Astrophysics

Stellar ages are an important parameter for studying the chemical evolution of the Galaxy. To improve age estimates, various complementary methods to the conventional isochrone-fitting method have been implemented in the last decade. The [Y/Mg] ratio has been proposed as a chemical clock for solar-metallicity stars, due to its strong dependence on stellar age. In this work, we study the behaviour of the abundance ratio [Y/Mg] in metal-poor stars, along with other solar-type disk stars, as a function of stellar age determined through isochrones. The analysis is based on the line-by-line differential technique, applied to a sample covering a wide metallicity range ($-$0.70 $\leq$ [Fe/H] $<$ +0.34), using high-resolution (R = 115,000) and high S/N spectra (= 270 - 1000) taken with the HARPS spectrograph at the ESO La Silla Observatory. We find that the stellar sample follows a metallicity-dependent [Y/Mg]-Age relation.

SIRMOS is a mission concept for a future NASA Astrophysics Explorer opportunity that aims to revolutionize our understanding of the universe by mapping the large-scale structure of galaxies in unprecedented breadth and detail to explore cosmic origins and evolution. Specifically, the primary science goals of SIRMOS are to discover how cosmic inflation seeded large-scale structure, reveal the nature of the accelerating expansion of the universe, and measure the sum of neutrino masses to exceptionally high precision. Its secondary science goals include determining how environment shapes galaxy evolution at cosmic noon and beyond, and probing the Milky Way's dust-enshrouded regions, reaching the far side of our Galaxy. To accomplish its transformative science goals, SIRMOS executes a 3-year cosmology survey over the Euclid footprint of ~14,000 deg$^2$, obtaining slit spectra for ~100 million galaxies at 1<z<4. SIRMOS is the first space mission designed specifically to leverage Euclid's wide near-infrared (IR) imaging survey for target selection and employs a digital micro-mirror device (DMD) to acquire up to 4,000 simultaneous spectra over a wide 0.9 deg$^2$ field of view. The instrument's excellent spectral resolution of $R=1300$ and continuous wavelength coverage from 1.25--2.5 $\mu$m capture the redshifts of distant galaxies with no gaps, reducing systematic biases to achieve ground-breaking science.

In Metacalibration the shear response of a weak lensing measurement is estimated by applying an artificial shear to the image, but the shear operation imprints a spin-2 modulation on the image noise power, which biases the measured response. The standard fix adds a sheared noise field that symmetrizes the anisotropy, at the cost of doubling the noise variance ($\sqrt2$ in the noise). The fusion correction presented in this note reaches the same unbiased response while adding only the minimum power needed. It measures the noise power transfer by passing an impulse through the Metacal process, forms the common-level azimuthal deficit that equalizes the spin-2 ($m{=}2$) and spin-6 ($m{=}6$) modulations across the metacal types, and adds just that deficit by filtering the rotated noise field. The fusion correction raises the per-pixel noise by only $\sim2\%$ for a round PSF (versus $\sqrt2$ for the standard correction), rising toward the $\sqrt2$ level only for highly elliptical PSFs.

We develop an effective field theory (EFT) of intrinsic alignments at the level of spin-2 field fluctuations of large-scale structure tracers, such as the shapes of galaxies and dark matter halos. Our perturbative model includes the non-linear treatment of the Zel'dovich displacement, and contains all necessary shape operators through the third order. We apply our field-level model to the full 3D distribution of galaxy shapes, whose sky projections are a known contaminant of cosmic shear measurements. Our field-level EFT model achieves a better description of the helicity fields of dark matter halo shapes than the standard non-linear alignment (NLA) and tidal torquing + tidal alignment (TATT) models in the literature, as evidenced by improved correlations with the simulations' initial conditions. We perform precision measurements of field-level bias parameters by means of a generalized least-squares problem, for which we derive an optimal estimator and analytic covariance matrices. We measure the full set of linear, quadratic, and cubic shape bias coefficients as a function of halo mass in the $\texttt{Quijote}$ N-body simulations. We then study the intrinsic alignments of galaxies in the $\texttt{FLAMINGO}$ hydrodynamical simulation, focusing on observationally relevant samples: spirals, ellipticals, luminous red galaxies (LRG) and emission-line galaxies (ELG). We detect linear and nonlinear alignment coefficients at high significance for LRG, spiral and elliptical galaxies. We also find evidence for non-zero density-weighted tidal bias coefficient of the simulated ELG. This work supports the notion that EFT-based models of alignments will be paramount in optimally extracting constraints from future shape correlations, and lays the foundation for the development of simulation-based priors for future galaxy shape samples.

Context. Cluster morphology reflects assembly history and dynamical state. High-resolution weak lensing can reveal departures from spherical symmetry, but its ability to recover two-dimensional shapes remains less explored. Aims. We assess how reliably weak lensing recovers projected cluster morphology and its dependence on orientation and dynamical state. We also compare large-scale weak-lensing morphology with that traced by strong lensing near the cluster centre. Methods. We study three clusters at $z=0.22$ from The Three Hundred Project, representing relaxed, mildly disturbed and unrelaxed systems. For each, we consider three random projections and three along the principal axes of the mass tensor. For each projection, we generate 128 weak-lensing catalogues with a source density of 30 arcmin$^{-2}$ and intrinsic ellipticity dispersion $\sigma_{\epsilon}=0.3$. We constrain mass and concentration from one-dimensional NFW and BMO fits, then recover ellipticity, position angle and centre using a two-dimensional elliptical NFW model. We also measure morphology from true convergence maps, Kaiser \& Squires reconstructions and strong-lensing tangential critical lines. Results. Recovered parameters depend on orientation and dynamical state. The relaxed cluster has similar inner and large-scale shapes, whereas disturbed systems appear more elliptical centrally. Two-dimensional weak-lensing modelling recovers the projected mass orientation despite source sampling and shape noise. Kaiser \& Squires reconstructions recover the position angle well but favour rounder mass distributions. Centroid offsets are larger in unrelaxed systems. Conclusions. Combining weak- and strong-lensing morphology probes cluster structure across physical scales and offers a promising way to investigate morphology and dynamical state.

The study of galaxies outside the Milky Way using observations of resolved stellar populations has experienced extraordinary growth over the past two decades. There now exist panchromatic photometry and precise astrometry for hundreds of millions of individually resolved stars in hundreds of galaxies that span $\sim10^9$ in luminosity, $\sim10^3$ in metallicity, and sample a wide range of environments. Here, we review advances in extragalactic astronomy enabled by resolved stellar population imaging. We summarize major observational programs and focus on four interconnected science areas: the star formation histories of galaxies, 'bursty' star formation, the stellar initial mass function, and the orbital histories of Local Group galaxies. We review the literature in each area, synthesize key findings, identify emerging trends, and discuss how new and future facilities (e.g., JWST, LSST, Euclid, Roman, CSST, ELTs, HWO) will enable further progress. Finally, we highlight shortcomings in current datasets and discuss promising directions for new areas of investigation.

We detect two high-confidence star-forming sources in the environment of a chemically near-pristine ([Fe/H] $<-3.66~;2\sigma)$ Damped Ly$\alpha$ system (DLA) using Keck/KCWI. These are found via the hydrogen Ly$\alpha$ emission line at $\Delta v=-1200$ kms$^{-1}$ (LAE1) and $\Delta v = -200$ kms$^{-1}$ (LAE2) relative to the DLA redshift ($z_{\rm abs} = 3.078$) at an impact parameter of $b=66$ physical kpc and $b=137$ physical kpc. We measure Ly$\alpha$ fluxes of $F(\rm Ly\alpha)_{\rm LAE1} =4.4\pm 0.7\times10^{-18}~\rm erg\,s^{-1}\,cm^{-2}$ and $F(\rm Ly\alpha)_{\rm LAE2} =3.8\pm 0.9\times10^{-18}~\rm erg\,s^{-1}\,cm^{-2}$. This marks the first detection of star formation in the environment of a chemically near-pristine DLA. We use red channel Keck/KCRM data to place limits on the associated He II 1640 A emission flux of these sources, $F(\rm He\,II)<3.8\times10^{-19}~\rm erg\,s^{-1}\,cm^{-2}~(3\sigma)$ and $F(\rm He\,II) <3.7\times10^{-19}~\rm erg\,s^{-1}\,cm^{-2}~(3\sigma)$. The weak and narrow properties of the Ly$\alpha$ emission, combined with the inferred position on the mass-metallicity relation, suggest a metal-paucity of these galaxies. Future rest-frame optical observations are required to pin down the metallicity of LAE1 and LAE2 and test if chemically near-pristine DLAs can be used as a signpost to search for primitive, metal-poor galaxies 2 Gyrs after the Big Bang.

Context. The star-formation rate (SFR) is one of the key quantities that characterizes the star formation process and has been extensively investigated both observationally and theoretically. Aims. We aim to provide a coherent multi-scale view of star formation by connecting Galactic-scale conditions (kpc) to the properties of individual star-forming clumps at sub-parsec scales. Methods. We perform a set of numerical simulations with large-scale turbulent forcing designed to reproduce physical conditions typical of the solar neighbourhood. Using adaptive zooming down to 0.03 pc, we obtain a population of star-forming clumps that is analyzed and compared with observational catalogues in a companion paper. Results. For column densities and velocity dispersions consistent with Galactic values, the resulting SFR is close to the rate inferred for the Milky Way. Comparing this value with the SFR expected from pure free-fall collapse shows that turbulence provides multiscale support that lowers the SFR by more than an order of magnitude. Additional regulation by stellar feedback, including ionizing radiation and protostellar outflows, likely reduces the SFR by an additional factor of 3-10. Comparisons with observations across multiple spatial scales show good overall agreement with this model. Conclusions. These results support a picture in which turbulence plays a central role in regulating star formation in the Milky Way. In combination with stellar feedback, it limits the star formation efficiency to only a few percent. Key words. stars: formation -- ISM: clouds -- physical processes: turbulence

The escape fraction of ionizing photons, $f_{\rm esc}$, is one of the least constrained quantities of the Epoch of Reionization (EoR), and the opacity of the intergalactic medium prevents its direct measurement at high redshifts. We constrain three power-law parameterizations, $f_{\rm esc}(z)$, $f_{\rm esc}(M_{\rm h})$, and $f_{\rm esc}(z, M_{\rm h})$, against JWST UV luminosity functions and EoR observables (the ionizing emissivity, the neutral hydrogen fraction, and the Thomson optical depth) using Markov Chain Monte Carlo, with priors that allow $f_{\rm esc}$ to either increase or decrease with redshift and halo mass. We then propagate the best-fit models into the semi-numerical simulation SimFast21 and compare their ionization morphology and 21 cm power spectra with those of a constant-$f_{\rm esc}$ model. All models reproduce the observations with nearly identical global reionization histories. The data favor an escape fraction that decreases with increasing redshift, from $\approx 0.8$ at $z = 5$ to $\approx 0.35$ at $z = 15$. The halo-mass-only model prefers $f_{\rm esc}$ increasing with halo mass, but this trend acts as a proxy for redshift evolution. When we vary both dependencies jointly, the data prefer a mass-independent $f_{\rm esc}$. At matched global neutral fraction, the ionization morphology is closely similar for all four prescriptions, and the 21 cm power spectra agree to within $\approx 10\%$. These results suggest that, once calibrated against the same observations, the details of the $f_{\rm esc}$ prescription, which are set by the physics of the interstellar medium, largely average out in both the global observables and the 21 cm power spectrum. Distinguishing them may require statistics beyond the power spectrum, such as sightline statistics of the Ly$\alpha$ and 21 cm forests, or forecasts that exploit their small differences in reionization timing.

We present discovery of SMASH J004005$-$733351, an intermediate-mass stripped helium star in the Small Magellanic Cloud with a dark companion. The system was identified in a new optical color-selected survey for stripped stars and confirmed through spectroscopic follow-up. We measure an orbital period of $P_{\rm orb}=19.95\pm 0.002$ hours and a radial-velocity semi-amplitude of $K=91.7 ^{+3.2}_{-3.1}\,{\rm km\,s^{-1}}$. Simultaneous modeling of the optical spectrum and ultraviolet-to-optical spectral energy distribution yields a stripped star evolutionary mass $M_{\rm stripped} = 3.84 \pm 0.54\,M_\odot$, temperature $T_{\rm eff} = 68.3 \pm 6.4$ kK, surface gravity $\log g= 4.76 \pm 0.12$, luminosity $\log(L/L_\odot)= 4.28 \pm 0.13$, radius $R= 0.99 \pm 0.09\,R_\odot$, and an unusually high surface hydrogen abundance of $X_{\rm H, s}=0.63 \pm 0.04$. The companion is undetected spectroscopically, and the orbital solution and stripped-star evolutionary mass imply a minimum companion mass of $M_2 \gtrsim 1.2\,M_\odot$. The absence of photometric variability from irradiation rules out a main-sequence companion. The companion is most likely a neutron star (NS), although a massive white dwarf or low-mass stripped star cannot be fully excluded. Binary evolution models predict that the stripped star will refill its Roche lobe after core helium exhaustion, likely producing a stripped or ultra-stripped supernova and ultimately a double NS binary if the system survives. SMASH J004005$-$733351 is among the first known stripped stars with a compact object companion. The system provides a new empirical benchmark for the late stages of binary interaction that lead to (ultra-)stripped supernovae and double NS binaries.

Type Ia supernovae (SNe Ia) are instrumental for a precise measurement of the Hubble constant ($H_0$) from the local distance ladder, yet the data used hitherto for this purpose are inhomogeneous and subject to severe selection effects. We present the first, preliminary, cosmological analysis of 772 SNe Ia from the Zwicky Transient Facility's second data release: an untargeted single-telescope sample whose volume-limited subset (z<0.06) is largely free of Malmquist bias. We correct the public data for known instrumental and calibration biases and the redshifts for peculiar motions. Using the 42 SH0ES calibrators (their host distances computed from Cepheids and geometric anchors) and a Bayesian hierarchical model of SN Ia standardisation, dust extinction, redshift and calibration uncertainties, we infer $H_0 = (71.6 \pm 1.5)$ km/s/Mpc after marginalising over deceleration with a flat prior (or $(72.3 \pm 1.1)$ km/s/Mpc if a prior on matter density from Pantheon+ is imposed), with the uncertainty dominated by the number of calibrators. We demonstrate robustness to the choice of light-curve and Milky Way dust models and to extensions of the model to include peculiar-velocity correlations, a host-mass step, and two stretch populations. These results are in agreement with previous distance-ladder measurements and $2.7\sigma$ ($4.1\sigma$) away from the value obtained from Planck data, suggesting that the resolution of the Hubble tension lies outside of SNe Ia---or the distance ladder entirely.

Galaxy mergers play a fundamental role in driving gas inflows, altering star formation, and redistributing metals, yet how these processes depend on merger type, merger stage, and progenitor galaxy properties remains incompletely understood. In this work, we investigate the resolved impact of mergers on star formation rate (SFR) and gas-phase metallicity using MaNGA integral-field spectroscopy and the MaNGA Galaxy Merger Catalog of Comerford et al. (2024). By comparing merger galaxies to matched controls, we quantify local offsets in SFR and metallicity as functions of merger type, merger stage, stellar mass, and galactocentric radius. We find that major mergers generally exhibit stronger SFR enhancement and greater metallicity dilution than minor mergers. In major mergers, SFR enhancement is often spatially extended, whereas in minor mergers it is weaker and more centrally concentrated. The SFR response in major mergers varies non-monotonically with merger stage, with stronger enhancement in the early (first-passage) and post-coalescence stages and weaker enhancement in the late (between-passage) stage. Metallicity dilution is generally strongest in early-stage major mergers and weaker at later stages, although this stage dependence is not monotonic across all stellar-mass bins. We also find stellar-mass dependence that lower-mass systems show stronger metallicity dilution in both major and minor mergers, while the strongest SFR enhancement occurs in intermediate- and high-mass major mergers. These results show that the resolved star formation and metallicity responses depend jointly on merger type, merger stage, and stellar mass and exhibit different behaviors across the merger sequence.

The NSF-DOE Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) will detect resolved stellar populations of intact dwarf galaxies and disrupted stellar streams in the Milky Way (MW) halo and beyond, opening a new avenue for near-field cosmology, particularly for constraining the faint galaxies during reionization. To interpret these data, we present and publicly release mock LSST catalogs of satellites, stellar streams, phase-mixed galaxies, and field galaxies around 13 MW-mass hosts in the FIRE-2 zoom-in simulations, generated with \textsf{py-ananke}. Using a surface brightness limit of $\mu_{g} \leq 34$ $\rm{mag}$ $\rm{arcsec^{-2}}$, we find that $\approx29\%$ of streams with $M_{\star} \gtrsim 5 \times 10^5$ $M_{\odot}$ are detectable with tidal tails, while another $\approx38\%$ are detectable only through their bound progenitors and would appear as satellites. We estimate that $\approx96\%$ of satellites and $\approx64\%$ of field galaxies (out to $\sim$3.5 Mpc) with $M_{\star} \gtrsim 10^{5}$ $M_{\odot}$ are detectable, decreasing to $\approx$59\% and $\approx$42\% for $M_{\star} \gtrsim 10^{4.5}$ $M_{\odot}$ owing to resolution limits. Including streams detectable as satellites reproduces the radial distribution of observed MW satellites, suggesting that some observed satellites may be bound remnants of disrupted systems. Our mock galaxies match the sizes of observed satellites with $M_{\rm{V}} \lesssim -6$. Star-formation histories computed from only the detectable stars broadly recover the simulated star-formation histories. As an application, we test the near-far technique for reconstructing the proto-MW ultraviolet luminosity function (UVLF) during reionization ($z \gtrsim 6$). Adding the detectable streams improves the recovered faint-end slope at $z = 7$ and reduces the halo-to-halo scatter by $\approx33\%$.

Context. Linking the star formation (SF) properties of dense clumps to their parent large-scale environment is a key step to interpret Galactic surveys. Achieving a consistent, multi-scale picture of SF requires a comparative analysis of observations and simulations. Aims. We exploit kiloparsec-scale magneto-hydrodynamic simulations designed to reproduce local Milky Way conditions. Leveraging the wide range of scales covered by the simulations (reaching a resolution of 0.03 pc), we aim to compare the properties of the simulated population of star-forming clumps with observational catalogues. Methods. After extracting the star-forming structures with the HOP clump-finding algorithm, we compare their physical (mass and size) and SF properties (SF rate and efficiency) with those of the Hi-GAL compact source catalogue. Results. Despite the different methodologies and the three-dimensional nature of our clump extraction, the simulated clumps show good agreement with the observed sample in their mass and size distributions. We discover a consistently linear relation between mass and SF rate (SFR) for the simulated clumps, which is remarkably independent of the initial conditions of the boxes. Using scaling relations to distinguish between turbulence- and gravity-regulated gas inflow onto the clump scales, we find tentative evidence in favour of a gravity-regulated regime of SF at the probed sub-parsec scales. Key words. methods: numerical - stars: formation - ISM: clouds

AM CVn stars are ultra-compact binaries in which a white dwarf (WD) accretes helium-rich material from a hydrogen-deficient donor. They are promising mHz gravitational-wave sources and potential progenitors of Type Ia supernovae. However, their evolutionary pathways remain uncertain. Three formation channels have been proposed: the WD, helium star, and cataclysmic variable channels. We aim to determine the atmospheric chemical composition of the underlying accreting WDs in two eclipsing AM CVn systems, YZ LMi and ZTF J0407-00, in order to constrain their formation channels. Using ultraviolet spectra obtained with the Hubble Space Telescope, we modelled the atmospheres of the accreting WDs, whose surface compositions are enriched by material transferred from the donor and therefore trace the donor's composition. In particular, the nitrogen-to-carbon abundance ratio provides a diagnostic of the donor's nuclear burning history and hence of the system's formation channel. We measure effective temperatures Teff = 24400 $\pm$ 1500 K and surface gravities logg = 8.36 $\pm$ 0.05 for YZ LMi, and Teff = 29900 $\pm$ 2200 K and logg = 8.37 $\pm$ 0.05 for ZTF J0407-00. The inferred masses of the two WDs are 0.84 $\pm$ 0.10 and 0.86 $\pm$ 0.12 solar masses, respectively. Carbon is not detected in either system, yielding lower limits on the nitrogen-to-carbon mass ratio of N/C > 117 and N/C > 185. We increase from one to three the number of AM CVn systems whose accreting WDs and chemical abundances have been analysed using detailed UV atmosphere models. The high N/C ratios rule out the helium star formation channel for both systems. The WD channel is favoured by the absence of detectable hydrogen at all observed wavelengths, although the evolved cataclysmic variable channel cannot be conclusively excluded.

