Papers for Friday, May 29 2026

The martian atmosphere hosts dynamical phenomena ranging from planet-encircling dust storms to mesoscale orographic clouds and nocturnal low-level jets. General circulation model show capability to simulate these phenomena, but is computationally expensive at resolution needed to resolve mesoscale features. While assimilation of satellite remote sensing observation enable forecasting capabilities using such models, observation record is often sparse, short and fragmented across instrument generators. These constraints motivate the development of a data-driven foundation model for the Martian atmosphere. Foundation models live in a complex design landscape. There is an interplay between the available data, the physics of the underlying processes and corresponding developments in AI. Even though the idea of a foundation model is to address multiple use cases in a data- and compute-efficient manner, it is important to have a clear picture what applications can sensibly addressed by a single model. The purpose of this paper is to elucidate this design landscape. We discuss available data ranging from atmospheric retrievals to reanalysis datasets as well as existing physical models. Moreover, we identify a wide range of candidate downstream applications. Finally, we consider relevant recent developments in artificial intelligence (AI) that can be leveraged in this context. Here, we put a particular emphasis on AI models for atmospheric physics, data-driven approaches to data assimilation as well as methods to work in a limited data setting.

The four principal energy conditions (ECs) in general relativity prohibit negative energies, repulsive gravity and superluminal energy flows. One must invoke exotic matter to violate any one of these, yet $\Lambda$CDM does so quite prominently during inflation and in the epoch of dark energy dominance. In this paper, we carry out model selection between the standard model and the $R_{\rm h}=ct$ universe using a combination of HII galaxy and cosmic chronometer measurements in the local Universe, and directly compare the results to the constraints imposed by the ECs. We find that the latter cosmology is not only strongly favored by these data, with a likelihood of $\sim 92\%$ versus only $\sim 8\%$ for the former, but that its optimized fit is fully compliant with all four ECs, while $\Lambda$CDM's best fit violates the so-called strong energy condition at $z\lesssim 2$.

We report a comparison of two state-of-the-art agentic AI systems, Claude Code (Anthropic) and Codex (OpenAI), tasked with autonomously executing a simple end-to-end gravitational wave data analysis pipeline on a shared computing infrastructure without human intervention. The pipeline comprises power spectral density estimation from raw Einstein Telescope simulated noise, geometric template bank generation, matched filter recovery of 100 binary black hole signal injections, automated results generation, and large language model-assisted production of a manuscript formatted in the style of Physical Review D. Both agents received identical written specifications and identical compute resources. The experiment was run twice: a first run with unrealistically loud injections, and a second run with signals rescaled to a physically motivated SNR range. The scientific results converged in both runs. However, the agents exhibited substantially different behaviors and computational costs: Claude Code completed the pipeline in ~3.4 minutes with silent deviations from the specification, while Codex required ~16 minutes across explicit self-correcting restarts, including an unsolicited performance optimization of the matched filter inner loop. The autonomously generated manuscripts also diverged in length, details, and quality. In the second run, a subtle difference in the interpretation of the SNR range instruction led to a genuine scientific divergence: Claude Code silently reinterpreted the instructions, while Codex followed the specification literally. We discuss the implications of these behavioral differences, such as speed versus auditability, silent versus transparent error handling, instruction interpretation, and the criticality of intermediate data representations in multi-model pipelines, for the deployment of agentic AI in scientific computing workflows.

