Papers for Friday, Feb 06 2026

The realization that primordial black holes (PBHs) might be some fraction of the dark matter begged the question, how often do PBHs enter the solar system? For a Neptune radius solar system the answer is, rarely. For an Oort cloud sized system the answer is different. Simulations of bombardment of the Oort cloud by dark matter suggest that dislodgement of protocomets and their entry into the inner solar system can match the observed frequency of comets, if that PBH fraction is high enough. Comets were traditionally considered as messengers, usually omens. After 50 years of puzzlement regarding dark matter, we need a hint from the dark universe about the size and nature of dark matter particles.

Measuring the mass distribution of supermassive black holes (SMBHs) over cosmic time remains particularly challenging for the low mass ($M_{\bullet}\lesssim10^8~M_\odot$) population at $z>1$. This population is also the most sensitive to SMBH seeding and early growth models. In this work we construct a semi-empirical model for the redshift evolution of the TDE rate under multiple SMBH mass function prescriptions, and show that the observed redshift-dependent rate of TDEs is very sensitive to the SMBH mass function and its evolution with redshift. We further incorporate galaxy-scale processes that evolve with redshift -- namely, increasing galaxy nuclear stellar densities, enhanced galaxy-galaxy merger rates, dust obscuration, and a possible top-heavy IMF at early cosmic times -- and quantify their combined impact on the TDE rate. We find that including these effects generally results in a volumetric TDE rate that increases with redshift until a maximum near cosmic noon, before declining at higher redshift where SMBHs that can disrupt stars become increasingly scarce. We forecast TDE rates in the Rubin LSST and the Roman High Latitude Time Domain Survey, alongside expectations for serendipitous TDE rates in the JWST COSMOS-Web survey. Finally, we provide a methodology for using a flux-limited survey of TDEs in LSST to directly constrain the redshift evolution of the SMBH mass function.

In both observed and simulated galaxies, disk morphologies become more prevalent at higher masses and lower redshifts. To elucidate the physical origin of this trend, we develop a simple analytical model in which galaxy morphology is governed by the competition between rotational support and turbulence in a gravitational potential of a dark matter halo and the galaxy itself, and a disk forms when the potential steepens due to the accumulation of baryons in the halo center. The minimum galaxy mass required for this transition decreases with an increasing dark matter contribution within the galaxy, making more concentrated halos more prone to forming disks. Our model predicts that galaxy sizes behave qualitatively differently before and after disk formation: after disks form, sizes are governed by the halo spin, in agreement with classical models, whereas before disk formation, sizes are larger and set by the scale on which turbulent motions, which dominate over rotation, can be contained. We validate our model against the results of the TNG50 cosmological simulation and, despite the simplicity of the model, find remarkable agreement. In particular, our model explains the increase with redshift in the critical halo mass for disk formation, reported in both simulations and observations, as a consequence of the evolution of the halo mass-concentration and baryonic mass-halo mass relations. This redshift trend therefore supports the recent proposal that it is the steepening of the gravitational potential that causes disk formation, while other effects discussed in the literature, such as potential deepening and hot gaseous halo formation, can still play important roles in the transition from early turbulent to dynamically cold disks.

The distribution of dark matter in the inner regions of galaxies poses a key challenge for small-scale {\Lambda}CDM cosmology. While cold dark matter simulations predict cuspy inner density profiles, observations of low surface brightness (LSB) and dwarf galaxies often favour cored profiles, an issue known as the cusp-core problem. We investigate this problem by comparing four dark matter halo profiles: NFW (cuspy), Einasto (intermediate), Burkert (cored), and pseudo-isothermal (pISO) (cored) in a pilot sample of $11$ galaxies from the GMRT archive atomic gas survey (GARCIA). We have performed mass modelling using Markov Chain Monte Carlo (MCMC) techniques, utilising rotation curves derived from robust 3D Kinematic modelling. Baryonic contributions from stars derived using stellar kinematics based on $3.6\mu\mathrm{m}$ or $r$-band photometry via Multi-Gaussian Expansion (MGE) combined with Jeans Anisotropic Model (JAM) and from gas, calculated directly from the gas surface density (HI + He) without assuming any predefined functional form, are included. Our mass modelling shows that all halo profiles provide statistically good fits, yielding consistent estimates of halo mass and stellar mass-to-light ratio. To validate our analysis, we examine the stellar-to-halo mass relation and find broad agreement with empirical models. Non-parametric density profiles derived from baryon-subtracted rotation curves show that NFW fits the inner regions best, while all profiles converge in the outskirts. Future studies with a larger sample from GARCIA will be helpful in refining this trend and addressing the cusp-core issue in greater depth.

Tailed radio galaxies are powerful tracers of interactions between active galactic nuclei (AGN) and the intracluster medium (ICM), providing unique insights into cluster dynamics. We present LOw Frequency ARray (LOFAR) 144 MHz and uGMRT 400 MHz observations of the cluster MACS J1354.6+7715 (z = 0.3967) to investigate the radio emission associated with its member galaxies and the cluster environment. The dominant tailed radio galaxy in the cluster exhibits a sharply bent tail extending over approximately 300 kpc, with the spectral index steepening from approximately -0.46 +/- 0.21 near the AGN core to approximately -2.43 +/- 0.30 in the outermost regions. Synchrotron modelling of the tail yields a radiative age of 150 +/- 10 Myr, implying a galaxy velocity of 1956 +/- 130 km s^-1, which is of order ~ 0.9 times the escape velocity. We find no evidence of relics or halos in our radio images, and the X-ray morphology from Chandra appears relatively undisturbed, suggesting that the system is a pre-merging candidate. Our results indicate that the radio galaxy is undergoing its first infall into the cluster, providing an excellent laboratory for studying the impact of the ICM on AGN activity and galaxy evolution, and demonstrating how multi-frequency radio observations of tailed galaxies can uniquely probe both AGN lifecycles and the early stages of cluster assembly.

With tens to hundreds of spectra of white dwarfs being taken each night from multi-object spectroscopic surveys, automated spectral classification is essential as part of efficient data processing. In this study, we design a neural network to classify the spectral type of white dwarfs using a combination of spectra from the Dark Energy Spectroscopic Instrument (DESI) data release~1 and imaging from Pan-STARRS photometry. The trained network has a near 100% accuracy at identifying DA and DB white dwarf spectral types, while having an 85-95% accuracy for identifying all other primary types, including metal pollution. Distinct spectral or photometric features map into separate structures when performing a Uniform Manifold Approximation and Projection (UMAP) dimensionality reduction. Investigating further and looking at multiple epoch spectra, we performed a separate search for objects that have strongly changing spectral signatures using UMAP, discovering 3 new inhomogeneous surface composition ('double-faced') white dwarfs in the process. We lastly show how machine learning has the potential to separate single white dwarfs from double white dwarf binary star systems in a large dataset, ideal for isolating a single star population. The results from all of these techniques show a compelling use of machine learning to boost efficiency in analysing white dwarfs observed in multi-object spectroscopy surveys, at times replacing the need for human-driven spectral classifications. This demonstrates our techniques as powerful tools for batch population analyses, finding outliers as a form of rare subclass detection, and in conducting multi-epoch spectral analyses.

Measurements of the cosmic 21 cm signal need to achieve a high dynamic range to isolate it from bright foreground emissions. Calibration inaccuracies can compromise the spectral fidelity of the smooth foreground continuum, thereby limiting the dynamic range and potentially precluding the detection of the cosmic line signal. In light of this challenge, recent work has proposed using the calibration-independent closure phase to search for the spectral fluctuations of the cosmic 21 cm signal. However, so far there has been only a heuristic understanding of how closure phases map to the cosmological 21 cm power spectrum. This work aims to establish a more accurate mathematical relationship between closure phases and the cosmological power spectrum of the background line signal. Building on previous work, we treat the cosmic signal component as a perturbation to the closure phase and use a delay spectrum approach to estimate its power. We establish the relationship between this estimate and the cosmological power spectrum using standard Fourier transform techniques and validate it using simulated HERA observations. We find that, statistically, the power spectrum estimate from closure phases is approximately equal to the cosmological power spectrum convolved with a foreground-dependent window function, provided that the signal-to-foreground ratio is small. Compared with standard approaches, the foreground dependence of the window function results in an increased amount of mode-mixing and a more pronounced proliferation of foreground power along the line-of-sight dimension of the cylindrical power spectrum. These effects can be mitigated by flagging instances where the window function is broad. Crucial to gaining the necessary sensitivity, this mapping will allow us to average the measurements of closure triads of different shapes based on their imprint in cylindrical Fourier space.

Hydrocarbons play a key role in shaping the chemistry of the interstellar medium (ISM), but their enrichment and relationship with carbonaceous grains and polycyclic aromatic hydrocarbons (PAHs) still lack clear observational constraints. We report JWST NIRSpec+MIRI/MRS infrared (IR; 3-28 micron) observations of the local ultra-luminous IR galaxy (ULIRG) IRAS 07251-0248, revealing the extragalactic detection of small gas-phase hydrocarbons such as benzene (C$_6$H$_6$), triacetylene (C$_6$H$_2$), diacetylene (C$_4$H$_2$), acetylene (C$_2$H$_2$), methane (CH$_4$), and methyl radical (CH$_3$) as well as deep amorphous C-H absorptions in the solid phase. The unexpectedly high abundance of these molecules indicates an extremely rich hydrocarbon chemistry, not explained by high-temperature gas-phase chemistry, ice desorption or oxygen depletion. Instead, the most plausible explanation is the erosion and fragmentation of carbonaceous grains and PAHs. This scenario is supported by the correlation between the abundance of one of their main fragmentation products, C$_2$H$_2$, and cosmic ray (CR) ionization rate for a sample of local ULIRGs. These hydrocarbons are outflowing at $\sim$160 km/s, which may represent a potential formation pathway for hydrogenated amorphous grains. Our results suggest that IRAS 07251-0248 might not be unique but represents an extreme example of the commonly rich hydrocarbon chemistry prevalent in deeply obscured galactic nuclei.

(Abridged) We present stellar kinematics of the MUSE Most Massive Galaxies (M3G) Survey, comprising 25 galaxies brighter than -25.7 mag in the Ks-band and stellar mass above ~6x10^11 Msun. Galaxies are divided between the brightest cluster galaxies (BCGs) and lower-ranked (in brightness) galaxies (non-BCGs) in three rich galaxy clusters within the core of the Shapley super cluster. We find several velocity maps with rich kinematic structure, including multiple spin reversals within the region encompassing central two effective radii, typically associated with BCGs. The majority of BCGs show rotation around the major-axis, at least in one of the visible velocity components. These kinematic structures are possible only if galaxies have non-axisymmetric shapes and contain several orbital families with both prograde and retrograde rotations. There are six fast rotators in the M3G sample, all among non-BCGs, and typically ranked below the 3rd brightest galaxy. Based on the properties of the h3 Gauss-Hermite moment, fast rotation can be linked to the dominance of prograde rotating short-axis tubes in the orbital distribution. Slow rotators are BCGs or the second and sometimes third brightest galaxies, indicating that the galaxy mass (brightness) is not the only driver of low spin, but that the location within the local environment also plays a role. Slow rotators, as evidenced from their multi-spin velocity maps, require more complex orbital structures. Furthermore, some BCGs show kinematic evidence for a secondary component at larger radii, likely not in equilibrium with the main galaxy and possibly made of stars accreted from other cluster galaxies. Multi-spin velocity maps, low angular momentum and additional kinematic components highlight the difference in the evolutionary histories of BCGs (including 2nd ranked galaxies) and non-BCGs.

We use data from the JWST ASPIRE Wide Field Slitless Spectroscopy (WFSS) program to measure the auto-correlation function of [O,{\sc iii}] emitters at 5.3$<z<$7.0 and the quasar--[O,{\sc iii}] emitter cross-correlation around 25 ASPIRE quasars (6.51$<z<$6.82; $\langle z\rangle=6.6$). We use synthetic source injection to calibrate the selection function, which we combine with the large-volume FLAMINGO-10k simulation (2.8,cGpc box) to construct realistic mock observations. Our simulation-based approach captures nonlinear structure growth and scale-dependent bias on small scales and derives covariance matrices that include cosmic variance. The clustering yields correlation lengths of $r_0^{\rm GG}=4.7^{+0.4}{-0.5},h^{-1}$,cMpc for the [O,{\sc iii}] auto-correlation with fixed slope $\gamma{\rm GG}=1.8$, and $r_0^{\rm QG}=8.7^{+0.8}{-0.9},h^{-1}$,cMpc for the quasar--[O,{\sc iii}] cross-correlation with $\gamma{\rm QG}=2.0$. We infer $\log(M_{h,{\rm min}}^{[{\rm O,III}]}/M_\odot)=10.5^{+0.1}{-0.1}$ for [O,{\sc iii}] emitters and $\log(M{h,{\rm min}}^{\rm QSO}/M_\odot)=12.1^{+0.3}{-0.4}$ for quasars. These imply duty cycles of $2.5^{+1.0}{-0.8}$,per,cent for [O,{\sc iii}] emitters and $0.3^{+4.0}{-0.3}$,per,cent for quasars, corresponding to UV-bright lifetimes of $t{\rm Q}=2.6^{+30}_{-2.5}$,Myr (less than 10,per,cent of a Salpeter $e$-folding time). The results indicate that the observed UV-luminous phase contributes little to total SMBH growth, placing tight constraints on early black-hole formation.