Numerical modeling of cosmic-ray (CR) spectra and the resulting non-thermal emission is important for understanding the physical mechanisms of CR acceleration and transport in astrophysical environments. Galaxy clusters and cosmic filaments provide particularly important environments for studying these processes, where shocks, turbulence, magnetic fields, and CRs jointly shape diffuse synchrotron emission. Spectrally resolved modeling of CRs, including cooling, re-acceleration, and hadronic interactions, requires solving time-dependent Fokker--Planck (FP) equations. An increasing number of studies employ FP solvers coupled with magnetohydrodynamical (MHD) simulations to follow the evolution of CRs in dynamically evolving environments. We present a new C/C++-based FP solver with GPU acceleration for post-processing outputs from cosmological MHD simulations. The code evolves CR proton and electron spectra along Lagrangian tracer trajectories and consistently includes re-acceleration and secondary-particle production processes. With the Chang--Cooper finite-difference scheme, the FP equation for each tracer is reduced to an independent tridiagonal system, which is solved on NVIDIA GPUs using a CUDA implementation of the parallel cyclic reduction (PCR) algorithm. The code uses sub-stepping between tracer snapshots, with the timestep constrained by the relevant CR cooling or re-acceleration timescale, and a batching algorithm that groups tracers with similar sub-stepping patterns for efficient execution. We find that the GPU acceleration increases the per-node throughput by a factor of $\approx$10 on the Leonardo Booster system operated by CINECA. The fast FP solver is useful for high-resolution simulations dedicated to comparison with next-generation radio observations and future multi-messenger applications combining radio, gamma-ray, and high-energy neutrino observations.

The thermodynamic state and turbulent properties of the cool circumgalactic medium (CGM) are investigated for 23 galaxies and galaxy groups at intermediate redshift ($z=0.4$--0.7) in the Cosmic Ultraviolet Baryon Survey (CUBS) midz sample using background QSOs within the virial radius. Kinematically resolved absorption-line measurements from Hubble Space Telescope/COS and STIS spectra, combined with photoionization modeling, yield gas densities of $n_\mathrm{H}\approx10^{-4}$--$10^{-2} \ \mathrm{cm}^{-3}$, temperatures of $T\approx(1$--$5) \times 10^4\,\mathrm{K}$, and non-thermal line broadening of $b_\mathrm{NT}\approx2$--$30 \ \mathrm{km \ s^{-1}}$ for individual cool clumps. Combined with published samples at similar redshifts, the results indicate that photoionization equilibrium accurately describes the cool CGM and that turbulent motions are predominantly subsonic. At fixed projected distance, cool-gas density decreases systematically with halo mass, while inferred cool-gas pressures in $M_h\approx10^{12}$--$10^{13}\,\mathrm{M}_\odot$ halos are consistent with hot-gas pressures inferred from stacked X-ray observations. The analysis uncovers a near constant total cool gas mass across a broad halo mass range, which directly translates to a declining baryon mass fraction in the cool phase from $\approx 6$--$19\%$ in halos of $M_h \approx 10^{12}\, \mathrm{M}_\odot$ to $\approx 0.6$--$1.5\%$ in halos of $M_h \approx 10^{13}\, \mathrm{M}_\odot$. Finally, several CUBS galaxies exhibit kinematically aligned low- and high-ionization species spanning up to two orders of magnitude in density, reflecting local fluctuations in the halo gas pressure.

The formation of supermassive black holes (SMBHs) in the early Universe has been a longstanding mystery due to the brief period available to assemble them. More recently, the unexpected discovery with the James Webb Space Telescope (JWST) of Little Red Dots (LRDs), compact sources exhibiting signatures of active galactic nuclei (AGN), has accentuated this challenge. Cosmological simulations investigating their formation and evolution confront the limitation that the compact scale of SMBH/LRD physics cannot be simultaneously resolved with the larger-scale cosmological environment. We address this limitation by utilizing a cutout technique, selecting a targeted region around an SMBH seed from a cosmological parent simulation and re-running the cutout at higher (sub-pc) resolution for shorter periods. We explore two SMBH formation scenarios: the standard, light seed stellar-remnant case, and the heavy-seed, direct collapse black hole (DCBH) channel. Within the high-resolution achieved by the cutouts, the DCBH, due to its larger mass, is able to induce a buildup of high density gas nearby and accrete gas in bursts of super-Eddington phases, growing in mass and producing an LRD-like spectrum. In contrast, the stellar remnant cannot do so and remains dormant, unable to affect the nearby gas or significantly evolve by gas accretion alone. Therefore, we find that observed high-redshift SMBHs and LRDs require the existence of heavy seeds to assemble dense gas around themselves, enabling efficient growth and producing red optical spectra with strong Balmer breaks resembling LRDs.

So far, the POETS survey has focused on studying at high angular resolution the properties of both 22.2 GHz H2O masers and the radio continuum emission near young stellar objects (YSOs). Now, we want to add the information coming from another star formation tracer, the Class II 6.7 GHz CH3OH (methanol) maser, towards the same POETS targets. We seek to probe the existence of 6.7 GHz maser emission near POETS sources with high sensitivity observations and study their kinematic properties with respect to local radio continuum and 22.2 GHz maser emission at high angular and spectral resolutions. Within the POETS survey, we used the Very Large Array (VLA) in the A configuration, operating at high spectral resolution (0.1 km/s) and achieving a sensitivity of a few mJy/beam per channel map, in order to (i) probe the emission from methanol gas in the 6.7 GHz maser transition and (ii) trace its absolute spatial distribution and local standard of rest velocity. We present a preliminary analysis of 6.7 GHz CH3OH maser emission toward a subsample of the POETS survey (22 fields observed so far), 60 % of which show detection above a brightness temperature threshold of 10^7 K. Five sources among this subsample are new detections. We draw a 6.7 GHz maser brightness function by studying the distribution of the intrinsic luminosity of the maser population and predict that more than 30 % of the whole population is undetected at typical interferometric sensitivities of a few 10 mJy/beam. We confirm that 6.7 GHz masers arise close to the young star they are associated with and quantify that, on average, 90 % of them are distributed within radii of 3000 au only. Furthermore, we find a tight correlation between the 6.7 GHz maser luminosity coming from a given source and the local free-free emission, suggesting that the radio continuum provides the dominant source of seed photons amplified by the methanol gas.

Supergiant Fast X-ray Transients (SFXTs) show extreme X-ray variability on timescales of minutes to hours, driven by accretion processes that remain poorly understood. IGR J16418-4532 is an intermediate SFXT with detected X-ray pulsations and a candidate cyclotron line, making it a key system for probing neutron-star accretion and magnetic fields in this class. We analysed a 148 ks NuSTAR observation and archival RXTE observations, using epoch folding to search for pulsations while correcting photon arrival times for a range of trial $a_x \sin i$ values, and performed phase-averaged spectroscopy with several continuum models. We detect coherent pulsations at $P_{\rm spin} = 1208.67 \pm 0.04$ s (NuSTAR) and $1209.4178 \pm 0.0084$ s (RXTE/PCA). The pulse detection depends clearly on the assumed projected semi-major axis and is most significant for $a_x \sin i = 55.1 \pm 3.5$ lt-s (NuSTAR) and $51.3 \pm 2.6$ lt-s (RXTE/PCA). Sliding-window pulse profiles show the orbital delay in the uncorrected data, which is fully removed after orbital correction. The inferred orbital parameters constrain the companion mass and radius to $\sim$12-18 $M_\odot$ and $\sim$13-16 $R_\odot$. This is the first constraint on the binary mass function of an SFXT obtained from the orbital motion of the neutron star. The spectrum shows a robust cyclotron absorption line at $\sim$50 keV, independent of the continuum model, implying $B \approx 5 \times 10^{12}$ G. Optimising pulse detection with trial $a_x \sin i$ corrections, rather than modelling pulse arrival-time delays, offers a route to dynamical mass measurements in other SFXTs whose variable pulse profiles limit conventional timing techniques.

Eclipse mapping is a well-established technique for constraining the spatial emission of hot Jupiter exoplanets. Brown dwarfs in ultra-short orbits around white dwarfs are an analog to hot Jupiters that can only ever be eclipsed within a limited range of latitudes. We adapt the eigenmapping method to disentangle the signals from the ever- and never-occulted regions. The result of this signal separation is a super-position of map structures, yielding sharp boundaries at the occultation region. We introduce a model that penalizes the harmonic complexity of the model map with Tikhonov regularization, whose parameters are tuned to reproduce the fit quality of the eigenmapping model. We use JWST NIRSpec/PRISM full-orbit observations of the eclipsing WD 1202-024 system as a template to construct and run injection-recovery tests on simulated light curves, isolating both latitudinal structures as well as emission from a physically-realistic general circulation model (GCM). In the latter, the narrow equatorial jet driven by the BD's rapid rotation manifests as an eclipse depth asymmetry, which our model reproduces as a latitude-dependent phase offset. Such a model, however, is only statistically preferred at approximately $3 \times$ the signal-to-noise ratio of the JWST data. When fitting to the actual JWST data of WD 1202, the full-phase eigenbasis model is statistically preferred. However, the resulting model map of WD 1202 B does not resemble the GCM predictions, with a concentrated day-side hotspot at the sub-stellar point with an angular size $\approx 15^\circ$. Interpreting this result more carefully requires follow-up work to disentangle systematics from true emission signals. This model framework provides a means to detect emission features from these rare types of eclipses, and ultimately to test predictions of models of atmospheric circulation across hot Jupiters and their BD analogs.

We present ASTRA, an autonomous framework for physics-validated analysis and hypothesis generation in astrophysics without per-step human intervention. It integrates dimensional analysis, structural causal models, Bayesian evidence computation, and multi-wavelength data fusion in a single automated workflow. Five test cases on real observational data recover known results: Herschel filament scaling, Chandra Deep Field South cross-matching, SDSS galaxy correlations, Gaia causal inference, and Bayesian virial model selection. A sixth case runs unsupervised on synthetic galaxy data. The main sequence and mass-metallicity relation are recovered, and the outlier detector, with a false-discovery-rate threshold and no contamination parameter, recovers the blind injected fraction on ten sealed datasets (purity > 0.99) and flags nothing on the 3,000-galaxy sample. A knowledge-isolation ablation shows pattern detection and physical validation are invariant to removal of domain knowledge, which affects only interpretation. In a direct comparison, agentic-LLM and pure-ML baselines match the statistical fitting but not the physics-validation stage. They rarely derive the equilibrium benchmark, split evenly on the physical verdict, and adopt a supplied erroneous benchmark in all six trap runs, an astrophysics-specific fine-tuned model completes zero of six runs. On live SDSS DR16 data it flags 197 of 4,999 galaxies at a data-determined threshold, ranked extremes classifiable from withheld spectroscopy. These are recovery validations and capability demonstrations rather than discoveries, with hypothesis generation demonstrated qualitatively.

Characterising the assembly history of the inner Milky Way is a key goal of upcoming spectroscopic surveys, yet disentangling its overlapping stellar components remains challenging. We investigate the chemodynamics of the centre of a Milky Way analogue in the Auriga Superstars cosmological hydrodynamical simulation suite, focusing on a high-resolution halo (~ 800 M_sun star particles) with a realistic galactic bar and accretion history. We classify stars within the inner 4 kpc into proto-galaxy, subsequent in-situ, and accreted components to assess their distinguishability using kinematics, dynamics, ages, and metallicities. Stellar net rotation declines sharply between [Fe/H]=0 and [Fe/H]=-1, marking the transition from disc-like in-situ stars to the proto-galaxy. While significant chemical and dynamical overlaps complicate the search for structures in energy-angular momentum (E-Lz) space, metal-poor stars ([Fe/H]<-1) at low energy form a remarkably pure (>97%) sample of proto-galaxy stars. Conversely, the high-energy, metal-poor tail offers the best chance of detecting accreted debris. However, at high energies the inner accreted halo is dominated by low-mass systems (M_star ~ 10^7 - 10^9 M _sun), not the earliest massive mergers. Dynamically, few clues remain from early mergers, and early enrichment is rapid and similar across progenitors. In-situ contamination is an issue for [Fe/H]>-1 throughout E-Lz space. Overall, while accurate stellar ages and high-precision chemical abundances may help further constrain the Milky Way's history, we should be cautious when associating stars with individual merger events in the inner galaxy.

Galaxy groups are key laboratories for investigating the interplay between active galactic nucleus (AGN) outbursts and the dynamical processes of the intra-group medium. We aim to characterize the morphology, spectral properties, and magnetic field structure of the diffuse nonthermal radio emission in two peculiar galaxy groups, NGC 3411 and NGC 5903, selected from an originally larger sample, in order to constrain its origin and its connection with the dynamics of the intra-group medium. We present new MeerKAT UHF- and L-band observations of the two groups, complemented by archival Chandra and XMM-Newton data already analyzed in previous works. In NGC 3411, we detect extended radio emission surrounding the central AGN over scales of ~70 kpc, and resolve previously undetected arc-shaped substructures on scales of ~20-30 kpc. This extended component exhibits a relatively uniform steep spectrum ($\alpha$ ~ -1.7). We discuss possible scenarios for its origin, including mini-halos, aged AGN plasma, weak shocks, and the possibility of a radio galaxy observed along the line of sight. In NGC 5903, MeerKAT reveals a complex filamentary morphology, including a previously unknown ring-like structure surrounding the central AGN. Spectral-index mapping shows localized flattening ($\alpha$ ~ -0.9) along the north arc, while polarization data reveal ordered magnetic fields and a patchy rotation measure distribution across the source. Together with the disturbed X-ray morphology, these results support a scenario in which fossil AGN plasma has been redistributed and locally reenergized by group-scale dynamical processes such as turbulence, shear, and weak compression. Our results demonstrate that galaxy groups can host a rich variety of nonthermal phenomena, whose properties can only be fully revealed through the combination of sensitive, high-resolution, and multifrequency radio observations.

We propose a novel test for the hypothesis that the dark matter of the Universe is composed entirely by asteroidal-mass primordial black holes. It relies on detecting the stochastic gravitational-wave background generated by the coalescence onto rapidly spinning supermassive astrophysical black holes of the light primordial black holes accumulated in spherically symmetric spikes. We discuss the scenarios in which the signal can be observed by the future space-based gravitational-wave observatories LISA and DECIGO.

We assess how propulsion and operational constraints affect exo-Earth characterization with a starshade rendezvous mission for a Habitable Worlds Observatory (HWO)-like telescope at Sun-Earth L2. Using end-to-end Monte Carlo simulations with EXOSIMS, we model a 60 m starshade for visible-band spectroscopy (500-1000 nm) and a 35 m starshade for near-ultraviolet characterization (250-550 nm). For the 60 m design, we compare AEPS Hall, NEXT ion, and Starlink-class Hall thrusters and examine sensitivity to propellant capacity, the fraction of each retargeting slew spent accelerating and decelerating, and on-orbit refueling. With 1000-3000 kg of initial propellant and no refueling, NEXT provides the highest characterization yield: 9-13% more characterizations than AEPS and 13-16% more than the Starlink-class option. Its higher specific impulse enables more retargeting slews per kilogram of propellant. With refueling, yields converge across thruster choices to about 120 cumulative characterizations over 10 years, while propulsion choice mainly affects the number of refueling events. For the 35 m starshade with AEPS, yields are less sensitive to fuel and are dominated by mission duration and geometric accessibility. Increasing the minimum solar keepout angle from 40 to 50 degrees has little effect on yield; increases from 50 to 65 degrees have a modest effect, while angles above 65 degrees rapidly reduce yield, with severe degradation near 80 degrees. These results distinguish fuel-limited and time- or keepout-limited regimes and guide propulsion selection, tank sizing, refueling policy, and keepout constraints for HWO starshade missions.

The PLATO Stellar Variability Mitigation Working Group designed a radial-velocity (RV) data challenge to assess the precision and accuracy achievable on RV semi-amplitudes in the context of the future PLATO follow-up. Using Sun-as-a-star observations obtained with HARPS-N, we generated three multi-planet systems with realistic sampling, an effective signal-to-noise ratio of S/N ~ 450, an exposure time of 15 minutes, and a total of approximately 1000 observations. The resulting data set is publicly available and can serve as a benchmark for the community to test and compare RV analysis methods. Eight independent teams participated in the challenge, aiming to recover the semi-amplitudes of both transiting and non-transiting planets. A meta-analysis of the submitted results shows that, with current data analysis methods, HARPS-N-like stability and the observing strategy studied in this paper, achieving a precision on semi-amplitudes better than 10% for habitable-zone signals around a solar-type star is challenging, and is typically limited to planets with masses of approximately 8-10 Earth masses. This performance is expected to improve for K dwarfs, where planets down to approximately 2-5 Earth masses may be characterized at a similar level of precision. Finally, based on the results of this challenge and the occurrence of false positives, we derive an empirical detection threshold for RV surveys, which can be used to distinguish robust planetary detections from candidates.

Red giants displaying solar-like oscillations allow precise stellar properties to be derived. Asteroseismic binaries (ABs), which are gravitationally bound systems where both stars show detectable oscillations, can provide constraints on the interior of two coeval stars, allowing us to model them jointly and potentially obtain constraints unavailable from either star individually. This makes ABs potential laboratories for calibrating stellar evolution theory. In this context, AB candidates (ABCs) are systems showing two oscillators, which are as of yet not confirmed as gravitationally bound. We aimed to confirm ABCs and other red giant binary candidates, as well as demonstrate the advantages of AB modeling inference. We obtained spectroscopic indicators of binarity for 60 oscillating red giants that have photometric (33 stars) and/or asteroseismic (38) indications of binarity. We confirm 12 of our 60 targets as spectroscopic binaries, 8 of which are ABs as well. Cross-matching with Gaia DR3 and APOGEE DR17, we identify a further 9 likely binaries, at least 6 of which are also ABCs. We then investigated the impact of simultaneously modeling the oscillation modes of both oscillators of an AB. We inferred stellar properties for; one binary of extra-Galactic origin containing one detectable red-giant-branch (RGB) oscillator; one AB with RGB oscillators; and two ABCs with RGB oscillators. We find that the mode frequencies of the two ABCs and the confirmed AB are well-described with a coeval modeling of the stellar components. We demonstrate that the simultaneous modeling of ABs with two RGB stars can be used to infer the stellar helium content down to $3\%$ precision, compared to $5\%$ when using only the brightest star. Finally, the metal-poor binary KIC2971380 hints for a need to correct the $\nu_{\rm max}$ scaling relation, supporting recent studies of extremely metal-poor oscillators.