The interplay between star formation and supermassive black-hole growth is central to galaxy evolution, but how host-galaxy morphology regulates star-formation enhancement and AGN triggering across the star-forming main sequence remains unclear. We investigate the star-formation properties and incidence of X-ray AGN across the star-forming main sequence using the DESI-eRASS1 dataset, focusing on host structure. Our analysis includes 1171 X-ray selected AGN and 45374 non-AGN star-forming galaxies at $z\le1.5$. We quantify star formation in AGN hosts relative to matched control samples using ${\rm SFR}_{norm}$ and examine its dependence on X-ray luminosity ($L_X$) and specific accretion rate ($\lambda_{sBHAR}$). We measure AGN incidence as a function of distance from the star-forming main sequence ($\Delta_{\rm MS}$), separating disk- and spheroid-dominated systems based on Sersic index. ${\rm SFR}_{norm}$ remains close to unity at low to intermediate $L_X$ and increases at higher luminosities, with the transition shifting toward higher $L_X$ in more massive systems. This trend depends on morphology: in the stellar-mass range $10.5\le\log(M_\star/M_\odot)<11.5$, disk-dominated AGN hosts exhibit enhanced ${\rm SFR}_{norm}$ at moderate $L_X$, while spheroid-dominated systems remain consistent with unity. No comparable morphology dependence is found when using $\lambda_{sBHAR}$. The incidence of X-ray AGN increases strongly with $\Delta_{\rm MS}$ in both redshift bins, with a steeper dependence at higher redshift. The $\Delta_{\rm MS}$-incidence relation is also morphology-dependent and evolves with redshift. The connection between star formation and AGN activity is governed by global gas availability but modulated by host-galaxy structure and cosmic epoch. Absolute AGN power is more tightly linked to host-wide star formation than accretion efficiency normalised by stellar mass.

In the era of large-scale photometric surveys, scalable and robust methods for classifying supernova (SN) populations are increasingly necessary. Often, spectroscopy is essential in addition to photometry to reliably classify SNe; however, complete spectroscopic follow-up is infeasible for all of the millions of transient light curves being collected by facilities such as the Vera C. Rubin Observatory. Using light curves of SNe Ia and Ibc observed with the Zwicky Transient Facility, we frame the classification of large SN populations as a mixing problem. We fit all objects using a semi-analytical SN model powered by radioactive decay, and we model the resulting distributions of fit parameters with a Gaussian Mixture model to optimize the shared population mixing fraction. This approach allows us to reliably constrain the ratio of the populations and classify SNe Ia and Ibc with $\geq$ 90% accuracy without any need for labeled training data, i.e., a spectroscopic dataset. We validate this method for varying population mixing fractions and explore the impact of including spectroscopic, photometric, or no redshift information, and a small amount of known labels. Overall, this method allows for fast and accurate SN classification and population characterization using only photometry.

The primary goal of the Ariel space telescope is to conduct the biggest spectroscopic survey of transiting exoplanets to characterize their atmospheres and weather. We propose to extend the Ariel survey to another domain of alien atmospheres - rogue planets and free-floating brown dwarfs. Their isolated nature means the observations are uncontaminated by light from a host star, and their short rotation periods, often similar to hot Jupiter orbital periods, provide an opportunity to study time-varying meteorology. Phase curve observations would especially help scientists understand atmospheric dynamics at the L/T transition, where multiple cloud species at different altitudes influence the time-varying spectra of brown dwarfs. Inferring timescales and length scales of these atmospheric features is key to understanding the meteorology of sub-stellar objects. We quantify how many isolated cool objects that Ariel's fine guidance sensor (FGS) is able to guide on. Among 2744 selected targets, none are bright enough under the planned 10 Hz FGS cadence; however, with a "slow" fine guidance mode of 1 Hz, Ariel could study 98 L0- to L5-type brown dwarfs. We simulate single-epoch and time-series spectroscopic observations of the brightest isolated brown dwarfs given currently known instrumental specifications. We show that the resolution and sensitivity of Ariel instruments in the 1.1-7.8 micron regime can measure cloud-induced variability at the sub-percent level. A survey of brown dwarf phase curve observations, unavailable to ground-based telescopes, would be the perfect complement to Ariel's survey of atmospheric variability in hot Jupiters.

