiber spectra centered on quasar, we detect 377 galaxies at a typical detection rate of $\sim$0.45% at $z \lesssim 1$, which increases with MgII equivalent width ($W_{2796}$). A significant fraction (74%) of these galaxies are associated with strong absorbers with $W_{2796} \ge$ 2Å. These absorbers trace galaxies spanning stellar masses of $\rm 8.4 \le \log(M_{\star}/M_{\odot}) \le 11.6$ and star formation rates (SFRs) of $\rm -1.2 \le log(SFR~[M_{\odot}yr^{-1}]) \le 2.7$, located at projected galactocentric distances of 4-24 kpc. We find the average MgII absorber strength increases from 2.1Å to 2.9Å between redshifts $z \sim$ 0.4 and 1.2, indicating evolution in the cool gas content of galaxy halos. The relatively constant absorber strength with galactocentric distance implies a clumpy structure of cool gas in the circumgalactic medium (CGM). Further, we find a positive correlation between $W_{2796}$ versus $M_\star$, and SFR, suggesting that the distribution of metal-enriched cool gas in the CGM is closely tied to the properties of the host galaxies. The redshift evolution of gas-phase metallicity suggests that strong MgII absorbers trace the general population of star-forming galaxies. The velocity dispersion of the cool gas increases with halo mass, and the wide range of line of sight velocity offset (-389 to 364 $\rm km\ s^{-1}$) between the galaxy systemic velocity and absorbers highlights the dynamical nature of CGM. However, the majority of this gas remains gravitationally bound to the dark matter halos, consistent with a picture of gas recycling via galactic fountains.

Globular clusters (GCs) host complex stellar populations whose chemical signatures imply early retention and reprocessing of stellar ejecta, yet direct evidence for intracluster gas is lacking. Here we present a unified theoretical framework for the accumulation, fate, and eventual removal of gas released by evolved stars in young GCs, and their implications for the production of multiple stellar populations. Using MIST stellar evolution tracks, we show that low-velocity (< 20 km/s) AGB winds, each released over 10^4 yr, are gravitationally retained in >10^5 MSun clusters. In addition, AGB winds in such clusters collide with each other and the previously retained winds, triggering a rapid `switch' to efficient gas retention. Expected gas retention fractions, mapped across cluster initial mass and size, agree well with the observed second population fractions in Milky Way GCs. We then show that the accumulated gas cannot form new stars because protostellar cores are disrupted by encounters with pre-existing stars over 1 - 10 kyr. Instead, the gas is accreted onto pre-existing main-sequence stars and compact objects. Bondi-Hoyle accretion and time-dependent core-halo models indicate that both white dwarfs and neutron stars can grow and collapse within a few 100 Myr, and that lower-mass main-sequence stars can be `rejuvenated' into the 4 - 6 MSun range required to reproduce key abundance patterns. Therefore, in our model, the multiple populations will be found in sufficiently massive clusters, with the second-population stars being formed from the inner subset of first-population stars that accreted large fractions of their mass from the AGB-processed retained gas. Finally, we argue that a combination of feedback processes will clear the gas by 10^9 yr, thus reproducing the gas-poor conditions observed for present-day clusters.

We report the first detection of gamma-ray emission from an explosive dispersal outflow in the Milky Way, revealing a new source class of high-energy emission. Using 15 years of Fermi-LAT data in the 0.2 $-$ 500 GeV range, we detect a significant ($ > 35\sigma $) $\gamma$-ray emission spatially coincident with the DR21 outflow, located at a distance of 1.5 kpc in the Cygnus-X star-forming region. The spectrum follows a power-law plus an exponential cutoff model with a spectral index $\Gamma = 2.08\pm0.02$ and $E_{\rm c} = 10089 \pm 2963$~MeV, integrating which we estimate a total $\gamma$-ray luminosity $L_{\gamma} \simeq (2.17\pm 0.15) \times 10^{35}$ erg s$^{-1}$ in the $0.1-500$ GeV band. This $\gamma$-ray emission is spatially coincident with additional multiwavelength data, including allWISE mid-IR and regions of dense gas. By comparing the observed $\gamma$-ray luminosity to the estimated kinetic energy of the outflow inferred from prior studies of DR21, we find that $\leq 15\%$ of the kinetic power of the outflow goes into particle acceleration. Our findings demonstrate that explosive dispersal outflows can contribute significantly to the diffuse $\gamma$-ray background of the Galaxy, highlighting their importance as particle accelerators in star-forming environments.

For one of the first set of Roman Coronagraph project images, we propose to target AB Aurigae. AB Aurigae is a complex and visually stunning system, surrounded by a gas rich protoplanetary disk showing numerous spiral arms, an enigmatic embedded protoplanet (AB Aurigae b) at 0\farcs{}6 separation, and hints of potential additional sites of planet formation. Even a marginally-successful dark hole generation (e.g. 10$^{-5}$--10$^{-6}$ contrast) with CGI would yield a vastly improved view of AB Aur b at optical wavelengths where current ground-based and HST data struggle to yield a high SNR detection and parameters (astrometry, photometry) unbiased by processing artifacts. Total intensity imaging and polarimetry together will provide new constraints on the disk's dust properties and the range of emission sources for AB Aur b. AB Aur images with the Roman Coronagraph will provide a striking, inspiring demonstrations of the instrument's power and promise for detecting fainter planets and disks.

We study the gravitational dynamics of quasi-hierarchical triple systems, where the outer orbital period is significantly longer than the inner one, but the outer orbit is extremely eccentric, rendering the time at pericentre comparable to the inner period. Such systems are not amenable to the standard techniques of perturbation theory and orbit-averaging. Modelling the evolution of these triples as a sequence of impulses at the outer pericentre, we show that such triples lend themselves to a description as a correlated random walk of the inner binary's eccentricity and angular-momentum vector, going beyond the von Zeipel-Lidov-Kozai mechanism. The outer orbit is seen to excite the inner eccentricity arbitrarily close to unity, eventually. These quasi-hierarchical triples constitute, therefore, a natural mechanism for creating highly eccentric binaries. We discuss applications for gravitational-wave mergers engendered by this process, and show that for a large portion of the parameter space, the time-to-coalescence is significantly reduced.

The relationship between Type Ia supernovae (SNe Ia) and their host galaxy stellar masses is well documented. In particular, Hubble residuals display a luminosity shift based on host mass, known as the mass step, which is often used as an extra correction in the standardisation of SN Ia luminosities. Here we investigate Hubble residuals and the mass step in the context of Si II $\lambda 6355$ velocities, using 277 near-peak SNe Ia from ZTF DR2. We divide the sample into high-velocity (HV) and normal-velocity (NV) SNe Ia, separated at 12,000 km/s, resulting in 70 HV and 207 NV objects. We then examine links between Si II $\lambda$6355 velocities, light-curve stretch $x_{1}$, colour $c$, and host properties to explore potential environmental and/or progenitor-related effects. Although we only find a marginal difference between the Hubble residuals of HV and NV SNe Ia, the NV mass step is $0.149 \pm 0.024$ mag ($6.3\sigma$), while HV SNe Ia show $0.046 \pm 0.041$ mag ($1.1\sigma$), consistent with zero. The NV-HV mass-step difference is $\sim 2.2\sigma$. The clearest subtype difference is seen in central regions ($d_{DLR} < 1$), where NV SNe Ia show a strong mass step but HV SNe Ia none, yielding a $3.1-3.6\sigma$ difference. A host-colour step appears for both: NV $0.142 \pm 0.024$ mag ($5.9\sigma$) and HV $0.158 \pm 0.042$ mag ($3.8\sigma$). Overall, NV and HV colour steps are consistent. HV SNe Ia show modest ($\sim 2.5$-$3\sigma$) steps in outer regions ($d_{DLR} > 1$), while NV SNe show stronger environmental trends. Thus, NV SNe Ia appear more environmentally sensitive, especially in central, likely metal-rich and older regions, while HV SNe Ia show weaker, subset-dependent trends, and applying a universal mass-step correction could introduce biases. Refined classifications or environment-dependent factors may improve future cosmological analyses beyond standard $x_{1}$ and $c$ cuts.

The Milky Way's (MW's) star formation history (SFH) offers insight into the chronology of its assembly and the mechanisms driving its structural development. In this study, we present an inference and analysis of the spatially resolved SFH and the MW disc growth. Our approach leverages both stellar birth radii estimates and the complete reconstruction of the MW stellar disc using a novel orbit superposition method from APOGEE data, allowing us to trace the orbit-mass weighted SFH based on formation sites while taking into account stellar mass loss. We find that the MW is a typical disc galaxy exhibiting inside-out formation: it was compact at $z > 2$ ($\rm R_{\rm eff} \approx 2$ kpc), had a peak in its star formation rate (SFR) 9--10 Gyr ago, and grew to a present-day size of $\rm R_{\rm eff} \approx 4.3$ kpc. A secondary peak in SFR $\sim 4$ Gyr ago is responsible for the onset of the outer disc, which comprises the metal-poor, low-$\alpha$ population. We find that in-situ star formation in the solar neighbourhood started 8--9 Gyr ago. The MW disc is characterised by a negative mean age gradient, as the result of the inside-out growth, with additional flattening induced by stellar radial migration. Our work showcases the importance of accounting for radial migration and stellar sample selection function when inferring the SFH and build-up of the MW disc.

We exploit the most robust, old, and cosmology-independent age estimates of individual stars from Gaia DR3 to place a lower bound on the age of the Universe, $t_U$. These constraints can serve as an anchor point for any cosmological model, providing an upper limit to the Hubble constant $H_0$. We consider the stellar age catalog of arXiv:2402.00561, selecting 3,000 of the oldest and most robustly measured main sequence turn-off (MSTO) and subgiant branch (SGB) stars, with ages $>12.5$ Gyr and associated error $<1$ Gyr. Ages are derived via isochrone fitting using the Bayesian code StarHorse, spanning the uniform range 0-20 Gyr, not assuming any cosmological prior on $t_U$. With a conservative cut in the Kiel diagram, strict quality cuts both on stellar parameters and posterior shapes, and removing potential contaminants, we isolate a final sample of 160 bona-fide stars, representing the largest sample of precise and reliable MSTO and SGB stars ages available to date. The age distribution of the final sample peaks at $13.6 \pm 1.0$ (stat) $\pm 1.3$ (syst) Gyr. Assuming a maximum formation redshift for these stars of $z_f = 20$ (a formation delay of $\sim$0.2 Gyr), we obtain a lower bound on $t_U$ of $t_U \geq 13.8 \pm 1.0$ (stat) $\pm 1.3$ (syst) Gyr. Considering the $10^{th}$ percentile of each star's posterior distributions, we find that, at 90% CL (stat), 70 stars favour $t_U > 13$ Gyr, while none exceeds 14.1 Gyr. An oldest age younger than 13 Gyr for this sample is incompatible with the data, even considering the full systematic error budget. This work presents the first statistically significant use of individual stellar ages as cosmic clocks, opening a new, independent approach for cosmological studies. While this already represents a major step forward, future Gaia data releases will yield even larger and more precise stellar samples, further strengthening these constraints.

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

We study an overpopulated gas of gravitationally interacting bosons surrounding a droplet of Bose-Einstein condensate - Bose star. We argue that kinetic evolution of this gas approaches with time a self-similar attractor solution to the kinetic equation. If the scale symmetry of the equation is broken by external conditions, the attractor solution exists, remains approximately self-similar, but has slowly drifting scaling dimension. The latter new regime of adiabatic self-similarity can determine growth of dark matter Bose stars in cosmological models.

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

Cosmic ray (CR) feedback in galaxy evolution has seen a theoretical resurgence in the past decade, but significant uncertainties remain in CR transport through the interstellar and circum-galactic media (ISM and CGM). While several works indicate CR effects may be notable in both star-forming and quenched massive galaxies, modeling the vast CR transport parameter space currently allowed by observations is computationally restrictive to survey. Analytic treatments of CR feedback have provided useful insights to potential ramifications in different regimes, but have relied on time-steady assumptions which may not well characterize CR effects at different cosmic epochs and galaxy mass scales. We present semi-analytic and numerical solutions describing the time-dependent evolution of CR pressure in the CGM under simplified assumptions, which allow for quick evaluation of the vast allowable CR transport parameter space. We demonstrate that time-dependent injection from bursty star formation and/or episodic black hole accretion can substantially alter CR pressure profiles, particularly in the outer halos of massive galaxies ($\gtrsim R_{vir}$). Our work further suggests that CR feedback may play a significant role in shaping the matter distribution around massive galaxies ($\gtrsim M_{\textrm{halo}} \sim 10^{13} M_\odot$), and we speculate that these time-dependent effects may connect to observed phenomena like ``Odd Radio Circles". Finally, we benchmark our semi-analytic formalism against a cosmic ray-magnetohydrodynamic (CR-MHD) cosmological zoom-in galaxy simulation directly modeling the CR scattering rate and emergent transport in full generality, highlighting the validity of our approach. We conclude by motivating careful consideration of time-dependent ``softening" effects in sub-grid routines for CR feedback, particularly for use in large cosmological volumes.

We present a detailed analysis of stellar rotation along the main sequences of NGC 1866 and NGC 1856, two young (~200-300 Myr) massive clusters in the Large Magellanic Cloud, using MUSE integral field spectroscopy. Differences in stellar rotation have been proposed as an explanation for the extended main sequence turn-offs and split main sequences in these clusters. In agreement with this idea, we find strong links between the photometric colours of the cluster stars and their projected rotation velocities, Vsini. While stars blueward of the split main sequences are characterized by a range of relatively low spins, those with redder colours are fast rotators. Following a statistical correction for inclination, we measure mean equatorial velocities for the red main-sequence stars in both clusters of V_eq=300 km/s, corresponding to 70-80% of the critical values predicted for such stars by current stellar models. We discuss these findings in the context of the different scenarios proposed to explain the stellar rotation distributions of young massive clusters. We further investigate whether the high rotation rates provide a natural explanation for the high fractions of Be stars we observe in both clusters, peaking at >~50% at the turn-off. We argue that if ~85% of the critical rotation rate is high enough to trigger the formation of a decretion disk, most upper main sequence stars in the clusters are expected to become Be stars before leaving the main sequence.

Some massive, quiescent galaxies at z>3 appear to contain considerable numbers of old stars (forming at z>7). Works inferring the star formation histories of at least one such galaxy observed with JWST have suggested that the assembly of so much stellar mass so early may challenge the well-established Cold Dark Matter (CDM) cosmological framework, or else indicate extraordinarily high past star formation efficiencies. However, these studies implicitly assume that all the stars in place at the epoch of observation assembled in-situ, i.e. in a single galaxy. In hierarchical models like CDM, massive galaxies assemble following successive mergers of smaller galaxies. Thus, inferences of the growth of stellar mass using the ages of stars within a descendant massive galaxy will be biased. In this paper, I use the TNG100 simulation to quantify this bias across a range of descendant galaxy masses and redshifts, for inferences made for different past epochs. I demonstrate that the assumption of in-situ stellar mass assembly can lead to significant biases in inferred stellar mass histories, with historic (i.e. looking back from the epoch of observation) stellar masses overestimated by over an order of magnitude in some cases. The bias increases with increasing halo mass, for inferences made further from the epoch of observation, and with decreasing descendant galaxy redshift. I derive corrections that can be applied to inferred stellar mass histories for more robust comparisons with dark matter halo mass functions at high redshift.