Pre-main-sequence (PMS) evolutionary models can assign different ages across stellar mass within the same population. We use joint Gaia and SPHEREx spectral energy distributions to infer effective temperatures, radii, and luminosities for members of Canis Major North (CMaN), a nearby association with independent lithium and kinematic age constraints near 23 Myr. The SPHEREx fluxes agree with 2MASS and WISE photometry to 3--6\%, and we anchor the absolute flux scale to Gaia, 2MASS, and WISE. Using the revised temperatures, we obtain a lithium age of $22.4^{+2.8}_{-1.5}$ Myr. For a 29-star PMS sample, population-wide HR-diagram fits yield $20.5^{+1.5}_{-1.4}$ Myr for unspotted SPOTS models, consistent with the external constraints, $18.4^{+1.4}_{-1.3}$ and $18.7^{+1.3}_{-1.2}$ Myr for the Feiden nonmagnetic and BHAC15 models, and substantially older ages of $32.2^{+2.3}_{-2.1}$ and $55^{+5}_{-5}$ Myr for the Feiden magnetic and PARSEC models. No grid returns a temperature-independent age. The Feiden, SPOTS, and BHAC15 models assign older ages to stars above $4000$ K, whereas PARSEC assigns increasingly older ages toward lower temperatures. The intrinsic luminosity dispersion is also mass dependent, approximately $0.14$ dex below $3450$ K but $0.05$ dex at intermediate temperatures. At a fixed age of 23.0 Myr, a single SPOTS filling factor cannot reproduce the width of the low-temperature sequence, whereas the empirical filling-factor distribution of young stars overpredicts it. Spotted isochrones can enclose every cool member only at ages of 37--50 Myr, inconsistent with the lithium and kinematic ages.

Recently, a sample of radio-weak active galactic nuclei (AGN) was discovered to exhibit extreme Jy-level radio flares at 37~GHz. The origin of these extraordinary flares remains unknown. All sources host low-mass supermassive black holes, and most of them can be classified as narrow-line Seyfert 1 galaxies. We employed multiwavelength observations to investigate one of these sources, SDSS J122844.81+501751.2, during a period of high 37~GHz activity. Our data include radio observations from Metsähovi Radio Observatory (MRO) at 37~GHz, OVRO at 15~GHz, and JVLA at 15, 22, and 33~GHz, as well as optical, UV, and X-ray observations from \textit{Swift}/XRT and UVOT. We studied the variability of the multiwavelength light curves (LC) using statistical tests, as well as derived the $e$-folding timescales of the flares. Utilising the timescales and the observed flare properties, we estimated the variability brightness temperatures and Doppler factors associated with the flares. Most individual LCs do not show statistically significant variability, which is likely due to the low number of measurements. The shortest timescale we estimated is only 1.1~hours, measured between MRO 37~GHz and JVLA 33~GHz detections. This is the fastest intrinsic radio variability reported in an AGN so far. This yielded an extreme variability brightness temperature of $T_\mathrm{B}$ = 4.20 $~\times$ 10$^{18}$~K and a variability Doppler factor of 438. We discuss magnetic eruptions near the black hole as a possible explanation for the extreme radio flares, and show that both incoherent and coherent processes can produce flares at these timescales. These flares challenge our current understanding of AGN radio variability. Whereas magnetic eruptions offer a viable explanation for the flares, more observations, preferably broadband and including polarisation, will be required to confirm their origin. (abridged)

We investigate inflationary magnetogenesis driven by a non conformal coupling in the case of large-field $\alpha$-attractor inspired models. We introduce potential-dependent electromagnetic coupling functions $f(\phi)$ that reproduce the scaling $f\propto a^p$ during slow roll. Starting from Starobinsky inflation, we analytically derive explicit couplings for $(E)$-model and $(T)$-model potentials. We then study how these functions affect electromagnetic amplification in the regime of non-minimal coupling between the inflaton field and the Ricci scalar $\phi^2 R$. In particular, we compare different values for the coupling strength $\xi$, accounting for electromagnetic backreaction and Schwinger pair production through the gradient expansion formalism. Our numerical results show that the non-minimal coupling affects the evolution of the electromagnetic sector and the resulting magnetic-field amplitude. We find that, within the analyzed configurations, minimally coupled and $\xi>0$ scenarios are compatible with the adopted CMB constraints, yielding conditional present-day magnetic-field estimates of order $10^{-23}$ G.

The escape velocity is a key probe of the Milky Way (MW) potential, but standard estimates can be biased by unrelaxed substructures. Using MW analogs from the TNG50 cosmological simulation, we investigate the impact of the dominant, highly radial Gaia-Sausage-Enceladus (GSE) debris on escape-velocity measurements. We introduce an adaptive selection strategy that balances statistical reliability with sample size to identify the power-law decline regime of the local halo velocity distribution. Applying this strategy to 16 MW analogs with prominent GSE-like structures and continuous high-velocity tails, we find that retaining GSE-like stars yields a systematic underestimate, with a recovery fraction of $97.5^{+2.1}_{-2.9}\%$, while removing GSE-like stars alone increases the recovery fraction to $99.4^{+2.1}_{-2.5}\%$. The $\sim 2\%$ underestimation of the escape velocity corresponds to an $\sim 6\%$ underestimation of the total mass. This improvement persists in LAMOST-like magnitude and footprint selection. GSE-like debris is therefore a key contributor to the systematic underestimation of escape-velocity measurements, with direct implications for the inferred MW mass.

Radio detection of very inclined extensive air showers (EAS) offers a promising way to study ultra-high-energy cosmic rays (UHECRs) and neutrinos above $10^{17}$ eV. We present a method to reconstruct the arrival direction and energy of EAS with zenith angles above $60^\circ$, applicable in principle to upward-going neutrino-induced showers. The approach combines a point-source-like description of the radio wavefront with the Angular Distribution Function (ADF), a phenomenological model describing the angular pattern of electric field amplitudes in the 50-200 MHz band. On realistic cosmic-ray simulations, we achieve better than $0.07^\circ$ resolution on arrival direction and ~15\% on primary energy. Applied directly to voltage traces, this method allows efficient cosmic-ray selection with accurate direction reconstruction and first-order energy estimation. We illustrate the method on the first cosmic-ray candidates detected by the GRANDProto300 prototype of GRAND, validating its detection principle and paving the way for high-precision neutrino searches.

Classical Be stars are rapidly rotating B-type stars surrounded by gaseous circumstellar disks, but the origin of their angular momentum remains uncertain. We investigate whether observed Be-star multiple systems are dynamically compatible with triple-assisted interaction, in which a tertiary companion drives Kozai-Lidov (KL) eccentricity excitation in an unresolved inner binary. We combine speckle-interferometric detections, reported inner periods, and proper-motion anomalies (PMa) with synthetic populations of hierarchical triples. Accepted configurations must satisfy dynamical stability, secular-timescale, inner-periastron interaction, and observational constraints. Refined mass-aware simulations identify HD 35079 and HD 55606 as the clearest period-plus-speckle dynamical matches. HD 205329 remains dynamically plausible but depends on the approximate PMa constraint. For HD 41335, the period-plus-speckle and PMa-plus-speckle constraints are separately compatible, whereas imposing all three simultaneously yields no accepted configurations at the adopted tolerance. HD 37330, HD 41600, and HD 71510 are additional PMa-dependent hierarchical-triple candidates. An independent angular-momentum estimate indicates a median required accreted mass fraction of approximately 4.8% under the adopted assumptions. We conclude that several observed Be-star multiple systems admit stable, KL-active architectures capable of driving inner binaries toward interaction. These results establish dynamical plausibility rather than a confirmed evolutionary history and motivate further speckle, spectroscopic, and astrometric monitoring.

There is current renewed interest in using Sun-Earth distant retrograde orbits (DROs) for a space weather forecasting mission, which would temporarily place spacecraft at a position near the Sun-Earth line, but closer to the Sun than the L1 point (such as the ESA HENON mission and ESA SHIELD concept). With in situ observations of the magnetic field on a DRO, the southward ($B_z < 0$) magnetic field of interplanetary coronal mass ejections (ICMEs), which is not routinely accessible remotely, could be measured several hours in advance. This $B_z < 0$ field is a decisive factor for forecasting geomagnetic storm intensity. We present an analysis of DROs at different sub-L1 distances for their efficacy for a space weather forecasting mission. An open-source numerical framework to generate DRO trajectories is presented. Our pre-calculated orbits in Heliocentric Earth Ecliptic coordinates can be introduced into numerical or empirical simulations of the ambient solar wind and ICMEs. We then analyze the corresponding forecast lead times, the resulting observational gaps depending on the number of spacecraft and distance of a DRO, and the "cone of acceptance" of the maximum longitudinal separation of a spacecraft to the Sun-Earth line. We define different domains regarding radial evolution and longitudinal CME structure, and show the historical coverage of sub-L1 ICME observations with our ICMECAT catalog. An optimal mission configuration can be selected based on the characteristics of DROs presented here, depending on the requirements of such a mission deemed acceptable with respect to results on CME evolution and coherence.

We report the discovery of periodic radio bursts from the T8 brown dwarf WISE J151721.13+052929.3 (WISE J1517+05), detected with ASKAP and MeerKAT. The emission is characterised by a stable periodicity of $1.149 \pm 0.002$ hr, placing WISE J1517+05 among the fastest rotating radio-detected ultracool dwarfs (UCDs). The radio bursts are broadband and highly variable, reaching a peak spectral luminosity of $L_{\nu} = 5.6 \times 10^{15}\,\mathrm{erg\,s^{-1}\,Hz^{-1}}$, making WISE J1517+05 the brightest periodic UCD to date. The high brightness temperature of the radio bursts ($T_B>10^{11}$ K), combined with the rotational modulation, strongly favour an auroral electron cyclotron maser emission (ECME) origin. In contrast to most known radio-bursting UCDs, the bursts exhibit relatively low and variable circular polarisation fractions (typically $\sim 20\%$). These properties suggest significant depolarisation of intrinsically highly polarised ECME, likely due to propagation effects in a structured magnetospheric plasma. Notably, we also observe a polarisation reversal within a single burst profile, which is currently unexplained. We model the emission using a dipolar magnetic field with emission arising from a single active field line, and find a moderate inclination angle of $i = 47.9^{+11.4}_{-9.2}$ degrees and a magnetic obliquity of $\beta = 40.1^{+9.2}_{-10.9}$ degrees. WISE J1517+05 expands the parameter space of radio-active UCDs toward higher luminosities and lower polarisation fractions, suggesting that current surveys may be sensitive to a larger population than previously recognised, while searches relying on methods that assume high circular polarisation fractions risk missing a subset of UCDs. More broadly, this discovery reinforces the idea that rapid rotation plays a key role in generating strong dipolar magnetic fields in UCDs that can give rise to auroral radio emission.

Solar coronal loop heating remains one of the greatest mysteries in astrophysics. In emerging flux regions, coronal loops form and are heated as strong magnetic flux tubes emerge through the photosphere. The loop footpoints gradually separate. In this study, we investigate the heating of quiet-region (QR) coronal loops whose opposite-polarity footpoints are already separated. Our observations reveal that convection-driven magnetic flux convergence at a loop's foot -- where smaller unipolar photospheric magnetic flux patches merge into a stronger flux patch -- correlates with loop brightening, and flux divergence at that foot correlates with that loop's disappearance. This behavior is similar to recent findings for solar coronal plumes. To investigate and quantify this effect, we track 10 QR coronal loops through their lifetimes using SDO/AIA 171 and 94 Angstrom images, along with SDO/HMI magnetograms. The coronal EUV luminosity shows a strong correlation with the magnetic flux in at least one footpoint, most strongly when the line-of-sight magnetic field strength (Blos) exceeds a threshold of about 200-500 G. A Bifrost MHD simulation of the quiet-Sun network and corona shows similar behavior but at smaller time-scales: magnetic flux convergence and divergence -- most pronounced at a loop footpoint -- correlate directly with increased and reduced emissivity due to heating and cooling, respectively. The simulation reveals an increase in Poynting flux, reconnection, and Joule heating with flux convergence at that footpoint. We hypothesize that an increased rate of nanoflares during flux convergence may explain the enhanced emissivity of these loops due to heating, with potentially broader implications for coronal heating.

Linear silicon-carbon chain molecules, SiC$_n$ (n = 3--6), have been detected in the circumstellar envelope of the carbon-rich AGB star IRC+10216. Here, we discuss the mechanisms likely to be at work in the synthesis of chains up to SiC$_8$ and present for the first time a detailed comparison between observations and model calculations. Using a combination of measured and postulated rate coefficients, we show that the column densities of the silicon carbide molecules observed in IRC+10216 can be reproduced to with a factor of four. Furthermore, our model calculations suggest that the column densities of SiC$_7$ and SiC$_8$ are a factor of 2--4 less than that of SiC$_6$. We discuss the influence of neutral-neutral reactions involving parent SiC$_2$ on chain growth and show that their neglect leads to a reduction in column densities of carbides up to a maximum of about six for SiC$_6$ and SiC$_7$. Our results suggest that the detection of SiC$_7$ and SiC$_8$ in IRC+10216 will be challenging but that astronomical searches should be undertaken.

Astronomical observations include images, spectra, and light curves, while the scientific literature describes these objects in natural language. We present AstroBridge, a framework that connects these observations to an LLM through a literature-assisted caption generation pipeline. We used catalog metadata to match observations with scientific texts that describe the same objects. A vision-language model generates descriptive captions from representations of observations, matched passages, and available metadata, creating observation-caption pairs without manual captioning. We train AstroBridge to predict captions directly from raw observations. Modality-specific frozen encoders extract representations that a shared, trainable fusion network aligns with the embedding space of an LLM. In caption-based evaluation of spectra, AstroBridge achieves 91.5% accuracy in distinguishing quasars from galaxies, compared to 69.0% from the base model prior to fine-tuning. Limitations remain in galaxy morphology, classification of minority supernova classes, and the factual quality of generated captions. We believe that AstroBridge's framework is a step towards the goal of aligning the totality of astronomy's diverse, exotic data through the lingua franca of text.

Rocky planets the size of Earth or larger are expected to undergo one or more giant impacts during the final stages of their formation. Some of these collisions occur after protoplanetary disk dissipation, potentially driving the loss of primordial hydrogen-rich atmospheres through elevated surface temperatures. However, whether giant impacts promote atmospheric loss or retention remains unclear because they both heat planetary interiors and increase atmospheric gravitational binding. Here we model the evolution of rocky planets after their largest post-disk giant impact, accounting self-consistently for the concurrent increase in gravitational binding energy and mantle thermal energy. Whereas the entire accreted mass contributes to the increase in gravitational binding energy, only part of the impact energy raises mantle temperature. Mantle melting consumes energy as latent heat, while the impactor's metallic core transfers little energy to the mantle and remains superheated at depth. Giant impacts therefore increase gravitational binding energy more than mantle thermal energy, shifting planets towards atmospheric retention. Larger, atmosphere-bearing planets emerge preferentially through collisional growth. By contrast, smaller planets without such impacts tend to lose their primordial atmospheres under sustained stellar irradiation. At the population level, these results suggest that sub-Neptunes have, on average, more massive rocky interiors than super-Earths.

Binary neutron-star (BNS) mergers are multimessenger sources whose kilonova emission and nucleosynthesis depend sensitively on neutrino microphysics and flavor conversion. Most BNS merger simulations assume $\mu$-$\tau$ neutrino degeneracy in a two-flavor treatment. We investigate the fast flavor instability (FFI) and the collisional flavor instability (CFI) in long-lived BNS merger remnants using axisymmetric general-relativistic three-flavor Boltzmann neutrino transport with a comprehensive treatment of muons and muonic interactions, following a handoff from 3D grey moment-based simulations. Our simulations largely reproduce the parent 3D simulations, recovering trapped weak equilibrium in the core, muonic non-equilibrium in the semitransparent outer disk due to prolonged demuonization, and cold weak equilibrium in transparent regions. Linear stability analysis reveals strong and widespread CFI in all three flavor sectors, including narrow resonance-like structures. Muonic interactions reshape the FFI distribution, shifting the $e\tau$-sector instability toward denser disk regions compared with the extended FFI outside the disk in the two-flavor model, while disk demuonization produces a strong $\nu_\mu$ excess and one-sided muon-lepton-number angular distributions that suppress FFI in the $e\mu$ and $\mu\tau$ sectors. Local three-flavor quantum kinetic equation (QKE) calculations reveal nonlinear coupling among flavor sectors that excites coherence even in an initially stable sector. Diagonal collisional repopulation is decisive for the nonlinear evolution and asymptotic flavor populations, and neglecting it overestimates flavor equilibration. We establish the necessity of three-flavor transport from both classical and quantum perspectives, and underscore the importance of consistently coupling flavor conversion with diagonal collisional repopulation in future CFI subgrid models.

Odd radio circles (ORCs) are a recently recognized class of faint, roughly circular diffuse radio sources, typically a few hundred kiloparsecs across, whose origin is still debated. We report the serendipitous discovery of a giant ORC, ORC~J1928$-$5056, in 856~MHz continuum data from the ASKAP observations. The emission forms a single, mildly elliptical structure $4^{\prime}$ across, corresponding to $0.63$~Mpc at the redshift $z=0.1507$ of the central galaxy LEDA~140850, the brightest cluster galaxy of Abell~3639, which makes it one of the largest single ORCs known. After subtracting the radio nucleus associated with the host galaxy, the ORC has a flux density of 73~mJy integrated within an area of $\sim 12$~arcmin$^2$, i.e.\ a mean surface brightness of only $1.7$~$\mu$Jy~arcsec$^{-2}$, and a rest-frame luminosity of $L_{1.4}=2\times10^{24}$~W~Hz$^{-1}$, comparable to those of the most luminous ORCs. Including its nucleus, the system reaches $L_{1.4}=6.6\times10^{24}$~W~Hz$^{-1}$, higher than that of any other ORC reported so far. The host is a massive ($M_{\ast}\sim10^{11}\,M_{\odot}$), passive elliptical galaxy with negligible star formation. It contains an AGN jet with a power-law spectrum of index $\alpha=-0.877\pm0.089$ between 856 and 1656~MHz. Finally, we discuss the implications for ORC formation models and the observations needed to establish the nature of this system.

In the conventional spherical overdensity definition of a dark matter halo, masses and radii, e.g. $M_{200{\rm m}}$ and $r_{200{\rm m}}$, are equivalent. However, halos do exhibit a physical boundary at the splashback radius $r_{\rm sp}$, which manifests as a sharp drop in density. Splashback radii are now routinely measured in stacked weak lensing profiles, but the expected trend of decreasing $r_{\rm sp}/r_{200{\rm m}}$ with mass has not been verified in observed galaxy groups or clusters. In this work, we show that several observational effects conceal the predicted mass-size relation. In particular, we quantify the impact of systematics on the mean density and lensing profiles of mock-observed halo samples, which are created by applying a realistic cluster-finding procedure to dark matter-only simulations. We reproduce the known impact of projection: preferentially observing systems in overdense regions. But, differing from previous works, we show that the same projection effect, combined with scatter in observed luminosities, causes a significant Eddington bias in the derived mass-observable relation and a complex suppression in mean density profiles over all radial scales. The magnitude of this effect is mass-dependent and coupled to the cluster-finding procedure and survey properties, making it challenging to model simply and motivating full forward-modeling of observed group and cluster samples. However, we demonstrate that a simple mitigation approach, effectively a weak lensing mass calibration, does well in approximately recovering the true mass-size relation. Finally, we show that only severe miscentering can bias the measurement of the halo size, but any miscentering can increase the measurement uncertainty.