A growing fraction of tidal disruption events (TDEs) exhibit radio emission that rises only years after the optical or infrared flare, indicating delayed outflow activity. In some events the outflow is inferred to be slow ($\sim 0.02 \, c$) and massive ($\gtrsim 0.01-0.1 M_{\odot}$), challenging models such as delayed jets and disk state transitions. We propose a new mechanism for such delayed outflows: repeated collisions between a TDE accretion disk and a pre-existing stellar extreme-mass-ratio-inspiral (EMRI) orbiting the black hole. In this scenario, the delay reflects the viscous time required for the initially compact TDE disk to expand and intercept the EMRI orbit, rather than delayed jet launching or off-axis viewing effects. Once star-disk collisions commence, repeated impacts eject outflows with velocities comparable to the orbital speed, $v_{\rm w} \sim 0.02-0.1c$. We develop a time-dependent model for the coupled evolution of the spreading disk and EMRI-induced mass-loss, identifying regimes where the outflow is dominated by disk material or ablated stellar debris. Depending on disk viscosity, orbital period, and collision efficiency, masses $\sim (10^{-3}-1) \, \rm M_\odot$ can be launched with energies up to $10^{51} \rm \, erg$, years after the TDE. These outflows produce radio emission through interaction with circumnuclear material or earlier TDE ejecta, consistent with observed late-time radio re-brightening. This model predicts a connection between delayed radio flares and EMRI-hosting systems, potentially including those exhibiting quasi-periodic eruptions (QPEs) powered by star-disk collisions, though the conditions for bright radio flares may not always match those necessary for detectable QPEs.

JWST has revealed an overabundance of apparent (`Coma'-like) cluster progenitors at $z>5$ that is $\sim$ two (300) times in excess of, and in $2.3\sigma$ ($4\sigma$) tension with, the number density of such objects at present day and theoretical predictions from $\Lambda$CDM. We present an analysis of protocluster candidates between $5<z<9$ from the literature, and in the TNG-Cluster and TNG300 simulations, aimed at resolving this tension. We first identify an inconsistency in how protocluster candidates are characterised: observational halo masses are estimated by summing the stellar mass over very large apertures ($\gtrsim 50\, R_{\rm vir}$), but are compared to the halo mass within the virial radius from simulations. In addition, these halo masses are commonly compared to the backward-tracked halo mass evolution of clusters, whereas a forward-tracked evolution of massive high-redshift haloes is more appropriate. Correcting these inconsistencies, while accounting for the merging of coincident protoclusters and the fluctuations associated with cosmic variance, entirely alleviates the tension. Ultimately, we find that $64\%$ of the protocluster candidates are instead likely to be proto-groups (i.e., $M_{200c}<10^{14}\, {\rm M_{\odot}}$) and none appear likely to become Coma-like clusters (i.e., $M_{200c}>10^{15}\, {\rm M_{\odot}}$) by $z=0$. Although some of these overdensities may not become clusters, they still trace extreme nodes of the cosmic web that may host early environmental effects, drive the first ionised regions, and contribute significantly to the cosmic star-formation rate density. These results demonstrate the need for more careful comparisons between observations and simulations of high-redshift protoclusters, and that improved selection criteria, potentially using the summation of the halo mass on Lagrangian scales, are vital for high-redshift protocluster science.

Population-II pulsating stars provide a route to extragalactic distances that is independent of the classical Cepheid distance scale and complementary to geometric and tip-of-the-red-giant-branch (TRGB) methods. We apply optical Wesenheit Leavitt laws for RR Lyrae and type II Cepheid stars calibrated with Gaia DR3 data and anchored by homogeneous globular-cluster distances based on trigonometric parallaxes to variable stars in the Large Magellanic Cloud (LMC). We adopt RRab stars as the baseline tracer because they define the absolute zero point of the calibration, dominate the LMC sample, and provide robust classifications. The uncertainty budget propagates the full covariance matrix of the calibration parameters, treating calibration uncertainties as correlated systematics rather than independent star-by-star errors. Using 12,193 RRab stars after outlier rejection, we determine mu_LMC = 18.423 +/- 0.002 (stat) +/- 0.020 (syst) mag. This combines the statistical uncertainty on the mean and the systematic uncertainty of the absolute calibration, which currently limits the total precision. Our result is lower than the detached-eclipsing-binary benchmark by 0.054 mag, corresponding to an approximately 1.7 sigma offset, and agrees with the TRGB distance obtained from the same globular-cluster scale to within 0.024 mag. RRc and T2Cep stars provide useful consistency checks, although the relative RRc-RRab and T2Cep-RRab offsets measured in the LMC differ from those calibrated in globular clusters. Geometric corrections between tracer barycenters and external reference positions are below 0.003 mag. Individual RRab distances map the three-dimensional structure of the LMC across a broad 10-degree-radius field. A planar model reproduces the dominant distance gradient and yields i = 21.3 +/- 0.7 deg and Theta = 145.2 +/- 2.2 deg, in agreement with previous determinations.