We present diffHOD-IA, a fully differentiable implementation of a halo occupation distribution (HOD) model that incorporates galaxy intrinsic alignments (IA). Motivated by the diffHOD framework, we create a new implementation that extends differentiable galaxy population modeling to include orientation-dependent statistics crucial for weak gravitational lensing analyses. Our implementation combines this HOD formulation with an IA model, enabling end-to-end automatic differentiation from HOD and IA parameters through to the galaxy field. We additionally extend this framework to differentiably model two-point correlation functions, including galaxy clustering and IA statistics. We validate diffHOD-IA against the reference halotools-IA implementation using the Bolshoi-Planck simulation, demonstrating excellent agreement across both one-point and two-point statistics. We verify the accuracy of gradients computed via automatic differentiation by comparison with finite-difference estimates for both HOD and IA parameters. We present science use cases leveraging gradients in the simulations to recover the IA parameters of a galaxy field representative of the TNG300 simulation. Finally, we apply diffHOD-IA in a Hamiltonian Monte Carlo analysis and compare its performance with halotools-IA and a neural-network-based emulator, IAEmu. Unlike emulator-based approaches, diffHOD-IA provides differentiability at the catalog level, enabling integration into field-level inference pipelines and extension to arbitrary summary statistics for next-generation weak-lensing analyses. Our code is publicly available.

We present a systematic study of the environments of 25 luminous quasars at $z > 6.5$ from the ASPIRE program. Using JWST/NIRCam WFSS data, we identified 487 galaxies at $5.3 \lesssim z \lesssim 7.0$ exhibiting [OIII] emission. Among these, 122 [OIII] emitters lie within $|\Delta v_{\rm los}| < 1000~{\rm km~s^{-1}}$ of the quasars, corresponding to a $\sim9.4$-fold enhancement relative to the average galaxy density at other redshifts. Furthermore, we identified 16 [CII]-emitting galaxies at the quasar redshifts from ALMA mosaic observations. A cross-correlation function (CCF) analysis between quasars and [OIII]+[CII] emitters yields a cross-correlation length of $r_0^{\rm QG} = 8.68^{+0.51}_{-0.55}~h^{-1}~\mathrm{cMpc}$ and a auto-correlation of $r_0^{\rm{QQ}}=15.76^{+2.48}_{-2.70}~h^{-1}~{\rm cMpc}$, indicating that $z \sim 7$ quasars reside in dark matter halos with $M_{\rm halo} = 10^{12.27^{+0.21}_{-0.26}}~M_\odot$. Notably, the number of [OIII]-emitting galaxies at quasar redshifts varies significantly from field to field, ranging from zero to twenty, highlighting a diverse quasar environment. Remarkably, seven quasars trace significant galaxy overdensities (i.e., protoclusters), with $\delta_{\rm gal} > 5$ within a volume of $V \sim 500~{\rm cMpc^3}$. We also find that $|\Delta v_{\rm los}|$ increases rapidly toward smaller galaxy-quasar separations in protocluster fields, consistent with galaxy kinematics around extremely massive halos in cosmological simulations. By combining JWST and ALMA data, we reveal the complex and diverse environments of these early quasars, providing robust evidence that the earliest luminous quasars are effective tracers of galaxy overdensities, albeit with substantial field-to-field variation.

We implement a Markov Chain Monte Carlo method to obtain posterior probability distributions for the parameters of the S2 star orbit around Sagittarius A*, for seven representative non-rotating black hole space-time solutions. In particular, we consider the Schwarzschild, Reissner-Nordström, Janis-Newman-Winicour, and Bardeen black hole space-times from General Relativity, as well as a black hole solution from Einstein-Maxwell-dilaton gravity, a hairy black hole solution from Horndeski theory, and a Yukawa-like black hole from $f(\mathscr{R})$ gravity. To constrain model parameters, we use the most recent publicly available observational data of the S2 star orbit, namely astrometric measurements, spectroscopic data, and the pericentre advance measured by the GRAVITY Collaboration. We further perform a consistent Bayesian comparison of models, calculating the log-Bayes factor of each space-time with respect to the Schwarzschild solution. Our results show that the currently available data indicate no statistically significant preference among the space-times considered. The Bardeen and Yukawa-like models are indistinguishable from Schwarzschild within current uncertainties, while the Reissner-Nordström, Janis-Newman-Winicour, Horndeski and Einstein-Maxwell-dilaton geometries show at most weak and non-decisive strength of evidence under the adopted priors and likelihood choices.

Large Gaia data set shows substantial misfit between models and observation for cool white dwarfs with $T_{\rm eff}<6000\,\rm K$, resulting in severe underestimation of masses of these stars. We aim to understand the underlying modelling issues. State of the art atmosphere models have been applied to analyse the Gaia DR3 sample of white dwarfs as well as quantum mechanical calculations to quantify formation and stability of different hydrogen species in the atmospheres of these stars. We reconcile the models and observations when we artificially suppress formation of $\rm H_3^+$ species, a process which substantially alters the chemical equilibrium at $T_{\rm eff}<6000\,\rm K$, resulting in an overabundance of free electrons and $\rm H^-$, and strengthening of $\rm H^-$ bound-free absorption. Removing the $\rm H_3^+$ species from chemical equilibrium consideration makes ionization of hydrogen atoms the main source of free electrons, with the resulting models reproducing well the Gaia white dwarfs cooling branch. Because $\rm H_3^+$ must form under the considered conditions, likely it is the overestimation of its partition function and resulting abundance or the formation of $\rm H_3^-$ or another anionic species that suppresses the formation of $\rm H^-$ as a countercharge for $\rm H_3^+$ in current models. Chemical equilibrium in cool, hydrogen atmospheres white dwarfs must be reconsidered in respect to the abundance of $\rm H_3^+$ species and presence of unaccounted charge species.

ALMA continuum measurements of the local ULIRG IRAS 07251-0248 E at 667$\mu$m reveal an extremely compact (R < 27 pc) and bright ($T_B$ >200 K) nucleus with an absorbing foreground envelope and a surrounding (R ~ 75 pc) disk or torus seen nearly face-on. The bright and unresolved nuclear emission implies large optical depths ($\tau_{667\mu m}$ >0.5, corresponding to $N_H > 10^{25}$ cm^-2) of hot dust at >500 K. In addition, JWST observations of the source show strong mid-infrared (mid-IR) absorption in the ro-vibrational bands of H2O nu_2=1-0 (5-7 $\mu$m) and of other species including CO, HCN, C2H2, CH4, and CO2, and Herschel/PACS observations exhibit strong and saturated absorption due to OH, H2O, CH^+, and CH. We propose a model in which the unresolved ALMA submillimeter and JWST mid-IR continua trace the same nuclear source, the former penetrating deep into the nucleus and the latter probing the nuclear photosphere. The continuum model, which includes trapping of photons (the "greenhouse" effect), indicates that the nuclear ($R_h$ ~ 13 pc) luminosity and luminosity surface density are ~10$^{12}$ Lsun and $\Sigma_{bol}$~ 5e8 Lsun pc^-2, arising from an active galactic nucleus (AGN) so buried that high-ionization lines are completely obscured. The observed mid-IR gas-phase molecular bands probe outflowing gas with velocities of ~160 km s^-1 and are reproduced with the predicted $T_{dust}$ profile, while the far-IR molecular absorption lines are generated in the surrounding thick disk or torus with $\tau_{100 \mu m}$~10. We conclude that IRAS 07251-0248 harbors a compact obscured nucleus (CON) that hides an AGN currently emitting at quasar luminosity. While the observed outflow could be driven by radiation pressure, we favor the scenario of a (partially) energy-conserving hot bubble caught in a very early phase of the expulsion of the highly concentrated gas at the galactic nucleus.

Long-period binary systems containing a B-type hot subdwarf (sdB) and a main-sequence companion are thought to originate from binary interactions involving stable mass transfer from the red giant, the progenitor of the sdB, to the MS companion. However, despite the recent progress in modelling their population, some of their observed properties are not entirely understood. Because determining their orbits requires extended campaigns of high-resolution spectroscopic observations, only a limited number of long-period sdB binaries have been studied with completely determined orbital parameters. A sample of 32 wide binary systems containing sdB stars was selected for the analysis of the radial velocity curves of both companions. The dataset consisted of high-resolution spectra obtained with the HERMES and UVES spectrographs. The orbital parameters were derived by simultaneously fitting Keplerian orbits to the radial velocities of the sdB and its companion. The atmospheric parameters of the cool companions were determined using the GSSP code, which analyses the master spectra of the systems with a grid of LTE atmospheric models. An additional sample of wide sdB binaries was built up by cross-matching the Gaia NSS catalogue with catalogues of sdB candidates and spectroscopically confirmed systems reported by Culpan2022A&A catalogues. The outcomes from both samples were compared with existing theoretical models to assess their consistency with current formation and evolutionary scenarios.

The Large and Small Magellanic Clouds (LMC and SMC, respectively) are the largest satellite galaxies of the Milky Way (MW) and their interactions with each other have given rise to multiple stellar substructures in their periphery as well as the gaseous Magellanic Stream. To better understand the origin of the stellar substructures and constrain their past orbit, we model the past 2.5 Gyr of the interactions between the MW and the LMC and SMC using N-body simulations. Due to the strong interactions, analytical orbit integrations are insufficient to analyze the past galaxy orbits accurately. Therefore, we use a genetic algorithm in combination with N-body simulations to determine the LMC and SMC initial positions and velocities 2.5 Gyr ago that result in the Magellanic Clouds (MCs) arriving near their observed locations and velocities at the current time. After running ~8,000 simulations, our best matching model includes two close interactions between the MCs (940 Myr and 140 Myr ago) and reproduces some observed features of the MCs, including the LMC disc warp, a ring-shaped overdensity in the LMC, the tidal expansion of the SMC, and a greater distance dispersion on the eastern side of the SMC. The LMC disc warp is caused by the most recent interaction with the SMC, which occurred ~140 Myr before the present. The interaction causes global ripples in the LMC disc with a mean amplitude of 1.3 kpc.

Solar flares are driven by release of free magnetic energy and often associated with restructurization of the magnetic field topology. Yet, observations of evolving magnetic field in the flaring volume are limited to very few cases including the 2017-09-10 X8.2 limb flare; thus, a verification of whether a similar evolution takes place in other solar flares is needed. Here we report one more, 2022-10-02, X1.1 class solar flare but seen on disk, whose microwave data permit mapping the magnetic field over the flaring source and tracking magnetic field evolution over the course of the flare. We found that the coronal magnetic field shows a prominent decay with the rate up to 10 G s$^{-1}$ in several (above) loop-top locations. The magnetic field is also confidently measured at the loop legs and the bottom part of the erupting filament. Prominent acceleration of electrons is detected where the magnetic field decays. We developed 3D models of the flare, whose magnetic field shows resemblance and also deviation from the magnetic field inferred from the microwave data. This study confirms that the coronal magnetic field decays during the rise phase of the solar flare. The amount of released magnetic energy is sufficient to support other components of the flare energy.

We performed a comprehensive analysis of 27 short period contact binary systems for which no light curve analysis had previously been reported. Photometric time-series data from the TESS mission were used in this analysis. The observational results were validated using additional TESS sectors, along with complementary photometric observations from the ASAS-SN survey. The photometric light curves of the 27 contact binary systems were analyzed with the BSN application. Model solutions were obtained through iterative fitting followed by MCMC-based refinement to derive reliable system parameters, and starspot configurations were incorporated for seven targets exhibiting O'Connell effect asymmetries. The absolute parameters of the target systems were derived using the empirical parameter relationship between orbital period and semi-major axis. Based on the results of the light curve solutions and the estimated absolute parameters, five of the analyzed systems are identified as A-subtype, while the remaining targets belong to the W-subtype. We analyzed a sample of 484 W UMa contact binaries to identify the physical and orbital parameters that most effectively distinguish A-subtype from W-subtype systems using t-statistics. Three targets exhibited extremely low mass ratios, and their orbital analysis confirmed that they are dynamically stable. The evolutionary states of the systems were examined, showing that lower-mass companions are generally more evolved, while more massive components remain less evolved. The positions of the systems and their stellar components were compared across four diagrams derived from empirical parameter relationship studies, showing good agreement with the linear fits.