Globular clusters (GCs) occupy a broad range of stellar colors and magnitudes while sharing nearly the same distance. Gaia Data Release 3 parallaxes retain systematic zero-point residual variations for GCs, even after the correction by the widely used standard correction model (L21). We derive an empirical residual correction by the Hierarchical Bayesian Model, separating cluster-level offsets from the differential information carried by the member sequences. We first evaluate the L21 baseline at a fixed reference color, which assigns the remaining color-dependent correction to the residual model. Then we model the residual zero point, $\delta Z(G,\nu_{\rm eff})$, with B-splines functions in color and magnitude--color interaction terms. The uncorrected cluster residuals exhibit a negative offset of approximately $25$--$40~\mu{\rm as}$. The L21 baseline removes most of this offset but leaves coherent color- and magnitude-dependent structure. Applying the residual model brings the mean residuals close to zero, especially across most of the sampled color range. In five-fold cross-validation that excludes entire clusters from training, the correction modestly reduces the magnitude- and color-trend RMS relative to the L21 correction. The resulting model therefore provides a differential refinement of the \textit{Gaia} DR3 parallax zero-point within the calibrated domain for GCs, rather than an independent determination of its absolute value.

The Central Molecular Zone (CMZ) at the center of the Galaxy provides a nearby laboratory for studying star formation under extreme physical and chemical conditions. Recent ALMA (Atacama Large Millimeter/Submillimeter Array) observations have identified 43 candidate protostellar outflows in three CMZ clouds. One of these, the Sgr C-F#2 outflow in Sagittarius C (Sgr C), has a highly collimated lobe extending approximately 0.8 pc in projection. Here we present a joint analysis of ALMA observations of SiO J=8-7, 5-4, and 2-1. We use local thermodynamic equilibrium (LTE) and non-LTE methods to constrain the SiO column densities, H2 number density, and gas temperature. The low SiO rotational temperatures and higher kinetic temperatures inferred from non-LTE methods suggest subthermal excitation. The elongated SiO morphology, shock-excited gas, position-velocity structure, and the alignment of the red shifted molecular lobe with JWST infrared knots altogether favor jet-dominated entrainment, whereas a broader disk-wind component close to the source cannot be excluded. The outflow shows asymmetries in its morphology and physical properties, which can be attributed to dense gas on the path of its lobe impeding its propagation and feedback from a nearby HII region imposing different pressure on its two sides.

In warm inflation, the primordial fluctuations are driven by random kicks from a hot radiation bath. Two features of these kicks matter: how long the bath remembers them, which shapes the power spectrum, and how their strengths are spread, which controls the rare, extreme fluctuations. In this paper, we investigate how primordial black holes and the accompanying induced gravitational waves can be used to discriminate between these two features. We use a simple model inspired by warm inflation, in which independent kicks of random strength add up to a narrow peak in the power spectrum. At leading order, the induced gravitational wave depends only on the power spectrum and is therefore insensitive to how the kicks are distributed. However, the black holes are very sensitive to these rare large fluctuations. Hence, two baths can yield the same gravitational wave signal while forming black holes at very different rates. A modest kurtosis range of 0.1 to 0.3 enhances black-hole formation by factors of ten to a million at fixed gravitational-wave amplitude, the larger factors for the rarer black holes. Counting peaks rather than all points, or widening the spectrum, lowers the enhancement by at most a factor of about four. In general a change in the power affects both phenomena, while the kurtosis affects only the black hole production.

We present a spatially-resolved detection of $3.3\,\mathrm{\mu m}$ emission from polycyclic aromatic hydrocarbons (PAHs) within the circumnuclear ${\sim}200\,\mathrm{pc}$ of the archetypal Seyfert galaxy NGC 4151, using new JWST NIRSpec/IFU spectroscopy. PAHs are detected down to the innermost $50\,\mathrm{pc}$, though it is likely that PAHs also exist at smaller radii, as PAH detections closer than this seem to be limited by continuum dilution. This is contrary to expectations that PAH grains, especially the smallest grains that carry the $3.3\,\mathrm{\mu m}$ feature, could not survive near an active galactic nucleus (AGN). Furthermore, the surface brightness of PAH emission increases as radius from the nucleus decreases. We interpret this as evidence that the AGN supplies energy for PAH excitation by driving ultraviolet emission in nearby H and $\mathrm{H_2}$ gas. We do not detect PAH emission within the narrow line region (NLR) that hosts highly ionized and outflowing gas, suggesting that the AGN may also destroy PAHs in these regions, depending on geometry. Together, these results show that an AGN has a complex, multifaceted role in the life cycle of PAHs and in PAH excitation.

T. Mazeh and coworkers pioneered a method using rotational photometric modulation as a proxy to infer stellar obliquities in Kepler transiting planetary systems, based on the expected positive correlation between spot-induced modulation amplitudes and stellar inclinations. They found that planet hosts cooler than the Sun showed larger modulation amplitudes than comparison stars, consistent with low stellar obliquities. For hotter hosts, however, they reported the opposite - a negative amplitude difference (hosts minus comparison stars) - which is difficult to interpret in terms of viewing geometry. We show that this comparison is affected by confounding variables not controlled for in the sample selection. One such confounder is apparent magnitude, whose distributions differ markedly between the two samples for hotter stars and affect the observed modulation amplitudes. We develop resampling and likelihood-based approaches that enable comparison of the amplitude distributions at fixed apparent magnitude, stellar radius, and rotation period. The previously reported negative amplitude difference for hot hosts is no longer present in either analysis. The likelihood-based analysis finds a positive amplitude difference up to $\sim 6100\,\mathrm{K}$ that becomes consistent with zero at higher temperatures, while the resampling analysis shows a similar but less pronounced trend. This result is qualitatively consistent with independent $v\sin i$ analyses suggesting low obliquities for cooler super-Earth and sub-Neptune hosts and broader obliquity distributions for hotter ones. This may also indicate a gradual change in the obliquity distribution with stellar temperature, although changes in spot distributions or selection effects could also contribute to the photometric trends in hot stars.

The International Liquid Mirror Telescope (ILMT) is an inexpensive optical instrument with a diameter of 4 metres, entirely dedicated to astronomical surveys. Its scientific programmes include the detection and study of transients, variable objects, asteroids, comets, low surface brightness galaxies, space debris, etc. The telescope achieved its first light on 29 April 2022 and was officially inaugurated on 21 March 2023. It has been operating regularly since October 2023 and continuously observes the sky passing through the zenith using the SDSS $g^{\prime}$, $r^{\prime}$, and $i^{\prime}$ filters in a narrow band of the sky ($22.3^{\prime}$) centred around the equatorial declination of $+29°21^{\prime}41^{\prime \prime}$. Here we report on the astrometric and photometric performance of the ILMT and summarise the main results obtained since the BINA3 workshop. A great way to raise public awareness is to build a scale model of a liquid mirror telescope. General guidelines for doing so are provided.

We present evidence of 2:1 harmonic periodicities in two supermassive black hole binary (SMBHB) candidates (PKS J0805-0111 and PKS 2131-021) in the Owens Valley Radio Observatory (OVRO) + University of Michigan Radio Astronomical Observatory (UMRAO) monitoring programs. This potential discovery follows the previous detection of a 2:1 harmonic periodicity in the SMBHB candidate J1309+1154 from these programs. If confirmed, these suggest a physical origin of blazars exhibiting strong periodicities favoring 2:1 commensurabilities in their light curves. There are significant differences between the 2:1 harmonics in these three blazars, which may be due to differences in their central engines. These three SMBHB candidates demonstrate the importance of careful dissection, i.e. cutting apart and close examination, of blazar light curves, to reveal underlying evidence of coherence between different aspects of the periodicities observed in blazars in the presence of correlated random noise variations. This is particularly important for blazar SMBHB searches, given that the observed periods thus far are all longer than 2 years, and can disappear for long timespans. Therefore confirming evidence, such as harmonics, may be crucial in confirming the reality of periodicities, and identifying blazar SMBHB candidates. We present four models that can account for 2:1 commensurable periodicities in blazar light curves, together with explanations for why, on these models, shorter period SMBHB candidates have not thus far been observed, but might be anticipated, or not, in the future, depending on the model, thereby making these models discriminatory. Arguments pro and con the reality of these periodicities are presented.

Recent cosmological data provide weak hints for smaller masses than what is required by neutrino-oscillation experiments, motivating investigations into variation of the neutrino masses with cosmic time. Here we study a model where the neutrinos couple to a quintessence field that acts as dark energy. We compute structure formation using fully dynamical and relativistic N-body and lattice simulations, with nonlinear field evolution and a weak-field metric expansion. Similar to previous studies, we find the generic appearance of neutrino lumps, but observe them to be highly dynamical and spinning. We study several models where the effective dark energy, including nonlinear effects of the scalar field on the cosmic expansion, can show phantom crossing. The relativistic physics available in our simulation framework can help distinguish such models from LCDM, through observations of neutrino and dark energy properties, and slip between the gravitational potentials due to anisotropic stress. The rich phenomenology offered by mass-varying neutrinos motivates further exploration and development of the simulation techniques.

Relativistic shear flows, as encountered in jets of powerful astrophysical sources, offer promising sites of particle acceleration up to the highest energies. This stochastic acceleration process is usually described with Fokker-Planck transport equations, which assume small momentum gains per scattering. The present paper introduces a covariant microscopic description of relativistic shear acceleration, building on the formalism of generalized Fermi acceleration and formulating angular scattering in the locally comoving frame in terms of stochastic differential equations. This allows us to model relativistic shear profiles and to study the transition from gradual to non-gradual shear acceleration, where the particle mean free path becomes comparable to the shear length scale. Assuming an infinite shear layer, linear in the flow four-velocity, we observe that the shear rate peaks where the flow is mildly relativistic, whereas Lorentz aberration suppresses the transverse velocity of particles where the flow is relativistic. Consequently, particles that leave the central layer experience long waiting times with a heavy-tailed, power-law distribution. The momentum evolution becomes subdiffusive and the acceleration time can substantially exceed local estimates. We successfully reproduce the Monte Carlo energy distributions using a two-state continuous-time random walk with Lévy-distributed waiting times. We also show how a momentum-dependent mean-free path can introduce breaks in the spectrum and extend our discussion to finite jet profiles. These effects should be accounted for in models of relativistic jets as sources of high-energy particles.

Open clusters exhibit diverse spatial structures that provide insight into their formation and dynamical evolution. We investigate the relationship between stellar mass segregation, network topology, and dynamical age in 871 dynamically unevolved open clusters ($\tau = t/t_{\rm rh} \leq 1$) from Gaia-based catalogs. We construct three-dimensional k-nearest-neighbor graphs and measure Degree Centrality (DC), Closeness Centrality (CL), and Betweenness Centrality (BC). For each measure, we define a network-based mass segregation ratio (MSR) by comparing the mean centrality of the most massive stars with that of all cluster members. We test the stability of these measures across connectivity parameters $k=5$--20 and compare them with the classical 3D MSR, $\Lambda_{\rm MSR,3D}$, and dynamical age. All three network ratios show positive correlations with $\Lambda_{\rm MSR,3D}$, strongest for closeness centrality, while their correlations with dynamical age are weak. These results demonstrate that network analysis provides a complementary approach to studying stellar structure and mass segregation in open clusters.

We investigate the three-dimensional (3D) formation and evolution of magnetohydrodynamic (MHD) shock waves and their role in plasma heating within a solar bipolar active region. Using 3D compressible, resistive MHD simulations, we model the emergence of magnetic flux from the convection zone into a magnetized corona. Our results reveal that initial plasmoid ejections launch hot plasma jets preceded by slow-mode shocks. Unlike established 2D models, these ejections originate from multiple sites along the emerging field's periphery, resulting in shocks with a complex, inverted-U 3D morphology. Beneath these fronts, the heated plasma forms flattened, sheet-like columns. Furthermore, we find that sustained gas pressure gradients, driven by dense plasma accumulation from plasmoids, power a cool, dense upflow adjacent to the main reconnection jet. During the main reconnection phase, the collision of ejected plasmoids with the ambient field triggers the formation of fast-mode termination shocks. By mapping viscous heating directly onto these irregular 3D shock surfaces, we demonstrate that energy dissipation is highly localized. This finding provides a physical link between shock-induced viscous heating and the observed temperature enhancements at the apex of post-flare loops.

Venus is home to vivid sulfur chemistry, with SO$_2$ as the major sulfur gas species and a global cloud layer between 47 and~70 km composed of H$_2$SO$_4$ and H$_2$O. The chemistry in the clouds has been extensively studied with 1D models, but none is able to reproduce the three orders of magnitude decrease of SO$_2$ inside the clouds. Sulfur allotrope chemistry could be a candidate for buffering sulfur atoms, as it can grow into long chains. Sulfur hydrides such as H$_2$S is considered as one of the main sulfur-bearing compounds, possibly linked to surface reactions or have a volcanic origin like on Earth. In this study, we use for the first time a 3D model to study the climatology of the sulfur allotrope in gas and condensed phase and hydride chemistry in the clouds with an explicit photolysis calculation and updated UV cross-section. H$_2$S is close to ppmv levels below the cloud base, the third most abundant sulfur-bearing species in this region after SO$_2$ and OCS. Below the clouds, S$_8$ gas phase is the most abundant sulfur allotrope. Above, the photolysis and condensation are preponderant, and the gas phase decreases to extremely low values. Polysulfur can therefore not be the unknown absorber at cloud-top altitudes. The condensed phase polysulfurs are present from 30 to above 100~km. S$_2$ condensed phase is the most abundant due to its low saturation mixing ratios. Polysulfur species represent a substantial sulfur reservoir in the upper cloud, equivalent to a few ppmv.

Hercules X-1 and Centaurus X-3 are the first ever detected - and as such identified - binary X-ray pulsars. Here we concern ourselves with the 35-day flux modulation of Her X-1, immediately found at its discovery, together with the binary period of 1.7 days and the pulsation with 1.24 s. The 35-day flux modulation shows two flux maxima, the so-called Main-On and the Short-On (with reduced flux). As noticed early on, the period, or the length of the cycle, is variable. The system constitutes an irregular clock, with a more or less stable mean period of near 34.85 d. We consider the repeated rapid increases of the flux from the off-state to the Main-On (the socalled Turn-Ons) as the best timing marker to study this clock. Here we present a complete list of Turn-On times over 55 years, from the discovery of Her X-1 to today (2026), based on historic work from the literature and on observational data provided by five monitoring instruments. We identify to following basic features of the irregular 35-day clock: The Turn-Ons show preference to occur at orbital phases 0.25 and 0.75. The duration of the 35-day cycle clusters around three discrete values - 20.0, 20.5 and 21.0 orbital cycles with a dominant peak at 20.5 Porb (57%). The long-term trend in the 35-day period duration is seen in the O-C (Observed minus Calculated) diagram. There are two sections, separated by the long Anomalous Low of 1999/200 (AL3), which can be modeled by parabolic functions with a smooth evolution of the 35-day period. A medium-term variation is observed in the form of Anomalous Lows, an essential shut-off (at least of soft) X-rays. We find an apparent underlying period of 5.4 yr. There are short-term (hundreds of days) variations (in part quasi-periodic) overlaid to the long-term trend. Straight ups and downs in the O-C diagram, demonstrating rather rapid 35 day period changes.

Context. Some debris discs contain cold molecular gas. The origin of this gas is one of the key questions in our understanding of the evolution of planetary systems. The effect of gas on the smallest dust grains, which are expected to be unbound due to radiation pressure, is not well understood. The unbound grains contribute to the brightness of scattered light and thermal emission from the disc halo at short wavelengths. Aims. We explored the conditions under which gas can prevent or slow down the escape of unbound grains and increase their number density in the disc halo sufficiently to affect its brightness and reveal properties of the gas. Methods. We numerically integrated the equations of motion of dust grains released on unbound orbits in optically thin, gaseous debris discs, taking into account stellar gravity, radiation pressure, Poynting-Robertson drag, and gas drag. Results. We find that gas drag can significantly slow down the escape of unbound grains only for very high gas masses, such as those expected if the gas is remnant protoplanetary gas and not of secondary origin. We also present an analytical model for estimating the density of unbound grains in gaseous discs. Conclusions. If a difference in the abundance of unbound grains between gaseous and non-gaseous debris discs were observed, it would imply that the gas in debris discs is protoplanetary. Currently, there is no evidence of such a difference, suggesting that the gas detected in debris discs is either secondary or strongly depleted protoplanetary gas.

Fast radio bursts (FRBs) are brief flashes of radio emission whose time, frequency, and polarization structure constrain their sources and propagation environments. FLITS (Fast-Look Interactive Transient Suite) is an open-source Python package with a browser interface for analysing detected bursts. It combines data inspection, interference mitigation, measurement, and modelling, including fits of the fitburst burst model, in a shared session, and reads SIGPROC filterbank, PSRFITS, and CHIME/FRB HDF5 data. The same routines measure larger samples from the command line and flag bursts whose automatic selections need checking. Trial dispersion measures can be scored by signal-to-noise, by burst structure, or with a smoothed-structure metric that also reports the range of dispersion measures consistent with the best one. Portable session files retain the selected data regions, excluded channels, calibration inputs, available results, input-data checksum, and software provenance, and supported measurements can be replayed from the command line and compared with their saved values. Uncertainty labels identify missing calibration information. A public reference workflow provides downloadable data and numerical checks.

In energetic astrophysical sources like the gamma-ray bursts (GRBs) and blazars, the relativistic electrons lose their energy efficiently through synchrotron radiation and inverse Compton (IC) scattering and can rapidly cool to energies below the minimum acceleration energy $\gamma_m$. It is widely known that such electrons develop a power-law spectrum $\gamma_e^{-2}$ below $\gamma_m$. However, this power-law spectrum is valid only if a steady-state population of electrons is assumed. In general, the cooled electrons below $\gamma_m$ evolve in a non-steady state and their spectrum deviates significantly from the power-law $\gamma_e^{-2}$. We present here a new electron spectrum $f_{\rm U}$ that describes this fast-cooled, generally-evolving, and non-steady-state population of electrons below $\gamma_m$. We consider two cooling cases: (1) when the electrons undergo radiative (i.e., synchrotron + IC) cooling, and (2) when the electrons experience both radiative and adiabatic cooling. We first derive $f_{\rm U}$ analytically and find an explicit expression of $f_{\rm U}$ for each cooling case. Secondly, we show that $f_{\rm U}$ is a solution to a Fokker-Planck equation in the entire energy range below $\gamma_m$ and derive a general version of $f_{\rm U}$ for each cooling case. We also compare $f_{\rm U}$ to a detailed numerical calculation of a blazar electron spectrum and find an excellent agreement for the whole energy range below $\gamma_m$. Thus, $f_{\rm U}$ gives us a general electron spectrum to describe the entire cooled electrons below $\gamma_m$. Our discovery of a new fast-cooling solution $f_{\rm U}$ below $\gamma_m$ may find it applicable in a wide range of energetic phenomena in high-energy astrophysics.