A common ingredient in cosmological perturbation theory (PT) is the expansion of the dark matter overdensity $\delta$ in the Lagrangian displacement $s$, which amounts to enforcing mass conservation perturbatively. In Eulerian PT (EPT), that expansion occurs already at the level of the continuity equation; in Lagrangian PT (LPT) it is done in the Poisson equation. We show that the resulting perturbative solutions for $\delta$ can diverge not because of the expansion in $s$ per se, but because of an exchange of an infinite sum with a Fourier integral that violates the conditions of Lebesgue's dominated-convergence (DC) theorem. We show that this DC obstruction (DCO) is one clear reason why the convergence of EPT is controlled by advection terms beyond the linear $\delta$. The same DCO underlies LPT: LPT's region of validity is the resummation region of a DC-violating series, bounded by shell crossing on one side and severely underdense regions on the other. Effective field theories (EFT) of large-scale structure need to smooth at short scales just to recover from that DCO, independent of whether non-linearities beyond mass conservation are important or not. An alternative is to never expand $\delta$ in $s$: instead evolve phase-space cumulants using the BBGKY hierarchy, initialized with the Zel'dovich approximation (ZA). The DCO is then absent by construction, so an EFT of BBGKY can focus on physics beyond mass conservation, which may allow pushing PT beyond shell crossing. The trade-off is the need for a closure relation, for which one can again use the ZA. We provide the building blocks for such a BBGKY+ZA recipe. A bottleneck for implementing it has been the ZA phase-space two-point function $\mathcal{P}$, which we successfully integrate numerically; we then write the higher ZA phase-space correlators needed for closure as products and convolutions of $\mathcal{P}$.

Rapidly rotating core-collapse supernovae are promising sources of multimessenger emission, as non-axisymmetric dynamics in the newly formed proto-neutron star can leave characteristic imprints on both gravitational waves and neutrinos. We present three-dimensional neutrino-magnetohydrodynamics simulations of the collapse of a rapidly rotating $35\,\mathrm{M}_\odot$ progenitor, performed with five different finite-temperature nuclear equations of state, to investigate how dense-matter physics affects the development of the low-$T/|W|$ instability and its associated multimessenger signatures. We find that the low-$T/|W|$ instability develops in all equation of state models considered, indicating that its occurrence is robust for this rapidly rotating progenitor. However, its onset time, dominant azimuthal structure, lifetime, and characteristic multimessenger frequencies vary among models, reflecting differences in the evolving proto-neutron star structure and rotation profile. The instability produces large-scale spiral modes that generate quasi-periodic gravitational wave emission and modulate the neutrino luminosities, especially along directions close to the equatorial plane. The dominant gravitational wave frequency associated with the instability correlates with the effective stiffness and compactness of the proto-neutron star: models with more compact/stiffer configurations emit at higher frequencies. This suggests that, in rapidly rotating core-collapse supernovae, the frequency of the low-$T/|W|$ instability-driven gravitational wave signal may provide a diagnostic of the dense-matter equation of state, complementary to the information carried by the neutrino signal.

We present results on X-ray absorption and the dust grain chemistry in the diffuse interstellar medium (ISM), based on a new Cycle 25 Chandra High Energy Transmission Grating Spectrometer (HETGS) observational campaign targeting the black hole transient GX 339-4. The X-ray source offers an optimal combination of moderate hydrogen column density and high X-ray flux, enabling the first detailed simultaneous fitting of the photoabsorption edges of Fe, O, Si, and Mg which are key elemental constituents of interstellar dust. We performed a joint spectral analysis of Chandra/HETGS data and archival observations from the Reflection Grating Spectrometer (RGS) on board XMM-Newton. We found that the dust grain chemical composition along this diffuse Galactic line of sight is best described by the silicate Mg-rich amorphous pyroxene (Mg0.75Fe0.25SiO3) and metallic iron. We also discuss the elemental abundances and depletions of Fe, O, Si, and Mg, and the presence of absorption features in the X-ray spectrum of this source associated with highly ionised plasma.