Hilda-group asteroids librate in Jupiter's interior 3:2 mean motion resonance. We estimate that the Hilda group is observationally complete up to absolute magnitude $H\leq16.3$. This provides a statistically useful sample of thousands of resonant objects, all within a narrow range of semimajor axes, to compare with theoretical expectaitons of their orbital distribution from dynamical theory. We use von Mises-Fisher statistics to calculate the sample mean planes and mean plane uncertainties for the Hilda group and its Hilda, Schubart, and Potomac collisional subfamilies. Although Laplace-Lagrange linear secular theory is considered inapplicable within mean motion resonances, we find that the Laplace plane and the orbital plane of Jupiter are both statistically indistinguishable from the sample mean plane of the Hildas. In future work, we intend to extend this investigation to resonant populations in the Kuiper belt so as to further test the validity of Laplace-Lagrange linear secular theory for the mean planes of resonant populations.

We apply Simulation-Based Inference ('SBI') to the cosmic dipole problem for the first time, measuring the distribution of quasar counts over the sky in the CatWISE2020 ('CatWISE') sample. We show that the quadrupole anisotropy in CatWISE can be attributed to the correlation between WISE's scanning law and photometric uncertainty in the $W1$ and $W2$ magnitudes, inducing an Eddington bias which varies with sky position. After explicitly modelling this with SBI, we use a neural likelihood estimator to find the posterior distribution for CatWISE's dipole, confirming the presence of a dipole twice as large as the CMB expectation but more seriously misaligned with the CMB direction ($\approx 3 \sigma$). We also use our learned likelihood to infer the Bayesian evidence, learning that models which increase the scale of CatWISE's photometric errors are most favoured. This is strong evidence that the sample's errors are underestimated or that there is an additional, unresolved systematic producing the same effect as Eddington bias. While our results indicate that the cosmic dipole excess is a persistent issue for $\Lambda$CDM, we showcase that SBI can untangle the subtle and complex systematic issues affecting any sample derived from real astronomical data.

We present mid-infrared (MIR) observations of the Seyfert 1 galaxy NGC 4151 using the Large Binocular Telescope Interferometer (LBTI). We took open-loop Fizeau images with 66-104 mas (5.8-9.1 pc) resolution in the N-band (at $8.7$ and $10.5~\mu m$), using the full resolution of the LBTI -- equivalent to that of a 28.8 m telescope. These images were complemented by AO imaging in the LM-bands ($3.7$ and $4.8~\mu m$), with 50-62 mas (4.4-5.4 pc) resolution. These images bridge the scales between previous Very Large Telescope Interferometer (VLTI)/MIDI and VLT/VISIR data, delivering ELT-like imaging resolution in the N-band. We resolve a dusty torus, (diameter 32 pc, PA$=125^{\circ}$), and detect dusty clouds within the narrow line region. Matching the resolution across four bands, we measured spatially-resolved SEDs of the central $\sim 100$ pc. Modified blackbody fitting revealed dust temperature and extinction profiles, indicating both heating from the accretion disk and additional shock heating due to the radio jet. The spatial coincidence of ionized emission (e.g., [Fe II] and [O III]), extended MIR structures, and radio features further supports the interpretation of shock heating. Comparison with NGC 1068 tests the Unified Model of Active Galactic Nuclei (Unified Model of AGN): Structures are similar, despite differences in orientation and Eddington ratio. NGC 4151's torus is smaller than NGC 1068's following a $r\propto L^{0.5}$ scaling. These thirty-meter-telescope class observations of NGC 4151 and NGC 1068 highlight the need to revise MIR radiative transfer models of AGN to account for jet-related heating.

Cosmic voids, the largest underdense regions in the Universe, provide unique laboratories for studying galaxy formation and constitute powerful probes of cosmology. Recent work has shown that individual galaxy bias (b_i), which quantifies how each galaxy traces the underlying dark matter field, exhibits a characteristic radial dependence within spherical voids, defining a void bias profile in which galaxies near void centers display systematically lower bias values. We investigate how the environmental modulation of individual galaxy bias depends on the adopted void-finding algorithm by comparing measurements across five distinct void definitions: spherical voids 'sparkling', watershed-based methods ('zobov' and 'revolver' in two modes), and free-form integrated-density voids ('popcorn'). We apply these complementary void-finding algorithms to the same galaxy sample drawn from the IllustrisTNG simulation (TNG300-1 at $z=0$) and compute individual galaxy bias profiles as a function of distance from void centers. We quantify the correlation between b_i and the membership of the void catalogs and explore how this relationship varies with the integrated underdensity threshold for density-based methods. We find that the radial gradient of individual bias within voids, generally increasing from negative values at the void centers to higher values at the boundaries, is robust across most void definitions. However, density-threshold methods preferentially select galaxies with b_i<0, while watershed methods without density constraints include substantial contamination from high-bias boundary galaxies. The correlation between negative bias and void membership is systematically strengthened as the integrated underdensity threshold becomes less restrictive, with popcorn achieving the highest purity in isolating anti-biased populations.

Quasars hosting $\gtrsim 10^{9}\,M_\odot$ black holes at $z>6$ challenge growth scenarios that start from light seeds and assume accretion within already formed galaxies. Motivated by the James Webb Space Telescope (JWST) discovery of Little Red Dots (LRDs), which suggests that $\sim 10^{6}\,M_\odot$ black holes can be active in compact, pre-galactic environments, we revisit early black hole growth with a minimal cosmology-based framework. We model the accretion history as the smaller of the Bondi inflow rate and the Eddington-limited rate, where the Bondi rate is set by the supply of overdense primordial gas whose density declines with cosmic expansion, and the Eddington rate captures regulation by radiative feedback. By fitting the observed masses and luminosities of J0313--1806 ($z=7.64$) and J0100+2802 ($z=6.30$) with Bayesian inference, we infer initial conditions that favor massive seed black holes with initial mass $M_0 \sim 10^{6}\,M_\odot$, formed at $z\sim20{-}30$ in environments with baryonic overdensity factors $f_\rho \gtrsim 50$ relative to the cosmic mean. The resulting growth histories include a prolonged supply-limited stage, and they reproduce the observed quasar masses without requiring sustained Eddington accretion or any super-Eddington episodes. The inferred seed mass scale is consistent with black holes produced by the collapse of quantum-degenerate fermion dark matter cores, providing a physically defined pathway to massive seeds at the redshifts implied by LRD phenomenology.

We present the observation of a secondary eclipse of the young hot Neptune, AU Mic b, in the infrared using the Spitzer Space Telescope. Using a primary transit from Spitzer to constrain the system parameters, we tentatively detect an eclipse centered at $BJD=2458740.848893^{+0.00010}_{-0.000099}$ with an observed depth of $171\pm{29}$ ppm given an uninformed prior. This corresponds to a dayside brightness temperature of $T=1031\pm{58}$ K, which exceeds the calculated equilibrium temperature of $606\pm{19}$ K. We explore some possible explanations for these results, including inefficient heat redistribution, gravitational contraction, stellar pulsations, instrument systematics and choice of eclipse depth prior, but find none of these to be likely explanations for the observed eclipse parameters. We also explore the impact of correlated noise in the systematic trends, and we find that splitting the systematics into low-pass (smoothing) and high-pass trends is required to reach an optimal minimization of the low-frequency systematics in the resulting detrended light curve. Future observations with JWST are needed to confirm our eclipse detection with Spitzer.

Neutron star binary mergers are often associated with short gamma-ray bursts (GRBs), but the recent detection of kilonovae coincident with long GRBs suggest that some mergers may produce long GRBs. Motivated by these developments, we perform a search for binary neutron star and neutron star-black hole gravitational-wave signals coincident with long GRBs using data from the third LIGO--Virgo--KAGRA (LVK) observing run. We analyze LVK data coincident with long GRBs detected by Fermi's GRB Monitor and Swift's Burst Alert Telescope when at least two gravitational-wave observatories were running. We find no evidence of a coincident gravitational-wave signal and set limits on the luminosity distance to each of these long GRBs under the assumption that they were powered by binary mergers.

We investigate the structure of strange dwarfs, modeled as hybrid compact stars composed of a self bound strange quark matter core surrounded by a white dwarf like crust, within a fully relativistic framework. Static configurations are constructed by solving the Tolman Oppenheimer Volkoff equations, and uniformly rotating configurations are modeled within the Hartle Thorne slow rotation expansion (to ${\cal O}(\Omega^2)$). We therefore interpret results at large fractional spins conservatively, and use the Kepler frequency mainly as a reference scale for comparing different masses and models. The stellar matter is described using a hybrid equation of state, in which the crust is modeled by a degenerate electron ion system and the core by the MIT Bag Model. By comparing strange dwarfs with conventional white dwarfs across a range of rotation rates, we show that rotation inflates the radius and can reduce (in a quantifiable way) the separation between the two families in the $(M,R)$ plane, potentially masking structural signatures associated with the presence of a quark core. Our results highlight the importance of accounting for rotational effects when interpreting mass radius measurements and other global observables in the context of searches for exotic compact objects in current and future high precision surveys.

Among thousands of extragalactic $\gamma$-ray emitters, only a handful of distant ($z >$ 3) sources are detected, yet they are cruial probes shedding light on the cosmic evolution of jets of active galactic nuclei and the initial phase of mass growth of supermassive black holes. Here, we report on a multi-band study of a radio quasar B3 1239+376 with $z$ = 3.82. By analyzing the Fermi-LAT data, a significant (globally 7.7$\sigma$) $\gamma$-ray source in its direction, with an estimated association probability of 0.91, is observed in a half-year period of 2025. The analyses also reveal the emergence of co-spatial $\gamma$-ray residues in prior epochs. Moreover, the $\gamma$-ray and infrared light curves are likely correlated, particularly, the two emissions climb to the peaking values at the same time. The temporal coincidence establishes a firm association relationship between the $\gamma$-ray source and the quasar. Therefore, B3 1239+376 is proposed as the {\it third} most distant $\gamma$-ray-emitting blazar to date. Benefiting from the multi-wavelength observations, broadband spectral energy distributions in different flux states are drawn and reproduced by the classic one-zone leptonic radiation model to investigate the jet properties. Considering the recent brightening in $\gamma$ rays, prompt follow-up observations are encouraged, especially radio interferometry observations which may catch the potential ejection of a new jet blob.

At a 112.4 pc distance, the PDS70 protoplanetary disk is a rare case that has been confirmed to host two accreting planets. This makes it the most important laboratory for studying dust growth in the context of planet formation. Here we present the first deep, full polarization observations at 873 $\mu$m wavelength. We detected $\sim$1%-2.5% linear polarization over the bulk of the $\sim$55-100 AU (sub)millimeter ring. The polarization position angles align preferentially with the projected minor axis of the disk. The standard interpretation is that the observed polarization is caused by dust self-scattering, with a maximum dust grain size of $\sim$100 $\mu$m. On $\gtrsim$10 AU scales, which can be resolved by the presented 873-3075 $\mu$m observations, the ring is marginally optical thick at 873 $\mu$m wavelength. Using Monte Carlo radiative transfer simulations, we found that an azimuthally asymmetric, marginally optically thick ring with a maximum dust grain size of $\sim$87 $\mu$m can reproduce the observed 873 $\mu$m polarization position angles and percentages. This study indicates that the coagulation of ice-coated dust in the protoplanetary disk may be limited by fragmentation or bouncing.

Context. The evolution of cataclysmic variables (CVs) - interacting binaries where a low-mass donor transfers matter to a white dwarf via an accretion disk - is critically controlled by magnetic braking (MB). Significant uncertainties persist regarding how distinct MB formalisms influence CV evolutionary pathways. Aims. We performed systematic simulations of CV evolution under five MB prescriptions using the MESA code: the classical Skumanich law and the Matt, Reiners & Mohanty (RM12), intermediate, and convection-boosted formalisms. Primary objectives included investigating their impact on orbital period distributions, mass-transfer rates, donor star evolution, and period gap characteristics. Methods. Evolutionary sequences were computed across all MB frameworks. We analyzed their effects on key observables: orbital period evolution, accretion rates, and period gap morphology. Results. Magnetic braking prescription selection fundamentally determines whether CV systems develop the characteristic period gap. The intermediate prescription provides optimal consistency with observations of nonmagnetic CVs, simultaneously reproducing the gap location and donor properties. Strong braking models (e.g., Skumanich) produce clear detachment phases, while self-consistent regulation models (Matt12 and RM12) maintain weak angular momentum loss and fail to form a gap, making them more prone to magnetic CVs. Conclusions. The presence or absence of the period gap is primarily governed by the strength and behavior of MB before the donor becomes fully convective. Future studies must further incorporate the regulatory effects of magnetic fields on donor structure to accurately predict the period distribution characteristics of magnetic CVs.