Fast radio bursts (FRBs) are bright extragalactic transients whose origin remains uncertain. The discovery of repeating FRBs, some with cyclic activity windows, opens new prospects for testing their progenitors. Neutron stars (NSs) are strong candidates, as they naturally emit radio pulses with temporal and spectral properties resembling those of FRBs, an interpretation reinforced by the detection of an FRB-like burst from the Galactic magnetar SGR 1935+2154. Nevertheless, the pulse energy of typical radio-emitting NSs remains several orders of magnitude below that of even the faintest observed FRBs. We explore a binary system in which a NS orbits a black hole (BH), so that NS radio pulses are gravitationally amplified through self-lensing, producing characteristic signatures in the energy distribution, activity windows, and waiting times that can be contrasted with observations. We implement a simple NS-BH binary model with a circular orbit undergoing Lense-Thirring precession, and compute how the pulses are lensed along the orbit, including pulse splitting and time delays. Pure Keplerian orbits produce activity windows several orders of magnitude shorter than those of periodic FRBs. Post-Keplerian orbits with Lense-Thirring precession are more promising, yielding windows of a few to tens of days. Lensing transforms an intrinsic log-normal NS pulse-energy distribution, producing a high-energy power-law tail spanning up to four orders of magnitude. Interpreting the observed millisecond waiting times between consecutive bursts as lensing-induced image delays, we infer BH masses of 10^3-10^4 solar masses, in the intermediate-mass (IMBH) range. However, the amplification in our model is insufficient to bridge the energy gap between Galactic magnetar radio pulses and FRBs. Moreover, the non-detection of NS-IMBH systems suggests a low abundance, so this channel is likely rare.

In this work, we present a systematic X-ray study of 85 TeV-detected blazars based on archival \emph{Swift}-XRT and \emph{NuSTAR} observations available up to May 2024. We derive unabsorbed X-ray fluxes and photon indices through spectral fitting, and investigate their light curves, spectral energy distributions, flux distributions, power spectral densities, and flux-index correlations. Using the fractional variability method, we identify 78 sources as variable in the soft X-ray band and 14 sources as variable in the hard X-ray band. For well-sampled soft X-ray light curves, the flux distributions are generally better described by log-normal functions, while the PSD slopes span $\beta_{\rm PSD}=0.1$--$1.6$, with most values between 1.0 and 1.6, where the PSD is defined as $P(f)\propto f^{-\beta_{\rm PSD}}$. We find positive correlations between TeV and X-ray luminosities, supporting a leptonic emission scenario. We also find a correlation between X-ray and disk luminosities, whereas no significant correlation is found between X-ray luminosity and black hole mass.

Satellite emissions at low frequencies can interfere with astronomical observations. Observations with the EDA2 have revealed recurrent Starlink emissions near 137~MHz, attributed to very high frequency (VHF) telemetry, tracking, and command (TT\&C) transmissions. We aim to characterise Starlink VHF emissions detected with the 21 CentiMeter Array (21CMA) to better assess their potential impact on future low-frequency radio astronomical observations and inform the development of methods to mitigate the resulting interference. We searched five coordinated VHF channels in observations obtained on 15 April 2025 (UTC) and demodulated and decoded candidate signals. Two valid packets are detected at 137.055~MHz, each lasting 1.027584~s and separated by 99.987~s. A blind comparison with 11\,305 active satellites identifies STARLINK-32838 (NORAD ID 62827) as the transmitter, with differential Doppler measurements linking both events to the same spacecraft. Orbital analysis shows that the satellite was undergoing orbit raising and that the limited number of detections was partly attributable to its being below the horizon for most of the observing time. Re-analysis of EDA2 detections indicates that such emissions are not confined to orbit raising. The stronger event's estimated flux density is 9.23~MJy at 1000~km, consistent with previous measurements at the order-of-magnitude level. Signal demodulation and decoding, combined with orbital analysis, can improve the identification and characterisation of satellite-related radio frequency interference. The detection of similar VHF emissions across different orbital phases indicates that their potential interference with low-frequency radio astronomy should not be considered solely in the context of orbit raising.

Coherent emission from merging plasmoids in relativistic reconnection is the leading model for radio emission originating in the outer magnetosphere of pulsars such as the Crab, and a candidate emission mechanism for fast radio bursts. This process has only been studied in 2D, and whether it survives in 3D, where the dynamics of structures in the reconnection layer can differ substantially, is still an open question. Here we present the first study of coherent wave generation from flux rope mergers in 3D relativistic reconnection. We use particle-in-cell simulations of relativistic reconnection with outflow boundary conditions and guide fields $B_g/B_0 = \{0,0.1,0.3\}$, and measure the efficiency $\eta$ with which inflowing magnetic energy is converted into escaping coherent waves. We find $\eta \sim 7\times10^{-4}$ without a guide field, a factor of a few below 2D results, and $\eta\sim(1\text{-}2) \times10^{-3}$ at moderate guide fields, comparable to 2D with no guide field. We propose a physical picture for why the efficiency remains comparable to 2D, based on how reconnected field is transported away from the diffusion regions. The escaping waves are linearly polarized, with a polarization angle set by the direction of the upstream field. In the presence of a guide field, waves escaping from opposite sides of the reconnection layer therefore differ in polarization angle by $\sim 2\arctan(B_g/B_0)$. Our results support relativistic magnetic reconnection as the origin of coherent radio emission from Crab-like pulsars, and strengthen its case as a potential emission mechanism for fast radio bursts.

The nature of the system NGC 1850-BH1 is discussed controversially in the literature. Located in the young (100 Myr) massive cluster NGC 1850 in the Large Magellanic Cloud, it was initially proposed to consist of a 5 $M_\odot$ main sequence turn-off star orbiting a stellar-mass black hole. However, subsequent analyses of the system have presented an alternative explanation, comprising of a lower mass (1-2 $M_\odot$) puffed-up donor star orbiting a rapidly rotating mass accretor. Efforts to discern the secondary's nature as a luminous star or a compact object in the original spectroscopy have remained inconclusive. In this work, we analyse a set of follow-up multi-epoch FLAMES-ARGUS spectra, which are bluer and of higher spectral resolution than the original data. Exploiting the spectral disentangling technique, we reveal the luminous secondary, and constrain the parameters of both components. We can describe the system self-consistently, adopting a 1.7 $\pm$ 0.4 $M_\odot$ puffed-up mass donor and a rapidly rotating ($v\sin{i} = 275$ km/s) 5.2 $\pm$ 2.6 $M_\odot$ luminous companion. While this rules out the black hole hypothesis, tensions with the analysis of the original data remain: Our inferred flux ratio of $\sim$ 35-50% in the red optical wavelength range is higher than the 10% upper limit found in previous work. The origin of this discrepancy remains unclear. Thanks to its location in a cluster of well-known mass and metallicity and its peculiar orbital properties, NGC 1850-BH1 has the potential to serve as a benchmark for mass-transfer efficiency studies.

Blue cores in brightest cluster galaxies (BCGs) trace recent central activity associated with cooling cluster atmospheres. We search for blue cores at $z<0.6$ in five eROSITA all-sky surveys using X-ray data, optical imaging, and optical spectroscopy. We identify 379 blue-core BCGs among 11352 systems (3.3%), although contamination increases toward higher redshift. Of these, 98 (0.86%) are X-ray bright. Their defining signature is a central $g-r$ color at least 0.2 mag bluer than the reference population within $a=20$ kpc before returning to the normal BCG envelope. Ha emission equivalent width correlates strongly with the blue continuum excess, consistent with young stellar components comprising ~0.1-1% of pre-existing stellar mass. Line ratios indicate widespread LINER-like excitation, with a larger star-forming contribution in blue Ha emitters but substantial non-stellar excitation. This activity is closely linked to the thermodynamics of the host-cluster gas. At $0.1R_{500}$, cooling times decrease from BCGs without significant Ha emission to red and then blue Ha emitters. Blue BCGs preferentially occur in clusters with $L_{\rm X,300}>10^{44}$ erg s$^{-1}$; red Ha emitters also favor higher X-ray luminosities. The blue-core fraction rises with optical richness. For systems with $t_{\rm cool}(0.1R_{500})<20$ Gyr, doubling richness increases the odds of hosting a blue-core BCG by $2.45\pm0.39$. This indicates that cluster scale carries information beyond cooling time, plausibly through the amount of gas available for cooling and condensation. The scarcity of blue BCGs without significant Ha emission disfavors isolated short bursts followed by long Ha-quiet fading phases. It can instead be explained by sustained or closely recurrent star formation over timescales much longer than 100 Myr, or by Ha persisting through additional excitation mechanisms as the young stellar component fades.

Be X-ray binaries (BeXRBs) are mostly transient X-ray binaries with usually a neutron star as the compact object and a Be star as their optical companion. We performed a comprehensive analysis of BeXRBs in quiescence with the extended ROentgen Survey with an Imaging Telescope Array (eROSITA), the soft X-ray instrument on board the Spectrum-Roentgen-Gamma satellite, using its first all-sky survey (eRASS1) data. The transient BeXRBs spend majority of time in their quiescent state, but are often studied during their outbursts. A quiescence study is useful to probe the emission mechanism of BeXRBs at low mass accretion rates. The spectra of BeXRBs detected in the eRASS1 main catalogue could be well fitted with a powerlaw as well as a blackbody model. In the absence of detection of a BeXRB, we report the luminosity upper limit for its position in the sky. The X-ray luminosity for the quiescent BeXRBs detected with eROSITA have $L_{X}\sim10^{33-36}$ erg s$^{-1}$ for both absorbed powerlaw and blackbody models in most cases. For the absorbed blackbody model, the emission seems to come from a fraction of the neutron star's surface. The quiescence luminosity of BeXRBs are used to distinguish between different accretion models at low mass accretion rates, like accretion in the propeller regime or from a cold accretion disc. The detection space of BeXRBs in quiescence for the eRASS1 data is compared against previously reported luminosities across multiple X-ray observatories.

Aims: We develop a deep-learning-based pipeline to construct a list of {\gamma}-ray sources and to quantitatively assess the impact of background uncertainties on source detection and characterization. This work extends and enhances the existing AutoSource-ID algorithm, previously adopted on optical observations, for applications on {\gamma}-ray data. Methods: Source detection was performed through image segmentation using a U-Net architecture, while dedicated deep neural networks (DNNs) were employed for source localization, flux estimation, and the classification of detected sources as either genuine or spurious. The training data were generated from Monte Carlo simulations based on 10 years of Fermi-LAT observations. Results: We present the first Fermi-LAT {\gamma}-ray all-sky source list derived using a deep-learning-based method (1FDL), containing more than 3800 sources with estimated positions, fluxes, and probability scores that quantify the likelihood of each detection being genuine or spurious. We further evaluated the robustness of the pipeline against variations in the interstellar emission model (IEM) and compared the resulting source list with the 4FGL-DR2 catalog. Conclusion: We find that the our deep-learning-based approach achieves performance comparable to, or better than, the likelihood-based methods employed in the standard Fermi-LAT catalog pipeline when tested against changes in the IEM. The 1FDL source list is broadly consistent with the Fermi-LAT 4FGL-DR2 catalog obtained over the same 10-year observational period, including a few new sources confirmed in the recent Fermi-LAT 16-year source list (FL16Y). These results demonstrate the potential of DNN methods for the detection and characterization of {\gamma}-ray sources and provide a foundation for their application in future high-energy astrophysical analyses.

Changing-look blazars (CLBs) move between the flat-spectrum radio quasar (FSRQ) and BL Lacertae (BL Lac) optical classifications. Either the accretion flow switches regime, or a brightening jet continuum swamps the broad lines while the system itself is unchanged. The two pictures predict the same optical behaviour but differ in the jet, so the $\gamma$-ray emission could potentially separate them. Catalogue quantities averaged over the mission cannot, because a permanently intermediate source and one alternating between two states return the same mean. We therefore use 17.9\,yr of \textit{Fermi}-LAT light curves at 3-, 7- and 30-day cadence, comparing CLBs with BL Lac and FSRQ controls selected and analysed identically. CLBs and FSRQs have indistinguishable fractional variability, with medians of 0.483 and 0.437 at 30-day cadence ($p = 0.94$), while BL Lacs are far less variable at 0.262 ($p = 1.4\times10^{-4}$). The result survives restricting the controls to low-synchrotron-peaked sources and matching in flux and sampling. Several further diagnostics group CLBs with FSRQs, as does their Eddington-scaled disc luminosity. Followed through time, CLB light curves show no excess of bimodal flux distributions, and the direction of the optical transition does not predict how the $\gamma$-ray spectrum evolves. CLBs do reach hard, BL Lac-like spectra more often than FSRQs, but never for longer than chance allows. Only in this, and in how their spectra respond to brightening, do they fall between the two classes. The changing-look phenomenon therefore leaves little imprint on the $\gamma$-ray jet, favouring a variable jet continuum over a change of accretion regime.

Recent analyses of simulated Milky Way-mass galaxies have highlighted the prevalence of satellites undergoing tidal disruption. However, these have focused on single hydrodynamical codes with a number of limitations, making it unclear how generic this result is. We compare satellite disruption in four models: two cosmological hydrodynamical simulations (Auriga and FIRE), cosmological $N$-body simulations with stellar particle tagging (Aquarius), and a semi-analytic model with varying host disk properties (SatGen). For all systems, we compute the fraction of stellar mass retained by the progenitor ($f_\text{bound}$) at the present day. We find a remarkable agreement between FIRE, Aquarius, and SatGen; all predict that $\sim$20 to 30 per cent of classical-mass satellites have $f_\text{bound} < 0.9$ ($\sim$5 to 10 per cent have $f_\text{bound} < 0.5$). Satellites in Auriga experience substantially more mass loss than other simulations, which we attribute to their massive central galaxies and large satellite sizes prior to infall. In the ultra-faint regime captured by Aquarius and SatGen, disruption rates are comparable to or exceeding those for classical satellites. The ubiquity of mass loss across models presents both an exciting opportunity (a plethora of stellar streams awaiting discovery) and a nuisance (for theorists using satellite counts to constrain dark matter).

To constrain the emergence of the first quiescent galaxies (QGs) and their connection to large-scale structure, we search for rare, high-redshift QGs in proto-clusters using spectral energy distribution modeling, multiple rest-frame color diagnostics, and visual inspection. Our sample includes 12 QG candidates with stellar masses log(M*/Msun) ~ 9-11 in four proto-clusters at z ~ 4-6 within GOODS-North (GOODS-N) and GOODS-South (GOODS-S). The selection uses 11 NIRCam filters in GOODS-N and 17 NIRCam plus 2 MIRI filters in GOODS-S, combined with 9 ancillary HST filters, covering 0.4-7.7 microns. We measure an increasing quiescent fraction with stellar mass, with averages of 1.0%(+0.7/-0.4; 5/502), 3.5%(+2.8/-1.7; 4/115), and 33.3%(+22.2/-17.5; 3/9) for log(M*/Msun) = 9 - 9.75, 9.75 - 10.5, 10.5 - 11.25, respectively, across four proto-clusters. Notably, the two GOODS-N proto-clusters at z=4.406 and z=5.194 have a quiescent fraction of 100% (2/2 at z=4.406; 1/1 at z=5.194) in their highest mass bin (log(M*/Msun) > 10.5), whereas the proto-clusters in GOODS-S at similar redshifts have zero massive quiescent galaxies. Contrary to the expectation that massive galaxies occupy cluster centers at z~0, our QGs are found primarily on the outskirts of overdensity peaks. We also find fewer robust QGs at z>5 (1/8) and none in the z=5.384 proto-cluster, consistent with simulations suggesting that efficient quenching mechanisms had not yet matured. Our results highlight the pronounced variations in quiescent fractions across proto-clusters at z>4. The emerging diversity of proto-cluster QG populations calls for a stronger understanding of the role of environment in early galaxy evolution.

We investigate how sensitive the effects of neutrino trapping on hot hybrid stars are to uncertainties in the hadronic and quark equations of state and in the thermodynamic construction of the hadron--quark transition. The hadronic phase is described by finite-temperature covariant density functional equations of state, and the quark phase by a three-flavor Nambu--Jona-Lasinio (NJL) model with repulsive vector interactions and two-flavor color superconductivity. Because confinement is absent from the NJL model, an effective pressure shift $B^*$ is used phenomenologically to locate the deconfinement transition. We construct isentropic stellar equations of state with and without trapped electron neutrinos, vary the quark vector coupling and the nuclear symmetry-energy slope, and compare global with local conservation of electron-lepton number within phase coexistence. Neutrino trapping generically shifts deconfinement toward higher density throughout the parameter range considered. Increasing the vector interaction stiffens quark matter and raises the maximum stellar mass, but only moderately for the couplings studied. We also examine stronger diquark pairing and RG-consistent regularization, instead of sharp momentum cut-off: both affect the pairing gap, phase boundaries, and quark-core composition more strongly than they alter the qualitative trends of the stellar mass--radius sequences. Conversely, trapping reduces the sensitivity to the hadronic symmetry-energy slope because the enhanced proton fraction drives matter toward greater isospin symmetry. Global and local lepton-number prescriptions produce rather similar mass--radius relations but substantially different internal phase structures: global conservation leads to a considerably more extended mixed phase.

Mapping the circumgalactic medium (CGM) in emission is a critical next step in understanding its role in the baryon cycle and galaxy evolution, and dwarf galaxies ($M_{\star}\lesssim 10^9 M_{\odot}$) are essential laboratories to study the effects of feedback on the CGM. Using the Marvelous Massive Dwarfs simulation suite, we model the CGM surface brightness (SB) around dwarf galaxies in H$\alpha$, [NII]$\lambda$6583, and [OIII]$\lambda$5007, lines accessible to current integral-field spectrographs (e.g., MUSE and KCWI) and to narrow-band imaging with the MOTHRA telephoto array. We investigate trends in SB magnitude, extent, and geometry as well as correlations with gas kinematics, recent star formation, and galaxy size. Emission in the three lines typically traces distinct CGM structures and phases. SB and the size of the emitting region can differ significantly at a given galaxy mass, but enhancements or suppression in either brightness or extent correlate well across lines. Typically, emission is preferentially eccentric and oriented along the galaxy's semi-minor axis. While outflows are key drivers in dispersing metals into the CGM and shaping SB, they remain difficult to identify in SB maps and contribute $\sim40\%$ of the total SB across lines and galaxy masses, while inflows contribute $\sim50\%$. Finally, we identify evidence for a positive correlation between SB and recent star formation and weaker but still significant evidence for a negative correlation between SB and HI disk size. These results link CGM emission to both a galaxy's recent star formation and its cumulative evolution, yielding predictions that ongoing surveys can test and further establishing emission mapping as a new window into the baryon cycle.

We present a deep low-frequency radio point-source catalogue centred on the North Celestial Pole (NCP) and extending $5^\circ$ in radius, derived from a single 24-h observation with the 21 CentiMeter Array (21CMA). Covering 75-175 MHz, the catalogue characterises extragalactic foreground point sources for Epoch of Reionization (EoR) studies. Previous 21CMA imaging has been limited by reduced dynamic range caused by direction-dependent effects, particularly the severe grating lobes of ultra-bright sources such as 3C 61.1 and ionospheric phase distortions. Here we apply 21CMAcali, a direction-dependent calibration and imaging pipeline, to mitigate these effects. The angular resolution ranges from 2.3 arcmin at 100 MHz to 1.4 arcmin at 168.75 MHz. The resulting maps show reduced artefacts and background noise, enabling more reliable recovery of faint sources. We construct a catalogue of 1246 radio point sources. Cross-matching with LoTSS-DR3, WENSS, and NVSS enables broad-band spectral fitting, while an independent in-band analysis yields a median spectral index of $\alpha=-0.825$ (where $S \propto \nu^{\alpha}$). The Euclidean-normalised differential source counts at 150 MHz, derived from a dedicated 50-MHz-wide multi-frequency synthesis (MFS) image, are broadly consistent with existing measurements and semi-empirical models at the bright end, whereas the deficit at lower flux densities ($S \lesssim 0.04$ Jy) mainly reflects limited sensitivity and incompleteness. This catalogue improves foreground point-source characterisation in the 21CMA NCP field, demonstrates the value of direction-dependent calibration, and provides a reference for deeper catalogues based on multi-day observations.