The Hubble Space Telescope is the only high-resolution ultraviolet spectroscopic facility that will exist until the Habitable Worlds Observatory (HWO) achieves first light in the mid-2040s. We describe a coherent class of science, coupling rest-frame extreme-ultraviolet (EUV; 1--4 Ryd, 228--912 Å) absorption and continuum spectroscopy of intermediate-redshift quasars at $z = 1-2$, shifting the rest-frame EUV photons into the HST/COS far-UV bandpass. This science on quasars and gas in the IGM and CGM is doubly perishable. The COS detector sensitivity is declining, just as new quasars are found (Milliquas, UVQS, and soon Rubin, Roman, and Euclid). Thus, the window to reach UV-bright quasars at $z>1$ QSOs narrows with every deferred orbit. Expanding HST UV orbit allocations in the 2030s would deliver a step-change in warm-hot CGM/IGM science and produce the first systematic, empirical EUV SED census of QSOs. These datasets will serve as the foundational low-redshift anchor for HWO science. This recommendation makes the scientific and strategic case for an expansion of the HST/COS spectroscopic data base on intermediate redshift AGN in their rest-frame EUV.

Dynamical modelling can be used to constrain the masses of central black holes; however, modelling massive galaxies is challenging due to their complexity. In this work, we report six new supermassive black hole mass measurements of massive early-type galaxies from stellar kinematics, which were extracted from adaptive optics-assisted SINFONI and MUSE observations. We combine the stellar kinematics with HST photometry to build DYNAMITE triaxial Schwarzschild orbit-superposition models. Our Schwarzschild models can recover the complex triaxial features of the galaxies and constrain the black hole masses of all six galaxies. We find that strong triaxial kinematic features can bias the mass measurements and correct for this effect. The derived black hole masses are (1.14^{+0.41}_{-0.63}) * 10^9 Msun for NGC 3706, (1.19^{+1.34}_{-0.80}) * 10^9$ Msun for NGC 3923, (1.14^{+1.08}_{-0.95}) * 10^9 Msun for NGC 4261, (4.68^{+2.99}_{-4.26}) * 10^8 Msun for NGC 4636, (3.51^{+3.37}_{-2.57}) * 10^9 Msun for IC 4296, and (2.43^{+1.53}_{-1.65}) * 10^9 Msun for IC 4329 at 3sigma confidence level. We compare our measurements with published results from axisymmetric Schwarzschild modelling and with our Jeans Anisotropic Models (JAM), and obtain mostly consistent black hole masses. Most of our black hole mass estimates can be well constrained using only MUSE observations. All of our mass measurements are in agreement with local black hole scaling relations.

Massive stars play a fundamental role in shaping the evolution of galaxies through feedback, chemical enrichment, and their end products as neutron stars and black holes. Despite major progress in the last decade, key uncertainties remain in the physics of massive stars, particularly in mass loss, internal mixing, binary interactions, and the upper end of the initial mass function. These uncertainties directly affect our understanding of stellar populations, gravitational wave progenitors, and the young Universe probed by JWST. HST is uniquely capable to address these open questions. UV diagnostics are essential for determining stellar parameters, tracing stellar winds, and identifying interacting binaries and stripped-envelope stars. Long-term spectroscopic monitoring further enables constraints on variability, wind structure, and presupernova mass loss. We outline a set of questions which need to be addressed in 2030s by combining UV - optical spectroscopy, time - domain monitoring, and archival baseline exploitation of massive stars and star forming regions. These observations will target massive stars across a range of metallicities, resolve the most luminous stellar populations, and identify compact-object binaries and post-interaction systems. Together, these efforts will pave the way to HWO and secure the long-term legacy of HST in massive star astrophysics.