Superbursts are rare events observed from bursting neutron star low mass X-ray binaries. They are thought to originate from unstable burning of the thick layer of Carbon on the surface of the neutron star, causing the observed X-ray flashes to last several hours. Given their fluence it has long been thought that superbursts may have significant effects on the accretion flow around the neutron star. In this paper, we first present evidence for a new superburst observed from 4U 1608-522 by MAXI during the 2020 outburst, around 00:45 UTC on 16 July 2020. We compare some of the properties of this superburst and the underlying outburst with the events recorded on May 5 2005 by RXTE and most recently in 2025 by MAXI. We then present our spectral analysis of NICER and Insight-HXMT data obtained before and after the 2020 superburst event. Our results indicate that the inner disk temperature and the radius show a systematic evolution in the following few days, which may be related to the superburst. We show that the timescale of the observed evolution can not be governed by viscous timescales unless the viscosity parameter is unrealistically low.

Not all galaxies at Cosmic Noon evolve in the same way. It remains unclear how the local environment -- especially the extreme overdensities of protoclusters -- affects stellar mass assembly at high redshift. The stellar mass function (SMF) encodes these processes; comparing SMFs across environments reveals differences in evolutionary history. We present the SMF of the Hyperion proto-supercluster at $z\sim2.5$, one of the largest and most massive protostructures known. This dataset provides the most statistically robust SMF of a single protostructure at $z>2$. By comparing the SMF of overdense peaks within Hyperion to the coeval field, we ask: how early, and how strongly, does a dense environment favor massive galaxies? Using COSMOS2020 photometry with ground-based and new HST grism spectroscopy, we construct a 3D overdensity map that assigns galaxies to peaks, outskirts, or the field. We perform 100 Monte Carlo realizations to propagate redshift and mass uncertainties, and derive SMFs normalized to the field. The peaks show a clear excess of massive galaxies: number densities at $\log(M_*/M_\odot)\sim 11$ are ~10x higher than the field, while those at $\log(M_*/M_\odot)\sim 9.5$ are enhanced by only ~3.5x. By contrast, the outskirts and Hyperion as a whole mirror the field. Environmental effects on stellar mass growth are thus evident by $z\sim 2.5$. The densest regions already host galaxies with accelerated growth, while the global SMF masks this signal. Protostructures therefore begin shaping the high-mass end of the SMF well before cluster quenching, and may drive the elevated star formation at Cosmic Noon.

We report on roughly 16 years of photometric monitoring of the transneptunian binary system (120347) Salacia-Actaea which provides significant evidence that Salacia and Actaea are tidally locked to the mutual orbital period in a fully synchronous configuration. The orbit of Actaea is updated, followed by a Lomb-Scargle periodogram analysis of the ground-based photometry which reveals a synodic period similar to the orbital period and a peak-to-peak lightcurve amplitude of {\delta}m = 0.0900 {\pm} 0.0036 mag (1{\sigma} uncertainty). Incorporating archival HST photometry that resolves each component, we argue that the periodicity in the unresolved data is driven by a longitudinally varying surface morphology on Salacia, and derive a sidereal rotation period that is within 1{\sigma} of the mutual orbital period. A rudimentary tidal evolution model is invoked that suggests synchronization occurred within 1.1 Gyr after Actaea was captured/formed.

Interpreting galaxy properties from astronomical surveys relies heavily on spectral energy distribution (SED) modelling, yet uncertainties in key model ingredients are often overlooked. By leveraging a $z\sim0$ galaxy sample from the EAGLE simulation, we generate synthetic SDSS spectral and VISTA photometric observations with controlled assumptions, to assess how variations in stellar spectral library, initial mass function (IMF) and metallicity prescriptions within the BPASS-framework affect inferred galaxy properties. Our analysis combines spectral fitting from 3800 to 9200 A with photometric constraints extending to 2.3 $\mu$m, enabling robust assessment across a broad wavelength baseline. Our findings reveal mass, age and star formation rate vary by $0.27\pm0.09$, $0.19\pm0.11$ and $1.4\pm1.0$ dex, respectively, greater than observational uncertainties reported in surveys. Notably, we find stellar spectral library choice is capable of transforming a galaxy from appearing star-forming to quiescent, while a fixed metallicity assumption yields systematic biases when the chosen metallicity is incorrect. These modelling differences impact the reconstructed total mass assembly history in galaxies by up to $\sim12$ percent and bias the demographic and star formation history conclusions drawn from surveys. As upcoming missions like Euclid, Roman and CASTOR aim to characterise galaxy evolution with unprecedented precision, our results highlight the need for careful propagation of SED modelling uncertainties and transparency in model selection.

Exoplanet observations have shown that the occurrence and orbital architectures of close-in super-Earths and sub-Neptunes are shaped by the presence of outer gas giant planets. This influence may emerge during the formation stage or from later dynamical evolution by a yet elusive physical process. In this work, we investigate the early stages of planetesimal accretion, modeling the joint collisional and dynamical evolution of planetesimals under the gravitational influence of a cold Jupiter and a viscously-dissipating massive protoplanetary disk. We find that an initially extended planetesimal disk of small ($\sim 1-10$ km) bodies evolves into massive, compact ($\Delta a/a\lesssim 0.1$) rings of several Earth masses in Moon-sized objects centered at $\sim0.1-0.5$ au. This prevalent outcome is the result of an initial stage of planetesimal accretion over the first 10 kyrs, followed by orbital transport driven by a secular apsidal resonance sweeping inward on Myr timescales. Our findings highlight the crucial role of giant planets in redistributing solids within the inner disk. This redistribution of planetary building blocks may help explain why systems with giant companions often depart from the "peas-in-a-pod" architecture.

The eddy fluxes of angular momentum in Jupiter's upper troposphere are known to converge in prograde jets and diverge in retrograde jets. Away from the equator, this implies convergence of the Eulerian mean meridional flow in zones (anticyclonic shear) and divergence in belts (cyclonic shear). It indicates lower-tropospheric downwelling in zones and upwelling in belts because the mean meridional circulation almost certainly closes at depth. Yet the observed banded structure of Jupiter's clouds and hazes suggests that there is upwelling in the brighter zones and downwelling in the darker belts. Here, we show that this apparent contradiction can be resolved by considering not the Eulerian but the transformed Eulerian mean circulation, which includes a Stokes drift owing to eddies and is a better approximation of the Lagrangian mean transport of tracers such as ammonia. The potential vorticity structure inferred from observations paired with mixing length arguments suggests that there is transformed Eulerian mean upwelling in zones and downwelling in belts. Simulations with a global circulation model of Jupiter's upper atmosphere demonstrate the plausibility of these inferences and allow us to speculate on the band structure at deeper levels.

The evolution of galaxies in rich environments such as clusters and groups can be significantly perturbed during their interaction with nearby companions (tidal interactions) or with the hot intracluster medium (ICM) trapped within the gravitational potential well of the massive host halo (ram pressure stripping). Both gravitational perturbations and the external pressure exerted by the hot ICM on the galaxy ISM during its high velocity journey within the cluster are able to remove most, if not all of it, producing extended tails of stripped material. Along with the different gas phases (cold atomic and molecular, ionised, hot), these perturbations can remove also dust, thus contributing to the pollution of the ICM. Probe Infrared Mission for Astrophysics (PRIMA) is offering a unique opportunity to observe this dust component, a crucial ingredient in the energetic balance of the stripped gas. We analyse how the two instruments onboard of PRIMA, PRIMAger (in imaging and polarimetric mode) and far-IR enhanced survey spectrometer (FIRESS), can be used to observe a selected sample of ram pressure stripped tails detected at other frequencies (HI, CO, Halpha, X-rays). These data can be used to determine the relative distribution of the dust component with respect to that of the other gas phases, derive its temperature, calculate different gas physical parameters (electron density, photoelectric heating efficiency, gas metallicity), and quantify the strength of the turbulent magnetic fields, all fundamental parameters used to constrain the most recent hydrodynamic simulations of gas stripping in clusters. The ultimate aim of this research is that of understanding the fate of the cold stripped material once mixed with the surrounding hot medium and study under which condition it can collapse into giant molecular clouds (GMC) to form new stars.

We present a detailed multi-wavelength afterglow study of the short GRB 250704B, extensively monitored in optical and near-infrared bands. Its afterglow displays an unusually long-duration plateau followed by an achromatic break and a steep decline, deviating from canonical GRB afterglows. While long plateaus are often explained by central engine activity, we find that for GRB 250704B, an energy injection model requires unreasonable parameters. The afterglow is better explained by an off-axis power-law structured jet with a narrow core ($\theta_c \approx 0.7^{\circ}$) viewed at a modest angle ($\theta_v \approx 1.9^{\circ}$). A comparison with GRB 170817A shows that both events are consistent with the off-axis structured jet scenario, where the shape of the light curve is governed primarily by the geometry of the jet and the viewing angle rather than the energetics, microphysical parameters, or external density. Our results underscore the importance of incorporating the jet structure in GRB modeling.

The particle mass of dark matter (DM) was previously constrained using kinematics of ultra-faint dwarf galaxies to $m > 3 \times 10^{-19}\,\mathrm{eV}$. This constraint, which excludes the "fuzzy" range of ultra-light dark matter from comprising all of the DM, relies on an estimate of the heating rate from fuzzy dark matter (FDM) wave interference using linear perturbation theory. Here, we compare the results of this perturbative calculation to full Schrödinger-Poisson simulations of the evolution of star particles in FDM halos. This comparison confirms theoretical expectations that FDM heating is stronger in fully nonlinear simulations due to the formation of a dense central soliton whose fluctuations enhance gravitational perturbations, and that bounds on the DM particle mass using this perturbative method are indeed conservative. We also show that these bounds are not affected by possible tidal stripping, since for dwarf satellites like Segue 1, the tidal radius is much larger than the observed size of the galaxy. We further show that the constraints on the mass cannot be evaded by invoking DM self-interactions, due to constraints on the self-interaction from large-scale structure. Lastly, we show that if the recently discovered system Ursa Major III/UNIONS I is a galaxy, the observed properties of this object strengthen the lower bound on the DM mass by over an order of magnitude, to $m > 8 \times 10^{-18}\,\mathrm{eV}$, at 95% confidence. This constraint could further be strengthened considerably by more precise measurements of the size and velocity dispersion of this and other similar galaxies, and by using full Schrödinger-Poisson simulations.

3I/ATLAS was discovered on UT 2025 July 1 and joins a limited but growing population of detected $\sim10^2-10^3$ m scale interstellar objects. In this paper we report photometric observations of 3I/ATLAS from the nights of UT 2025 July 3, UT 2025 July 9, and UT 2025 July 10 obtained with the Southern Astrophysical Research Telescope (SOAR). The photometric observations are taken with the Goodman High Throughput Spectrograph (HTS) in the $r'$-band. These data provide 28 photometric data points to the rapidly growing composite light curve of 3I/ATLAS. They reveal that the object did not exhibit obvious long-term variability in its brightness when these observations were taken. These observations appear to have captured two moderate and independent brightening events on UT 2025 July 9, and UT 2025 July 10. However, we perform a series of stellar contamination, stacking, and aperture experiments that demonstrate that the increases in brightness by $\sim0.8$ magnitudes appear to be a result of poor seeing and stellar contamination by close-proximity field stars. We report the mean brightnesses of 3I/ATLAS on each night of magnitude 18.14, 17.55, and 17.54 for UT 2025 July 3, 9, and 10, respectively. Moreover, the presence of cometary activity in extant images obtained contemporaneously with these data precludes them from revealing insights into the rotation of the nucleus. We conclude that the activity of 3I/ATLAS on UT 2025 July 9 and UT July 10 was consistent with the near-discovery activity levels, with no obvious outburst activity.

We present long-baseline observations of the Fomalhaut outer debris disk at 223 GHz (1.3 mm) from ALMA Cycle 5, which we use along with archival short-baseline observations to produce a 0".57 resolution mosaic of the disk at a sensitivity of 7 $\mu$Jy/bm. We use radial profiles to measure the disk at the ansae and find that the southeast (SE) side of the disk is 4 AU wider than the northwest (NW) side as observed by ALMA. We also find that the peak brightness of the NW ansa is $21\pm1\%$ brighter than the SE ansa. We perform MCMC fits of the ALMA visibilities using two analytical, eccentric disk models. Our results suggest that the model including a dispersion parameter for the proper eccentricity ($\sigma_{e_p}$), which accounts for additional scatter in the eccentricity of individual orbits, is preferred over the model without one. Such a model implies that self-gravitation, particle collisions, and close-packing could play a role in shaping the overall structure of the Fomalhaut disk as is seen in eccentric planetary rings. Crucially, neither model can reproduce the brightness or width asymmetry near the NW ansa. No emission from the Intermediate Belt is detected, allowing us to place a 3-$\sigma$ upper limit of 396 $\mu$Jy at 1.3 mm. We also discover a spectral line in archival Cycle 3 data centered at $\nu_{\rm obs}\approx230.25$ GHz at the location of the ``Great Dust Cloud," whose redshift from the expected CO line for Fomalhaut confirms the source is a background galaxy.

[abridged] Accurately accounting for the AGN phase in galaxy evolution requires a large, clean AGN sample. This is now possible with SRG/eROSITA. The public Data Release 1 (DR1, Jan 31, 2024) includes 930,203 sources from the Western Galactic Hemisphere. The data enable the selection of a large AGN sample and the discovery of rare sources. However, scientific return depends on accurate characterisation of the X-ray emitters, requiring high-quality multiwavelength data. This paper presents the identification and classification of optical and infrared counterparts to eRASS1 sources using Gaia DR3, CatWISE2020, and Legacy Survey DR10 (LS10) with the Bayesian NWAY algorithm and trained priors. Sources were classified as Galactic or extragalactic via a Machine Learning model combining optical/IR and X-ray properties, trained on a reference sample. For extragalactic LS10 sources, photometric redshifts were computed using Circlez. Within the LS10 footprint, all 656,614 eROSITA/DR1 sources have at least one possible optical counterpart; about 570,000 are extragalactic and likely AGN. Half are new detections compared to AllWISE, Gaia, and Quaia AGN catalogues. Gaia and CatWISE2020 counterparts are less reliable, due to the surveys shallowness and the limited amount of features available to assess the probability of being an X-ray emitter. In the Galactic Plane, where the overdensity of stellar sources also increases the chance of associations, using conservative reliability cuts, we identify approximately 18,000 Gaia and 55,000 CatWISE2020 extragalactic sources. We release three high-quality counterpart catalogues, plus the training and validation sets, as a benchmark for the field. These datasets have many applications, but in particular empower researchers to build AGN samples tailored for completeness and purity, accelerating the hunt for the Universe most energetic engines.