This work presents integrated flux and velocity channel maps of the planetary nebula Abell 30 (A30) inner knot system. The observations were taken with the INTEGRAL spectrograph at the William Herschel Telescope (WHT). Our IFU data cube partially covers knots J1, J2, and completely covers knots J3, J4 in the system. Optical Recombination Lines of C II, He I, He II, N III, O II and Collisionally Excited Lines of [Ar IV], [Ar V], [N II], [Ne III], [Ne IV], and [O III] were detected. Our integrated flux maps visualise the ionisation structure and the chemical inhomogeneity in the system previously reported by other groups. We find that ORLs are concentrated in the polar region (J1, J3), whereas the equatorial knots (J2, J4) are dominated by CELs. The flux ratio map of the diagnostic [O III] lambda 5007/4363 Angstrom lines reveals the electron temperature distribution, which shows cold cores of 15,000 K in knots J3 and J4 surrounded by a hot outer layer of above 20,000 K. Our channel maps show positive and negative velocity excursions from the systemic value among the ions. Several ions show variation in their velocity structures from their lower-energy-level counterparts, including [Ar IV] and [Ar V], [Ne III] and [Ne IV], and He I and He II. New recurrent velocity structures are identified in the low-density regions where the ions move much faster compared to their surrounding environments. The velocity dispersion measurements highlight extreme turbulence in some of the ions (sigma_vrad approx 140 km/s), consistent with supersonic/hypersonic motion driven by shocks. The forbidden line species [N II] exhibits lower turbulence (sigma_vrad approx 50-60 km/s), tracing denser, less-turbulent gases. Based on our data, we conclude both the ionisation and kinematic studies hint at shock heating and multiple ejection history in the evolutionary pathway of A30.

We introduce the Accretion-Modulated Internal Shock model (AMIS) as a possible framework for explaining the observational properties of long gamma-ray burst (GRB) prompt emission. In this scenario, the envelope of the prompt light curve follows the time-dependent mass-supply history to the central engine, associated with stellar collapse and, where applicable, fallback accretion, whose early-time onset can be approximated by $\dot{M}\propto t^{0-1/2}$ and which subsequently may decay as $\dot{M}\propto t^{-5/3}$, producing a photon count rate with a single fast-rise-exponential-decay (FRED)-like profile. In general, the prompt-emission envelope is regulated by a time-dependent mass supply to the central engine, while internal shocks produce the rapid variability. Since we only aim to introduce this framework here, we focus on the simplest single-FRED shape of the prompt emission profiles, while more complex cases involving multiple episodes and interacting shocks will be explored in forthcoming studies. The model indicates correlations between spectral evolution, FRED-pulse narrowing at high energies, and the mass-supply-controlled envelope. Stochastic Lorentz factor variations of ejected mass- or rate-driven shells, superimposed on the Accretion-Modulated envelope, explain the coexistence of smooth global trends and irregular short-timescale features, such as the widths of individual pulses in long GRB light curves, offering diagnostic tools for probing the inner engine activity.

Radio observations provide powerful diagnostics of energy release, particle acceleration, and transport processes in solar flares. However, despite recent progress in radio interferometric imaging spectroscopy, current instruments still face limitations in image fidelity and resolution, restricting detailed spectroscopic studies of flaring regions. Here we present high-fidelity imaging spectroscopy of a M1.3 GOES class flare with MeerKAT, a precursor to the future-generation array SKA-Mid. Radio emissions at the observed frequencies typically originate in the low corona, offering valuable insights into magnetic reconnection and primary energy-release sites. The obtained images achieve an unprecedented dynamic range exceeding 10^3, enabling simultaneous analysis of bright coherent bursts and faint incoherent emission from the active region. Multiple spatially distinct coherent sources are identified, implying contributions from different populations of accelerated electrons. The incoherent emission extends beyond AIA structures, highlighting MeerKAT's ability to detect dilute but hot plasma invisible to Extreme Ultraviolet instruments. Combined with co-temporal Hard X-ray images and magnetic field extrapolations, the radio sources are located within distinct magnetic structures, further revealing their association with different populations of accelerated electrons. These results demonstrate MeerKAT imaging spectroscopy as powerful diagnostics of solar flares and pave the way for future solar flare studies with SKA-Mid.

Prior to its infall, the Sagittarius (Sgr) dwarf galaxy was a major satellite with a mass of $M_{\rm sgr}\sim 10^{11}$ M$_\odot$. For the past $5-6~\mathrm{Gyr}$ , it has been heavily stripped by the Milky Way (MW), losing most of its mass while crossing the MW disc multiple times. Recent models of Milky Way disc perturbations $-$ including the spiral arms, the stellar bar, the Gaia phase spiral, and stellar and gaseous disc corrugations $-$ have identified these crossings as possible formation triggers, but have generally treated each perturbation in isolation. Here, we adopt a holistic perspective and ask whether a single disc-crossing impulse can simultaneously account for these features as observed today. We focus on simulations of single disc-crossing events by a Sgr-like perturber, and present a forensic analysis of the role of the powerful impulse in forming spiral arms, disc corrugations, the phase spiral and the `$L_{z}-\bar{V}_{R}$ wave', determined from a star's angular momentum and radial velocity, respectively. We find that a single disc crossing can reproduce reasonably well (e.g. structure, amplitude, phase) the observed local disc corrugation, and the Outer, Local and Sagittarius-Carina arm segments, implying that the last significant impulse due to a transit took place $700-1200~\mathrm{Myr}$ ago. Moreover, the $L_{z}-\bar{V}_{R}$ wave and phase spiral appear within the simulations over the same epoch and their general structure is reasonably well replicated, but not in detail. We conclude that Sgr's last significant crossing roughly a Gyr ago could be the primary cause of large-scale MW disc perturbations, but it cannot fully account for the $L_{z}-\bar{V}_{R}$ wave. Consequently, other triggers, possibly the Galactic bar or interactions with other satellites, must be considered in order to fully explain the current dynamical state of the MW's disc.

Observations of JWST have revealed that several close-in exoplanets have sulfur-rich atmospheres through SO$_2$ detections. Atmospheric sulfur is often thought to originate from solid accretion during planet formation, whereas recent simultaneous detections of SO$_2$ and NH$_3$ challenge this conventional scenario. In this study, we propose that ammonium salts, such as NH$_4$SH tentatively detected in comets and molecular clouds, play a significant role in producing sulfur-rich disk gases, which serve as the ingredient of giant planet atmospheres. We simulated the radial transport of dust containing volatile ices and ammonium salts, along with the dissociation, sublimation, and recondensation of these materials, thereby predicting the atmospheric chemical structures and transmission spectra of planets inheriting these compositions. Assuming that ammonium salts sequester 20% of the elemental nitrogen and sulfur budgets, our results reveal that they enhance sulfur and nitrogen abundances in disk gases to 2-10 times the solar values near the salt dissociation line. Photochemical simulations demonstrate that SO$_2$, NS, H$_2$S, NO, and NH$_3$ become the dominant N and S chemical species in the atmospheres on planets that inherited the gas compositions inside H$_2$O snowline. SO$_2$ features clearly appear in the infrared transmission spectra when the salt-bearing grains enhance the sulfur abundance of disk gas by pebble drift. Our model provides a novel scenario that explains the SO$_2$ detected in some exoplanet atmospheres solely from disk gas accretion. Volatile-element ratios, particularly N/S and C/O, would provide a key to disentangle our scenario from the conventional solid-accretion scenario.

The fractal dimension $D$ is used to map the large-scale galaxy distribution in the Universe by color types: blue, green and red. Using a $NUVrK$-complete COSMOS2020 subsample of 618,952 galaxies observed up to $z=4$, number densities were derived and plotted against two cosmological distance measures, the luminosity and comoving (galaxy area) distances, in order to estimate $D$ for each galaxy color type in two redshift intervals: $z\gtrless1$. We found a general gradient $D_{\mathrm{blue}}> D_{\mathrm{red}}>D_{\mathrm{green}}$ with $D=1.40-2.03$ for $z<1$. For $1<z\leq4$, the gradient changes to $D_{\mathrm{blue}}>D_{\mathrm{green}}D_{\mathrm{red}}$, and the fractal dimension values are lower, $D=0.03-0.44$. These results suggest that the fractal dimension is a sensitive diagnostic for how galaxy populations trace the evolving cosmic web, and confirm the fractal dimension as a useful tool for observational mapping of large-scale structure by galaxy color.

We investigate the relative alignment between density structures and magnetic fields in eight young protostars from the ALMA B-field Orion Protostellar Survey. Column density maps are derived from 870 $\mu$m dust continuum emission, and the Histogram of Relative Orientations (HRO) method is applied to quantify the correlation between magnetic field orientations and density structures on envelope scales ($\sim$10$^{3}$~au). We find that the relative alignment shows overall weak evidence of systematic evolution with column density, suggesting that column density alone does not fully determine the alignment. The magnetization level also plays a crucial role, with weakly magnetized envelopes exhibiting predominantly parallel or random alignment, whereas strongly magnetized ones show perpendicular configurations even at moderate densities. These results reveal that density and magnetization jointly shape the morphology of protostellar envelopes and the coupling between gravity and magnetic fields during early stages of star formation.

Active Galactic Nuclei (AGN) outflows can regulate host galaxy evolution via AGN feedback. Ionised gas outflows have been linked to enhanced radio emission. In the first paper of this series, AGN detected with the International LOFAR Telescope (ILT) at 6" were more likely to host an [O III] 5007 outflow than AGN not detected, although only high-powered jets were ruled out as the origin of radio emission. New wide-field, sub-arcsecond resolution imaging at 144 MHz with the ILT now enables a resolved morphological study of this sample. We present the first wide-field, sub-arcsecond images of the Boötes Deep Field at 144 MHz, detecting 4074 sources in the $\sim$0.3" image with a central sensitivity of 33.8 uJy $\mathrm{beam^{-1}}$. For 47 AGN matched in AGN luminosity, we probe radio emission on kiloparsec-scales to investigate correlations with [O III] outflows. This sample spans $z<0.83$, $10^{40}<L_{\mathrm{[O III]}}<10^{43}~\mathrm{erg~s^{-1}}$, and $10^{21}<L_{\mathrm{144MHz}}<10^{24.5}~\mathrm{W~Hz^{-1}}$. We find that if we detect an AGN on both large-scales (6") and small-scales (0.3"), 90$\pm$7 per cent have an [O III] outflow, compared to 63$\pm$9 per cent of sources detected on large-scales, but undetected on small-scales. Furthermore, 17$\pm$6 per cent of sources without an [O III] outflow are detected on kiloparsec-scales, compared to 51$\pm$12 per cent of sources with an [O III] outflow. This implies a connection between [O III] outflows and kiloparsec-scale radio emission, which is likely AGN-driven. In contrast, AGN without an [O III] outflow are dominated by diffuse radio emission, likely to be associated with star formation.

We review late-time cosmic acceleration after DESI Data Release~2 (DR2), emphasizing the interplay between Type~Ia supernovae (SNe~Ia), anisotropic BAO, CMB calibration, and perturbation-sensitive probes (RSD and weak lensing). DESI DR2 delivers percent-level BAO distance ratios over $0\lesssim z\lesssim2.5$, including a Ly$\alpha$-forest anchor at $z_{\rm eff}=2.33$. In CMB-calibrated combinations, flat $\Lambda$CDM exhibits a mild parameter mismatch, while allowing evolving dark energy (e.g.\ CPL $w_0$--$w_a$) can improve the fit; the preference is dataset-dependent and is particularly sensitive to redshift-dependent SN calibration/selection residuals at the few$\times10^{-2}$\,mag level. To sharpen likelihood-level interpretation, we provide two diagnostics: (i) an $r_d$-independent BAO-shape observable, $F_{\rm AP}(z)\equiv D_{\rm M}(z)/D_{\rm H}(z)$, constructed directly from published $(D_{\rm M}/r_d,\,D_{\rm H}/r_d)$ with covariance propagation; and (ii) a linear-response map from SN Hubble-diagram systematics $\delta\mu(z)$ to induced biases in $(w_0,w_a)$, yielding an explicit calibration requirement for DESI-era claims of evolving $w(z)$. We synthesize parametric and non-parametric reconstructions of $w(z)$ and $\rho_{\rm DE}(z)$ and map the resulting phenomenology to microphysical dark-energy and modified-gravity models subject to perturbation stability and gravitational-wave propagation constraints.