In this era of large surveys and statistical studies of galaxies, the beauty in the details of individual galaxies is often lost. We present a deep study of the spiral galaxy W2246f with MUSE, exploring the spatially-resolved stellar and ionized gas properties to understand how it formed and evolved over time. The unusually deep observations of this galaxy give us a rare opportunity to study this phenomenon with better spatial resolution than can normally be achieved with the current IFU surveys of galaxies at a similar redshift ($z\sim0.09$). We analyse the stellar and gas kinematics, as well as the spatially resolved stellar populations and gas properties, including gas metallicity and the dominant ionization sources. The derived properties include the stellar mass, radial profiles of luminosity- and mass-weighted mean ages and metallicities, and ionized gas characteristics such as E(B-V), H$\alpha$ extinction, dust-corrected H$\alpha$ flux, oxygen abundance using the O3N2 calibrator, and H$\alpha$-based star formation rate. Analysis of the stellar populations revealed a negative metallicity gradient, and the mass-weighted ages showed uniformly flat ages across the disc while the luminosity-weighted ages show a negative gradient. We find that the gas metallicity and star formation rate density also drop in the central region of the galaxy where the older luminosity-weighted stellar populations are found. Analysis of the WHAN and WHaD diagrams reveal that in fact the central region is retired while the rest of the disc is star forming. We conclude that W2246f is a nice example of a cLIER galaxy, where the central kpc is dominated by old, metal-poor stars with little star formation. The central LIER emission is primarily powered by hot evolved stars, while the rest of the disc displays ongoing star formation. These findings are consistent with a scenario of inside-out quenching.

We investigate conditional diffusion modeling for three-dimensional 21 cm lightcone emulation, focusing on cubes with a sky-plane size of $64\times64$ and a line-of-sight depth up to 1024 cells. Relative to earlier 2D studies, the 3D setting is substantially harder because memory limits enforce very small micro-batches while the underlying voxel distribution is highly skewed and long tailed. We perform controlled comparisons across preprocessing choices, dynamic-range compression settings, architecture depth, and training duration using $25{,}600$ training lightcones and validation ensembles at fixed parameter points. For validation, each reference parameter point contains 800 21cmFAST realizations with independent initial conditions, and we use 800 samples per model and per reference set for the reported ensemble comparisons. We evaluate generated lightcones with complementary diagnostics in both image and summary-statistic spaces: brightness-temperature slices, the global signal, the power spectrum, and reduced scattering coefficients. Across the tested configurations, preprocessing is the dominant factor governing stable training and the resulting physical fidelity. Among the configurations explored here, Yeo-Johnson preprocessing combined with moderate amplitude compression gives the most consistently favorable trade-off, with the strongest quantitative support coming from rankings based on the standard-deviation-normalized mean absolute error ($\mathrm{MAE}_{\rm std}$) of the global signal and qualitatively compatible behavior in the complementary diagnostics. At the same time, visually plausible 3D samples still retain measurable biases in two-point and higher-order statistics. We therefore view the present work as a simulation-level baseline for three-dimensional 21 cm emulation and for future studies that incorporate more realistic observational effects.

GRB 221009A, the Brightest Of All Time (BOAT), presents a challenge for afterglow modelling due to its low Galactic latitude and consequent high line-of-sight extinction. This has led to a wide range of conflicting values for the optical spectral index and dust extinction in the literature. We present a re-analysis of the afterglow spectra, using VLT X-Shooter data at 0.5, 4, and 10.5 days, and JWST NIRSpec$/$MIRI data at 13.3 days post-burst. We fit the data with single and smoothly broken power-law models and perform a joint fit with a double smoothly broken power-law (DSBPL) across all epochs. Our analysis reveals a strong degeneracy between the assumed extinction and the inferred intrinsic spectral index, particularly in the optical, explaining the diversity of previous results. The joint DSBPL fit yields a total line-of-sight extinction of $A_{V} = 4.40 \pm 0.01$ and a blue continuum, with an intrinsic spectral index of $\beta = 0.447 \pm 0.001$. Although marginally preferred by the spectral fits, a wind medium can be rejected by the temporal evolution of the afterglow light curve. The fit spectral index and temporal decline are only consistent with a uniform density medium if an early jet break at $\sim 0.5-1.0$ days is invoked. Our results imply a hard electron distribution index of $p = 1.89 < 2$, challenging standard particle acceleration models and suggesting a narrow, energetic jet core dominates the early optical-to-X-ray emission.