We propose that galaxy structural changes - and the rapid rise of a population of galaxies with early-type morphologies at cosmic noon ($1<z<3$) - can be explained with EASE: Early, Accelerated, Secular Evolution. The mechanism relies on the torques exerted by stellar spirals in late-type galaxies that are present and active at $z>1.5$ as revealed by JWST/NIRCam. The process is at once secular, because the transformative structural changes (heating, compaction, bulge formation) occur over many ($\approx10-30$) orbital periods, but accelerated, because orbital times were significantly shorter than at the present day. In a first application, we take galaxy effective radius as a proxy for galaxy structure and, using new measurements of the abundance and properties of stellar spirals observed in a collection of JWST deep fields, show that EASE predicts a distribution of early-type sizes that is smaller than late-type galaxies and consistent with what is observed. The success of EASE relies on an updated picture of the influence of spiral arms, in which transience plays a key role. We present a new calculation of the characteristic wave equation in the fluid approximation that applies to steady and non-steady open spirals beyond the more traditional tight-winding limit. This shows open, transient spirals above the Jeans length growing and decaying on the order of a dynamical time in a wider region around and inside corotation than canonical steady spirals. We show that this transient activity spreads out angular momentum gains and losses, and the associated dynamical heating, giving spirals a more extended influence than a single steady spiral. The ubiquity of spirals in star-forming galaxies with $M_*>10^{10.5}M_{\odot}$ across the redshifts where early-type galaxies appear in large numbers suggests that EASE can play an important role in the morphological transformation of galaxies.

The habitable zone is defined as the orbital region around a star where planetary feedback cycles buffer atmospheric greenhouse gases that, in combination with solar luminosity, maintain surface temperatures suitable for liquid water. Evidence supports the existence of buffering feedbacks on Earth, but whether these same feedbacks are active on other Earth-like planets remains untested, as does the habitable zone hypothesis. While feedbacks are central to the habitable zone concept, one does not guarantee the other-i.e., it is possible that a planet may maintain stable surface conditions at a given solar luminosity without following the predicted $CO_2$ trend across the entire habitable zone. Forthcoming exoplanet observations will provide an opportunity to test both ideas. In anticipation of this and to avoid premature conclusions based on insufficient data, we develop statistical tests to determine how many observations are needed to detect and quantify planetary-scale feedbacks. Our model-agnostic approach assumes only the most generic prediction that holds for any buffering feedback, allowing the observations to constrain feedback behavior. That can then inform next-level questions about what specific physical, chemical, and/or biological feedback processes may be consistent with observational data. We find that [23, 74](95% CI) observations are required to detect feedback behavior within a given solar luminosity range, depending on the sampling order of planets. These results are from tests using conservative error tolerance-a measure used to capture the risk of false positives. Reducing error tolerance lowers the chance of false positives but requires more observations; increasing it reduces the required sample size but raises uncertainty in estimating population characteristics. We discuss these trade-offs and their implications for testing the habitable zone hypothesis.

Blueshifted absorption is the classic spectroscopic signature of an accretion disc wind in X-ray binaries and cataclysmic variables (CVs). However, outflows can also create pure emission lines, especially at optical wavelengths. Therefore, developing other outflow diagnostics for these types of lines is worthwhile. With this in mind, we construct a systematic grid of 3645 synthetic wind-formed H-alpha line profiles for CVs with the radiative transfer code SIROCCO. Our grid yields a variety of line shapes: symmetric, asymmetric, single- to quadruple-peaked, and even P-Cygni profiles. About 20% of these lines -- our `Gold' sample -- have strengths and widths consistent with observations. We use this grid to test a recently proposed method for identifying wind-formed emission lines based on deviations in the wing profile shape: the `excess equivalent width diagnostic diagram'. We find that our `Gold' sample can preferentially populate the suggested `wind regions' of this diagram. However, the method is highly sensitive to the adopted definition of the line profile `wing'. Hence, we propose a refined definition based on the full-width at half maximum to improve the interpretability of the diagnostic diagram. Furthermore, we define an approximate scaling relation for the strengths of wind-formed CV emission lines in terms of the outflow parameters. This relation provides a fast way to assess whether -- and what kind of -- outflow can produce an observed emission line. All our wind-based models are open-source and we provide an easy-to-use web-based tool to browse our full set of H-alpha spectral profiles.

The 2020 Decadal Survey on Astronomy and Astrophysics tasked future space observatories with the goal of detecting and characterizing a large sample of Earth-like exoplanets. To achieve this, these observatories will require coronagraphs and wavefront control algorithms in order to achieve $10^{-10}$ or better starlight suppression. The Space Coronagraph Optical Bench (SCoOB) is a vacuum compatible testbed at the University of Arizona which aims to advance and mature starlight suppression technologies in a space-like environment. In its current configuration, SCoOB is a charge-6 vector vortex coronagraph outfitted with a Kilo-C microelectromechanical systems deformable mirror capable of achieving sub-$10^{-8}$ dark hole contrast at visible wavelengths using implicit electric field conjugation (iEFC). In this work, we demonstrate the use of a self-coherent camera (SCC) for dark hole digging and maintenance on SCoOB. The SCC introduces a small off-axis pinhole in the Lyot plane which allows some starlight to reach the focal plane and interfere with residual speckles. This enables high-order focal-plane wavefront sensing which can be combined with active wavefront control to null the speckles in a specified region of high contrast known as the dark hole. We discuss considerations for implementation, potential limitations, and provide a performance comparison with iEFC. We also discuss the design optimization and fabrication process for our SCC Lyot stops.

We present evidence of a negative eccentricity gradient in the debris disk of the nearby A-type main sequence star, Fomalhaut. Fitting to the high-resolution, archival ALMA 1.32 mm continuum data for Fomalhaut (with a synthesised angular resolution of $0.76{\times}0.55''$; 4-6\,au), we present a model that describes the bulk properties of the disk (semi-major axis, width, and geometry) and its asymmetric morphology. The best-fit model incorporates a forced eccentricity gradient that varies with semi-major axis, $e_f\propto a^{n_\mathrm{pow}}$, a generalized form of the parametric models of Lynch & Lovell 2022, with $n_\mathrm{pow}{=}{-1.75}{\pm}0.16$. We show that this model is statistically preferred to models with constant forced and free eccentricities. In comparison to disk models with constant forced eccentricities, negative eccentricity gradient models broaden disk widths at pericenter versus apocenter, and increase disk surface densities at apocenter versus pericenter, both of which are seen in the Fomalhaut disk, and which we collectively term Eccentric Velocity Divergence. We propose single-planet architectures consistent with the model and investigate the stability of the disk over 440 Myr to planet-disk interactions via N-body modeling. We find that Fomalhaut's ring eccentricity plausibly formed during the protoplanetary disk stage, with subsequent planet-disk interactions responsible for carving the disk morphology.

The space coronagraph optical bench (SCoOB) at the University of Arizona is a high-contrast imaging testbed designed to operate in a vacuum to obtain a contrast better than 1e-8 in optical wavelengths using vector vortex coronagraph (VVC) masks. The testbed performance in a half-sided D-shaped dark hole is 2.2e-9 in a << 1% BW, 4e-9 in a 2% BW, and 2.5e-8 in a 15% BW. While the testbed has met the design specification contrast requirements in monochromatic wavelengths, comprehensive end-to-end numerical modeling to assess contrast limits across different bandpasses has yet to be conducted. In this work, we discuss the results of numerical modeling for the SCoOB testbed in both monochromatic and 10% bandwidths at 525 nm and 630 nm. This modeling incorporates measured VVC retardance, modeled polarization aberrations, measured surface and reflectivity errors, and diffuse and surface reflectivity. We explore and discuss the various factors contributing to the contrast limits.

The Jupiter Icy Moons Explorer (JUICE) spacecraft is a European Space Agency (ESA) mission to study the Jovian system, currently undergoing an eight-year cruise phase. The Planetary Radio Interferometric and Doppler Experiment (PRIDE) is one of eleven experiments contributing to the JUICE mission. PRIDE aims to conduct radio science experiments using ground-based radio telescopes, through both single dish and Very Long Baseline Interferometry (VLBI) observations. The University of Tasmania (UTAS) is an important contributor to PRIDE and JUICE, though its continental-wide network of radio telescopes in Australia. Over 35 PRIDE observations of JUICE were conducted during the period 2023-24, which enabled detailed analysis of space weather activity in this period, as well as the Lunar-Earth flyby campaign in August 2024. In this paper, we describe PRIDE VLBI observations of JUICE, and the first successful results of PRIDE with the University of Tasmania infrastructure.

The Sun's atmosphere hosts swirling plasma structures, known as solar vortices, which have long been thought to channel wave energy into higher layers. Until now, no direct observations have confirmed their role in the heating of the atmosphere. Here, we present the first direct evidence that solar vortices act as structured waveguides, carrying magnetoacoustic modes (waves that behave like sound waves but travel through magnetized plasma) that leave clear wave-heating signatures. By mapping vortex regions at multiple heights and analysing the waves they contain, we show that magnetoacoustic waves efficiently transfer energy, offset losses from radiation, and dominate energy transport in the lower chromosphere. These results challenge the long-standing assumption that vortices primarily support twisting disturbances traveling along magnetic field lines (Alfven waves), revealing instead that magnetoacoustic modes play the leading role in the lower atmosphere. This redefines the role of vortices in magnetized plasmas and has broader implications for wave-plasma interactions in regions of strong magnetic fields.

$\text{CO}_{\text{2}}$ ice clouds are important for polar energy balance and the carbon dioxide cycle on Mars. However, uncertainties remain regarding their physical and radiative properties, which control how polar $\text{CO}_{\text{2}}$ clouds interact with the global Martian climate. Here, we use Mars Climate Sounder (MCS) observations of atmospheric radiance to estimate these physical and radiative properties. We find that Martian $\text{CO}_{\text{2}}$ clouds are typically composed of large particles from a narrow size distribution with an effective radius of 46 $\mu$m and an effective variance of $2.0 \times 10^{-3}$ in the southern hemisphere, and an effective radius of 42 $\mu$m and an effective variance of $2.0 \times 10^{-3}$ in the north. The similarity in sizes of $\text{CO}_{\text{2}}$ ice particles in both hemispheres may be due to the fact that $\text{CO}_{\text{2}}$ clouds tend to form near the same pressure level in each hemisphere, despite the higher surface pressures in the north. We use a simplified convective cooling model to show that the small effective variance we derive may be a consequence of the fact that $\text{CO}_{\text{2}}$ is also the dominant atmospheric constituent on Mars, which allows $\text{CO}_{\text{2}}$ ice particles to reach sizes upwards of 10 $\mu$m within seconds. At the same time, the fact that the Martian atmosphere is so thin means that large particles fall rapidly to the surface, reducing the range of particle sizes that can remain in the atmosphere for any extended period of time. This study is part of ongoing work to add $\text{CO}_{\text{2}}$ ice opacity profiles to the MCS retrieval pipeline.

The fifth-generation Sloan Digital Sky Survey (SDSS-V) includes the first large-scale spectroscopic survey of white dwarfs (WDs) in the era of Gaia parallaxes. SDSS-V collects multiple exposures per target, making it ideal for binary detection. We present a search for hydrogen atmosphere (DA) double white dwarf (DWD) binaries in this rich dataset. We quantify radial velocity variations between sub-exposures to identify binary candidates, and also measure the orbital period for a subset of DWD binary candidates. We find 63 DWD binary candidates, of which 43 are new discoveries, and we provide tentative periods for 10 binary systems. Using these measurements, we place constraints on the binary fraction of the Galactic WD population with $< 0.4$ AU separations $f_{\mathrm{bin,0.4}} = 9\%$, and the power-law index of the initial separation distribution $\alpha = -0.62$. Using the simulated binary population, we estimate that $\leq 10$ super-Chandrasekhar binaries that merge within a Hubble time are expected in our sample. We predict that $\leq 5$ systems in our sample should be detectable via gravitational waves by LISA (Laser Interferometer Space Antenna), one of which has already been identified as a LISA verification source. We also estimate a total of about 10,000 - 20,000 LISA-detectable DWD binaries in the galaxy. Our catalog of WD+WD binary candidates in SDSS-V is now public, and promises to uncover a large number of exciting DWD systems.

The corona is a crucial region that connects the solar surface to the solar wind and serves as the primary site of solar activity. The 2024 total solar eclipse (TSE) provides a unique opportunity to investigate the large-scale coronal structure. Combined with TSE observations, we study the impact of the magnetic structure of the far-side active region, located in the eastern hemisphere of the Sun that has not yet rotated into the Earth Field-of-View (FoV), on a global Magnetohydrodynamic (MHD) simulation. To address the limitation of single-view measurements in the routine synoptic map, we correct the magnetic field in the far-side region by incorporating full-disk magnetograms measured several days after the TSE, allowing us to capture the temporal evolution of the photospheric magnetic field in near real-time. Simulation results demonstrate that the local magnetic field in the far-side active region can significantly influence the global coronal structure by altering the position of the heliospheric current sheet (HCS), and further affect the global distribution of plasma parameters, even in polar regions. A comparison of the simulation results with white-light (WL) TSE + LASCO C2 observations and in situ measurements by the Parker Solar Probe (PSP) reveals that the composite synoptic map improves the accuracy of coronal modeling. This work provides robust support for advancing our understanding of coronal evolution, as well as deepens the link between the photosphere and large-scale coronal structure. Furthermore, it establishes a theoretical foundation for the future development of multi-view, stereoscopic measurements of the photospheric magnetic field.

Image-based searches have become a complementary approach for identifying pulsars, particularly at MHz frequencies where scattering and high dispersion measures affect high-time resolution observations. In this work, we searched the Galactic Plane (GP) data release from the GaLactic and Extragalactic All-Sky Murchison Widefield Array eXtended (GLEAM-X) survey, a widefield continuum radio survey covering the 72 - 231 MHz frequency range, at the positions of known pulsars in the ATNF catalogue (version 2.6.2) that lie within its sky coverage. We present the spectral energy distribution for 193 known pulsars located at |b| < 11deg. Notably, 106 of these represent the first detections below 400 MHz. We also cross-match the GLEAM-X: GP compact source catalogue with unassociated sources in the Fermi Large Area Telescope (LAT) catalogue, filtering for gamma-ray spectral and variability properties, as well as coincidence with Active Galactic Nuclei (AGN). We have identified 106 possible pulsar candidates. This work demonstrates the importance of sensitive, low-frequency Galactic plane surveys for detecting emission from known pulsars and presents a potential way of searching for new pulsar candidates that would otherwise be missed by traditional time-domain searches.

We present lithium abundances for 119 main-sequence stars in the 6.3 Gyr open cluster NGC 188, using high-resolution, high signal-to-noise ratio spectra from WIYN/Hydra. We observe the stars over multiple nights and measure radial velocities for each night, which we combine with Gaia proper motions to identify multiplicity and cluster membership. We identify 95 single members, 14 binary members, 9 members with uncertain multiplicity, and 1 single likely member. We determine effective temperatures using empirical color-temperature relations, surface gravities from isochrones, and microturbulence from empirical relations for main-sequence stars. Our sample includes G and K dwarfs with temperatures between 6000 and 5300 K, which expands significantly on earlier observations. We find that lithium abundances in NGC 188 are lower than predictions from standard stellar evolution theory. As expected, stars in NGC 188 are more lithium-depleted than those in the younger Hyades and Praesepe clusters (650 Myr). However, their abundances are higher, or at least comparable, to those in the slightly younger cluster M67 (4.5 Gyr), challenging the idea that older stars have lower lithium than younger ones. Lithium depletion may depend on factors beyond age and mass.