Exomoons around free-floating planets (FFPs) can survive their host planet's ejection. Such ejections can increase their orbital eccentricity, providing significant tidal heating in the absence of any stellar energy source. Previous studies suggested that liquid water could exist on such moons under thick CO$_2$-dominated atmospheres, but these models faced challenges with CO$_2$ condensation and atmospheric collapse, particularly in the high-pressure regimes that favoured long-term habitability. To address this, we employ a self-consistent model, including radiative transfer and equilibrium chemistry with condensation, to simulate a more stable hydrogen-dominated atmosphere for a range of initial chemical compositions, including C, O, and N. We find that such atmospheres can effectively trap heat via collision-induced absorption of H$_2$, maintaining surface temperatures suitable for liquid water for time-scales of up to 4.3 Gyr, depending on the surface pressure, while not prone to condensation-induced collapse. Wet-dry cycling caused by the strong tides together with the alkalinity of dissolved NH$_3$ could create favourable conditions for RNA polymerisation and thus support the emergence of life.

The chemical evolution in star forming regions is driven by the interplay between gas and ice mantles. Identifying the ice compositions at the early stage of star formation thus provides constraints on the chemical processes inaccessible from gas-phase characterizations. As part of the CORINOS program, spectra from the James Webb Space Telescope (JWST) MIRI MRS were taken toward four Class 0 protostars: IRAS 15398-3359, Ser-emb7, L483, and B335. The spectra were processed with simultaneous fitting of a continuum and silicate absorption to produce optical depth mid-infrared spectra of the ices at 5-28 $\mu$m (360-2000 cm$^{-1}$) toward these four sources. Simple molecules such as water (H$_2$O), carbon dioxide (CO$_2$), methanol (CH$_3$OH), formic acid/formate (HCOOH/HCOO$^-$), ammonia/ammonium (NH$_3$/NH$_4$$^+$), and formaldehyde (H$_2$CO) are the most abundant features in these ices, while complex organic molecules (COMs) represent a smaller contribution. Likely COMs include hydroxylamine (NH$_2$OH), methylamine (CH$_3$NH$_2$), and ethanol (CH$_3$CH$_2$OH). Absorption features belonging to functional groups such as -CH$_3$ and -OH suggest that additional COMs are present, but these cannot be unambiguously assigned due to overlapping bands. Formation pathways toward these COMs utilizing radical-radical combination reactions based on laboratory simulation experiments is presented. By extension, COMs predicted by these reactions, but absent from the spectra, are discussed. The results provide insight into the chemical environment of these ices and also highlight the critical need for caution and sufficient evidence in order to confidently identify COMs in ice.

Integral field spectroscopy (IFS) provides spatially resolved spectra, enabling detailed studies that address the physical and kinematic properties of the interstellar medium. A critical step in analyzing IFS data is the decomposition of emission lines, where different velocity components are often modeled with Gaussian profiles. However, conventional fitting methods that treat each spectrum independently often yield spatial discontinuities in the fitting results. Here, we present Emission Line Fitting Optimization (ELFO), a Python package for IFS spectral fitting. ELFO uses the results of neighboring spectra to determine multiple initial guesses and selects the result that exhibits spatial smoothness. We tested ELFO on IFS data of two quasars obtained from the Multi-Unit Spectroscopic Explorer, where it successfully corrected anomalous fits, revealed previously unresolved substructures, and made large-scale kinematic structures more evident. With minor modifications, this method can also be easily adapted to other IFS data and different emission lines.

We present a comprehensive temporal and spectral analysis of the long-duration gamma-ray burst GRB 110801A, utilizing multi-band data from the Neil Gehrels Swift Observatory and ground-based telescopes. The $\gamma$-ray emission exhibits a distinct two-episode (``double-burst'') structure. Rapid follow-up observations in the optical and X-ray bands provide full coverage of the second burst. The optical light curve begins to rise approximately 135 s after the trigger, significantly preceding the second emission episode observed in X-rays and $\gamma$-rays at $\sim 320$ s. This chromatic behavior suggests different physical origins for the optical and high-energy emissions. Joint broadband spectral fitting (optical to $\gamma$-rays) during the second episode reveals that a two-component model, consisting of a power-law plus a Band function, provides a superior fit compared to single-component models. We interpret the power-law component as the afterglow of the first burst (dominating the optical band), while the Band component is attributed to the prompt emission of the second burst (dominating the high-energy bands). A physical synchrotron model is also found to be a viable candidate to explain the high-energy emission. Regarding the afterglow, the early optical light curve displays a sharp transition from a rise of $\sim t^{2.5}$ to $\sim t^{6.5}$, which is well-explained by a scenario involving both reverse shock (RS) and forward shock (FS) components. We constrain the key physical parameters of the burst, deriving an initial Lorentz factor $\Gamma_0 \sim 60$, a jet half-opening angle $\theta_j \sim 0.09$, and an isotropic kinetic energy $E_{\rm k,iso} \sim 10^{54.8}$ erg.

Recent observations with the James Webb Space Telescope (JWST) reveal that the merger fraction among Ly$\alpha$ emitters (LAEs) at redshifts $z > 3$ is significantly higher than previously estimated. In this study, we focus on three high signal-to-noise merging LAE systems at $3 < z < 4$, selected from the VLT/MUSE-Deep survey in the GOODS-S field. We combine new \textit{JWST}/NIRCam broadband and medium-band imaging with archival \textit{HST}/ACS data to perform spatially resolved spectral energy distribution (SED) fitting using the \textsc{Bagpipes} software package. Our analysis reveals that two of the systems are minor mergers, while the third is a major merger. The close agreement between spatially resolved and integrated stellar mass estimates indicates that recent star formation does not significantly outshine the light from older stellar populations in these systems. Moreover, both the individual components and the systems as a whole lie on the star-forming main sequence, further supporting the conclusion that these mergers have not yet triggered substantial starburst activity. Furthermore, we detect prominent color gradients and disturbed dust distributions in these merging systems, indicating that the mergers have already induced significant internal structural perturbations. These morphological and dust-related changes may facilitate the escape of Ly$\alpha$ photons -- potentially through mechanisms such as gas redistribution or a reduced covering fraction of neutral hydrogen -- thereby playing a key role in shaping the observed properties of LAEs.

Wide-orbit binaries serve as crucial laboratories for understanding stellar evolution and identifying quiescent compact objects. In this work, we search for compact objects in wide-orbit binaries by merging the LAMOST multi-epoch catalogs from LRS and MRS in the 12th data release. We specifically focus on sources with at least 20 observation epochs that clearly exhibit long-term radial velocity (RV) variations while remaining stable over short time scales. By constraining the mass function with Lomb-Scargle periods and RV ranges, we identified 76 single-lined spectroscopic binary candidates harboring potential compact objects with robust orbital solutions. These systems exhibit orbital periods ranging from 10 to 1000 days, with semi-amplitudes of velocity $K_1 \lesssim 50$ km/s and mass functions $f(M_2)$ between 0.05 and 0.6 $M_{\odot}$. Combining $f(M_2)$ with SED-derived stellar parameters, we identify 6 strong compact object candidates with main-sequence companions (Class A), 24 systems likely consisting of either compact objects with giant/subgiant companions or mass-inverted Algol-type binaries (Class B), and 46 candidates with relatively lower mass ratios (Class C). Cross-matching with the Gaia DR3 nss_two_star_orbit catalog yields 16 sources, all of which exhibit orbital solutions consistent with our results. This study demonstrates the essential role of long-term spectroscopic monitoring in searching for compact objects in wide-orbit binaries and validating orbital solutions. The strategy of leveraging extended time baselines will be increasingly effective as spectroscopic databases continue to grow, enabling the systematic discovery of compact objects in wide orbits across the Galaxy.

The large-scale limit or outer scale of turbulence in the solar wind is associated with the correlation length of the magnetic field. Determining correlation lengths from magnetic field time series in magnetic clouds is complicated by the presence of the global flux rope: without removal of the flux rope trend, correlation length measurements will be sensitive to the flux rope as well as the turbulence, and give overestimates of the outer scale when turbulence amplitudes at the outer scale are small relative to the flux rope amplitude. We have used force-free flux rope fits to detrend magnetic field time series measured by Parker Solar Probe in two magnetic clouds and calculated the turbulence correlation length in the clouds using the detrended data. The detrended correlation length in terms of the proton inertial length, $d_p$, was $2.7\times10^{4} d_p$ in one cloud (observed at 0.77 au) and $1.6\times10^{4}d_p$ in the other (observed at 0.39 au), significantly smaller than the values obtained without detrending. Increments in the flux rope fits scaled equivalently to a $k^{-3}$ wavenumber power spectrum; this contribution from the flux rope considerably steepened the total spectrum at the largest scales but had a negligible effect in the inertial range, where scaling in both clouds equivalent to $\sim$$k^{-5/3}$ was observed. Finally, we discuss the possible relation of turbulence correlation lengths to mesoscale structure in magnetic clouds.

Electromagnetic scattering and absorption by material particles is a fundamental physical problem with a broad range of applications, going from laboratory experiments, biology and material sciences, all the way up to environmental studies and astrophysical investigations. In spite of its primary importance, an exact theoretical treatment is only possible for a limited range of ideal cases, while realistic situations require the development of numerical solutions. In the course of the years, several techniques were developed to model the effects of scattering and absorption in more general cases, using approaches such as the Discrete Dipole Approximation (DDA), the Finite Difference Time Domain (FDTD) method, the Transition Matrix formalism (T-matrix) or the Mean Field Theory (MFT). Among these possibilities, the T-matrix approach grants the highest degree of flexibility in modeling aggregates of spherically symmetric particles with arbitrary overall morphology and composition, but its application has been limited by the challenging computational requirements of the method in realistic cases. This paper describes the Nano-Particle Transition Matrix Code project (NP_TMcode), a new implementation of the T-matrix formalism that, taking advantage of high performance parallel hardware architectures, allows the solution of increasingly complex models, while substantially reducing the computing time. The paper describes the code structure, with a particular focus on the algorithm optimization, and it presents the results of the performance analysis for a set of development applications.

By modelling the upper layers of the Sun in terms of a two-layer setup where a free-surface exists within the computational domain, we numerically study the interaction between the surface gravity, or the fundamental ($f$) mode, and the magnetic fields. Earlier such works were idealized in the sense that the static magnetic fields were imposed below the photosphere, i.e., the free-surface, to detect signatures of sub-surface magnetic fields and flows on the $f$-mode. In this work, we perform three-dimensional (3D) numerical simulations where the interior fluid below the photosphere is stirred helically at small scales, thus facilitating an $\alpha^2$-dynamo. This allows us to investigate how these self-consistently generated large-scale magnetic fields influence the properties of the $f$-mode. We find that when the magnetic fields saturate near the equipartition values with the turbulent kinetic energy of the flow, the $f$-mode is significantly perturbed. Compared to the non-magnetic case, or the kinematic phase of the dynamo when fields are too weak, we note that the frequencies and the strengths of the $f$-mode are enhanced in presence of saturated magnetic fields, with these effects being larger at larger wavenumbers. This qualitatively confirms the earlier findings from observational and numerical works which reported the $f$-mode strengthening due to strong sub-surface magnetic fields.

Hyperaccreting stellar-mass black hole systems are leading candidates for the central engines of gamma-ray bursts (GRBs). Their jets are thought to be powered by either the Blandford-Znajek (BZ) process or neutrino-dominated accretion flows (NDAFs), but discriminating between these mechanisms remains challenging. To address this, we propose using the luminosity decay slope (parameter d) of GRB light curves to distinguish between the BZ and NDAF mechanisms, thereby linking the light-curve morphology to the central engine physics. By analysing 85 single-peaked GRBs with fast-rise, exponential-decay (FRED) profiles observed by Swift/BAT using 64 ms background-subtracted light curves, we fit the decay slope (parameter d) with the empirical Kocevski-Ryde-Liang (KRL) function and compare the results with theoretical predictions for the BZ (d approximately 1.67) and the NDAF (d approximately 3.7 to 7.8) mechanisms. We find that the decay slope (parameter d) can differentiate central engine mechanisms, with 15 GRBs consistent with the BZ mechanism and 22 supporting the NDAF mechanism. However, most events exhibit slopes within the range between 2 and 4, suggesting a hybrid of mechanisms, with NDAF being dominant.

The study of multiwavelength flux and spectral variations during rapid flares from blazars provides strong constraints on the physical parameters of the compact emission regions responsible for these still poorly understood events. Although a full description of the continuous and transient emission from blazars seems to require more sophisticated scenarios, particle acceleration and loss mechanisms can be approximately described within the simple leptonic one-zone framework, enabling a systematic study of their impact on the observable properties of multiwavelength flare light curves. Our goal is to identify characteristic signatures in these light curve profiles that permit one to discriminate between the main physical processes situated inside the relativistic jet and commonly invoked to explain blazar flares. The present study exclusively focuses on modeling rapid flares from BL Lac type objects, which can be described within the synchrotron self-Compton (SSC) emission scenario. Combinations of several commonly employed mechanisms to describe the gain and loss of energetic particles in onezone models during flaring events are studied in a systematic way: particle injection; diffusive shock and stochastic acceleration and reacceleration; particle escape; adiabatic losses; radiative losses through synchrotron and inverse-Compton radiation. The current study is limited to the case of "hard-sphere" scattering. A large variety of light curve shapes arises from the different scenarios under study. Characteristic signatures, in particular energy-dependent time delays and differences in the shapes of the rising part of the flare, should allow the distinction to be made between different injection and acceleration scenarios, given the availability of sufficiently high-quality multiwavelength data sets. This is illustrated with a simplified application to a flare event from the blazar Mrk 421.