We investigate single-field inflation models that can produce large curvature perturbations at sub-Mpc scales while remaining consistent with cosmological observations across multiple regimes. We highlight the tension between generating enhanced small-scale perturbations and maintaining agreement with the scalar spectral index $n_s$ measured by ACT and SPT, which disfavors several conventional single-field inflation models. To address this issue, we propose three viable classes of inflationary potentials: bump/dip-modified, step-like, and double-inflection-point. Each can sufficiently amplify primordial perturbations while predicting $n_s$ that lie within the $2\sigma$ range of current observational bounds. In addition, we examine the primordial power spectra predicted by these models and constrain their parameter spaces using cosmological observations at different scales, including CMB, BAO, PBH, PTA, and CMB-distortion. Our results show that some of the models considered can simultaneously satisfy the ACT/SPT constraints and account for the current PTA observations, although doing so while respecting the constraints on the PBH abundance remains challenging.

The LMC is a benchmark galaxy for studying stellar evolution, chemical enrichment, and galaxy interactions due to its proximity and intermediate metallicity. While its star formation history (SFH) has been extensively studied using colour-magnitude diagram (CMD) fitting techniques and the chemical enrichment is largely based on red giant branch (RGB) stars, the asymptotic giant branch (AGB) population - a key tracer of intermediate-ages - has received less attention in these analyses. We aim to reconstruct the SFH of the LMC using AGB stars and to study their reliability as tracers of chemical abundances. The initial sample of 879 AGB stars from the Gaia DR3 long-period variable catalog was extended to 2047 fundamental-mode pulsators by applying separate O-rich and C-rich period-Wesenheit relations; OGLE-III cross-matching then showed that only 256 of these stars are Mira variables. We reconstructed the SFH using two period-age calibrations: the theoretical relation of Trabucchi and Mowlavi (2022) and the empirical calibration of Zhang and Sanders (2023). For the chemical abundance analysis, we used APOGEE DR17 spectra for 296 AGB and 271 RGB stars, applying a refined line-by-line abundance pipeline with a tailored line selection to derive Mg, Si, and Ca abundances. The two calibrations yield significantly different SFHs, and neither matches independent CMD-based results equally well, so we present both rather than one fiducial choice. Our SFH reveals three distinct phases: an ancient population at 9-10 Gyr, a quiescent phase at 4-8 Gyr, and a starburst peaking at 1.5-2 Gyr. Our chemical analysis demonstrates that carefully selected Mg, Si, and Ca lines yield significantly reduced intrinsic scatter compared to APOGEE DR17 results. AGB stars prove to be reliable tracers of both the SFH and chemical enrichment of the LMC, provided that careful line selection and calibration are applied.

The nuclear equation of state shapes both the structure of rapidly rotating neutron stars and the orbital motion in their surrounding spacetime. Its uncertainty affects the mass and radius at which the innermost stable circular orbit reaches the stellar surface, a condition that defines the transition between disks whose inner edge is set by the surface and those truncated by orbital instability. We quantify how measurements of the electric dipole polarizability of neutron-rich nuclei reduce the uncertainty in this transition and in the orbital properties at the disk inner edge. We compute uniformly rotating neutron stars in general relativity for a family of equations of state that systematically vary the symmetry energy, derived from relativistic energy density functionals with density-dependent point-coupling interactions. We compare the results for the full family with those for the subset consistent with the measured dipole polarizabilities of finite nuclei. The dipole polarizability constraint reduces the spread in transition mass and equatorial radius by factors of about seven to ten across the spin frequencies considered. Along this transition, it also confines the orbital frequency at the disk inner edge to a band narrower than $20$~Hz at each spin. Combined with a measured neutron-star spin, a kilohertz quasi-periodic oscillation interpreted as disk orbital motion further restricts the mass--radius region, allowing an independent mass estimate to probe the symmetry-energy constraint. The dipole response of finite nuclei thus informs both the structure of rotating neutron stars and the orbital properties of their inner accretion disks.

Hydrogen-deficient carbon (HdC) stars are rare supergiants believed to form through the merger of two white dwarfs (WDs). They comprise the dust-producing R Coronae Borealis (RCB) stars and the dustless HdC (dLHdC) stars. While dedicated Galactic surveys find the two subclasses in roughly equal numbers, no dLHdC star had previously been identified in the Magellanic Clouds, despite 30 known RCB stars in these two galaxies. We present the first systematic search for dLHdC stars in the Large and Small Magellanic Clouds, aiming to measure the dLHdC-to-RCB ratio in environments of distinct metallicities and well-constrained star formation histories. Candidates were selected from the Gaia DR3 Magellanic catalogue using colour-magnitude cuts combining Gaia, SkyMapper DR4, and VMC DR6 photometry, complemented by a random-forest classifier trained on known Galactic dLHdC stars. The search reached an overall detection efficiency of ~96%. All candidates were followed up spectroscopically with WiFeS on the ANU 2.3m telescope. We discovered the first two Magellanic dLHdC stars: SP77 29-5 in the LMC and SMSS 005551.43-723139.2 in the SMC, the latter belonging to the rare Sr-rich subclass. The resulting dLHdC-to-RCB number ratio of ~1:15 overall is far below the near-unity Galactic value. We argue this deficit is intrinsic rather than observational. Convolving the delay time distribution from a sub-class of white dwarf mergers with each Cloud's star formation history, we estimate that ~80% (LMC) and about two-thirds (SMC) of HdC stars originate from mergers with short delay times, which at low metallicity are biased towards higher total WD masses, and thus towards the luminous regime associated with RCB stars rather than the fainter dLHdC population.

Nova super-remnants (NSRs) are vast shell-like structures encompassing recurrent novae (RNe), created through the excavation of large amounts of local interstellar medium by repeated nova eruptions. Simulations predict that such NSRs should surround all novae. Indeed, NSRs have now been discovered around the Galactic RNe KT Eridani, RS Ophiuchi and T Coronae Borealis, and the Large Magellanic Cloud RN LMCN 1971-08a, to place alongside the prototypical NSR in M31, associated with the extreme RN, M31N 2008-12a. Highly energetic novae ejecta impacting the inner boundary of the NSR shell alongside inter-ejecta shocks are predicted to generate high levels of X-ray emission in the form of an extended shell-like structure. A search for X-ray emission from a present NSR surrounding the Galactic RN, V745 Scorpii, using observations from the extended Roentgen Survey with an Imaging Telescope Array (eROSITA) on board Spektrum-Roentgen-Gamma (Spektr-RG, SRG) led to the identification of a shell coincident with the nova. Based on (i) the structure being aligned with the location of the central nova; (ii) its size being consistent with the sizes of other known NSRs; (iii) the similarity between the emission radial profiles of the X-ray structure and the confirmed NSR around M31N 2008-12a; (vi) the presence of a corresponding infrared cavity; (v) the resemblance of the radial profile of the synthetic X-ray ring derived from a modelled NSR structure with the radial profile of the observed ring; and (vi) the lack of other sources capable of creating such a large structure, we propose this X-ray structure to be another Galactic NSR to be uncovered, and the first NSR to be captured through its X-ray emission.

The Dark Energy Science Collaboration has prepared a multitude of pipelines to process the upcoming Vera C. Rubin Observatory data and perform different scientific analyses. Here, we present the methodology to constrain the mass information of galaxy clusters from weak lensing, which is encompassed by the v2.0 release of the Cluster Lensing Mass Modeling (CLMM) code. This Python library provides the ingredients for both the modeling and data reduction of lensing observables, and the improvements in the new version were customized to handle the first WL analyses of LSST clusters, including, e.g., stacking functionalities and WL multipoles. This new version of CLMM has allowed various cluster analyses using LSST-DESC simulated data, precursor survey and Rubin commissioning and survey validation data, and is ready to be used for the first cluster cosmology analyses. CLMM is an open-source software package collaboratively written in Python, providing multiple example notebooks, including a set that can reproduce all figures in this work, and extensive documentation, publicly available at this https URL.

Compact radio sources are occasionally observed to undergo extreme scattering events (ESEs): large, chromatic flux-density variations, often by more than a factor of two, over a few months. These were interpreted to be a smooth plasma lensing phenomenon due to AU-scale structures in the ISM. Although ESEs were discovered decades ago, observationally, only a few tens of ESEs have been reported, often from individual sources monitored at very high cadences. As such, the nature of the plasma lenses generating such events remains elusive. In this article, we present the most comprehensive sample of ESEs to date, using the ASKAP Variables and Slow Transients (VAST) survey. We report the discovery of a three-tier sample --- 72 sources that show promising ESE events (gold), 76 sources that are likely ESE-exhibiting (silver), and an additional 88 sources where ESE events are one plausible explanation (bronze). We show that the light curves demonstrate varied morphologies, which can be interpreted in terms of the source size and the strength of the lens in the paradigm of a simple one-dimensional Gaussian lens model. The spatial distribution of ESEs shows an appreciable excess in the direction of the Galactic center and along the Galactic loops. Using this sample, we infer an overall rate of 0.012 such events per year per deg^2 (or 0.006 events per source per year) for our (gold+silver) sample, for sources with mean flux density above 5 mJy at 888 MHz (0.01% of all isolated point sources detected in VAST).

Microlensing of strongly lensed quasars probes unresolved accretion disks, but many inference methods use static magnification maps with fixed relative microlens positions. Using the GPU-accelerated simulator Microcaustics, we generate ten-year multiband light curves for three quadruply lensed quasar configurations. We compare dynamical microlensing with independent microlens motions against coherent bulk motion, and a microlens mass distribution against equal masses, keeping the velocity distribution of individual microlenses and mean mass fixed. We infer population disk sizes using ridge regression on the means and lower and upper scatters of ten variability and event metrics. We measure biases by applying models trained with simplified physics to simulations including both effects. Models trained on coherent motion interpret the additional variability from evolving caustics as smaller disks. For populations of 128 independent realizations, jointly inferred radii are consistently smaller by 6-28%. Microlens dynamics increase caustic-crossing rates pooled across all four macroimages by 5-15% and r-band high-magnification-event (HME) rates by 13-25%, while shortening median HME durations by 4-12%. Omitting the mass distribution produces configuration-dependent disk-size offsets from -12% to +5%. Including the mass distribution decreases caustic-crossing rates by 6-8% and HME rates by 6-12%. It also narrows the spread of ten-year averaged microlensing time-delay differences between macroimages by a median of 9-12% per system, while microlens dynamics have a smaller, image-pair-dependent effect. These results demonstrate the importance of microlens dynamics for population disk-size inference and motivate simulations that include dynamical microlensing and a microlens mass distribution.

We present the most extensive catalogue of variable stars in NGC 205 to date, based on archival HST/ACS imaging of a single field $\sim 4^\prime$ from the galaxy centre (GO-15902). We detect 1441 RR Lyrae stars (1064 RRab, 363 RRc, and 14 of uncertain mode) and 35 anomalous Cepheids, and measure their periods, amplitudes, and intensity-mean magnitudes in the F606W and F814W bands. The variable population is dominated by RR Lyrae stars, as expected for a predominantly old (>10 Gyr) field with no strong young component. From the red giant branch tip we derive a distance modulus of $\mu = 24.68 \pm 0.06$ mag. The distribution of the RR Lyrae stars in the Bailey diagram, the fraction of RRc stars, and the presence of a substantial population of high-amplitude short-period RRab stars, indicate a range of metallicities extending to a metal-rich component, while the ratio of RR Lyrae stars to red giant branch stars indicates an extended star formation history, with only a modest fraction of the stellar mass formed in the first few Gyr. The anomalous Cepheids place NGC 205 among the slow evolvers on the relation between their frequency and host luminosity, and comparison with evolutionary models constrains their progenitors to $[\mathrm{Fe/H}] \lesssim -2.1$, indicating that metal-poor gas remained available well after the galaxy had begun to enrich. In a forthcoming paper, we will use the RR Lyrae periods and intensity-mean magnitudes to derive individual metallicities for these stars and trace the chemical enrichment history of NGC 205.

Although stochastic low-frequency (SLF) variability is ubiquitous among hot, massive stars, its physical origin remains uncertain. One proposed explanation is that this variability is produced by internal gravity waves (IGWs) excited in the stellar interior by convection in the stellar core or subsurface layers. Strong magnetic fields, however, are expected to significantly attenuate such waves. In this work, we model the conditions for magnetic gravity-wave suppression in 17 magnetic hot stars that exhibit significant SLF variability. We find that in many cases, IGWs excited at frequencies comparable to the observed variability should be strongly suppressed by the magnetic field, sometimes across a substantial fraction of the frequency range containing the observed SLF power. This finding challenges IGWs as a universal explanation for SLF variability in massive stars and motivates the consideration of alternative origins.

There is significant evidence that white dwarfs can explode via the double detonation mechanism, whereby an initial detonation in an accreted helium shell triggers a second detonation of the carbon-oxygen core. This scenario has been invoked for white dwarfs near a solar mass to produce Type Ia-like supernovae, but low-mass explosions have been relatively unexplored despite the most common white dwarf being near 0.6 solar masses. We predict faint and fast transients emerging from double detonations of white dwarfs with total masses around 0.6 solar masses and accreted helium shells up to 0.3 solar masses. The models are computed through the moving-mesh nuclear hydrodynamics code Cattails and the Monte Carlo radiation transport code Sedona. A continuum of core-powered and shell-powered transients are produced with no more than 0.03 solar masses of radioactive nickel in the core or shell material, respectively. The light curves are rapid and sub-luminous, peaking near -17 magnitudes within 5 to 10 days. The ejecta is dominated by intermediate mass elements and unburnt core that imprint noticeable features in the spectrum. This is the first parameter survey to investigate double detonations at such low masses, and these systems could produce a historically missed population of supernovae. Our predictive models could help large sky surveys find these events.

Helium abundance is a key input to stellar models that are used to infer accurate ages, masses, and compositions for individually resolved stars in the Milky Way (MW), underpinning Galactic archaeology. Since spectroscopically measuring He abundances is difficult, stellar models often assume a fixed "chemical enrichment law" dY/dZ (the slope linearly relating a star's helium mass fraction Y to its metal mass fraction Z). If incorrect, this assumption can introduce significant systematics in inferring stellar properties. Using the FIRE-3 cosmological baryonic zoom-in simulations, we investigate helium versus metal enrichment in the stars of MW-mass galaxies. Given the nucleosynthetic yields in FIRE-3, overall metal production is dominated by core-collapse supernovae (CCSN) at all progenitor metallicities. He production is dominated by CCSN for progenitor metallicities of Z <= 0.1 Zsun, but by stellar winds for progenitors near Zsun. Our simulations produce a range of dY/dZ slopes slopes with best-fit values of ~0.75-2.1 depending on the age of the stars considered at present day; on average consistent with the range of values from MW observations but with no single "universal" enrichment law. The dY/dZ slope also shows galaxy-to-galaxy variance in our simulations, and to leading order increases over cosmic time within the same galaxy, based on the peculiarities of the formation histories of each MW-mass system. Despite choosing a fixed set of nucleosynthetic yields for stellar feedback processes in FIRE-3, we predict variance in dY/dZ for stars in MW-mass galaxies, and observations of MW stars must be interpreted in this context.

We present JWST/MIRI Low Resolution Spectroscopy (LRS) of 3I/ATLAS obtained post-perihelion at a heliocentric distance of 2.21 au. Our spectrum contains a prominent 10 micron silicate emission feature with a broad, smooth shape that is distinct from those commonly observed in Solar System comets. We model the spectrum using thermal emission from amorphous carbon, amorphous olivine, and amorphous pyroxene grains. Our models strongly favor a pyroxene-dominated, amorphous silicate composition and show a degeneracy between silicate grain size and the relative abundance of silicate and carbon dust. Across a set of representative models, the best-fitting crystalline abundance is zero, and we place an upper limit of 5.3% on the crystalline fraction of the silicates. We identify an emission feature near 6.83 microns that is consistent with aliphatic C-H-bearing material. The overwhelmingly amorphous silicate composition supports previous work that measured unusual volatile and isotopic composition in suggesting that the material incorporated into the object experienced little thermal processing and preserves information about the conditions in which this interstellar planetesimal formed.

We present a systematic search for broad H$\beta$ emission at $7<z<9.5$ in 21,770 JWST/NIRSpec PRISM spectra drawn from four blank fields and six lensing clusters with photometry spanning 1942 arcmin$^2$. We find a sample of 20 sources with statistically significant broad-H$\beta$ emission, including 13 new sources. Our entire sample has colors and morphologies consistent with little red dots (LRDs), compared to only 37\% of broad-line emitters at $3.5<z<6$. Interpreting the broad-lines as indicators of Broad-line Active Galactic Nuclei (BLAGN), we infer black hole masses of $4.2\times10^{6}-2.1\times10^{8}$\,$M_{\odot}$. We calculate completeness corrections and construct the black hole mass function at $z\sim8$. The normalization of the black hole mass function rises by $\approx1.0$~dex from $z\sim8-5$, consistent with average black hole growth at $f_{\textrm{Edd}}\approx0.1$. Comparing with cosmological simulations, the $z\sim8$ black hole mass function requires heavy ($10^5$\,$M_{\odot}$) seeds or super-Eddington accretion onto light or intermediate mass seeds to match its normalization. Finally, we infer bolometric luminosities for the sample and construct a bolometric luminosity function. We integrate over this luminosity function to derive a black hole accretion density (BHAD) of $4.8^{+5.8}_{-2.6}\times10^{-7}~M_{\odot}~\textrm{yr}^{-1}~\textrm{Mpc}^{-3}$, showing broad agreement with previous photometric work, but disagreement with previous X-ray models, reinforcing the idea that BLAGN are more common in the early universe than previously expected.

The progenitors of intermediate-luminosity red transients (ILRTs) spanning the luminosity gap between novae and supernovae are under debate, and electron-capture supernovae (ECSNe) have been proposed as a strong candidate. ECSNe from super asymptotic giant branch (super-AGB) stars have been theoretically predicted to be much brighter than ILRTs, but attenuation by dusty winds of their super-AGB progenitors may ease this tension. Here we construct a semi-analytical framework for calculating the light curves of ECSNe with dust attenuation and re-emission, by combining recent ECSN light curve predictions with a model for dust physics. Even by varying both the wind mass-loss rate and the ECSN model parameters, we find it challenging to simultaneously fit the light curve and color evolution of ILRTs. This poses a potential challenge to the standard models of ECSNe for explaining ILRTs. For explaining ILRTs, we propose either the existence of a population of ECSNe with much lower explosion energies ($\sim$10$^{48}$-$10^{49}$ erg) and dimmer plateaus, or alternative model(s) to ECSNe that realize such low explosion energies.