Observing and characterizing pre- and protostellar cores in the earliest and densest stages of star formation is challenging due to their short timescales and high densities, limiting the suitable tracers and targets. We conducted ALMA-Atacama Compact Array (ACA) stand-alone observations of ortho-H$_2$D$^+$ (1$_{\rm 1,0}$-1$_{\rm 1,1}$) emission, which is believed to trace cold high-density regions, toward three dense cores in the Taurus molecular cloud: (1) L1544, likely in the densest prestellar phase; (2) MC 35-mm, a candidate for the first hydrostatic core; and (3) MC 27/L1521F, which hosts a Class 0 very-low luminosity object. These observations provide high angular resolution data for the line across a set of cores selected to represent consecutive stages around the onset of star formation, offering a unique opportunity to trace the time evolution of $\sim$10$^4$ years. With the single-dish total-power array, we detected ortho-H$_2$D$^+$ emission in all three cores, revealing its presence over scales of $\sim$10,000 au. In the interferometric 7 m array data with a beam size of 3.$''$5 ($\sim$500\,au), emission was detected only toward the central continuum source of MC 35-mm, with a significance of $\sim$3$\sigma$. No significant detections were found in the other targets, placing an upper limit on the H$_2$D$^{+}$ abundance of $\sim$10$^{-11}$ in the dense components traced by the interferometric continuum emission. These results suggest that ortho-H$_2$D$^+$ predominantly exhibits an extended distribution over several thousand au in the early stages of star formation. Detection in compact, dense central structures may only be achieved within a few $\times$ 10$^{4}$ years immediately before or after protostar formation.

We derive a relativistic magnetohydrodynamics (RMHD) theory for a dilute electron-ion gas governed by the Boltzmann-Vlasov equation, using the method of moments. This yields an extended MHD framework beyond standard astrophysical formulations, which typically include only the shear-stress component parllel to the magnetic field. We analyze our framework in the linear regime and show that it leads to the firehose instability when the bakground longitudinal pressure becomes large. In these extreme scenario, the transverse and semi-transverse shear-stress components become large and may play a role in accretion disk dynamics.

Recent studies suggest that dark energy may be dynamical rather than being a mere cosmological constant $\Lambda$. In this work, we examine the viability of two physically well-motivated dynamical dark energy models -- holographic dark energy (HDE) and Ricci dark energy (RDE) -- by confronting them with the latest observational data, including ACT cosmic microwave background anisotropies, DESI baryon acoustic oscillations, and DESY5 supernovae. Our analysis reveals a fundamental tension between early- and late-universe constraints within both frameworks: ACT favors a quintom scenario where the dark energy equation of state (EoS) evolves from $w>-1$ at early times to $w<-1$ at late times, while DESI+DESY5 exhibits a distinct preference for quintessence where $w>-1$ across cosmic evolution. The joint analysis yields constraints that align more closely with the ACT preference. Critically, the canonical RDE model fails to provide a coherent description of cosmic evolution, as it manifests severe tensions (even exceeding $10\sigma$ significance) between early- and late-universe parameter reconstructions. Based on the combined data, Bayesian evidence decisively disfavors both HDE and RDE models relative to the $\Lambda$ cold dark matter model, with ACT providing decisive disfavor and DESI+DESY5 yielding moderate disfavor. Our results show that the HDE and RDE models remain excluded by the new data, reinforcing earlier conclusions drawn from previous datasets.

The $R^2$-Higgs inflation is one of the simplest yet best-fit models consistent with Planck data. The higher spectral index $n_s$ recently reported by the combined cosmic microwave background (CMB) data from the Atacama Cosmology Telescope (ACT), South Pole Telescope (SPT), and Planck, along with baryonic acoustic oscillation data from the Dark Energy Spectroscopic Instrument (DESI), disfavors the single-field-like regime of $R^2$-Higgs inflation at approximately $2\sigma$. Following a doubly covariant formalism, we show that the $R^2$-Higgs inflation, when modified by a dimension-six $R^3$ term, can account for the high $n_s$ reported by CMB+BAO. In this regard, we find that preheating may play a pivotal role. We also show that if the nonminimal coupling between the Ricci scalar $R$ and the Higgs field is $\mathcal{O}(10)$, then preheating via the production of Higgs quanta may help explain the reported observations.

The Polarimetry in the Ultraviolet to Find Features in INterStellar dust (PUFFINS) is a SmallSat mission concept designed to obtain ultraviolet (UV) spectropolarimetric observations to probe the interstellar dust grain properties and to understand wavelength-dependent extinction and star formation. PUFFINS plans to observe 70 UV bright target stars at varying distances within a 180-320 nm wavelength range with 0.02% polarimetric accuracy. PUFFINS uses a simple telescope design with all reflective optics coated with protected aluminum to enhance reflectivity in the UV. The telescope and the spectropolarimeter, which consists of a Wollaston prism and a half-wave retarder, have been carefully selected to be greater than Technology Readiness Level 6 (TRL6). The telescope is designed to exhibit negligible instrumental polarization and crosstalk, significantly reducing the time needed for polarimetric calibration in orbit. The optimum and careful selection of the target stars will enable PUFFINS to observe an expanded and well-defined sample to test the predictions by interstellar grain alignment theory in the observation phase of 9 months. This paper outlines the details of the optical and optomechanical design and evaluates the polarimetric performance of PUFFINS.

Detection of short gamma-ray bursts (SGRBs) is critically important for the research of compact object mergers and multi-messenger astrophysics, but a significant part of SGRBs fall below the trigger threshold of GRB detectors, and thus are often missed. Here we present a systematic search for and verification of missed SGRBs using Fermi/GBM subthreshold triggers, jointly analyzing data from GBM, GECAM-B, and GECAM-C. Among 466 Fermi/GBM sub-threshold events (with reliability >= 5) from 2021 to 2024, 181 are within GECAM's field of view. We find that 49 out of 181 are confirmed astrophysical transients, and 41 can be classified as SGRBs. Thus, the SGRB detection rate of Fermi/GBM is increased to about 50 per year. Additionally, a complete multi-instrument monitoring and systematic verification of GBM sub-threshold events is expected to further increase the SGRB rate to about 80 per year, which is about 100% improvement relative to the GBM-triggered SGRBs. These results may have important implications on the local formation rate of SGRBs and the binary neutron star merger rate. We also searched for potential temporal coincidences between these SGRBs and gravitational waves from the LIGO-Virgo-KAGRA O4 run resulting in no detection.

Recently, astrometric and spectroscopic observations resulted in the discovery of several low-mass binaries with invisible components, which are expected to be compact objects. In about two dozen cases, the masses of these components are consistent with neutron stars. We use low-frequency archival data obtained with the Large Phased Array in Pushchino to search for radio emission from five of these systems. For all the systems, we do not detect persistent or periodic emission. In one case (2MASS J1527+3536), we identify a single radio burst with a flux of 13 Jy and a duration of 0.13 s. However, the dispersion measure of the burst does not correspond to an expected value for the source. We discuss several possibilities to explain the properties of this burst.

Recent detections of kilonova-like emission following long-duration gamma-ray bursts GRB211211A and GRB230307A have been interpreted as originating from the merger of two neutron stars. In this work, we demonstrate that these observations are also consistent with nucleosynthesis originating from a collapsar scenario. Our model accurately predicts the observed optical and infrared light curves using a single weak $r$-process component. The absence of lanthanide-rich material in our model, consistent with the data, challenges the prevailing interpretation that a red evolution in such transients necessarily indicates the presence of heavy $r$-process elements.

To fulfill the requirements of space object cataloging and enable automated intelligent responses to anomalous events, we designed a novel observation scheduling system named Sky Survey Schedule (SSS). This framework facilitates coordinated operations across multi-site observational networks comprising dozens of instruments, while simultaneously supporting asteroid monitoring and time-domain astronomy studies. The system implements two principal observation modes: fixed sky regions and target-centered tracking. The former is used for sidereal or static observation, while the latter provides dedicated follow-up capabilities for transient targets. The sky regions are divided into latitude bands, each of which is subdivided into sectors to ensure minimal overlap and comprehensive coverage. These sectors are mapped to high-level HEALPix sky grids, enabling rapid cross-referencing and correlation between instruments. At the core of SSS lies an adaptive weighting architecture that integrates multiple parameters. Initial target priorities are determined from orbital catalogs containing both known and uncorrelated objects according to cataloging requirements. The system implements dynamic weight adjustments through feedback mechanisms: confirmed stable objects receive decaying weights, long-unobserved targets experience weight recovery, while anomalies (e.g., newly detected or lost objects) trigger priority escalation. These target-specific weights combine with observational factors - including phase angle constraints, lunar interference, Earth shadowing, and elevation limits - to generate space-time priority matrices. This quantitative framework systematically incorporates operator-defined priorities for specific regions/targets through configurable weight modifiers. Observation plans are dynamically optimized considering:....

To understand how massive galaxies are influenced by their surroundings, we present new ALMA and NOEMA observations as part of A MUltiwavelength Study of ELAN Environments (AMUSE$^2$). These observations target submillimeter sources discovered in single-dish surveys around nine quasars hosting Ly$\alpha$ nebulae at $z=2\sim3$, including two Enormous Ly$\alpha$ nebulae (ELANe). Through detection of mid-$J$ CO lines, we confirm physical associations of 15 SMGs, which are located outside the expected virial radii of the central dark-matter halos hosting the quasars. We find $73^{+29}_{-21}\%$ of SMGs have line profiles better described by double Gaussian models, with a median peak-to-peak separation of 350 $\pm$ 25 km/s, suggesting rotating disks or interacting pairs. Modified blackbody fits of the far-infrared photometry yield a median $\beta$ of 2.0 $\pm$ 0.2 and $T_{dust}$ of 34 $\pm$ 3 K. Overall, SMGs outside quasar halos share similar physical properties with those in the field, but combining data from other studies reveals depleted gas fractions within quasar halos. This suggests that dense environments significantly impact massive star-forming galaxies only within halo scales at cosmic noon. Additionally, spatial analyses of 15 SMGs indicate they trace large-scale structures, possibly filamentary or elongated pancake-like, with a scale height of 2-5\,cMpc. Our measured distributions and densities of star-formation rates align with models, though likely represent lower limits.

Accurately distinguishing between quiescent and star-forming galaxies is essential for understanding galaxy evolution. Traditional methods, such as spectral energy distribution (SED) fitting, can be computationally expensive and may struggle to capture complex galaxy properties. This study aims to develop a robust and efficient machine learning (ML) classification method to identify quiescent and star-forming galaxies within the Farmer COSMOS2020 catalog. We utilized JWST wide-field light cones from the Santa Cruz semi-analytical modeling framework to train a supervised ML model, the CatBoostClassifier, using 28 color features derived from 8 mutual photometric bands within the COSMOS catalog. The model was validated against a testing set and compared to the SED-fitting method in terms of precision, recall, F1-score, and execution time. Preprocessing steps included addressing missing data, injecting observational noise, and applying a magnitude cut (ch1 < 26 AB) along with a redshift range of 0.2 < z < 3.5 to align the simulated and observational datasets. The ML method achieved an F1-score of 89\% for quiescent galaxies, significantly outperforming the SED-fitting method, which achieved 54%. The ML model demonstrated superior recall (88% vs. 38%) while maintaining comparable precision. When applied to the COSMOS2020 catalog, the ML model predicted a systematically higher fraction of quiescent galaxies across all redshift bins within 0.2 < z < 3.5 compared to traditional methods like NUVrJ and SED-fitting. This study shows that ML, combined with multi-wavelength data, can effectively identify quiescent and star-forming galaxies, providing valuable insights into galaxy evolution. The trained classifier and full classification catalog are publicly available.

This paper presents the DDF Pipeline, a radio astronomy data processing tool initially designed for the LOw-Frequency ARray (LO- FAR) radio-telescope and a candidate for processing data from the Square Kilometre Array (SKA). This work describes the DDF Pipeline software and presents a coarse-grain profiling execution to characterize its performance.

Thermal and magneto-thermal simulations are an important tool for advancing understanding of neutron stars, as they allow us to compare models of their internal structure and physical processes against observations constraining macroscopic properties such as the surface temperature. A major challenge in the simulations is in modelling of the outermost layers, known as the envelope, exhibiting a drop of many orders of magnitude in temperature and density in a geometrically thin shell. This is often addressed by constructing a separate envelope model in plane-parallel approximation that produces a relation between the temperature at the bottom of the envelope, $T_b$, and the surface temperature, $T_s$. Our aim is to construct a general framework for approximating the $T_b$-$T_s$ relation that is able to include the dependencies from the strength and orientation of the magnetic field. We used standard prescriptions to calculate a large number of magnetised envelope models to be used as a training sample and employed single-hidden-layer feedforward neural networks as approximators, providing the flexibility, high accuracy, and fast evaluation necessary in neutron star simulations. We explored the optimal network architecture and hyperparameter choices and used a special holdout set designed to avoid overfitting to the structure of the input data. We find that relatively simple neural networks are sufficient for the approximation of the $T_b$-$T_s$ relation with an accuracy $\sim 3\%$. The presented workflow can be used in a wide range of problems where simulations are used to construct approximating formulae.

In this work the theory of diffusive shock acceleration is extended to the case of non-classical particle transport with Lévy flights and Lévy traps, when the mean square displacement grows nonlinearly with time. In this approach the Green function is not a Gaussian but it exhibits power-law tails. By using the propagator appropriate for non-classical diffusion, it is found for the first time that energy spectral index of particles accelerated at shock front is $\gamma = [\alpha (\mathrm{r} + 5) - 6 \beta]/[\alpha(\mathrm{r}-1)]$, where $0 < \alpha < 2$ and $0 <\beta < 1$ are the exponents of power-law behavior of Lévy flights and Lévy traps, respectively. We note that this result coincides with standard slope at $\alpha=2, \beta=1$ (normal diffusion), and also includes those obtained earlier for the subdiffusion ($\alpha=2, \beta<1$) and superdiffusion ($\alpha<2, \beta=1$) regimes.

Local distance indicators such as standard sirens, in combination with spectroscopic redshift measurements of their host galaxies, allow us to estimate the present-day expansion rate of the Universe parameterised by Hubble's constant, H_0. However, these observed redshifts are systematically modified by the effect of galaxy peculiar velocities. Although these velocities may be estimated from the local density field by the process of velocity-field reconstruction, the intrinsic errors and covariance in these estimates contribute to the error in the H_0 determination. In this paper we demonstrate how the impact of peculiar velocities can be propagated into H_0 measurements from local distance indicators with observed redshifts, incorporating the full covariance of the velocity field induced by bulk flows. We apply our methods to cosmological simulations, testing the importance of this effect in the context of future analyses of gravitational wave sources with electromagnetic counterparts used as bright sirens. We conclude that H_0 errors may be increased by up to a factor of 2 in comparison with neglecting peculiar velocity covariance, with the highest impacts expected for sources at nearby distances or with small distance errors. Our analytical methods may also be applied to other local distance indicators, such as Type Ia supernovae.