Galaxy groups are affected by outflows from central Active Galactic Nuclei due to the shallower gravitational potential compared to galaxy clusters. The group binding energy is comparable to the energy output from AGN, making it an important factor in mutual evolution. We present a multi-wavelength analysis of three dynamically active groups: SDSSTG8102, SDSSTG16393, and SDSSTG28674, which are part of the XMM-Newton Group AGN Project X-GAP sample, a statistically complete sample of 49 galaxy groups. We combine uGMRT 400 MHz observations with 144 MHz LOFAR and XMM-Newton observations to study the radio sources associated with the Brightest Group Galaxies (BGGs). The BGGs in SDSSTG8102 and SDSSTG16393 have extended radio emission with asymmetric distortions in their morphologies. SDSSTG28674 has a compact flat-spectrum radio source associated with the BGG and an extended lobe on one side, connected by a faint bridge detected with LOFAR. Integrated spectral indices of the three BGGs are $-0.96\pm0.09$ (SDSSTG8102), $-1.35\pm0.09$ (SDSSTG16393), and $-1.6\pm0.02$ (SDSSTG28674). X-ray images reveal elongated morphologies in all three groups, with SDSSTG28674 showing evidence of a binary merger, while thermodynamical maps highlight temperature variations. In SDSSTG8102, lobes are bent and displaced by IGrM flows, while SDSSTG16393 hosts steep-spectrum relic-like plasma coinciding with X-ray emission. SDSSTG28674, with its ultra-steep spectrum lobe and disturbed morphology, likely traces merger-driven activity, consistent with a remnant or revived radio phoenix. The spectral diversity across the systems reflects different stages of AGN fading governed by duty cycle, source age, and confinement by the hot IGrM.

We present MESS, a fully automated algorithm for identifying and characterizing double-lined spectroscopic binaries (SB2) in large databases of multi-epoch spectra. MESS extends the two-dimensional TODCOR approach to a global multi-epoch formalism, deriving the radial velocities (RVs) of both components at each epoch while optimizing the templates jointly across all observations. Template optimization searches a continuous synthetic-spectra manifold spanning an eight-dimensional parameter space: effective temperature, surface gravity, and rotational broadening for each star, together with a common metallicity and the flux ratio. Single-lined spectroscopic binaries (SB1) and single stars (S1) are handled within the same framework by fitting one optimized template, with either epoch-dependent RVs (SB1) or a single shared RV (S1). Model selection among S1/SB1/SB2 uses the Bayesian information criterion with an effective sample size that accounts for intra-spectrum correlations, and is complemented by the Wilson relation between the two RVs to infer the mass ratio and systemic velocity without a full orbital solution. We validate MESS on 1500 simulated LAMOST MRS systems (SNR=50), with primary RV semi-amplitudes predominantly below the instrumental resolution, achieving an overall classification accuracy of ~95%. We also derive full orbital solutions for two SB2 systems detected in our LAMOST analysis, including a faint-secondary case with flux ratio ~0.1, and present example outputs for one SB1 and three constant-velocity stars. A companion paper will report the survey-wide application to LAMOST DR11 and the resulting SB1/SB2 catalogs.

We present a novel framework to infer the mass of clusters that host hierarchical binary black hole (BBH) mergers detected with gravitational-waves (GWs), on a single event basis. We show that the requirement that a second-generation (2G) remnant be retained, and subsequently undergo a dynamical encounter, places strong constraints on the mass of the cluster. Using a Plummer model as a readily interpretable baseline, we derive analytic scaling relations between the peak of the inferred host mass posterior, the GW-driven recoil velocity of the remnant, and the parameters that determine the structure of the host. We then perform exact numerical marginalization over thermal and recoil velocities, angles, and cluster structure parameters, to infer the host-mass posterior. We apply our framework to putative hierarchical mergers GW241011 and GW241110, and infer the masses of their hosts on a single-event basis. We find that these are consistent with either heavy globular clusters or nuclear star clusters, with inferred masses spanning $10^{5.7 - 7.7} M_{\odot}$ at $68\%$ confidence depending on the 2G recoil velocity distribution used.

The cosmic dipole anomaly, currently detected at a significance exceeding 5$\sigma$ in several independent survey poses a significant challenge to the standard model of cosmology. The Ellis & Baldwin formula provides a theoretical link between the intrinsic dipole anisotropy in the sky distribution of extragalactic light sources and the observer's velocity relative to the cosmic rest frame, under the assumptions that the sources follow a power-law luminosity function and exhibit power-law spectral energy distributions. In this work, we demonstrate that this relation can be generalized to arbitrary luminosity distributions and spectral profiles. We derive the corresponding expression for the effective spectral index and apply it to a sample of quasars observed in the W1 band of the CatWISE survey. We show that the anomalous cosmic dipole persists beyond the power-law assumption. These results provide a more general and robust framework to interpret measurements of the cosmic dipole in future large-scale surveys.

In this paper, we examine the motion of test particles and relativistic accretion mechanisms within the spacetime of a rotating and embedded BH. In this case, the geometric properties of the metric and their dynamical consequences for particle trajectories are systematically studied, with a specific focus on circular orbits together with their existence criteria and stability constraints. Also, the effective potential and the corresponding effective force are constructed to quantify the influence of rotation and embedding parameters on the attractive and repulsive sectors of the gravitational interaction. Closed-form expressions for orbital frequencies as measured by a distant observer are derived, enabling a quantitative analysis of relativistic precession phenomena, including periastron advance and Lense-Thirring precession. Furthermore, we conduct general-relativistic hydrodynamic simulations of BHL accretion onto rotating embedded BHs. In addition, within the framework of the BHL accretion mechanism, the numerical solution of the GRH equations shows that the embedding parameter \alpha systematically modifies the morphology of the shock cone formed around embedded BHs compared to the Kerr model. In particular, a wider opening angle of the cone is produced, the compression of matter in the post-shock region is weakened, and the dynamical variability of the flow is enhanced. The time-dependent mass accretion rate exhibits increasing oscillation amplitudes and long-term variations with increasing \alpha, while these amplitudes are found to be suppressed by the frame-dragging effect associated with the BH spin parameter. At the same time, increasing values of $\alpha$ lead to a strengthening of the QPO frequencies formed around embedded BHs in the LFQPO regime, enhancing their observability and increasing the likelihood of detecting commensurate frequency ratios such as 3:2.

Tree codes that approximate groups of distant particles with multipole expansions are the standard way to accelerate the computation of self-gravity on particles. While momentum-conserving fast multipole methods exist, parallelisation is non-trivial and previous implementations have been limited to self-gravity with fixed softening lengths. We aim for a practical, parallel version of Dehnen's momentum-conserving Cartesian fast multipole method for the computation of the gravitational force in smoothed particle hydrodynamics (SPH) with adaptive gravitational force softening. We parallelise the dual tree walk by replicating the node-node interaction on the parents of each leaf node in the tree. While this duplicates work, it greatly simplifies the parallelisation and can be implemented with relatively minor changes from the previous non-conservative force algorithm in Phantom. We also adapt the tree opening criterion for adaptive softening lengths, such that all interactions within the softening kernel are handled pairwise (as in SPH) rather than with multipole expansions, also allowing the gravity calculation to be performed alongside the SPH force evaluation. We demonstrate that the new code conserves linear momentum to machine precision while giving similar force accuracy and computational performance to the previous (non-symmetric) fast multipole method in Phantom . The new method also gives better conservation of the angular momentum and orbital phase in a binary polytrope evolution. The symmetric fast multipole method is now the default for computing self-gravity in the public code.

Radio observations offer a dust-independent probe of star formation and active galactic nucleus (AGN) activity, but sufficiently deep data are required to access the crossover luminosity between these processes at high redshift ($z>4.5$). We present three spectroscopically confirmed high-redshift radio sources (HzRSs) detected at 1.3 GHz at $z=4.9$-$5.6$, with radio luminosities spanning $L_{\rm 1.3 \, GHz}\approx2$-$5\times10^{24} \, \rm W \, Hz^{-1}$. These sources were first identified as high-redshift candidates through spectral energy distribution (SED) fitting of archival Hubble, JWST NIRCam+MIRI, and ground-based photometry, and then spectroscopically confirmed via the $\rm H\,\alpha$ emission line using wide-field slitless spectroscopy from JWST COSMOS-3D. The star formation rates (SFRs) measured from SED fitting, the $\rm H\,\alpha$ flux, and the 1.3 GHz luminosity, span $\sim100$-$1800\, M_{\odot} \, \rm yr^{-1}$, demonstrating broad agreement between these SFR tracers. We find that these three sources lie either on or $0.5$-1.0 dex above the star-forming main sequence at $z=4$-6 and have undergone a recent burst of star formation. The sources have extended rest-UV/optical morphologies with no evidence for a dominant point source component, indicating that an AGN is unlikely to dominate their rest-UV and optical emission. Two of the sources have complex, multi-component rest-frame UV/optical morphologies, suggesting that their starbursts may be triggered by merging activity. These HzRSs open up a new window towards probing radio emission powered by star formation alone at $z> 4.5$, representing a remarkable opportunity to begin tracing star formation, independent of dust, in the early Universe.

Bayesian imaging inverse problems in astrophysics and cosmology remain challenging, particularly in low-data regimes, due to complex forward operators and the frequent lack of well-motivated priors for non-Gaussian signals. In this paper, we introduce a Bayesian approach that addresses these difficulties by relying on a low-dimensional representation of physical fields built from Scattering Transform statistics. This representation enables inference to be performed in a compact model space, where we recover a posterior distribution over signal models that are consistent with the observed data. We propose an iterative adaptive algorithm to efficiently approximate this posterior distribution. We apply our method to a large-scale structure column density field from the Quijote simulations, using a realistic instrumental forward operator. We demonstrate both accurate statistical inference and deterministic signal reconstruction from a single contaminated image, without relying on any external prior distribution for the field of interest. These results demonstrate that Scattering Transform statistics provide an effective representation for solving complex imaging inverse problems in challenging low-data regimes. Our approach opens the way to new applications for non-Gaussian astrophysical and cosmological signals for which little or no prior modeling is available.

We present a comprehensive analysis of the photometric variability of (presumably single) nitrogen-rich Wolf-Rayet (WN) stars in the Magellanic Clouds, using long-term observations from the OGLE survey. Our sample comprises 47 stars with no nearby Gaia counterparts. We characterize both overall and short-term variabilities, examining data dispersion and identifying periodicities. To validate our findings, we also compare the OGLE light curves with data from the MACHO and TESS missions. Variability is ubiquitous in our WR sample: about one third of stars display high variability, or four fifths if we include cases with moderate variations. The observed changes are found to be periodic in 11 cases, with timescales of 2-56 d. Such periodic variations originate in corotating wind structures, binary effects, or pulsations, thereby increasing the number of systems known to show these phenomena. Surprisingly, nine targets display (quasi-periodic) outbursts, making such changes a new type of WR variability. The variability shows a transient character, in about 30$\%$ of the sample, with changing amplitudes for periodic signals or for outbursts (they even sometimes completely disappear from view). Finally, we identified six long-period variables, four of which have been confirmed by at least two independent surveys.

We present updated microlensing analysis results based on high-cadence ($\sim$2~min) Subaru Hyper Suprime-Cam (HSC) observations of the Andromeda Galaxy (M31) in 2014, 2017, and 2020, yielding a total of 39.3 hours of data. We use a point-lens finite-source model for the microlensing light curve model and employ multi-stage selection procedures to identify microlensing candidates. From more than 25,000 variable candidates detected across all nights, we identify 12 microlensing candidates with light-curve timescales shorter than 5~hours, and among them, 4 secure candidates with high-significance detections. We estimate detection efficiencies using light-curve-level simulations that account for observational conditions and finite-source effects. Using a hierarchical Bayesian framework that combines the light-curve fitting information for each candidate with the Poisson statistics of the number of candidates, we derive constraints on parameters that characterize the abundance and mass scale of primordial black hole (PBH) dark matter. First, we derive upper limits on the PBH abundance under the null hypothesis that all events are assumed to be false detections. Next, employing the PBH hypothesis in which all (or only secure) candidates are assumed to be due to PBH microlensing, we derive the allowed region of the PBH parameters; the inferred mass scale is $M_{\rm PBH}\sim10^{-7}$--$10^{-6}M_\odot$, and the PBH abundance to the total dark matter is $f_{\rm PBH}\sim \mathcal{O}(10^{-2}{\rm -}10^{-1})$. Our results demonstrate that HSC-M31 monitoring remains a uniquely powerful probe of PBHs, and highlight the need for further studies for example, using Rubin Observatory LSST observations of the Large Magellanic Cloud.