We present a homogenised K-band photometric catalogue for the central ${\approx}12$ arcmin$^2$ (${\approx}0.9$ kpc$^2$) of the Triangulum spiral galaxy M33, combining four independent PSF-based near-infrared datasets obtained with UKIRT between 2003 and 2018. These comprise the 2003-2007 UIST multi-epoch monitoring survey, the 2005 UFTI K-band mosaic (for which we present new PSF photometry), new WFCAM PSF reductions for the four central tiles, and a single K-band epoch from the 2018 UKIRT Hemisphere Survey (UHS DR3). Cross-matching all four catalogues and retaining stars detected in at least two of them yields 847 unique stars comprising 21,085 valid K-band measurements spanning a baseline of 15.11 yr. Photometric homogenisation onto the 2MASS/Vega system via 82 low-scatter calibration stars removes systematic inter-dataset offsets of up to 0.22 mag. Of the 847 monitored stars, 771 (91 per cent) are classified as variable ($\sigma_{\rm rms} > 0.10$ mag), including 385 high-amplitude variables ($A_K \geq 1.0$ mag): prime Mira-type long-period variable candidates for period determination. Cross-matching with archival Spitzer IRAC photometry yields 156 matched stars, of which 120 satisfy $\langle K\rangle - [3.6] > 0.5$ mag, identifying dust-enshrouded AGB candidates inaccessible to all-sky optical surveys. This catalogue constitutes the most extensive near-infrared photometric baseline assembled for AGB stars in any spiral galaxy beyond the Milky Way, providing the photometric foundation for the period-luminosity analysis and star-formation-history reconstruction in the companion Paper VIII. The full catalogue is available at the Centre de Données astronomiques de Strasbourg (CDS).

Detecting unknown faint moving objects using optical imaging is challenging. Long exposure times are infeasible for such targets, as the resulting image streaking causes a loss of signal-to-noise ratio due to energy dispersal across multiple pixels. To address this, synthetic tracking, a track-before-detect method, replaces long exposures with many short exposures, integrating them in post-processing to recover the moving signal. Enabled by modern CMOS detectors with fast readout and low read noise, this technique synthesizes telescope tracking by searching over a grid of velocities. However, the conventional brute-force implementation imposes a significant computational burden: integrating N_f frames of size (N_x,N_y) requires O(N_x N_y N_f^3) operations. This cost becomes prohibitive for megapixel-scale frames with N_f~100. Although dynamic programming can reduce the computational complexity by a factor of N_f, it requires a prohibitive memory of O(N_x N_y N_f^2), unsuitable for large-format detectors. This article presents a novel algorithm to achieve the computational efficiency of dynamic programming while maintaining a memory footprint of just O(N_x N_y N_f) by slightly approximating the computation of frame shifts for alignment. By expressing the shift as a sum of terms proportional to the digits frame index in binary and rounding up each of these terms, frames can be integrated efficiently by hierarchically adding intermediate sums that are shared across different velocities with the same higher bits in binary. The approximation only introduces a small tracking error that increases logarithmically with the number of frames. This advancement enables synthetic tracking to be executed with high energy efficiency, making it practical for deployment on standard workstations rather than requiring high-performance computing infrastructure such as GPU servers or CPU clusters.

The primordial sound waves in the baryon-photon plasma are imprinted on the large-scale galaxy distribution as Baryon Acoustic Oscillations (BAO), serving as a cosmological standard ruler to constrain dark energy and the Hubble parameter. The upcoming 21cm intensity-mapping arrays are designed to map the 21cm emission across large volumes and measure the BAO scale. However, radio interferometers suffer from instrumental systematics that can hinder detection of the cosmological 21cm signal by leaking bright foregrounds into the signal-dominated modes. This work aims to demonstrate that a self-supervised model can predict the instrument systematic state (here, the amplitude of a spectral ripple in the beam width) in interferometric visibilities and potentially disentangle the instrument from the sky without a forward model. Based on the fact that an instrument stays the same as the sky rotates in a drift-scan observation, and that the same sky is observed under different instrument states, we train a convolutional autoencoder to compress the information in the simulated visibilities and separate this information into instrument-only and sky-only latent vectors. The result shows excellent prediction of the unknown instrument systematic for 15 held-out instrument states with $R^2 = 0.9975$ with a linear probe, against $R^2 = -3.55$ for a random-encoder baseline. The instrument-latent carries no detectable sky signal, as measured with a total-power sky proxy, for any held-out test data. The sky-latent vector and instrument-latent vector show partial separation but not complete disentanglement, identifying sky-latent purity as the primary open problem. The results show the ability of the model to recognize the systematic and show a promising path towards an ML-based foreground cleaning pipeline. Full instrument-sky disentanglement constitutes the natural next step.

Models of the dark sector in which the dark matter participates in nontrivial interactions can create detectable signatures in cosmological observables, providing non-terrestrial means of probing the nature of dark matter. In this work, we test dark matter-baryon scattering, dark matter-dark radiation interactions, and dark matter annihilation using measurements of the CMB and BAO. We leverage the latest SPT-3G D1 CMB measurements of the primary anisotropies, alongside the D1 MUSE lensing data, to set up-to-date bounds on these models. From the combination of Planck, ACT DR6, and SPT-3G D1 data, we constrain the velocity-independent dark matter-baryon scattering cross-section to $\sigma_\mathrm{DM-b} < 4.6\times10^{-26}~\mathrm{cm^2}$, the dark matter-dark radiation momentum transfer rate to $\Gamma_\mathrm{0,nadm}<5.2\times10^{-8}\,\text{Mpc}^{-1}$, and the effective dark matter annihilation parameter, quantifying the fractional thermally averaged cross-section, to $p_\mathrm{ann}<3.7\times10^{-28}~\mathrm{cm^3/s/GeV}$, all at the 95% confidence level. The improved sensitivity to the first two models is in particular driven by the precision measurements of CMB lensing at small scales provided by SPT-3G D1 MUSE lensing data. For annihilating dark matter, due to the degeneracy of the effect with the optical depth to reionization, we observe a non-trivial relationship between the upper bound on $p_\mathrm{ann}$ and the large-scale polarization information. When combining CMB data with the latest measurements from the Dark Energy Spectroscopic Instrument (DESI), upper bounds on extended model parameters can appear to tighten as the model space attempts to accommodate the known discrepancy between these data. Future CMB and BAO measurements will provide better clarity on reconciling this discrepancy and enhance our ability to test dark matter interactions.

We investigate the dependence of the mass-metallicity relation (MZR) on star formation and galaxy morphology at 1.7<z<3.5, using JWST/NIRISS wide-field slitless spectroscopy of >1000 galaxies. The observations span >85 arcmin^2 from the pure-parallel PASSAGE and OutThere surveys. We derive gas-phase metallicities using a Bayesian framework that combines multiple strong emission-line ratios calibrated against direct auroral-line metallicity measurements from JWST. We constrain stellar masses, star formation rates (SFRs), and morphological properties using ancillary HST and JWST imaging. We stack spectra by stellar mass to constrain the MZR over log(M*/M)~6.5-11, and find that it is well described by a second-order polynomial, with a steep low-mass slope and metallicities<10% solar at log(M*/M)<7.5. Additional stacking by SFR and morphology reveals strong evidence for a fundamental metallicity relation (FMR). Specifically, at log(M*/M)<9.5, galaxies with lower SFRs are more metal-rich than those with higher SFRs at fixed mass. At log(M*/M)<9.5, we find that larger galaxies, and those having lower SFR surface densities, bulges, and/or spiral features are significantly metal rich relative to their smaller, higher SFR surface density, bulge-less, and/or non-spiral counterparts. These results suggest the secondary dependencies of the MZR reflect variations in the baryon cycle, such that recent metal-poor gas accretion drives concentrated star formation and metallicity dilution, while structurally developed galaxies retain more chemically enriched gas reservoirs.

The high-mass black hole population inferred from ground-based observations can substantially affect the number of binaries detectable by the Laser Interferometer Space Antenna (LISA). We use population constraints based on data from the latest LIGO/Virgo/KAGRA Gravitational-Wave Transient Catalog (GWTC-5.0), as well as constraints from the O3 search for intermediate-mass black hole binaries, to forecast the number and masses of binary black holes detectable by LISA. Using the released GWTC-5.0 population posterior, we obtain $6.6^{+5.5}_{-2.2}$ expected detections with signal-to-noise ratio $>8$ in 4 years (median and $90\%$ credible interval). The alternative population models we consider use a broken power law with two or three Gaussian peaks for either the primary-mass distribution or a common mass distribution for both black holes. For the three-peak model with the common mass distribution, extrapolating from $300$ to $1000M_\odot$ roughly doubles the median expected number of LISA detections to $\sim14$. The upper end of its $90\%$ credible interval rises from tens to thousands of expected detections, although approximations may limit the reliability of the most extreme counts. For the reference GWTC-5.0 population, $39^{+22}_{-11}\%$ of the binaries detectable by LISA merge during the mission or within $10$ years after its end and are potential multiband sources. Essentially all of these mergers would be detectable by a reference Cosmic Explorer configuration if it is operating at merger. Ground-based measurements of the high-mass population can therefore inform both LISA forecasts and the prospects for observing the same binaries through inspiral and merger.

Dwarf galaxies are dark matter-dominated systems that are sensitive to feedback and display bursty star formation histories. This makes them ideal probes of the processes that regulate star formation. This work investigates the timescales of star formation rate (SFR) variability in isolated dwarf galaxies using high-resolution cosmological zoom-in simulations of $50$ dwarf galaxies drawn from the Marvelous Massive Dwarfs and Extended Marvelous Dwarfs simulation suites ($7.3 <$ \lmstar $< 9.1$). We measure star formation histories in $10$ Myr bins and characterize their variability with power spectral densities (PSDs). At the population level, the PSDs of both disk and non-disk galaxies follow a broken power-law, with a break timescale near $100$ Myr. Individually, our galaxies show both smooth and bursty star formation. A subset of disk galaxies show quasi-periodic SFR oscillations about their mean, which we refer to as cyclic star formation. The dominant timescale of these oscillations scales linearly with half-light radius and is approximated by the orbital period at that radius. Cyclic galaxies have Magellanic Spiral (Sm) morphologies and host lopsided dipole gas disks. In these systems, the bulk of the gas in the lopsided disk moves between its maximum and minimum distance from the galactic center, compressing the star-forming gas once per radial orbit and driving the SFR cycle. Cyclic star formation adds a narrow Lorentzian component to the PSD, peaked at radial orbital frequency of the disk ($\sim 200-500$ Myr), which is comparable to burst timescales inferred from observations.

JWST surveys find more UV-bright galaxies at $z>10$ than galaxy-formation models predict, but the roles of recent star formation, stellar mass and dust remain uncertain. We analyse 1365 spectroscopically confirmed JADES galaxies at $3\leq z\leq9$, fitting NIRCam photometry and NIRSpec emission lines with \ceri. Our model includes flexible star-formation histories (SFHs) under three priors, two-component dust attenuation and nebular emission. We account for spectroscopic selection through population reweighting and assess the reliability of inferred trends. At $z=3$--5, rising SFHs are more common in low-mass galaxies, whereas most galaxies above $10^{9.5}\,{\rm M}_{\odot}$ have declining SFHs. The apparent increase in rising fractions with redshift cannot be distinguished from the adopted SFH prior alone. At fixed stellar mass, recent star formation is the strongest predictor of UV brightness. UV-brighter galaxies have higher recent SFRs, younger stellar populations and less attenuation at fixed SFR. Below $10^9\,{\rm M}_{\odot}$, they are also more likely to have rising SFHs, with odds increasing by up to a factor of 2.3 per magnitude brighter, although the strongest trend requires caution. In contrast, galaxies with $M_{\mathrm{UV}}<-20$ at $z=3$--5 are predominantly massive, and approximately half have declining SFHs. Dust partly offsets burst-driven UV brightening: attenuation increases with recent SFR and declines gradually after the inferred SFR peak. In model sensitivity tests, dust has the largest effect on bright-end counts, whereas removing galaxy-to-galaxy SFH scatter changes them by at most 0.17~dex. Thus, bursts can make low-mass galaxies unusually UV-bright for their mass, while the absolute bright end of the UVLF is primarily shaped by stellar mass and dust attenuation.

Magnetic fields are vital in determining the physical conditions of baryons in massive halos. They are, however, notoriously difficult to observe. This impacts problems from our understanding of galaxy formation, to the observed deficit in the amplitude of thermal Sunyaev-Zel'dovich (tSZ) power spectrum that affects cosmological inferences. Although Faraday rotation measures (RMs) offer a direct probe of magnetic fields, it weights magnetic fields by the free-electron density. Several probes of free electrons, including fast radio burst (FRB) dispersion measures (DMs) and kinematic SZ (kSZ) effect, are now maturing into precision tools. We combine RM$^2$ stacks from SPICE-RACS around DESI galaxy groups and ROSAT clusters with optical depth profiles constrained jointly by the FRB DM-redshift relation and the kSZ effect, and obtain 95% upper limits on the rms line-of-sight magnetic field of $<3.9$-$11.6~\mu$G ($<2.3$-$6.4~\mu$G) in groups (clusters) for a 10~kpc coherence length. Combining these with thermal pressure profiles inferred from tSZ-shear cross-correlations, we obtain 95% lower limits on the plasma $\beta$ of $>0.31$ ($>11$) in groups (clusters). Although current constraints are only limits, we forecast a first detection with larger datasets from the Deep Synoptic Array (DSA). We present the first forecast of the DSA RM grid density ($\sim365$ RMs deg$^{-2}$), which when combined with 10$^4$ FRBs would measure the field in groups to $3$-$13\%$ precision, compared to current constraints of $38$-$75\%$. Although the interpretation of current measurements remains challenging owing to depolarization along turbulent halo sightlines and the unknown coherence length, larger samples and DSA/Square Kilometer Array observations may resolve these uncertainties by measuring polarization-fraction profiles and the RM structure function using extended radio sources, respectively.

The nearby M81 galaxy---a tidally interacting $L^*$ spiral disk---offers a unique perspective on the interplay of secular and external processes in shaping galaxy properties. We present the most detailed, panoramic map of M81's stellar populations to date, using archival Hubble Space Telescope ACS photometry from the ANGST survey spanning the full optical extent of its disk. From color-magnitude diagram fitting, we recover spatially-resolved star formation histories (SFHs) over the last $\sim180\,$Myr. M81's global SFH is remarkably steady in the last $\sim180\,$Myr with slight enhancements seen $\lesssim15\,$Myr ago. The average SFR surface density rises toward the center before falling off within the innermost $\sim4\,$kpc. The disk is also notably lopsided, with the eastern half having formed $\sim50\%$ more stars than the western half over the same area---a trend missed by FUV-based SFR indicators due to dust systematics. Finally, the long-term SFHs of both M81 and M82 point to a pericenter passage $\sim1\,$Gyr ago. By identifying M81-M82 analogs in the TNG50 cosmological simulation, we rule out the more recent pericenter times of $150-220\,$Myr predicted by some works, as such passages are inconsistent with M81's undisturbed SFH over the last $\sim180\,$Myr. With this work, M81 becomes only the third $L^*$ spiral---after M31 and NGC 6946---to have its SFH spatially resolved across large areas of its disk.

The Dark Energy Spectroscopic Instrument (DESI) measures baryon acoustic oscillations (BAO) in the Lyman-$\alpha$ (Lyman-alpha) forest and provides a robust probe of the expansion history in the matter-dominated era. Yet, non-linear structure formation broadens and shifts the BAO peak. To undo these effects, we extend standard Zel'dovich reconstruction, routinely applied to galaxy surveys, to the Lyman-alpha forest. We validate our methodology on large-volume idealized Lyman-alpha forest mocks painted on top of the \textsc{AbacusSummit} $N$-body simulations, using linear control variates to suppress sample variance and thereby reduce the error bars by a factor of up to $\approx \sqrt{50}$. In fully sampled periodic boxes, reconstruction halves the radial BAO damping scale and reduces the uncertainties on the radial ($\apar$) and transverse ($\aperp$) scaling parameters by $\approx25\%$ and $\approx15\%$, respectively. It also reduces the non-linear shift from $\Delta\apar=+0.3\%$ to $+0.10\pm0.07\%$, while $\aperp$ remains unbiased. To make this approach readily applicable to observational data, we demonstrate the impact of a survey mask with a DESI-like density of $50\,\mathrm{deg}^{-2}$. For this mask, we compare two approaches to estimate the displacement field: either directly from the Lyman-alpha forest or using an external tracer with a number density of $\bar n \simeq 10^{-3}\,h^3\mathrm{Mpc}^{-3}$, such as Lyman-break galaxies and Lyman-$\alpha$ emitters---both key targets for DESI-II. Both approaches give comparable gains and reduce the uncertainties on $\apar$ and $\aperp$ by $\approx 27\%$ and $\approx 10\%$, respectively, with mild improvements for futuristic high-density surveys with $160\,\mathrm{deg}^{-2}$. Correspondingly, the figure of merit improves by factors of $1.66$ for fully sampled boxes, $1.65$ for a DESI-like, and $1.76$ for a high-density survey.

We investigate axion-like particle (ALP) production in the interior of Betelgeuse via nuclear de-excitation of thermally populated excited states of $^{23}$Na and $^{55}$Mn. As these ALPs propagate to Earth, they can produce photons either through their conversion in the Galactic magnetic field or through their decay. Using INTEGRAL-ISGRI and NuSTAR observations, we search for these photon signals, find no significant excess, and derive 95% CL exclusion limits on the ALP couplings. For magnetic-field conversion of ALPs, the $^{23}\mathrm{Na}$ ($^{55}\mathrm{Mn}$) line observed with INTEGRAL-ISGRI constrains $|g_{a\gamma}g_{ap}| < 4.1\times10^{-21}$ ($6.9\times10^{-19}$) $\mathrm{GeV}^{-1}$ for $m_a < 10^{-10} \mathrm{eV}$. For ALP decays, the $^{23}\mathrm{Na}$ ($^{55}\mathrm{Mn}$) line observed with INTEGRAL-ISGRI (NuSTAR) constrains $|g_{a\gamma}g_{ap}|$ down to $3.0\times10^{-22}$ ($2.9\times10^{-19}$) $\mathrm{GeV}^{-1}$ at $m_a \simeq 400$ ($83$) keV, weakening in both cases as $m_a^{-3/2}$ for lower ALP masses, and as $m_a^{-2}$ for $^{23}$Na below $m_a \sim 1$ keV, with sensitivity extending to $m_a \simeq 440.2$ ($124$) keV. Although our $^{23}\mathrm{Na}$-based limits are the strongest for both channels, their larger transition energy makes them more sensitive to the precise evolutionary stage of Betelgeuse, whereas the $^{55}\mathrm{Mn}$-based limits are considerably more robust against such uncertainties.

We study the Lane--Emden equation of index $n=5$, the critical polytropic case separating finite-radius from infinite-radius self-gravitating equilibria. The scaling family $\theta_\lambda(\xi)=\lambda^{1/2}\theta(\lambda\xi)$ generates a neutral mode $\phi_0=\tfrac12\theta+\xi\theta'$ about the Schuster profile. Schuster's transformation and a logarithmic variable reduce the equation to the autonomous Hamiltonian system $\ddot\nu=\tfrac14(\nu-\nu^5)$ with a first integral. Besides the Schuster (separatrix) and Srivastava solutions, every orbit crossing $\nu=0$ is given in closed form by a Weierstrass $\wp$-function, and the closed forms agree with direct numerical integration to about $10^{-12}$. Up to scaling and sign, the Schuster solution is the only solution regular at the center, and it separates positive solutions from solutions with infinitely many zeros. In homology-invariant variables the singular solution $\theta=(2\xi)^{-1/2}$ is a center exactly at $n=5$, where its stability changes. For a distance-varying Emden--Fowler system with a shifted equilibrium we prove that at $n=5$ the unique equilibrium is linearly and nonlinearly unstable. Finally, the linearization about the Schuster profile is the Schrödinger operator $L=-\Delta_r-5\theta_S^4$ on $L^2((0,\infty),\xi^2d\xi)$. Its Friedrichs extension has essential spectrum $[0,\infty)$, a threshold resonance at $0$ carried by the non-normalizable scaling mode, and exactly one negative eigenvalue, $\lambda_0\approx-1.21$, so the Schuster profile is a saddle point of the associated energy functional.