Context. RR Lyrae stars are key distance indicators and tracers of old stellar populations in the Milky Way and its satellites. Accurate period and amplitude measurements are essential for constraining stellar evolution and mapping Galactic structure. The Javalambre VARiability (J-VAR) survey provides valuable time-series data across seven optical bands, including gri and four medium and narrow bands. Aims. Our goal is to construct and analyze light curves for RR Lyrae stars identified in the first data release (DR1) of the J-VAR survey using the Gaia DR3 variable stars catalog as a reference. Methods. The light curves of 315 RR Lyrae were analyzed by fitting templates from the Sloan Digital Sky Survey (SDSS) multiband template library. The periods and amplitudes for the seven bands in J-VAR were independently obtained from the best-fitted templates. Results. The J-VAR periods show strong agreement with Gaia DR3 values, which confirms the reliability of the applied methodology. The Bailey diagram for each J-VAR filter reveals the expected trend for RRab and RRc stars, with larger pulsation amplitudes at bluer wavelengths. After normalizing by the r-band amplitude, an exponential trend is found, with the bluer J-VAR filter centered at 395 nm having twice the amplitude of the reddest J-VAR passband at 861 nm. The normalized amplitudes of the RR Lyrae stars from Gaia and the Zwicky Transient Facility (ZTF) are consistent with the J-VAR trend. Finally, the SDSS templates derived from broadbands also provide a proper description for the medium and narrow band light curves. Conclusions. The J-VAR RR Lyrae catalog offers reliable pulsation parameters and light curves in seven optical filters, allowing the systematic study of amplitude trends from 395 to 860 nm and offering a unique benchmark for theoretical models.

GJ 536 is a low-mass star, located 10 pc away from the Sun, that hosts a low-mass planet orbiting with a period of 8.71 days. Based on an analysis of the radial velocity (RV) time series obtained from the available data of the spectrographs HARPS, HARPS-N, CARMENES and HIRES, we announce the discovery of a second low-mass planet orbiting the star. We performed a RV global analysis on RV, spectroscopic activity indicators, and ASAS photometry, within the multidimensional Gaussian process framework, updated the parameters of GJ 536 b, and found significant evidence of the presence of a second planet. GJ 536 c is a low-mass planet ($m_{p} \sin i$ = 5.89 $\pm$ 0.70 M$_{\oplus}$), orbiting with a period of 32.761 $\pm$ 0.015 days, at a distance of 0.1617 $\pm$ 0.0028 au from its parent star. It induces an RV semi-amplitude of 1.80 $\pm$ 0.20 m$\cdot$s$^{-1}$. Given its distance to the star, it receives a flux of 1.692 $\pm$ 0.069 F$_{\oplus}$, for an equilibrium temperature of 290.5 $\pm$ 9.5 K. We update the mass of the planet GJ 536 b to $m_{p} \sin i$ = 6.37 $\pm$ 0.38 M$_{\oplus}$. The orbits of both planets are consistent with circular. We explored the use of statistical Doppler imaging on the photometric and RV data, and find a tentative projected obliquity of the stellar rotation axis of 58$^{+16}_{-19}$ deg. Current evidence does not support the presence of additional planets with masses > 5 M$_{\oplus}$for orbital periods up to 100 days, or > 10 M$_{\oplus}$ for periods up to 1000 days.

Recently James Webb Space Telescope (JWST) have observed an excess of luminous galaxies at high redshifts ($z \gtrsim 10$). In this work, we investigate whether supermassive primordial black holes (SMPBHs) can explain it by their influence on the ultraviolet luminosity function (UV LF) of high-redshift galaxies. Through Markov Chain Monte Carlo analysis, we constrain the parameters relevant with SMPBHs against current JWST observational data. The results reveal that SMPBHs with masses $M_{\rm PBH} \sim 10^{6.3\text{-}8.3} M_\odot$, abundances $f_{\rm PBH} \sim 10^{-7}\text{-}10^{-5}$, and sub-Eddington ratios $\lambda_E \ll 1$ can effectively enhance the bright end of the UV LF, consistent with JWST observations.

Over the past decade, a significant amount of effort has been put into investigating the ultraviolet (UV) and optical variability of active galactic nuclei (AGNs). Comprehensive studies of intensive multi-wavelength monitoring and surveys of local and high-redshift AGNs have shown that X-ray illumination of AGN accretion discs is a potential explanation for the observed variability. Our main objective is to study the UV/optical power spectra of AGNs under the assumption of X-ray reverberation and to test whether this model can explain the observed power spectra of distant quasars. To do this, we computed the disc transfer function in the case of X-ray reverberation using a recent physical model and studied its dependence on the parameters of the model. This model allows us to explore the variability of X-ray illuminated discs under the scenario in which the X-ray corona is powered by the accretion process or by an external source. We then calculated UV/optical power spectra using the disc transfer function and assuming a bending power law for the X-ray power spectrum. We fitted our models to the observed power spectra of quasars determined by a recent power spectrum analysis of the SDSS Stripe-82 light curves. We demonstrate that X-ray reverberation can fit the power spectra of quasars in our sample well at all wavelengths, from $\sim 1300$Å up to $4000$Å. Our best-fit models imply that the X-ray corona is powered by the accretion disc, and that the black hole spin is probably lower than 0.7, while the X-ray corona height is in the range of $20 - 60 R_{g}$. This is in agreement with previous findings from the application of the X-ray reverberation model to the quasar micro-lensing disc size problem, as well as recent time-lag measurements.

\textit{What is the cosmological information content of a cubic Gigaparsec of dark matter? } Extracting cosmological information from the non-linear matter distribution has high potential to tighten parameter constraints in the era of next-generation surveys such as Euclid, DESI, and the Vera Rubin Observatory. Traditional approaches relying on summary statistics like the power spectrum and bispectrum, though analytically tractable, fail to capture the full non-Gaussian and non-linear structure of the density field. Simulation-Based Inference (SBI) provides a powerful alternative by learning directly from forward-modeled simulations. In this work, we apply SBI to the \textit{Quijote} dark matter simulations and introduce a hierarchical method that integrates small-scale information from field sub-volumes or \textit{patches} with large-scale statistics such as power spectrum and bispectrum. This hybrid strategy is efficient both computationally and in terms of the amount of training data required. It overcomes the memory limitations associated with full-field training. We show that our approach enhances Fisher information relative to analytical summaries and matches that of a very different approach (wavelet-based statistics), providing evidence that we are estimating the full information content of the dark matter density field at the resolution of $\sim 7.8~\mathrm{Mpc}/h$.

Motivated by the observation of extended stellar cores in dark matter (DM) dominated dwarf galaxies, this study investigates a simple mechanism by which stellar cores can form as a result of DM halo expansion. Several non-CDM models predict that the DM distribution thermalizes over time, transforming initially cuspy halos into cores. This transformation weakens the gravitational potential, allowing the stellar component to expand and form diffuse, core-like structures. Using analytical models and adiabatic invariants, we examine stellar systems with purely tangential, purely radial, and isotropic orbits evolving under a slowly changing potential. Across a wide range of initial and final conditions, we find that stellar cores form relatively easily, though their properties depend sensitively on these conditions. Orbit types preserve their nature during the DM halo expansion: tangential and radial orbits remain so, while isotropic orbits remain nearly isotropic in the central regions. Systems with circular orbits develop stellar cores when the initial stellar density logarithmic slope lies between -0.5 and -1.2, whereas radial systems do not form cores. Isotropic systems behave similarly to tangential ones, producing cores that are isotropic in the center but develop increasing radial anisotropy outward; the anisotropy parameter "beta" grows from sim 0.07 at the core radius to sim 0.5 at three core radii. The theoretical and observational literature suggests initial DM profiles with steep slopes and stellar distributions that are shallower and isotropic at the center. Given these conditions, the mechanism predicts stellar cores with radii at least 40 % that of the DM core and inner logarithmic slopes shallower than 0.6.

The MAG payload onboard India's first solar mission, Aditya-L1, is a dual-senssor fluxgate magnetometer designed to measure th interplanetary magnetic field (IMF) while operating in a halo orbit around the first Sun-Earth Lagrangian point (l1). Since becoming operational in January 2024, MAG has continuously recorded local magnetic field data and has captured several solar transient events over the past one year. During these events, the IMF, typically around 5 nT, exhibited significant enhancements in magnitude. This study focuses on three such solar events observed in March, May, and October 2024. Analysis of the magnetic field power spectra during these events reveals fluctuations consistent with Kolmogorov type turbulence, characterized by a spectral slope close to -5/3. To emphasize changes in spectral behavior, the event-day spectra are compared with those from a day when the quiet solar wind conditions prevail. A marked contrast is observed: while the quiet periods exhibit anisotropic turbulence, the extreme events display quasi-isotropic behavior, with spectral slopes closely following the Kolmogorov spectrum across all three IMF components. The results, including detailed variations in spectral slope and turbulence characteristics, are presented and discussed in this paper.

One of the scenarios for bar formation in galaxies involves their interaction with a more massive companion. The stellar component is then transformed from a disk into a bar-like prolate spheroid. I investigated a subsample of 77 bar-like galaxies tidally induced in the cluster environment, selected among the previously studied sample of bar-like galaxies from the IllustrisTNG simulations. I present six clear, convincing examples of bar-like galaxies formed after an interaction with a progenitor of a massive brightest cluster galaxy (BCG) and describe the properties of their bars. For the whole sample, the time of bar formation is strongly correlated with and typically slightly greater than the time of the pericenter passage. All galaxies are strongly stripped of dark matter and gas, and their rotation is similarly diminished. A larger pericenter distance typically requires a higher host mass in order to transform the galaxy, but the interactions show no preference for prograde configurations. The final strength of the bars does not correlate with the amount of tidal stripping experienced because of the variety of initial properties of the progenitors and the subsequent evolution over the next pericenter passages. In spite of difficulties in the interpretation of some cases involving mergers and multiple interactions, the results confirm in the cosmological context the reality of tidal bar formation in cluster environments previously studied using controlled simulations.

Galactic diffuse gamma-ray emission is produced by the interaction of high-energy cosmic rays propagating through the Milky Way with interstellar gas and radiation fields. Its measurement can provide crucial insights into the acceleration and transport of cosmic rays throughout our Galaxy. Here, we present a new analysis of the TeV Galactic diffuse gamma-ray emission using 8 years of HAWC data. This data was processed with the updated Pass 5 processing, enhancing the sensitivity and resolution of the instrument. For the analysis, we make use of Gammapy, an open-source package for gamma-ray astronomy, and recent models of the Galactic diffuse emission at TeV energies. After subtracting the emission from sources using an algorithm akin to that developed for the foreseen CTAO Galactic plane survey, we find significant remaining emission throughout the Galactic plane. We show the latitudinal and longitudinal flux profiles of the emission in multiple parts of the galaxy taking into account various sources of uncertainty and compare to existing models. We find significant emission beyond 3 degree latitude, consistent in shape with the prediction for the interaction of cosmic rays with the interstellar gas. We also demonstrate that our results are consistent with recent LHAASO results when equivalent analysis methods are used.

Double degenerate white dwarf (WD) mergers can exhibit extreme magnetic fields exceeding $10^{8}$ G and rapid rotation, but their spectral-energy distributions and high-energy emission mechanisms remain poorly characterised. ZTF J1901+1458 stands out as the most compact and strongly magnetised object discovered in this class to date. Recent Chandra observations have revealed that the white dwarf is also a source of soft X-ray emission, inconsistent with a photospheric origin. We analyse new phase resolved UV spectroscopy from the HST combined with optical and near-infrared photometry and spectroscopy, with newly developed magnetic atmosphere models to determine its effective temperature, radius, mass, average surface magnetic field strength, and cooling age. Our results demonstrate that the spectral break at $\approx$3000 Å, observed in several highly magnetised WDs, is well-reproduced by our new models, which take into account the effect of magnetic opacities on the structure of the atmosphere. Our best-fit parameters for the WD yield an effective temperature ($T_{\rm{eff}}=28,015\pm 20$ K) and larger radius ($2630\pm10$ km) than previously reported. Furthermore, the near-infrared data exclude the presence of a stellar or brown dwarf companion hotter than $\approx$700 K. We also jointly analyse the previously published Chandra data and new XMM-Newton X-ray spectra. The faint X-ray emission, $L_X =(1.3\pm0.2)\times10^{27}$ erg/s is very soft and highly pulsed on the rotation period of the WD. We suggest that the X-rays are powered by accretion or via the interaction of the WD magnetosphere with CSM. If the rapidly rotating magnetic field could power a weak wind along open field lines, material could be extracted directly from the surface of the WD. Alternatively, accretion of fallback material from the merger or the tidal disruption of a planetary body are possible sources of CSM.

A combined effect of the density-stratified turbulence and a large-scale shear for arbitrary Mach numbers causes the alpha effect and the effective pumping velocity of a large-scale magnetic field. This results in generation of the large-scale magnetic field in colliding protogalactic clouds, merging protostellar clouds and protoplanetary discs. Compressibility of the turbulent velocity field (i.e., finite Mach number effects) does not affect the contributions caused by the inhomogeneity of turbulence to the $\alpha$ tensor and effective pumping velocity. The isotropic part of the alpha tensor is independent of the exponent of the turbulent kinetic energy spectrum. There is also an additional contribution to the effective pumping velocity of the mean magnetic field caused by product of the fluid density stratification and the divergence of the mean fluid velocity due to collapsing (or expanding) astrophysical clouds. However, the alpha tensor is independent of the effects of collapsing or expanding of clouds.

(abridged) The acceleration of particles at the Sun and their propagation through interplanetary space are key topics in heliophysics. Specifically, solar energetic electrons (SEEs) measured in situ can be linked to solar flares and coronal mass ejections (CMEs), which can be observed remotely in radio, optical, UV and X-rays. Solar Orbiter, equipped with a wide range of remote-sensing and in situ detectors, provides an excellent opportunity to investigate SEEs and their solar origin from the inner heliosphere. The Comprehensive Solar Energetic Electron event Catalogue (CoSEE-Cat) provides details for all SEE events measured in situ by Solar Orbiter, as well as associated flares, CMEs, and radio bursts. The catalogue contains key parameters of the SEEs, as derived from the Energetic Particle Detector (EPD), complemented with basic parameters of associated X-ray flares provided by STIX, information on eruptive phenomena seen by EUI, characteristics of type III radio bursts observed by RPW, and indications of CME observed by Metis and SoloHI. The conditions in interplanetary space were characterised using SWA and MAG measurements. Finally, data-driven modelling with the Magnetic Connectivity Tool provided an independent estimate of the solar source position of the SEEs. The first data release contains 303 SEE events observed from November 2020 until the end of 2022. In this paper, we describe the catalogue and provide a first statistical analysis. Preliminary results support the flare-related origin of events with an impulsive ion composition and the association of gradual events with extended structures such as CME-driven shocks or erupting flux ropes. We also show that the commonly observed delays of the solar release times of the SEEs relative to the associated X-ray flares and type III radio bursts are at least partially due to propagation effects.