Understanding how galaxies trace the underlying matter density field is essential for characterizing the influence of the large-scale structure on galaxy formation, being therefore a key ingredient in observational cosmology. This connection, commonly described through the galaxy bias, $b$, can be studied effectively using machine learning (ML) techniques, which offer strong predictive capabilities and can capture non-linear relationships. We aim to incorporate the linear bias parameter assigned to individual galaxies into a ML framework, quantify its dependence on various halo and environmental properties, and evaluate whether different algorithms can accurately predict this parameter and reproduce the scatter in several bias relations. We use data from the IllustrisTNG300 simulation, including the distance to different cosmic-web structures computed with DisPerSE. These data are complemented with an object-by-object estimator of the large-scale linear bias ($b_i$), providing the individual contribution of each galaxy to the bias of the entire population. Our ML framework uses three models to predict $b_i$: a Random Forest Regressor, a Neural Network and a probabilistic method (Normalizing Flows). We recover the full hierarchy of galaxy bias dependencies, showing that the most informative features are the overdensities, particularly $\delta_8$, followed by the distances to cosmic-web structures and selected internal halo properties, most notably $z_{1/2}$. We also demonstrate that Normalizing Flows clearly outperform deterministic methods in predicting galaxy bias, including its joint distributions with galaxy properties, owing to their ability to capture the intrinsic variance associated with the stochastic nature of the matter-halo-galaxy connection. Our ML framework provides a foundation for future efforts to measure individual bias with upcoming spectroscopic surveys.

Sub-Neptunes with hydrogen-rich envelopes are expected to sustain long-lived magma oceans that continuously exchange volatiles with their overlying atmospheres. Capturing these interactions is key to understanding the chemical evolution and present-day diversity of sub-Neptunes, super-Earths, and terrestrial planets, particularly in light of new JWST observations and upcoming missions. Recent advances in both geochemistry and astrophysics now allow the integration of experimental constraints and thermodynamic models across melt, metal, and gas phases. Here we extend a global chemical equilibrium model to include non-ideal behavior in all three phases. Our framework combines fugacity corrections for gas species with activity coefficients for silicate and metal species, enabling a fully coupled description of volatile partitioning. We show that for planetary embryos (0.5 M$_\oplus$ at 2350 K), non-ideality introduces only modest corrections to atmosphere-magma ocean interface (AMOI) pressures, volatile inventories, and interior compositions. In contrast, for sub-Neptunes with higher temperatures ($\approx$ 3000 K) and pressures, non-ideal effects are more pronounced, though still modest in absolute terms$-$typically within 20% and at most a factor of two. Including activity and fugacity coefficients simultaneously increases the AMOI pressure, enhances water retention in the mantle and the envelope. Our results demonstrate that non-ideality must be treated globally: applying corrections to only one phase leads to incomplete or even misleading trends. These findings highlight the importance of self-consistent global thermodynamic treatments for interpreting atmospheric spectra and interior structures of sub-Neptunes and super-Earths.

Recent results from combined cosmological probes indicate that the Dark Energy component of the Universe could be dynamical. The simplest explanation envisages the presence of a quintessence field rolling into a potential, where the Dark Energy energy density parameter $\Omega_{DE}=\Omega_{\Lambda}+\Omega_{x}$ results from the contribution of the ground state energy $\Omega_{\Lambda}$ and the scalar field energy $\Omega_{x}$. Provided that $\Omega_{DE}\approx 0.7$, negative values of $\Omega_{\Lambda}$ can be consistent with current measurements from cosmological probes, and could help in explaining the large abundance of bright galaxies observed by JWST at $z> 10$, largely exceeding the pre-JWST expectations in a $\Lambda CDM$ Universe. Here we explore to what extent such a scenario can account also for the early presence of massive Black Holes (BHs) with masses $M_{BH}\gtrsim 10^7\,M_{\odot}$ observed at $z\gtrsim 8$, and for the large over-abundance of AGN with respect to pre-JWST expectations. Our aim is not to provide a detailed description of BH growth, but rather to compute the maximal BH growth that can occur in cosmological models with negative $\Omega_{\Lambda}$ under the simple assumption of Eddington-limited accretion onto initial light Black Hole seeds with mass $M_{seed}\sim 10^2\,M_{\odot}$ originated from PopIII stars. To this aim we develop a simple analytic framework to connect the growth of dark matter halos to the maximal growth of BHs within the above assumptions. We show such models can account for present observations assuming values of $\Omega_{\Lambda}\approx -1$, simultaneously boosting both galaxy and AGN number counts without invoking any additional physics. This would allow us to trace the observed excess of bright and massive galaxies and the early formation of massive Black Holes and the abundance of AGN to the same cosmological origin.

We present deep, medium-resolution $\lambda=1-5\,\mu$m JWST/NIRSpec spectroscopy for 14 quiescent galaxies at $3<z<5$ with $\log_{10}(M_*/\mathrm{M_\odot}){\,>\,}10$, obtained as part of the EXCELS survey. We perform a complete re-reduction of these data, including a custom optimal-extraction approach to combat the spectral "wiggles" that result from undersampling of the NIRSpec spatial PSF. We constrain the star-formation histories and stellar metallicities of these objects via full-spectral fitting, finding a clear stellar age vs stellar mass correlation, in which more massive galaxies assembled their stellar mass at earlier times. This confirms spectroscopically that the archaeological "downsizing" trend was already in place by $z\simeq4$. The slope of our measured relation ($\simeq1.5$ Gyr per dex in stellar mass) is consistent with literature results at $0 < z < 3$. We do not observe objects with $\log_{10}(M_*/\mathrm{M_\odot})\lesssim10.5$ and ages of more than a few hundred Myr at this epoch, suggesting that recently reported examples of higher-redshift quiescent galaxies at these masses are likely to soon rejuvenate. We measure relatively high stellar metallicities for the majority of our sample, consistent with similar objects at $0 < z < 3$. Finally, we explore evidence for $\alpha$-enhancement in six older and more luminous galaxies within our sample, finding considerable disagreements in the chemical abundances measured using different stellar population models, different fitted rest-frame wavelength ranges, star-formation history models and fitting codes. We therefore conclude that inferring detailed stellar chemical abundances for the earliest quiescent galaxies remains challenging, and higher signal-to-noise spectra are required (SNR per resolution element $>100$ for $R\simeq1000$).

We conducted a timing analysis of over 18 years of data on the young ($\tau_{\rm c} = 112$ kyr, $P = 114$\,ms) relativistic binary PSR~J1906+0746, using six radio telescopes: Arecibo, FAST, Green Bank, Lovell, MeerKAT, and Nançay. This pulsar is known to orbit a compact high-mass companion with a period of 3.98\,hrs in a mildly eccentric orbit ($e = 0.085$). By combining all data and maintaining a coherent timing solution over the full span, we obtained a more precise measurement of the advance of periastron, $\dot{\omega} = 7.5841(2)$\,$°$\,yr$^{-1}$, the Einstein delay, $\gamma = 4.59(2) \times 10^{-4}$\,s, and the secular change in orbital period, $\dot{P}_{\rm b} = -5.65(2) \times 10^{-13}$\,s\,s$^{-1}$. Assuming the validity of general relativity, we obtain a total mass of 2.6133(1)\,$M_{\odot}$ and component masses of 1.316(5) $M_{\odot}$ for the pulsar and 1.297(5) $M_{\odot}$ for the companion, consistent with a double neutron star system. However, when fitting for the secular change in the projected semi-major axis we obtain $\dot{x} = -1.8(6) \times 10^{-13}$\,s\,s$^{-1}$, the component masses are shifted by $\sim 3.5\sigma$, which is expected from the correlation of $\dot{x}$ and $\gamma$. The $\dot{x}$ has a similar magnitude to that observed in PSR~J1141$-$6545, which is due to spin-orbit coupling; if confirmed, it would indicate that, as in the latter system, the companion of the PSR~J1906+0746 system is a massive fast-rotating white dwarf formed before the pulsar. Additionally, we report and characterize a large glitch near MJD 56664, with a fractional frequency increase comparable to those observed in the Vela pulsar.

Winds launched at the scale of the accretion disc or dusty torus in Active Galactic Nuclei (AGN) are thought to drive energy-conserving outflows that shape galaxy evolution. The key signature of such outflows, the presence of a hot ($T \gtrsim 10^9 \, \rm K$), shocked wind component, is hard to detect directly. Observations of AGN outflows typically probe a separate outflow phase: cool/warm gas with $T \lesssim 10^5 \, \rm K$. Here, we show that the density of cool outflowing gas scales with AGN luminosity, serving as an indirect diagnostic of the elusive hot, shocked wind. We use hydrodynamic simulations with the moving-mesh code AREPO to target the interaction between a small-scale AGN wind of speed $\approx 10^4 \, \rm km \, s^{-1}$ and galactic discs containing an idealised, clumpy interstellar medium (ISM). Through a new refinement scheme targeting rapidly-cooling, fast-moving gas, our simulations reach a resolution of $\lesssim 0.1 \, \rm pc$ in the cool, outflowing phase. We extract an ensemble of cool clouds from the AGN-driven outflows produced in our simulations, finding that their densities increase systematically with AGN wind power and AGN luminosity. Moreover, the mass distribution and internal properties of these cloudlets appear to be insensitive to the initial properties of the ISM, and shaped mainly by the dynamics of radiative, turbulent mixing layers. The increase in cool outflow density with kinetic wind power and AGN luminosity has profound implications for observational estimates of outflow rates and their scaling with AGN luminosity. Depending on the available outflow and density tracers, observationally-derived outflow rates may be overestimated by orders of magnitude.

We evaluate the capability of current and next-generation gravitational wave detectors, such as Advanced LIGO, Einstein Telescope and DECIGO, to constrain cosmographic parameters using electromagnetically bright standard sirens. By adopting a third-order Taylor expansion, we analyze how signal-to-noise ratios and the number of events impact the estimates of the Hubble constant ($H_0$), the deceleration ($q_0$) and jerk ($j_0$) parameters. Our results show that while Advanced LIGO provides a calibration-free measurement of $H_0$ at the few-percent level, it remains insensitive to higher-order parameters. In contrast, the Einstein Telescope and DECIGO reach sub-percent accuracy for $H_0$. Notably, DECIGO achieves a precision better than 10\% for the deceleration parameter $q_0$ and a few tens of percent for the jerk parameter $j_0$.

We explore the consequences of allowing non-Hermitian structures in quantum cosmology by extending the Wheeler DeWitt framework beyond strictly Hermitian dynamics. Using a controlled semiclassical reduction, we show how anti Hermitian contributions propagate into both early universe primordial fluctuations and late-time structure growth as effective damping or gain terms. Confronting this framework with inflationary observables, growth of structure and the observed near flatness of the universe, we derive strong infrared constraints that suppress non Hermiticity across cosmic history. We demonstrate that these bounds are mutually consistent between early and late-time probes and can be partially relaxed in theories beyond General Relativity. Our results establish cosmology as a novel arena for testing foundational aspects of quantum mechanics and suggest that Hermiticity may emerge dynamically along the semiclassical branch describing our universe.

Studying the cross-correlation function between the soft and hard X-ray emission in Neutron Star Low Mass X-ray Binaries provides crucial insight into the structure and dynamics of the innermost accretion regions. In this work, we investigate the CCF of the Z-source GX 349+2 using an XMM-Newton observation. We noted that asymmetric CCFs with lags of a few hundred secondsbetween soft and hard band LCs in the horizontal branch, whereas CCFs remained symmetric in normal and flaring branches. We also performed a CCF study during the flux transition duration and observed lags of the order of a few tens to hundreds of seconds. Monte Carlo simulations were performed to assess the robustness of these CCFs, confirming their significance at a 95% confidence level. Spectral analysis during the flux transitions further suggests that the inner accretion disk extends close to the last stable orbit. We propose that the observed hard lags arise from the readjustment of the boundary layer/coronal region located near the inner edge of the accretion disk. From the measured lags, we estimate the characteristic size of the boundary layer. We show that the observed lags could also be associated with the depletion timescale of the boundary layer with low viscosity.