In this paper, we show that the optical depths of any OH $\Lambda$-doublet quartet obey one exact linear relation in every velocity channel. No approximation is needed. The only exception is the $^{2}\Pi_{1/2}$ $J{=}1/2$ level, which has three transitions only, because its $F{=}0{\leftrightarrow}0$ line is strictly forbidden. The relation is $\tau_{S_1}(v)/\mu_{S_1}^{2}+\tau_{S_2}(v)/\mu_{S_2}^{2}=\tau_{M_1}(v)/(a\mu_{M_1}^{2})+\tau_{M_2}(v)/(b\mu_{M_2}^{2})$, where $a=2J^{2}+J-1$, $b=2J^{2}+3J$, and the $\mu_i^{2}$ are reduced transition dipole moments derived from the catalogued Einstein $A$ coefficients. It holds equally for gas in local thermodynamic equilibrium (LTE), for non-LTE gas, for masers and for conjugate gas. We suggest that it is a powerful tool for measuring the variation of fundamental physical constants.

Estimating the separation of two unresolved or nearly unresolved sources from recorded intensity images is difficult when source brightness, mutual coherence, and phase are unknown and the point-spread function (PSF) departs from a Gaussian. We formulate Hermite--Gaussian (HG) projections of one- and two-dimensional Airy amplitudes and prove that ratios of mode probabilities with equal longitudinal parity exactly cancel the brightness, coherence, and phase nuisance parameters under a symmetric two-source model. For a one-dimensional Airy slice we achieve an explicit multi-ratio separation inversion. For the physical two-dimensional circular-pupil PSF we obtain exact finite-pupil overlap integrals and locally invertible separation responses. Motivated by these analytical invariants, we examine Airy-informed convolutional neural networks (CNNs) on synthetic Airy images with known separations. At 150,000 training images, the approximate mean absolute errors are 0.018 in plotted separation units, 10 times better comparing to 0.18 for non-Airy Gaussian PSF approximation. Applied to an archival Hubble Space Telescope image of the double nucleus of NGC 4486B, the Airy-informed CNN gives estimates of approximately 9.6--12.0 pc for training sets of 100,000--150,000 images, broadly consistent with the historical approximately 12 pc value. We distinguish exact optical-mode nuisance cancellation from empirical robustness of an image-only learned estimator and identify the limits imposed by PSF mismatch and extended galaxy structure.

The relic abundance of light stable axion dark matter is usually set by misalignment. We study whether the inflationary fluctuations of the axion can dominate instead, and we follow the modes analytically through an instantaneous transition from de Sitter expansion to radiation domination, neglecting the axion mass during inflation and keeping it afterward. Since the energy density is quadratic in the field, a fluctuation-dominated abundance carries an isocurvature perturbation even when the mean displacement vanishes. For a canonical minimally coupled axion the spectrum is scale invariant, and fluctuation-dominated dark matter exceeds the Planck isocurvature limit by about eight orders of magnitude. An inflaton-dependent kinetic function or a nonminimal coupling to the Ricci scalar tilts the spectrum blue, moving the fluctuation power from CMB scales to small scales. Imposing the Planck limit at the pivot scale, we find that fluctuation-dominated dark matter with a constant kinetic slope requires the spectral tilt $n_\eta-1\gtrsim0.27$ and the axion mass $m_{\eta} \gtrsim200 \rm{GeV}$ at $H_I=10^{10}\rm{GeV}$, and $n_\eta-1\gtrsim0.34$ and $m_\eta\gtrsim4.5\,$keV at $H_I=10^{13}\rm{GeV}$. A kinetic function with a running slope lowers these masses to $1.4~\rm{GeV}$ and $0.7\,$eV, respectively. For the QCD axion, whose oscillations start late, we estimate that any single power-law spectrum blue enough to satisfy the pivot limit gives too little fluctuation abundance, and misalignment dominates.

We introduce a semi-agnostic modeling framework for black hole binary inspirals beyond general relativity that fixes the field content without selecting a particular theory. We expand in the post-Newtonian order and in powers of $l/L$, where $l$ is the characteristic length-scale that controls deviations from General Relativity and $L$ is the characteristic length-scale of the system. We focus on the case of a massless scalar field coupled with the metric, at leading post-Newtonian order. Taking into account the scaling with $l/L$ of both the interaction terms and the quantities that characterise the sources, we find that the inspiral can be described in terms of a small number of universal parameters. Such a parametrisation is suitable for obtaining combined bounds from multiple sources and performing searches for specific fields.

Both Weakly-Interacting Massive Particle (WIMP) and Axion-Like Particle (ALP) are attractive particle dark matter candidates. In this paper we consider a scenario in which both WIMP and ALP are present. The two species interact via a non-derivative quadratic coupling modeled on the axion-nucleon interaction in QCD. We show that even a small (Planck-suppressed) coupling can drastically modify the cosmological history of both species. In the very early Universe, the ALP field acquires a vacuum expectation value, and the system undergoes an inverse phase transition at a temperature around or below the weak scale. WIMPs may remain in equilibrium far beyond the usual freeze-out time, eventually decoupling via a novel "coherent freeze-out" mechanism. WIMP annihilation cross sections several orders of magnitude above the canonical thermal target value can be consistent with the observed relic density in the coherent freeze-out scenario. At the same time, coherent oscillations of the ALP field do not begin until after the phase transition, and the initial conditions for these oscillations are set by the thermal physics of the phase transition. The ALP relic density is then predicted unambiguously in terms of the WIMP mass and coupling. We term this scenario "ALP miracle", since the observed relic density is obtained when these parameters are around their natural values, the weak and the Planck scale. The ALP miracle scenario prefers the ALP mass above about $10^{-3}\,\mathrm{eV}$, far larger than other popular ALP dark matter models. The ALP miracle parameter space overlaps with a currently allowed region of the QCD axion band, a large fraction of which is expected to be probed by the proposed IAXO experiment.

We study the minimum cosmic reheating temperature allowed by recent measurements of primordial nuclear abundances and of the cosmic microwave background. We find that reheating by decays of a light particle into electrons and neutrinos is compatible with both at temperatures around 0.4 MeV, an order of magnitude below the bound for purely electromagnetic channels. This scenario has implications for cosmology and laboratory searches. For example, nearly standard neutrino radiation can coexist with a smaller active neutrino mass density at unchanged physical masses, by up to a factor of five for normal ordering. The weaker suppression of clustering changes matter power at the percent level, which forthcoming galaxy surveys and lensing measurements may probe. Late reheating also suppresses sterile neutrino production at mixings within the projected reach of laboratory experiments.

Shift symmetric Horndeski gravity can be a simple, well posed theory with protection against quantum corrections. Overturning conventional thought that such a theory cannot cross the phantom divide ($w=-1$) we present both analytic and numerical proof that it can. We carry out a detailed dynamical systems analysis showing the evolution of ghost free and stable regions within the model family, identify the fixed point and dynamical attractor structure, and derive the interaction of the $w=-1$ curve with these phase space structures. This reveals two mechanisms for cosmologies crossing the phantom divide while preserving shift symmetry.

We investigate axionic quintessence in heterotic string compactifications. Starting from the ten-dimensional theory, we derive the four-dimensional axion effective action, including gauge couplings and non-perturbative potentials, and identify the curvature terms that can correct it. We examine the geometric requirements for ultralight axions generated by exponentially suppressed worldsheet instantons, finding significant restrictions through an exploratory scan of toric Calabi-Yau hypersurfaces. In an illustrative K3-fibred setup, the minimal benchmark also encounters a tension with the positivity of the one-loop corrected gauge kinetic functions. Aligned worldsheet-instanton contributions provide a way to alleviate this tension and yield an ultralight axion with a phenomenologically relevant decay constant. Our analysis also identifies lower-action instantons whose contributions must be controlled to preserve the ultralight axion. We then study the resulting class of quintessence potentials and qualitatively compare their late-time cosmological solutions with observationally preferred ranges.

Standard sirens provide a direct probe of the cosmic distance-redshift relation and therefore a powerful test of whether gravitational waves (GWs) propagate as predicted by general relativity on cosmological scales. In many extensions of general relativity, GW propagation is modified by an anomalous friction term, which alters the amplitude evolution and leads to a GW luminosity distance that differs from its electromagnetic counterpart. In this work, we develop a non-parametric reconstruction of this anomalous friction from dark standard sirens. We reconstruct its redshift dependence, encoded in the friction function $\alpha_M(z)$, with a Gaussian process (GP) and derive the corresponding GW-to-EM luminosity-distance ratio $\Xi(z)$ by integration, explicitly retaining the relation between the local friction modification and its accumulated effect on the observed distance, while enforcing a monotonic and invertible GW luminosity distance. We apply the method to the GWTC-5.0 catalog, jointly inferring the source population, modified propagation, and background cosmological parameters. We find no evidence for departures from GR, with $\alpha_M=0$ and $\Xi=1$ consistent with the posterior over the redshift range probed by the catalog. The result is stable under variations of the GP kernel, smoothness and amplitude priors, resolution prescription, and likelihood treatment. We further introduce function-space diagnostics for comparing flexible and parametric reconstructions, including prior calibration, prior-to-posterior contraction, common summaries of propagation-population degeneracies, and principal-component analysis. These tools make explicit which features are informed by the data and which are imposed by the function-space prior, providing a framework for interpretable non-parametric tests of gravitational-wave propagation.

Dense neutrino plasmas support collective flavor motion. We derive the first explicit dispersion relation about a flavor-nondiagonal background, focusing on the coprecession solution underlying spectral-split formation during the prompt neutrino burst of an electron-capture supernova. We show that slow phase modulations are unstable Goldstone modes, causing the coprecession plane to wobble with increasing amplitude. The instability emerges in the hydrodynamic limit, governed by conservation laws and without resolving flavor-precession resonances. Coprecessing neutrino plasmas resemble magnetized plasmas: a coherent flavor field drives flavor isospins to precess, and the phase-twist instability is the flavor analog of the firehose instability.

The gravitational-wave spectrum produced by ultra-relativistic bubbles in a first-order cosmological phase transition can be approximated in terms of their energy density as a function of bubble size. Bubble collisions and post-collision classical evolution negligibly change it. The dominant energy loss is particle scattering, often in the Landau--Pomeranchuk--Migdal regime. So the GW spectrum depends on the particle-physics coupling (interpolating between the `envelope' and `bulk flow' limits), on the interaction type (gauge, Yukawa, scalar quartic, ...), and on whether particle number is conserved. Finally, we consider broken global symmetries, which give a mixture of `elastic' and `inelastic' collisions.

We study asymmetric post-inflationary reheating in a framework with two sequestered MSSM-like sectors (the ``visible'' and ``dark'' sectors) with different supersymmetry-breaking scales, with dark matter corresponding to the lightest dark baryons. In this setup, independent Affleck-Dine dynamics in the two sectors offers a natural explanation for the comparable abundances of visible and dark matter. We relate the resulting temperature hierarchy to the inflaton's partial decay widths in different kinematical regimes, where it may decay into dark sector particles via 2-, 3- or 4-body processes. The latter case yields the most asymmetric reheating scenario, and we discuss the implications of this regime for the dark sector's thermal history, namely regarding the corresponding strong and weak interactions. While in this kinematical regime the contribution of light dark sector degrees of freedom to $\Delta N_{\rm eff}$ is negligible, we show that it increases significantly in the regime where 3-body decays are possible, particularly near the threshold for dark Higgs pair-production where $\Delta N_{\rm eff}^{\max} \simeq 0.078$. The current combined BBN+CMB+BAO bound leaves only a narrow allowed interval of the 2-body decay regime immediately above threshold, while next-generation CMB experiments could probe slightly below it.

This Letter investigates gravitational-wave tests of the horizon area law. Although they provide a striking consistency check of general relativity (GR), these tests rely on models that assume GR, making their interpretation inherently model dependent. We show with a specific example---simulations of merging boson stars---that exotic compact objects can mimic merging black holes and pass an area-law test at a confidence as high as $\sim 92\%$ despite not even having event horizons.

We study how magnetic fields affect the onset of quark saturation, which limits the domain of applicability of a purely baryonic description. We consider matter composed of electrically neutral $ddu$ baryons, including neutron- and $\Delta^0$-like states. Using a simple constituent-quark model, we compute the baryon wave functions and spectra in magnetic fields. The magnetic field polarizes the spin-flavor structure, compresses the internal wave function in the transverse direction, and strongly suppresses the transverse kinetic energy. From the baryon wave functions, we construct the one-body reduced density matrix and derive the corresponding single-quark distributions in longitudinal momentum and Landau-level space. We then use these distributions to evaluate quark occupation probabilities in an ideal baryon gas and determine the onset of quark saturation. At finite magnetic field in the $+z$-direction, the $d_\downarrow$ quark in the lowest Landau level reaches saturation first. The resulting saturation density depends nonmonotonically on the magnetic-field strength: it decreases at weak fields and increases at stronger fields. This behavior reflects the competition between spin-flavor polarization, which promotes saturation, and transverse spatial squeezing, which delays saturation by broadening of the quark transverse momentum distribution.

Scatter plots draw one mark per observation, so observations that share a location are hidden. In a two-item Likert survey of 2,757 respondents, 98.7% of the data lie under other points and the plot shows only 36 dots. The density-distribution sunflower plot of Dupont and Plummer addresses this by drawing raw points in sparse regions and sunflowers, whose petals count observations, in dense ones. It is not available in R, and its single petal weight for dense cells fails when cell counts span more than an order of magnitude: small dense cells collapse to one petal, and the count a reader decodes can be wrong by 150% or more. We propose geometric petal tiers, in which each cell uses the smallest weight among 1, b, b2, . . . observations per petal that keeps its flower within P petals. Every flower then has between about P/b and P petals, and the relative error of every decoded count is below b/(2P), 17.9% at the defaults b = 5 and P = 14. We also define tie diagnostics and decision rules that use them to choose between an ordinary scatter plot, jitter or transparency, a classic sunflower plot and geometric tiers. Both are implemented in the ggplot2 extension ggsunflower. We illustrate the methods on survey, automotive, historical and large commercial data, and in a simulation over 35 conditions geometric tiers keep the worst-cell error at or below 14% where a single weight reaches a median of 251%.

We study the possibility of the formation of primordial black holes (PBHs) using an inflaton potential constructed by stabilizing all Kähler moduli employing both the perturbative and non-perturbative corrections in the large volume scenario in type-IIB/F string theory. We further introduce a small perturbation in one of the Kähler moduli that modifies the existing potential in the field space. The effective correction in the moduli space is made by introducing a localised Gaussian bump, which induces an ultra-slow-roll feature in the inflaton potential during the early cosmological inflation. The evolution of the amplitude of the curvature power spectrum is solved numerically by using the Mukhanov-Sasaki equation, with Bunch-Davies initial conditions. The inclusion of the Gaussian bump produces a sustainable enhancement in the amplitude of curvature power spectra around $k\sim 1.12 \times 10^{9} Mpc^{-1}$ for the formation of PBHs. The abundance of PBHs ($f_{PBH}$) is calculated using the Press-Schechter formalism for different values of critical density contrast and presented in the background of contemporary $f_{PBH}$ bounds and checked for viability with existing microlensing bounds, corresponding to a mass value $10^{-6}M_\odot$ for $\delta$ threshold value $\delta_c=0.439$. The Hawking temperature and evaporation time are also determined for these black holes and found to be of the order of $2.78\times 10^{-15}$ GeV and $8.5\times10^{38}$ Gyr, respectively. The enhancement of curvature power spectra lies in the sensitivity region of the SKA observations, suggesting an indication that scalar-induced gravity waves may be probed in future observations.

This work investigates the properties of spin polarized strange quark matter SQM and the resulting structure of strange quark stars SQSs within a thermodynamically self consistent quasiparticle framework. By developing a dynamic bag constant intrinsically coupled to the medium dependent reduction of quark effective masses we ensure strict internal thermodynamic consistency. This coupling gives rise to a distinct non monotonic behavior in the speed of sound significantly stiffening the Equation of State EoS at high densities. Consequently our model predicts maximum stable gravitational masses up to 2.19 Mo. These results demonstrate that hot magnetized SQM provides a robust and viable mechanism to explain ultra massive pulsars such as PSR J0740 6620 and PSR J0952 0607 without requiring unrealistic thermal or structural assumptions.

The detection and localization of gamma-ray sources via maximum-likelihood analysis is a complex parameter optimization problem. We address this challenge using quantum annealing, a computational approach that solves optimization tasks by encoding them into the ground state of an Ising Hamiltonian. Specifically, we apply this method to observations from AGILE's Gamma-Ray Imaging Detector (GRID) in the 30 MeV-50 GeV band. We reformulated the standard analysis as a Quadratic Unconstrained Binary Optimization (QUBO) problem. We tested this method on a set of AGILE observations generated with AGILEpy, solving the QUBO with simulated quantum annealing. The method reproduces the classical flux and position estimates within their statistical uncertainty and identifies the correct grid node among the candidate positions in 97% of the maps. These promising results demonstrate that quantum annealing could be used in this optimization problem, laying the ground for its deployment on actual quantum annealers.

Selected astrophysical methods for testing particle-physics models are reviewed. Stellar structure and evolution constrain additional channels of energy loss and transport; high-energy photon propagation probes photon mixing with new particles and modifications of electron-positron pair production; large-volume neutrino telescopes are used to search for magnetic monopoles, neutrinos from superheavy dark-matter decay, and non-standard neutrino propagation. Recent applications of these methods are discussed, involving the tip of the red-giant branch in the color-luminosity diagram, gamma-ray burst 221009A, and data from the Baikal Gigaton Volume Detector (Baikal-GVD) and the IceCube experiment. In each case, particle-physics parameters are inferred through a forward model that accounts for the response to new physics, propagation, detection, and nuisance parameters.

In light QCD axion models, finite-density corrections to the axion potential can source a nonvanishing axion field inside neutron stars. Extending our previous analysis of radial oscillations, we study the nonradial ($l=2$) oscillation spectrum of such axion condensed neutron stars in the relativistic Cowling approximation, keeping the fluid and axion perturbations fully coupled and dynamical. The condensate modifies the fluid spectrum in two ways: the altered equilibrium structure raises the $f$- and $p$-mode frequencies by up to $\sim20\%$, while the dynamical coupling to the axion field partially compensates this shift, almost entirely for the $f$-mode. Fluid modes with frequencies above the axion mass acquire a new damping channel through axion emission. The $f$-mode remains below this threshold for all configurations supporting a condensate, whereas the $p$-modes are damped on timescales that can be as short as $\sim10$ ms, shorter than their gravitational-wave damping times, except for certain axion masses where the outgoing axion amplitude nearly vanishes. The spectrum also contains a family of strongly damped axion-dominated quasinormal modes, with imaginary parts of order kHz, and a sequence of gravitationally bound axion states analogous to gravitational atom levels. Below the propagation threshold, the bound $p$-modes undergo avoided crossings with these levels, exchanging their fluid- and axion-dominated character.