The accretion of dark matter (DM) onto compact objects and the potential gravitational collapse of neutron stars due to this accretion has become a promising indirect probe of DM properties, complementing terrestrial experiments. We show that the accretion flux of DM on stellar objects is amplified in binary systems due to the complex gravitational interaction of said particles with the binary. We perform few-body Monte Carlo simulations to show that this amplification factor is $\sim4-5$ for circular binaries, small DM velocity dispersions and mass ratios $q\gtrsim0.3$. We use this factor to improve previous constraints on the scattering cross section of non-annihilating bosonic DM with baryonic matter, and derive upper bounds on this cross section from the observation of the binary NS merger associated with GW170817. We also show that the maximally accretable mass fraction of DM by binary NSs is $\lesssim10^{-3}$, even for extreme DM densities only possible in DM spikes, due to the dynamical friction exerted by the ambient DM.

M dwarfs are the most abundant stars in the Galaxy, and their low masses make them natural favourites for exoplanet radial-velocity (RV) searches. Nevertheless, these stars often demonstrate strong stellar activity that is yet to be fully understood. We use high-precision ESPRESSO, HIRES, and HARPS spectroscopy to perform a stellar-activity analysis on the nearby early M dwarf GJ 526 ($d=5.4$ pc). We carry out joint modelling of: (i) stellar rotation in RV, FWHM, and Mount Wilson S-index through Gaussian processes, (ii) long-term trends in these three physical quantities, (iii) RV planetary signals. We constrain the stellar-rotation period to $P_\text{rot}=48.7\pm 0.3$ d, and discover a weak sinusoidal signature in RV, FWHM and S-index of period $P_\text{cyc}=1680^{+50}_{-40}$ d. We propose phase-space trajectories between RV and activity indicators as a novel means to visualise and interpret stellar activity. Current evidence does not support planetary companions of GJ 526.

We present a theoretical framework for seeding and growing supermassive black holes (SMBHs) in dark-matter halos along their assembly histories. Seeds are bred out of Pop-III stars formed during the first collapse of pristine gas in mini-halos that have reached the ${\rm H}_2$-cooling limit, modulated by UV radiation from star formation and dynamical heating from fast halo assembly. Such breeding persists until the enrichment of the intergalactic medium (IGM) enables Pop-II stars to form. Post-seeding growth of black holes (BHs) is driven by distinct channels, starting with episodic super-Eddington accretion associated with nuclear bursts induced by global disturbances of galaxies, followed by sustained sub-Eddington accretion via capturing sub-clouds formed in self-gravitating gas clouds (SGCs) in halos of fast assembly, and ending with merger-dominated, quiescent growth. We implement the model in subhalo merger trees to build a coherent framework to follow the SMBH-galaxy-halo co-evolution over their full lives in the full structure hierarchy. BH seeds are bred with a broad mass spectrum of $M_{\rm BH} = 10$--$10^5\,{\rm M}_\odot$ at $z \approx 20$--$30$ in mini-halos with masses of $10^5$--$10^8\,{\rm M}_\odot$. Nuclear bursts provide the key condition for seeds to grow into SMBHs. The $M_{\rm BH}$-$M_*$ relation is a multi-piece, redshift-dependent function shaped by the interplay among different growth channels. Our model predictions are broadly consistent with existing observations; especially, a population of BHs reminiscent of `little red dots' (LRDs) discovered by JWST naturally results from the seeding and growing processes. Potential future tests of the model are discussed.

The real nature of little red dots (LRDs), a class of very compact galaxies in the early Universe recently discovered by the James Webb Space Telescope, is still poorly understood. The most popular theories competing to interpret the phenomena include active galactic nuclei and enhanced star formation in dusty galaxies. To date, however, neither model gives a completely satisfactory explanation to the population as a whole; thus, alternative theories have arisen, including tidal disruption events (TDEs). By considering observational constraints on the radio emission of LRDs, we discuss whether TDEs are adequate alternatives solving these high-redshift enigmas. We utilise radio flux density upper limits from LRD stacking analyses, TDE peak radio luminosities, and volumetric density estimates. We find that the characteristic values of flux densities and luminosities allow radio-quiet TDEs as the underlying process of LRDs in any case, while the less common radio-loud TDEs are compatible with the model under special constraints only. Considering other factors, such as volumetric density estimates, delayed and long-term radio flares of TDEs, and cosmological time dilation, TDEs appear to be a plausible explanation for LRDs from the radio point of view.

The High-Altitude Water Cherenkov (HAWC) Observatory comprises 300 water Cherenkov detectors, each equipped with four photomultipliers, located on the Volcán Sierra Negra in Mexico at 4,100 masl. This observatory can detect gamma rays in an energy range from 300 GeV to 100 TeV and cosmic rays from 100 GeV to 1 PeV. One of HAWC's primary challenges is characterizing air showers and estimate their physical parameters, a highly complex task due to the nature of the data and the processes involved. Currently, HAWC employs two energy estimators for gamma rays: the ground parameter method and a neural network-based approach. However, for cosmic rays, only the likelihood-based estimator is available. In this work, we leverage machine learning techniques to achieve more accurate estimation of the physical parameters of cosmic rays. These techniques are explored as an alternative for reconstructing the physical properties of extensive air showers using simulated data aligned with the observatory's configuration. Various models were trained and evaluated through an optimized pipeline and the most effective one was selected as the final implementation after a comprehensive comparison. This approach improves the accuracy of physical parameter estimation, contributing significantly to the detailed characterization of cosmic ray events.

The direct detection of circumstellar discs through high-contrast imaging provides key insights into the history and dynamics of planetary systems. Pole-on discs, especially faint debris discs, are difficult to detect and require careful consideration during post-processing to remove stellar residuals from the data while preserving the disc signal. Reference-star differential imaging (RDI) serves as one of the primary post-processing methods for disc observations. We aim to develop a method of reference frame selection that is optimised for the reduction of pole-on discs. Method: We performed principal component analysis based RDI on seven known disc targets and 20 disc-free targets with varying observational conditions, using reference libraries built from frames preselected to best match different observational, atmospheric, and stellar parameters of the science frames. The contrast of the disc-free reductions was measured, and forward modelling was used to estimate the signal loss from over-subtraction using synthetic pole-on discs with two different widths and four different radii. The signal-to-noise ratio (S/N) of the real disc targets was measured. Results: Diverse reference libraries built using subsets of frames that closely matched different parameters achieved the best disc S/N and smallest deviation from the best contrast of each target, outperforming libraries built using a single criterion as a selection metric. Libraries built using frame-to-frame Pearson correlation coefficient alone as a selection criterion achieved the best mean contrast overall. Both selection metrics performed consistently well for all disc radii and observational conditions. We also found that reference libraries built using frames observed close in time to the science frame performed well for discs at small separations, giving the best contrast for ~30% of the targets at a radius of 20px.

Numerical modeling of galactic cosmic rays (GCRs) penetration through the heliosphere to the vicinity of the Sun is considered. Galactic cosmic rays are charged particles with energies exceeding 10 MeV/nucl., originating from far beyond the boundaries of our Solar System. As they penetrate through the heliosphere - the region of space filled by the solar wind - they interact strongly with the interplanetary magnetic field. In this paper, we present numerical approaches to solving the so-called Parker transport equation for the isotropic velocity distribution function of GCRs. This equation includes a convective term, anisotropic diffusion, adiabatic cooling, and drifts. Additionally, the diffusion coefficient is spatially and energy-dependent, varying by several orders of magnitude. Our numerical approaches are based on the finite-difference method (Crank-Nicolson scheme) and the stochastic differential equations (SDE) method. The numerical methods were validated against a known analytical solution under simplified conditions. For the general problem formulation, which involves anisotropic diffusion and the Parker spiral interplanetary magnetic field configuration, we used the most efficient and flexible SDE method and compared the numerical results with the data from the works of Kota & Jokipii (1983) and Burger (2012). Special attention was devoted to incorporating drift along the heliospheric current sheet in the model.

Nanohertz gravitational waves (GWs) from supermassive binary black holes (SMBBHs), detectable via pulsar timing arrays (PTAs), offer a novel avenue to constrain dark energy. Based on cosmological simulations and semi-analytic galaxy formation models, this study explores the detectability of individual nanohertz SMBBH sources using next-generation PTAs and their potential for constraining dark energy under an optimistic scenario considering only the presence of white noise. By constructing light-cone SMBBH populations across hardening timescales ($\tau_H = 0.1/5/10$Gyr) and computing signal-to-noise ratios (SNR), we find advanced PTAs can resolve $10^2$--$10^3$ sources with SNR $> 8$ (primarily at $z < 1$ with chirp masses of $10^8$--$10^{10}M_{\odot}$). If electromagnetic counterparts can be identified, optimal configurations ($\sigma_t = 50$ns, $N_p = 1000$, $T_{\text{obs}} = 30$yr with$ \tau_H \leq 5$Gyr) could constrain the dark energy equation-of-state (EoS) parameter $w$ to $\Delta w \sim 0.023$--$0.048$, where the constraints only exhibit weak dependence on $\tau_H$ within $0.1$--$5$Gyr. If only $10\%$ of GW sources have detectable electromagnetic counterparts, constraints weaken to $\Delta w = 0.075$ ($\tau_H = 0.1$Gyr) and $\Delta w = 0.162$ ($\tau_H = 5$Gyr) under the most optimal parameter configuration. What's more, conservative PTAs ($N_p = 500$, $\sigma_t = 100$--$200$ns) with additional $30$-year data accumulation could double resolvable source counts and improve $\Delta w$ precision by $\sim 40\%$.

Space weathering of lunar minerals, due to bombardment from solar wind (SW) particles and micrometeoroid impacts, modifies the mineralogy within tens of nanometers of the surface, i.e., the rim. Via remote sensing, spectroscopic signatures of these modifications have long been used to gauge surface exposure times on the Moon. However, the relative contributions of the solar wind and micrometeroids in the creation of rim features are still debated, particularly for the few-nm clusters known as nanophase iron (npFe$^0$), which commonly form in ferrous minerals. We address this issue in the laboratory, using deuterium ions and low-energy electrons as a synthetic solar wind plasma to irradiate ilmenite FeTiO$_3$), a common lunar mineral. Characterization by high-resolution scanning transmission electron microscopy and electron energy-loss spectroscopy shows that the solar wind alone creates rims with all the main characteristics of lunar samples. We conclusively identify npFe$^0$ and quantify its distribution as a function of depth and fluence, allowing us to estimate the SW exposure of Apollo soil 71501. Our results confirm that small npFe$^0$ (<10 nm in diameter) form due to the solar wind. Similar experiments could provide microscopic details of space weathering, improving the link between surface modification processes and macroscopic remote sensing data.

3I/ATLAS, the third discovered interstellar object, has a heliocentric speed of 58 km/s and exhibits cometary activity. To constrain the origin of 3I/ATLAS and its past dynamical evolution, we propagate the orbits of 3I/ATLAS and nearby stars to search for stellar encounters. Integrating orbits in the Galactic potential and propagating the astrometric and radial-velocity uncertainties of 30 million Gaia stars, we identify 25 encounters with median encounter distances less than 1 pc. However, because the encounter speeds between 3I/ATLAS and each encounter exceed 20 km/s, none is a plausible host under common ejection mechanisms. We infer stellar masses for most stars and quantify the gravitational perturbations exerted by each individual star or each binary system on 3I/ATLAS. The strongest gravitational scattering perturber is a wide M-dwarf binary. Among all past encounters, the binary's barycenter and 3I/ATLAS reach the small encounter distance of 0.242 pc and the encounter speed of 28.39 km/s,1.64 Myr ago. We further demonstrate that the cumulative influence of the stellar encounters on both the speed and direction of 3I/ATLAS is weak. Based on the present kinematics of 3I/ATLAS to assess its origin, we find that a thin-disk origin is strongly favored, because the thin disk both exhibits a velocity distribution closely matching that of 3I/ATLAS and provides the dominant local number density of stars.

The firm co-existence of intermediate-mass black holes (IMBHs, $M_{\rm BH} \approx 10^3-10^6 M_odot$) in nuclear star clusters (NSCs) remains uncertain because the limited number of verified instances within the local Universe, limited within 3.5 Mpc. They are crucial for our understanding about the formation and evolution of supermassive black holes (SMBHs). The upcoming Extremely Large Telescope (ELT) promises to revolutionize the detection of these mysterious objects. In this study, we simulated the kinematics of an IMBH within the nuclear star cluster of VCC 1861, one of the faintest galaxies in the Virgo Cluster. Using Jeans Anisotropic Modeling (JAM) and stellar density profiles derived from Hubble Space Telescope (HST) data and the HSIM program, we created mock High Angular Resolution Monolithic Optical and Near-infrared Integral field spectrograph (HARMONI) observations for the ELT. We then extract stellar kinematics from these mock data and recover the BH mass using the JAM model with Markov Chain Monte Carlo simulation method. Our results demonstrate the ELT's capability to detect IMBHs with masses comprising 5% of the NSC's mass at the distance of the Virgo Cluster.

Ethylene oxide (c-C$_{2}$H$_{4}$O) and its isomer, acetaldehyde (CH$_{3}$CHO), are important complex organic molecules owing to their potential role in the formation of amino acids (R-CH(NH$_{2}$)-COOH) in ISM. The detection of c-C$_{2}$H$_{4}$O in hot molecular cores suggests that the possible existence of larger ring-shaped molecules containing more than three carbon atoms, such as furan (c-C$_{4}$H$_{4}$O), which shares structural similarities with ribose (C$_{5}$H$_{10}$O5), the sugar component of DNA. In this study, we report the first detection of the rotational emission lines of c-C$_{2}$H$_{4}$O and CH$_{3}$CHO towards the hot molecular core G358.93$-$0.03 MM1, based on observations from the Atacama Large Millimeter/Submillimeter Array (ALMA) in band 7. The fractional abundances of c-C$_{2}$H$_{4}$O and CH$_{3}$CHO relative to H$_{2}$ are $(2.1\pm0.2)\times10^{-9}$ and $(7.1\pm0.9)\times10^{-9}$, respectively. The column density ratio between CH$_{3}$CHO and c-C$_{2}$H$_{4}$O is $3.4\pm0.7$. A Pearson correlation heat map reveals strong positive correlations ($r$ $>$ 0.5) between the abundances and excitation temperatures of c-C$_{2}$H$_{4}$O and CH$_{3}$CHO, suggesting a possible chemical connection between those two molecules. To investigate this further, we conducted a two-phase warm-up chemical model using the gas-grain chemical code UCLCHEM. A comparison between our derived abundances and the predictions from our chemical model and existence model demonstrates good agreement within factors of 0.73 and 0.74, respectively. We propose that c-C$_{2}$H$_{4}$O may form in G358.93$-$0.03 MM1 via the grain surface reaction between C$_{2}$H$_{4}$ and O, but CH$_{3}$CHO may be produced through the surface reaction between CH$_{3}$ and HCO.