Binary systems composed of two carbon-oxygen white dwarfs (WDs) are a leading progenitor candidate for Type Ia supernovae. One widely discussed scenario is the dynamically driven double-degenerate double-detonation (D$^6$) of a sub-Chandrasekhar-mass WD binary, where detonations are triggered by dynamical interaction. However, some systems are expected to undergo violent mergers, in which the primary ignites through direct carbon ignition as the secondary strikes its surface. We present the first 3D nebular-phase radiative-transfer calculations of a violent merger, using a $1.1 M_\odot$ and $0.7 M_\odot$ sub-Chandrasekhar binary. Our simulations employ a full NLTE (non local thermodynamic equilibrium) treatment of excitation and ionisation, including non-thermal electron contributions. By comparing 1D and 3D realisations, we show that multidimensional modelling improves the ionisation state and reveals features absent from 1D calculations, most notably [O I] from unburned material associated with the secondary. The model reproduces much of the panchromatic spectrum of the normal SN 2021aefx, but underpredicts [Ni II] while producing strong high-ionisation stable-Ni features, illustrating that stable-Ni signatures depend not only on abundance, but also on ionisation state. Although the model does not reproduce the strong [Ar II] and [Ne II] emission observed in the 03fg-like SN 2022pul, our calculations suggest that this event may require a similar merger configuration, involving full disruption of the secondary or a more massive companion with more extensive burning. Finally, viewing-angle variation is substantial, with signatures distinct from D$^6$-like scenarios, suggesting that JWST nebular samples, combined with multidimensional modelling, can discriminate between channels.

This paper tests whether Kolmogorov--Arnold Networks (KAN 2.0) are genuinely more noise-robust than Multi-Layer Perceptrons (MLP) and XGBoost for stellar classification (star/galaxy/quasar, 100,000 SDSS DR17 objects). A naive comparison suggests so: KAN retains +9 percentage points over MLP at SNR=5. But equalizing baseline accuracy via weight decay eliminates the gap -- a properly regularized MLP matches KAN to within 1 p.p. at all SNR levels, both with and without spectroscopic redshift. The same holds on an independent DESI DR1 sample with different photometric bands. KAN's robustness thus traces to implicit regularization by C^2-smooth B-spline activations, not to architecture. Per-class analysis (20 trials) shows that stars degrade fastest (F1: 0.97 to 0.75 at SNR=5), while QSOs remain stable. KAN's native feature importance and SHAP on MLP produce different rankings (Spearman rho = -0.37), capturing complementary aspects of the classification. Colour-index features (u-g, g-r, r-i, i-z) widen KAN's relative advantage, and a hybrid pipeline routing uncertain MLP predictions to KAN improves low-SNR accuracy. KAN is best understood as a convenient auto-regularizer whose genuine advantage is built-in interpretability.

Massive stars continuously enrich the surrounding interstellar medium by supplying it with stellar material driven by their powerful winds. B supergiant stars (BSGs) in particular are a type of massive star characterized by strong winds and notable photometric and spectroscopic variability. We aim to conduct a pilot study of the optical spectroscopic variability of the BSG HD75149 between 2004 and 2025. Its extended temporal baseline and pronounced variability amplitude make it particularly well suited for investigating the physical origin of the observed short-term variability within a consistent hydrodynamical and radiative-transfer framework. We analyzed 25 nightly averaged optical spectra obtained with different instruments and telescopes, some of them with observations over several consecutive days. We measured the radial velocities (RVs) and equivalent widths (EWs) of 17 spectral lines (H, HeI, SiIII, NII, MgII, CII). We modeled the Halpha emission, absorption, and P-Cygni profiles using the ISOSCELES grid and the delta-slow hydrodynamic regime. Halpha shows variability in intervals of a few days, including P-Cygni changes, while metal lines show small RV amplitudes, consistent with pulsating oscillations. The largest variation in the mass-loss rate corresponds to an increase of a factor of 1.8 within four days. In contrast, the terminal velocity remains barely affected during the same time interval. The pronounced variation observed in hydrogen lines, in contrast with the variability of other lines, suggests that it is due to mass-loss rate episodes driven by a slow wind occurring on a timescale comparable to photometric variations. We found no evidence of a close binary companion in the sample used, but we cannot completely exclude the possibility of a wide or low-inclination companion.