Wide-field images made by radio interferometers are invariably affected by direction-dependent systematic effects such as the ionosphere or the beam pattern. Calibration along a set of discrete directions in the sky is the default technique to estimate and correct these systematic errors. However, additional processing such as smoothing and mosaicing are required to reconcile the step wise variation of the estimated systematic errors at the edges of the discrete directions (facets). We overcome the discrete nature of direction-dependent calibration by using image-domain gridding as the model for the calibration. Instead of discrete directions in the sky, calibration is performed using a basis that represents a set of sub-grids in the Fourier space. This automatically removes the need for extra operations to recover the wide-field systematics error model without any discontinuity. We provide results based on LOFAR data where we compare the traditional facet-based (discrete directional gains) calibration with the proposed approach. The comparison shows improved image quality, mainly because of the physical plausibility of the proposed approach as opposed to using a piecewise constant model for direction-dependent systematic errors.

We test claims of large-scale anisotropy in the local expansion rate using cluster scaling relations as distance indicators. Using a Bayesian forward model, we jointly fit the X-ray luminosity--temperature (LT) and thermal Sunyaev-Zel'dovich--temperature (YT) relations, marginalising over the latent cluster distances and modelling selection effects as well as peculiar velocities. The latter are modelled using reconstructions of the local peculiar velocity field where we self-consistently account for possible anisotropic redshift--distance relations via an approximate scheme. This treatment proves crucial to the inferred anisotropy and breaks the degeneracy between anisotropy in scaling relation normalisations and underlying cosmological anisotropy. We apply our method to 312 clusters at $z \lesssim 0.2$, testing dipolar, quadrupolar and general (pixelised) anisotropy models. Bayesian model selection finds no more than weak evidence for any anisotropic model. For dipole models, we obtain upper limits of $\delta H_0 / H_0 < 3.2\%$ and bulk flow magnitude $< 1300\,\mathrm{km\,s^{-1}}$. Our results contrast with previous claims of statistically significant anisotropy from the same data, which we attribute to our principled forward modelling of both redshifts and scaling relation observables through latent distances and our treatment of the impact of anisotropic redshift--distance relations when modelling the local peculiar velocity field. Our work highlights the importance of accurately modelling peculiar velocities when testing isotropy with distance indicators, and motivates the further development of reconstructions that self-consistently treat large-scale deviations from the Hubble flow.

The impact of the most recent cosmic microwave background (CMB) data from the Atacama Cosmology Telescope (ACT) is studied for a model of cosmic inflation which predicts a non-zero vacuum expectation value (VEV) $M$ for a large-field regime. Since lower values of $M$ are compatible with the higher spectral index $n_s$ provided by the ACT+Planck joint analysis, we establish new limits on this parameter while also considering further CMB data from the latest BICEP/Keck Array release for CMB polarization modes. We find $\log_{10}M/M_{Pl}=-2.5^{+1.1}_{-1.3}$ at 68\% confidence level, compatible with $M/M_{Pl}\simeq 0.003$, which is interesting for post-inflationary processes, such as preheating. We conduct a lattice simulation for the inflaton field for the first few e-folds, as the model is compatible with the production of relics such as oscillons, which are possible candidates as sources of gravitational waves and primordial black holes. We find that the model indeed produces localized, quasi-spherical structures compatible with oscillons, which might lead to signatures detectable by future experiments. However, in agreement with recent works, we find that although the abundance of gravitational waves that could be generated in this regime has an amplitude well within the sensitivities of these detectors, the frequency range is on the GHz limit, away from the expected frequencies. Finally, we estimate the impact of a coupling of the type $y\phi\sigma^2$ to the inflaton, in the realization of perturbative reheating, directly impacting the predictions of the model, as lower values of $M$ are consistent with both the entire allowed temperature range, and the limits imposed by BICEP/Keck Array+Planck+ACT.

A newly born neutron star is expected to exhibit significant deviations from spherical symmetry, which decay with time. Determining how much deformation remains at present is crucial for gravitational-wave astronomy. This study is the first investigation into the evolution of quadrupole deformation during the solid crust formation phase to obtain a plausible value at present. The equilibrium structure before solidification is modeled using a fluid description, and the deformation is introduced through an assumed driving force. As the star cools, this force weakens, leading to a gradual decay of the deformation. Eventually, the deformation vanishes in the fluid region but partially remains in the crust, sustained by elastic forces, after solidification. By comparing the equilibrium models before and after solidification, we estimate the residual ellipticity and demonstrate that the spatial profile of the elastic shear is imprinted in the crust. The relic ellipticity is only a few percent of the original value, with its absolute magnitude depending on the deformation mechanism during the hot era, which cannot be specified owing to the lack of elaborate models. This work provides a first step toward linking early neutron star deformation with future gravitational-wave observations.

Tidal interaction is a unique, detectable signature in gravitational wave signals from inspiraling binary neutron stars (BNSs), which can be used to constrain the neutron star (NS) equation of state (EoS). The tidal interaction is resonantly amplified as the orbital frequency approaches the NS fundamental mode (f-mode) frequency. It has been shown that the exclusion of tidal resonance in parameter estimation leads to a significant bias in the inferred NS tidal deformability and hence the NS EoS [Pratten et al. PRL 129, 081102 (2022)]. The strength and location of tidal resonance depend sensitively on the f-mode frequency, which is typically modeled using its universal relation with the tidal deformability that is derived for an isolated, non-spinning NS assuming only linear fluid perturbations. In a BNS inspiral, the f-mode frequency can be corrected by at least three known effects: nonlinear hydrodynamics, background spin, and relativity. We use Hamiltonian Monte Carlo simulations to estimate the systematic bias on tidal deformability when each frequency correction is ignored. Our study considers both loud, individual events and the stacking of a population of detections. Both scenarios are expected when the next-generation detectors are available with a sensitivity level increased by about an order of magnitude.

Searches for late--time gravitational--wave echoes following compact binary mergers are often interpreted as probes of exotic near--horizon or horizonless physics. We show that a well--motivated class of ultraviolet--finite quantum gravity and modified gravity theories, those based on diffeomorphism--invariant, analytic, entire--function nonlocality, generically suppress observable echo signals. The suppression follows from Paley--Wiener bounds associated with the analyticity of the nonlocal regulator, which enforce exponential damping of high--frequency reflection amplitudes and smear sharp effective potentials in the black--hole interior. We demonstrate that for regular black holes with horizons, the standard ingoing boundary condition eliminates the cavity required for echoes, while for regular horizonless compact objects the nonlocal kernel strongly attenuates both inner and photon--sphere reflections. As a result, repeated reflections during the ringdown phase are exponentially suppressed in frequency space and washed out in the time domain. Our results imply that the absence of echoes in current gravitational--wave data is consistent with covariant nonlocal gravity theories and does not, by itself, favor classical horizons over regular or horizonless ultraviolet completions. The analyticity and Paley--Wiener bounds that enforce echo suppression are required to ensure unitarity, ghost freedom, and ultraviolet finiteness of the underlying quantum theory. As a result, the classical ringdown phenomenology already encodes quantum--gravity consistency conditions. We emphasize that the absence of echoes in such theories does not rely on quantum decoherence or stochastic effects, but instead reflects the analytic structure imposed by quantum gravity on the classical limit.

We analyze in some detail the years leading up to Albert Einstein's visit to Argentina, from the moment he rose to fame after the publication of the results of the 1919 solar eclipse, until his arrival at the port of Buenos Aires in March 1925. We will see that this major event in the country's cultural life did not arise from a vacuum but was the product of diverse interests and unique international and local circumstances. The social and political situation surrounding the eminent scientist and the impetus provided by individuals and institutions in Buenos Aires played a decisive role, ultimately converging in the "successful" reception of this extraordinary figure in a country on the scientific periphery of the first quarter of the 20th century. We also review the written references and knowledge circulating in the local milieu on topics related to the theory of relativity in the years prior to his arrival in the country.

Ending the inflation by vacuum decay is considered infeasible due to the graceful exit problem. Even if considering an alternative field other than the inflaton to realize a first-order phase transition (FoPT) during inflation, it is usually challenging for concrete model building, as bubble nucleations might not be fast and dense enough to successfully end the inflation. In this work, we propose a FoPT at the grand-unification-theory (GUT) scale within the Starobinsky inflation. The key construction is an exponentially evolving potential barrier dynamically controlled by the rolling inflaton, so that almost no bubble is nucleated during the early inflationary era, but with massive bubble nucleations near the end of inflation. With lattice numerical simulations, we have successfully tested this GUT-FoPT during Starobinsky inflation, and the resulting gravitational-wave energy density spectrum reproduces previous analytical estimation with a distinctive oscillation feature at high frequencies.

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

We formulate within Palatini Supergravity a model of induced-gravity inflation excellently consistent with ACT DR6. The inflaton belongs in the decomposition of a conjugate pair of Higgs superfields which lead to the spontaneous breaking of a U(1)B-L symmetry at a scale close to the range (0.102-5.85)x10^16 GeV. The inflaton field is canonically normalized thanks to a real and shift-symmetric contribution into the Kaehler potential. It also includes two separate holomorphic and antiholomorphic logarithmic terms, the argument of which can be interpreted as the coupling of the inflaton to the Ricci scalar. The attainment of inflation allows for subplanckian inflaton values and energy scales below the cut-off scale of the corresponding effective theory. Embedding the model in a B-L extension of the MSSM we show how the mu parameter can be generated and non-thermal leptogenesis can be successfully realized. An outcome of our scheme is split SUSY with gravitino mass in the range (40-60) PeV, which is consistent with the results of LHC on the Higgs boson mass.

The present study investigates the linear stability of Riemann ellipsoids in both the inviscid limit and in the presence of weak viscosity. In the inviscid regime, we derive a generalised Poincare equation governing small fluid oscillations and construct a family of polynomial solutions that extends the classical results of Cartan to flows with a uniform strain field. This formulation provides an analytic dispersion relation for three-dimensional ellipsoidal disturbances and remains computationally efficient at arbitrary harmonic degree, in contrast to the virial tensor method or to short-wavelength (WKB) approximations. The viscous effects are incorporated through a boundary-layer analysis based on Prandtls theory, leading to first-order viscous corrections to the inviscid spectrum and allowing a systematic investigation of viscosity-driven instabilities. Stability diagrams are presented over the space of admissible Riemann ellipsoids, illustrating the roles of rotation, internal strain, and diffusion, with implications for rotating shear flows in geophysical and astrophysical contexts.

We investigate the impact of a nonstandard electron mass $m_e$ on early-Universe thermal history, focusing on neutrino decoupling and Big Bang Nucleosynthesis (BBN). In the standard cosmology, neutrino--electron interactions keep neutrinos in thermal contact with the electromagnetic plasma until shortly before $e^\pm$ annihilation. Varying $m_e$ shifts the decoupling epoch and the entropy transfer from $e^\pm$ annihilation, thereby modifying the neutrino energy density and the inferred effective number of relativistic species, $N_{\mathrm{eff}}$. Independently, during BBN the rates of charged-current weak processes, and hence the neutron-to-proton ratio, depend on $m_e$. By confronting BBN predictions for the primordial light-element abundances with observations and imposing cosmological constraints on $N_{\mathrm{eff}}$, we obtain a bound on $m_e$ in the early Universe of $m_e = 0.504^{+0.007}_{-0.006}$ MeV or $m_e=0.510\pm0.007$ MeV ($1\sigma$), depending on the considered nuclear reaction network (NACRE II or PRIMAT, respectively). The allowed range is close to the present laboratory value at the level of 1.4\%, thus supporting the constancy of the electron mass over cosmological timescales.

Finite nuclei constrain the dense-matter equation of state (EOS), yet they are self-bound quantum droplets far from the thermodynamic limit. Motivated by an analogy to quantum dots, we show that the nuclear chart nevertheless defines a mesoscopic regime in which mesoscopic chemical-potential analogs $\{\mu_B,\mu_Q,\mu_S\}$ can be extracted directly from nuclear and hypernuclear binding energies after consistent Coulomb subtraction. These are discrete finite-difference response functions -- local slopes of the strong-interaction energy landscape -- not equilibrium grand-canonical chemical potentials. The nuclear chart itself supplies an "ensemble of nearby droplets": finite differences across neighboring nuclei suppress shell- and pairing-scale oscillations while retaining the smooth bulk trend, producing robust slopes without a macroscopic limit. Thus, the data provide empirical local derivatives that any strangeness-enabled EOS must reproduce near saturation. Mapping the measured (hyper)nuclear landscape at $T\simeq 0$, we find smooth, numerically stable responses, including a large, negative strangeness chemical-potential analog, and we identify specific hypernuclear measurements that can directly test and sharpen these EOS constraints.

This document summarizes talks and discussions from the workshop "deci-Hz Gravitational Wave Observations on the Moon and Beyond" that took place at Johns Hopkins University between September 1 and September 3, 2025. The workshop focused on experimental proposals to observe gravitational waves in the deci-Hz band, including lunar detectors, laser interferometers in space, and atom interferometry; gravitational wave sources in the deci-Hz frequency band; and the multi-messenger and multi-band astronomy that would be enabled by these observations.