T Coronae Borealis (T CrB) is a symbiotic recurrent nova system expected to undergo its next outburst within the next two years. Recent hydrodynamic simulations have predicted the nucleosynthetic yields for both carbon-oxygen (CO) and oxygen-neon (ONe) white-dwarf models, but without accounting for thermonuclear reaction-rate uncertainties. We perform detailed Monte Carlo post-processing nucleosynthesis calculations based on updated thermonuclear reaction rates and uncertainties from the 2025 evaluation. We quantify the resulting abundance uncertainties and identify the key nuclear reactions that dominate them. Our results show that both the CO and ONe nova models robustly produce characteristic CNO isotopes. More pronounced abundance differences emerge for elements with A $\ge$ 20. Sulfur is the most robust observational discriminator between the CO and ONe nova models, with a model-to-model difference of a factor of $\approx$30 and minimal sensitivity to reaction rate uncertainties. Neon, silicon, and phosphorus exhibit even larger abundance differences (factors of $\approx$150-250), providing strong diagnostic potential. While their predicted yields are subject to larger uncertainties, these remain smaller than the model-to-model differences, allowing these elements to serve as useful, though less precise, tracers of white-dwarf composition. Chlorine, argon, and potassium also differ between models, but the 1$\sigma$-abundance ranges for the CO and ONe models overlap, reducing their present usefulness as composition tracers. We find that only nine nuclear reactions dominate the abundance uncertainties of the most diagnostically important isotopes, and their influence is largely independent of the underlying white-dwarf composition. These results provide guidance for future experimental efforts and for interpreting ejecta compositions in the next eruption of T CrB.

We present a reanalysis of the metallicity of the double red clump (RC) stars from the Milky Way bulge. Two leading explanations for the existence of the double RC concern possible differences in chemical composition (multiple populations of stars) or distance (X-shaped bulge). We aim to verify the chemical composition hypothesis by determining the mean metallicity of each RC. We use infrared photometric data and metallicities from a previous study (that are based on the Michigan/Magellan Fiber System spectra). In contrast with previous studies, we assign stars to RCs or the red giant branch using a Bayesian approach. Our resulting difference between mean metallicity of the two RCs equals: $0.23^{+0.19}_{-0.24}$ or $0.28^{+0.17}_{-0.18}~\mathrm{dex}$, if the red giant branch bump is included or not, respectively. Because of the high statistical error, the result does not confirm the multiple populations hypothesis.

Aims. We derive the stellar mass function (SMF) of quiescent and star-forming galaxies at z <= 0.2 using 12-band optical photometry from the third data release (DR3) of the Javalambre Photometric Local Universe Survey (J-PLUS) over 3,284 deg^2. Methods. We select approximately 890,000 galaxies with r <= 20 mag and photometric redshifts in the range 0.05 <= z <= 0.20. Stellar masses and star formation rates were derived through spectral energy distribution fitting with CIGALE, confronted with spectroscopic samples. Galaxies are classified as star-forming or quiescent based on their specific star formation rate (sSFR), adopting log(sSFR [yr^-1]) = -10.2. We compute SMFs for both populations using the 1/Vmax method, apply completeness corrections, and fit Schechter functions. Results. The SMFs from J-PLUS DR3 are well described by Schechter functions and agree with previous photometric and spectroscopic studies. The characteristic mass for quiescent galaxies, log(M*/Msun) = 10.80, is 0.4 dex larger than that of star-forming galaxies. The faint-end slope is steeper for star-forming galaxies (alpha = -1.2) than for quiescent ones (alpha = -0.7). The quiescent fraction rises by 40 percent per dex in stellar mass, reaching fQ > 0.95 at log(M*/Msun) > 11. Comparisons with the GAEA semi-analytic model reveal an excess of star-forming galaxies at intermediate masses. Conclusions. J-PLUS DR3 stellar mass functions and quiescent fractions are consistent with the literature and provide robust constraints for galaxy formation models. Quiescent galaxies represent 45 percent of number density above log(M*) > 9, but 75 percent of stellar mass density. The use of 12 optical bands, including 7 narrow filters, improves redshift precision by 20 percent, enabling more accurate SED fitting and galaxy classification.

Hydrogen-deficient binary stars comprise one star which has been stripped of its hydrogen through mass transfer to a binary companion. Observations show that the companion is able to accrete several solar masses without spinning up to critical rotation, and so there must be a mechanism to drain spin angular momentum from the accretor. We test magnetically coupled winds and magnetic star-disc coupling as possible mechanisms and find that, while the disc coupling is negligible, the winds are sufficient to allow the accretor to gain mass without spinning up to critical rotation. However, in order to fully replicate observations, time-dependent scalings of the dynamo-generated magnetic field are needed.

Context: While the LMC's influence on MW stellar streams has been extensively studied, streams associated with the Clouds have received far less attention. Beyond the Magellanic Stream, only four stream candidates (S1-S4) have been reported. Aims: We focus on the S3 stream, a long ($\sim30^\circ$) and narrow ($\sim1.2^\circ$) structure at 60-80 kpc, nearly aligned with the LMC. Our goals are: 1) to validate the stream through a kinematic analysis of S3 candidates with Gaia DR3 data; 2) to enlarge the sample of potential members; and 3) to model the stream in order to test its association with either the MW or the LMC. Methods: We selected new S3 candidates with a neural network classifier trained on Gaia DR3 data, and further reduced contamination through a cut in the proper-motion space. To investigate the origin of S3, we evolve stream models within time-dependent, deforming MW and LMC haloes, thereby accounting for possible effects of the MW-LMC interaction. Results: We identify 1,542 high-confidence new S3 stream candidates and find that the stream's apparent width has grown from $\sim1.2^\circ$ to $\sim3$-$4^\circ$ compared to previous studies. We also present a list of 440 potential S3 red clump stars, which are valuable targets for spectroscopic follow-up thanks to their well-defined luminosities and ability to yield precise distances. Both modelling and a comparison of S3 stars' closest approach distance and velocity with the LMC's escape velocity indicate that S3 is unlikely to originate from the LMC, instead representing a distant ($\sim75$ kpc) MW stream. Conclusions: S3 is the most distant ($\sim75$ kpc) extended ($\sim30^\circ$ long, $\sim3$-$4^\circ$ thick) MW stream known, offering a unique probe of the outer halo and the LMC's recent influence. Its angular width corresponds to a physical thickness of $\sim4$-5 kpc, making S3 among the thickest streams discovered.

The ongoing discussion about the atomic chemical composition of the Sun is commented on. The main focus in this review is on the deviation of the solar composition from that of most other solar-type stars in that its ratio of volatiles (like the elements C, N, O, S, P and Zn) to the refractories (most metals, like Ba, Ca, Ti, Y, Al, Sc and Zr) tends to be higher in the Sun by 10 to 20%. What does this tell about the formation and evolution of the Solar System? Scenarios in terms of galactic evolution, formation of the pre-solar nebula, of the evolution of the protoplanetary disk, of the engulfing of planets, and of other processes within the Solar System are considered, as well as the evolution of binary stars with similarly different chemical composition. Finally, implications, if any, on the habitability of the Solar System are commented on.

A recent observation of the exoplanet K2-18b sparked interest among scientists - large amounts of carbon dioxide and methane were detected in an H2-rich background atmosphere. If the planet is a hycean world (liquid water ocean + hydrogen-dominated atmosphere), it could be habitable under certain conditions. The presence of carbon, hydrogen and oxygen was already confirmed, however, there was no detection of nitrogen or its compounds. Molecular nitrogen is difficult to detect directly. This study concentrates on possible photochemical products of N2 such as HCN, NH3 and HC3N. We set approximate limits on the amount of nitrogen bearing species by varying atmospheric parameters, such as the Eddy Diffusion coefficient and the amount of N2 present from 10 ppm to 10%. If the bulk nitrogen-containing gas in the atmosphere is N2, photochemistry produces only trace amounts of the aforementioned species. However, if ammonia is the main source of nitrogen, then the quantities of NH3, CH5N and HCN approach detectable range. HC3N and NO are bad tracers of the nitrogen source in the atmosphere, because they are produced in similar amounts in all tested scenarios. Assuming equilibrium chemistry at the surface of K2-18b results in underprediction of CO2 abundance. This result combined with the non-detection of ammonia by JWST suggests the planet is not a typical sub-Neptune, but could be indeed a hycean world or magma ocean planet. We also found that C2H6 is produced in significant amounts - if it is detected in the future, it could serve as a proxy for DMS presence.

The kinematic Sunyaev-Zel'dovich (kSZ) effect in the cosmic microwave background (CMB) is a powerful probe of gas physics and large-scale structure (LSS) in our universe. We consider the "projected-field" kSZ estimator, which involves cross-correlating a foreground-cleaned, filtered, squared CMB temperature map with an LSS tracer, and requires no individual tracer redshifts. We compare $\verb|class_sz|$ halo model calculations of projected-field kSZ cross-correlations with measurements of these signals from the Websky numerical simulations. We cross-correlate halo density maps from Websky with various CMB secondary signals. We first validate our halo model by comparing its predictions for thermal SZ (tSZ) and patchy screening ($\tau$) cross-correlations to measurements of these signals from Websky. We consider three different halo redshift ranges in our comparisons. We also construct our own kSZ, tSZ, and $\tau$ maps to validate the form of the relevant profiles. Following the tSZ and $\tau$ validation, we compare projected-field kSZ calculations between the halo model and the simulations. We use filters constructed for $\textit{Planck}$ and the Simons Observatory (SO) to assess the accuracy of the halo-model kSZ predictions for experiments of differing sensitivity. Overall, we find good agreement, particularly at $\textit{Planck}$ sensitivity. However, we find an $\approx$ 20$\%$ difference between our halo model and the simulations for SO, which significantly exceeds the predicted error bars. We note that our halo model includes only the dominant expected term in the projected-field kSZ signal; the magnitude of the difference between our model and the simulations is consistent with previous predictions for terms arising from other contractions in the theory calculation. These terms will need to be included to obtain unbiased inference from upcoming projected-field kSZ measurements.

Despite being only 85 pc away, the open cluster Coma Berenices (Coma Ber) has not been extensively studied. This is due in part to its sparseness and low proper motion, which together made Coma Ber's membership challenging to establish. Gaia data for $\approx$400 previously cataloged candidate cluster stars allowed us to identify $\approx$300 as members. With [Fe/H] measurements for nine members, we found that Coma Ber has a solar metallicity, and then fit isochrones to its color--magnitude diagram to determine that it is 675$\pm$100 Myr old. With photometry obtained by the Transiting Exoplanet Survey Satellite (TESS) and Zwicky Transient Facility (ZTF), we measured rotation periods for 137 of Coma Ber's low-mass stars, increasing the sample of members with measured periods by a factor of six, and extending the rotational census for the cluster from its late F stars through to its fully convective M dwarfs. By measuring the equivalent width of the H$\alpha$ line for $\approx$250 stars and collecting X-ray detections for $\approx$100 ($\approx$85% and $\approx$33% of the cluster's members, respectively), we characterized magnetic activity in Coma Ber and examined the dependence of chromospheric and of coronal activity on rotation in these stars. Despite having a metallicity that is 0.2 dex below that of their coeval cousins in Praesepe and the Hyades, low-mass stars in Coma Ber seem to follow a similar rotation--activity relation. In detail, however, there are differences that may provide further insight into the impact of metallicity on this still poorly understood relation.

We present Stokes I continuum analysis for a volume-limited sample ($<40~\rm{Mpc}$) of hard X-ray selected active galactic nuclei (AGNs) using $4-12$ GHz observations with the Karl G. Jansky Very Large Array (VLA). All of the 25 sources analyzed here have previously been observed with the Very Long Baseline Array (VLBA) to probe their subparsec projected physical scales, but detected emission has only been measured for 12 of the sources at $C$ band (4.4 GHz), despite expectations. We determined that coronal emission is unlikely to be a dominant emission mechanism for the sources not detected by the VLBA, and the emission measured with the VLA is likely produced beyond parsec spatial scales. We also explore potential radiation mechanisms for the circumnuclear radio emission that is produced beyond the observable ~parsec physical scales probed with the VLBA but within the $\leq30-110$ parsec spatial scales observed with the VLA. From an energetics perspective, we find that all targets have extranuclear radio emission that is compatible with AGN winds, assuming a maximum of 10% of the bolometric output can supply the mechanical energy observed. We also find that the excess emission is likely too strong for star formation alone when compared to results from optical spectroscopy, but may contribute in smaller capacities.

The Nancy Grace Roman Space Telescope (Roman) will conduct a Galactic Exoplanet Survey (RGES) to discover bound and free-floating exoplanets using gravitational microlensing. Roman should be sensitive to lenses with mass down to ~ 0.02 $M_{\oplus}$, or roughly the mass of Ganymede. Thus the detection of moons with masses similar to the giant moons in our Solar System is possible with Roman. Measuring the demographics of exomoons will provide constraints on both moon and planet formation. We conduct simulations of Roman microlensing events to determine the effects of exomoons on microlensing light curves, and whether these effects are detectable with Roman. We focus on giant planets from 30 $M_{\oplus}$ to 10 $M_{Jup}$ on orbits from 0.3 to 30 AU, and assume that each planet is orbited by a moon with moon-planet mass ratio from $10^{-4}$ to $10^{-2}$ and separations from 0.1 to 0.5 planet Hill radii. We find that Roman is sensitive to exomoons, although the number of expected detections is only of order one over the duration of the survey, unless exomoons are more common or massive than we assumed. We argue that changes in the survey strategy, in particular focusing on a few fields with higher cadence, may allow for the detection of more exomoons with Roman. Regardless, the ability to detect exomoons reinforces the need to develop robust methods for modeling triple lens microlensing events to fully utilize the capabilities of Roman.

Latin Hypercube Sampling (LHS) is a prominent tool in simulation design, with a variety of applications in high-dimensional and computationally expensive problems. LHS allows for various optimization strategies, most notably to ensure space-filling properties. However, LHS is a single-stage algorithm that requires a priori knowledge of the targeted sample size. In this work, we present LHS in LHS, a new expansion algorithm for LHS that enables the addition of new samples to an existing LHS-distributed set while (approximately) preserving its properties. In summary, the algorithm identifies regions of the parameter space that are far from the initial set, draws a new LHS within those regions, and then merges it with the original samples. As a by-product, we introduce a new metric, the LHS degree, which quantifies the deviation of a given design from an LHS distribution. Our public implementation is distributed via the Python package expandLHS.

The population study of stellar-mass black hole (sBH) binaries with ground-based gravitational wave detection has achieved tremendous success in recent years. Future observation of extreme mass-ratio inspirals will similarly require proper population analysis that identify the formation channels, measuring the branch ratio(s) and characterizing major properties within each major channel. In this work, we propose that the measurement of eccentricity, inclination, and component mass provides critical information to distinguish different formation channels and probe detailed formation mechanisms. Focusing on the dry and wet extreme mass-ratio inspirals, we establish the theoretical expectation of these observables in each formation channel. We also discuss how their distributions can be used to probe lifetime and turbulence level of active galactic nuclei disks, accretion patterns of supermassive black holes and population properties of sBHs within nuclear star clusters.

We describe some properties of the hyperbolically symmetric black hole (hereafter referred to as the $HSBH$) proposed a few years ago. We start by explaining the main motivation behind such an idea, and we determine the main differences between this scenario and the classical black hole (hereafter referred to as the $CBH$) scenario. Particularly important are the facts that, in the $HSBH$ scenario, (i) test particles in the region inside the horizon experience a repulsive force that prevents them from reaching the center, (ii) test particles may cross the horizon outward only along the symmetry axis, and (iii) the spacetime within the horizon is static but not spherically symmetric. Next, we examine the differences between the two models of black holes in light of the Landauer principle and the Hawking results on the eventual evaporation of the black hole and the paradox resulting thereof. Finally, we explore what observational signature could be invoked to confirm or dismiss the model.

String theory has strong implications for cosmology: it tells us that we cannot have a cosmological constant, that single-field slow-roll inflation is ruled out, and that black holes decay. We elucidate the origin of these statements within the string-theoretical swampland programme. The swampland programme is generating a growing body of insights that have yet to be incorporated into cosmological models. Taking a cosmologist's perspective, we highlight the relevance of swampland conjectures to black holes, dark matter, dark energy, and inflation, including their implications for scalar fields such as quintessence and axions. Our goal is to inspire cosmological model builders to examine the compatibility of effective field theories with quantum gravitational UV completions and to address outstanding cosmological tensions such as the Hubble tension. This comprehensive literature review presents clear definitions, cosmological implications, and the current status - including evidence and counterexamples - of the following swampland conjectures: the anti-de Sitter distance conjecture (AdSDC), the completeness conjecture (CC), the cobordism conjecture, the de Sitter conjecture (dSC), the swampland distance conjecture (SDC), the emergence proposal (EP), the Festina Lente Bound (FLB), the finite number of massless fields conjecture (or finite flux vacua conjecture (FFV)), the no global symmetries conjecture, the no non-supersymmetric theories conjecture, the non-negative null energy condition conjecture, the positive Gauss-Bonnet term conjecture, the species scale conjecture, the gravitino swampland conjecture (GSC), the tadpole conjecture, the tameness conjecture, the trans-Planckian censorship conjecture (tPCC/TCC), the unique geodesic conjecture, and the weak gravity conjecture (WGC), including the repulsive force conjecture (RFC).

The main objective of this study is to investigate the viability and stability of a pulsar filled with anisotropic matter in $f(\mathcal{Q}, \mathbb{T})$ gravity, where $\mathcal{Q}$ represents non-metricity and $\mathbb{T}$ is the trace of the energy-momentum tensor. In this context, we employ non-singular solution and a particular model of this gravity. We use junction conditions to evaluate unknown constants in the metric coefficients. Observations from the pulsar SAX J1748.9-2021 star are employed to validate the model, producing stable configurations that address both geometric and physical characteristics. This framework establishes relationships between various physical quantities, including fluid parameters, anisotropy, mass-radius relation, redshift, the Zeldovich condition, energy conditions, causality conditions, adiabatic index, Tolman-Oppenheimer-Volkoff equation, the equation of state parameter, and compactness. Our findings confirm the viability and stability of the proposed pulsar star in this theoretical framework.

The time-ordered multilayer integrals have long been cited as major challenges in the analytical study of cosmological correlators and wavefunction coefficients. The recently proposed family tree decomposition technique solved these time integrals in terms of canonical objects called family trees, which are multivariate hypergeometric functions with energies as variables and twists as parameters. In this work, we provide a systematic study of the analytical properties of family trees. By exploiting the great flexibility of Mellin representations of family trees, we identify and characterize all their singularities in both variables and parameters and find their exact series representations around all singularities with finite convergent domains. These series automatically generate analytical continuation of arbitrary family trees over many distinct regions in the energy space. As a corollary, we show the factorization of family trees at zero partial-energy singularities to all orders. Our findings offer essential analytical data for further understanding and computing cosmological correlators.

Loop contributions to cosmological correlators and to the associated wavefunction are of key theoretical and phenomenological interest. Here, we investigate and compare different renormalisation schemes proposed in the literature to handle ultraviolet divergences and develop new schemes adapting $\eta$ regulators to de Sitter spacetime. We focus on one-loop contributions to the quadratic wavefunction coefficient of a shift-symmetric massless scalar in de Sitter spacetime, which is a good toy model of primordial curvature perturbations. We show that different implementations of dimensional regularisation agree with each other and with unitarity and scale invariance in the final renormalised result. Imposing unitarity in the form of the cosmological optical theorem, we define a class of unitary and analytic $\eta$ regulators that agree with dim reg but feature considerable technical and conceptual simplifications. We show that the imaginary part of all one-loop wavefunction coefficients is universally fixed in terms of the logarithmic running of the real part, under the assumptions of scale invariance, Bunch-Davies vacuum and light bulk fields. Our work resolves discrepancies in the literature, establishes regulator-independent predictions for the imaginary part at one loop, and provides a practical framework for computing quantum contributions to cosmological correlators.

We present the spectrum of primordial gravitational wave (GW) expected from the presence of primordial black holes (PBH) and inflaton in the early Universe. For the first time, we combine the waves produced by the PBH decay, with their density fluctuation counterpart, as well as their effects on the GW produced by the inflaton {\it after} (high frequency modes) and {\it before} (low frequency modes) the end of inflation. We generalize our study for a potential $V(\phi)\propto \phi^k$ during reheating. We also extend our study, taking into account a possible memory burden effect to see how it can affect the shape of the spectrum.

General relativity, treated as a low-energy effective field theory, predicts quantum corrections to Newton's law of gravitation arising from loops of matter and graviton fields. While these corrections are utterly negligible when considering the Standard Model particle content, the situation changes dramatically in the presence of a hidden or dark sector containing a very large number of light degrees of freedom. In such cases, loop-induced modifications to the Newtonian potential can accumulate to levels testable in laboratory and astrophysical probes of gravity at short distances. In this work we systematically derive and constrain the impact of large dark sectors on precision tests of Newton's law, translating effective field theory predictions into the experimental language of Yukawa-type deviations and inverse-square law deformations. By mapping precision fifth-force constraints onto bounds on species multiplicities and masses, we show that current and future experiments already impose nontrivial constraints on the size and structure of hidden sectors coupled only gravitationally. Our results provide a model-independent framework for confronting dark-sector scenarios with precision gravity data, and highlight the complementarity of particle physics and short-distance gravitational tests in probing new physics beyond the Standard Model.

Accurate segmentation of solar filaments in H-alpha observations is critical for determining filament chirality, a key factor in the behavior of Coronal Mass Ejections (CMEs). However, existing methods often fail to capture fine-scale filament structures, particularly barbs, due to a limited ability to model long-range dependencies and spatial detail. We propose EdgeAttNet, a segmentation architecture built on a U-Net backbone by introducing a novel, learnable edge map derived directly from the input image. This edge map is incorporated into the model by linearly transforming the attention Key and Query matrices with the edge information, thereby guiding the self-attention mechanism at the network's bottleneck to more effectively capture filament boundaries and barbs. By explicitly integrating this structural prior into the attention computations, EdgeAttNet enhances spatial sensitivity and segmentation accuracy while reducing the number of trainable parameters. Trained end-to-end, EdgeAttNet outperforms U-Net and other U-Net-based transformer baselines on the MAGFILO dataset. It achieves higher segmentation accuracy and significantly better recognition of filament barbs, with faster inference performance suitable for practical deployment.

The recent NICER observation of PSR J0614-3329, revealing the smallest reliably measured neutron star radius of $R = 10.29^{+1.01}_{-0.86}$ km at mass $M = 1.44^{+0.06}_{-0.07} M_\odot$, provides an unprecedented constraint on the equation of state of dense matter. We investigate the implications of this measurement for the origin of nucleon mass within the parity doublet model framework, which naturally incorporates both chiral variant and chiral invariant mass components. We construct unified equations of state by employing the parity doublet model with isovector scalar meson $a_0(980)$ for hadronic matter up to twice nuclear saturation density, smoothly connected to a Nambu-Jona-Lasinio-type quark model at higher densities through a crossover transition. By systematically varying the chiral invariant mass $m_0$ and quark matter parameters, we determine which values simultaneously satisfy all current astrophysical constraints, including gravitational wave observations from GW170817, NICER measurements of several pulsars, and the existence of two-solar-mass neutron stars. The inclusion of PSR J0614-3329 dramatically refines the allowed range of the chiral invariant mass from the previous constraint of $580~\text{MeV} \lesssim m_0 \lesssim 860~\text{MeV}$ to $800~\text{MeV} \lesssim m_0 \lesssim 860~\text{MeV}$, raising the lower bound by approximately 220 MeV. This result indicates that the chiral invariant mass must constitute at least 85\% of the nucleon mass, challenging the traditional picture of nucleon mass generation through spontaneous chiral symmetry breaking alone and highlighting the importance of gluon condensation and other non-chiral mechanisms.

Our study explores gravitational baryogenesis in the context of f(R, Lm, T) gravity, where R denotes the Ricci scalar, Lm represents the Lagrangian density of the matter field, and T stands for the metric contraction of T_{mu nu}. We focus on a linear model: f(R, Lm, T) = alpha R + beta Lm + gamma T, and examine the parameter constraints for a successful baryon asymmetry generation in four different eras of the cosmos under the assumption of a power-law cosmic expansion. The computed baryon-to-entropy ratio is found to be consistent with the observed order of asymmetry ratio, 9.42 x 10^-11. Furthermore, the study is extended to the generalized framework of gravitational baryogenesis, where the outcome shows strong agreement with the current observational data. Our findings indicate that the f(R, Lm, T) framework provides a compatible theoretical foundation for producing the observed matter imbalance of the cosmos, thereby emphasizing its potential significance in early-universe cosmology.

In this work, we investigate the generation of the ambipolar electric field in a gravitationally stratified, collisionless plasma atmosphere. In such environments, gravity tends to separate charged species. To prevent separation an electric field, classically described by the Pannekoek-Rosseland expression, is usually imposed externally. Here, we propose a self-consistent method to recover this field based on a multi-mode Fourier expansion of the electrostatic interaction. We show that, under suitable conditions, this approach naturally leads to the ambipolar electric field and restores charge neutrality. The method is tested in both isothermal and multi-temperature plasma configurations. This framework provides a foundation for future developments that may include collisions, ionization, and asymmetric boundary conditions to model more realistic stellar atmospheres.

We present an extended investigation of a recently introduced model of gravitationally confined, collisionless plasma (Barbieri et al. 2024a), which showed that rapid temperature fluctuations at the base of the plasma, occurring on timescales much shorter than the electron crossing time, can drive the system into a non-thermal state characterized by anti-correlated temperature and density profiles, commonly referred to as temperature inversion. To describe this phenomenon, a temporal coarse-graining formalism was developed (Barbieri et al. 2024b). In this work, we generalize that approach to cover regimes where the timescales of temperature fluctuations are comparable to or exceed the electron crossing time. We derive a set of kinetic equations that incorporate an additional term arising from the coarse-graining procedure, which was not present in the earlier formulation. Through numerical simulations, we analyze the plasma dynamics under these broader conditions, showing that the electric field influences the system when fluctuation timescales approach the electron crossing time. However, for timescales much larger than the proton crossing time, the electric field becomes negligible. The observed behaviours are interpreted within the framework of the extended temporal coarse-graining theory, and we identify the regimes and conditions in which temperature inversion persists.

Red giants (RGs) provide a promising astrophysical environment for capturing dark matter (DM) via elastic scattering with stellar nuclei. Captured DM particles migrate toward the helium-rich core and accumulate into a compact configuration. As the DM population grows, it can become self-gravitating and undergo gravitational collapse, leading to adiabatic contraction through interactions with the ambient medium. The resulting energy release, through elastic scattering and, where relevant, DM annihilation during collapse, locally heats the stellar core and can trigger helium ignition earlier than that predicted by standard stellar evolution. We analyze the conditions under which DM-induced heating leads to runaway helium burning and identify the critical DM mass required for ignition. Imposing the observational constraint that helium ignition must not occur before the observed luminosity at the tip of the RG branch, we translate these conditions into bounds on DM properties. Remarkably, we find that RGs are sensitive to DM, particularly with masses around $10^{11} \,{\rm GeV}$ and spin-independent scattering cross sections near $10^{-37}\,{\rm cm}^2$, which is comparable to the reach of current terrestrial direct detection experiments.

We propose a {\em boomerang mechanism} for the explanation of the excess radio background detected by ARCADE. In an early stage, at a temperature $T \sim 100\,{\rm keV}$, a fraction of relic neutrinos is resonantly converted into dark neutrinos by mixing induced by a pre-existing lepton asymmetry. Dark neutrinos decay much later into a dark photon, mixed with photon, and a dark fermion, with a lifetime longer than the age of the Universe, as required by a solution to the excess radio background. This scenario circumvents the upper bound on the neutrino magnetic moment but still implies a testable lower bound.

We explore the possibility of realizing a non-singular bounce in the early universe within the framework of modified gravity with spacetime torsion. In Einstein Cartan theory, torsion is embedded in the spacetime by adding an antisymmetric part in affine connection . We consider generalized version of the framework as $f(\bar{R})$, $\bar{R}$ being the scalar of the modified curvature tensor. $f(\bar{R})$ gravity is recast in Einstein frame as non-minimally coupled scalar tensor theory where the scalar field gets coupled with a rank 2 antisymmetric torsion field through derivative couplings. We investigate whether the introduction of three additional torsion-dependent terms in Einstein frame help to realize a bounce. We first explore this cosmological system in the background of a homogeneous and isotropic FRW spacetime but inclusion of the torsion terms are insufficient to produce a bounce in this symmetric setting. Motivated by this limitation, we relax the symmetry and generalize the background to include inhomogeneity and anisotropy. In this setup, the dynamics is modified in such a way that a bouncing solution is possible without invoking phantom fields or energy condition violations. We have also found the exact solutions of all the fields and reconstructed the modified gravity form.

We explore the role of color superconductivity in quarkyonic matter under the conditions of color and electric neutrality at $\beta$- and strong equilibrium, as relevant for neutron stars. By explicitly incorporating the color-superconducting pairing gap into the phenomenological model of a smooth transition from hadron to quark matter, we extend the known quarkyonic framework to include this essential aspect relevant at high densities. The momentum dependence of the pairing gap, motivated by the running of the QCD coupling and introduced similarly to chiral quark models with nonlocal interaction, is a novel element of the model that is crucial for enabling the simultaneous onset of all color-flavor quark states in the presence of color superconductivity. While asymptotically conformal behavior of the present model is ensured by construction, we demonstrate that reaching the conformal limit in agreement with the predictions of perturbative QCD is provided by the proper momentum dependence of the thickness of the hadron shell in momentum space. We employ the flexible meta-modeling approach to nuclear matter, analyzing the structure of the hadron shell in momentum space and focusing on the effects of color superconductivity in quarkyonic matter. Similar to the effects induced by the onset of the quarkyonic phase, color superconductivity leads to stiffening of the equation of state of the NS matter. This causes a significant impact on observable properties of neutron stars, which are analyzed and compared to recent astrophysical and theoretical constraints. We argue that the developed model of color-superconducting quarkyonic matter provides a new, consistent tool for studying the scenario of smooth quark-hadron transition in NSs.