Ring systems have been observed around Centaur Chariklo (10199) and other small bodies but their origin and dynamical histories are still debated. These small body ring systems challenge conventional models for the origin of planetary rings, especially when considering Centaurs' often erratic cometary activity, their non-spherical shapes, and their relatively short dynamical lifetimes (~$10^7$ years). A collisional origin for these rings is disfavored based on the low probability of collisions within their lifetimes, and so their mechanism of formation remains an open question. In this work, we use Swiftest, a N-body integrator with collisional fragmentation and higher-order gravitational harmonics, to test a hypothesis that rings could be formed from regolith ejected from a cometary outburst that is subsequently captured into a stable orbit. We show that ejected surface regolith is captured in orbit around ellipsoidal Centaurs like Chariklo and Chiron to form a proto-ring disk for at least 100 rotations. This captured disk may serve as a starting point that can evolve into observed ring systems. Inter-particle collisions and the ellipsoidal gravity field facilitate this capture. Among the tested scenarios, a landslide or avalanche-like ejection from the equatorial plane shows the highest rate of capture, ~30 - 90% depending on the initial ejection parameters. This implies that rings could be an indicator of past activity on a Centaur and may be a more common feature among Centaurs depending on their shape and frequency of outbursts.

Metal-poor solar-type stars display a significant reduction in metal-line blanketing at short wavelengths, leading to an excess of near-ultraviolet (NUV) flux compared to their metal-rich counterparts. We utilize GALEX NUV and $\it{Gaia}$ DR3 photometry along with ground-based spectroscopy to establish a correlation between NUV excess and [Fe/H]. We construct a sample of 492 solar-type (F5-G9) halo stars with NUV excess and measured metallicitices. We perform our own observations with the KOSMOS spectrograph at Apache Point Observatory's 3.5m telescope to measure the abundances of 13 halo stars, 11 of which did not have previous metallicity measurements. Our targeted 13 halo stars span $-$2.92 $<$ [Fe/H] $<$ $-$1.97 and are all $\alpha$ enhanced with [$\alpha$/Fe] = 0.05-0.73. For our full sample of 492 objects, we find an anti-correlation between NUV excess and [Fe/H] that is statistically significant at the 8$\sigma$ level. GALEX NUV excess can be used to distinguish very metal-poor (VMP) stars ([Fe/H] $<$ $-$2) from their metal-rich counterparts. However, there is significant dispersion in the relation due to NUV chromospheric variability caused by rotational effects and magnetic cycle activity. The NUV chromospheric variability inhibits our ability to reliably distinguish extremely metal-poor (EMP) stars ([Fe/H] $<$ $-$3) from VMP stars based on photometry alone. UV spectra of EMP halo stars are needed to better calibrate their atmospheric properties and variability.

We present the construction of stationary solutions of Bose-Einstein condensate dark matter (BECDM) around a point-like gravitational source representing a black hole. The problem is formulated for general axisymmetric configurations, and we focus on two cases: the ground-state core solution and the first nonzero winding number configuration corresponding to a line vortex solution. The stationary equations are solved using an imaginary-time approach, which enables the construction of families of solutions across a wide range of self-interaction and black hole masses. We analyze the impact of these parameters on the density distribution and on the stability properties of the solutions, assessing stability through the turning point criterion based on the enthalpy functional, which allows us to identify stable and unstable branches along each family of solutions. It has been shown in the past that spherical core solutions act as attractors in the collapse of BECDM around black holes in the non-interacting case ($g=0$), supporting their astrophysical relevance. In the present work, the existence of a maximum mass for configurations with attractive self-interaction ($g<0$) allows us to infer the parameter range in which such solutions may also arise in this regime. Building on this picture, we show that stable vortex solutions of BECDM can also exist in the presence of a black hole, whose stability properties suggest that these configurations may likewise be compatible with physically relevant formation scenarios.

Condensate clouds are a defining feature of brown dwarf and exoplanet atmospheres, producing a broad range of colours on the CMD and giving rise to spectral features such as the distinct $\sim 10 \mu$m spectral imprint. Cloud cover is likely to be heterogeneous in many objects, with observed rotational variability providing evidence for the presence of thick and thin cloud regions rotating in and out of view. Yet current 1D atmosphere models often fail to reproduce the spectra of highly cloudy substellar objects, especially those with complex cloud structures. We address these limitations by upgrading the Exo-REM atmosphere model, and by devising a more nuanced approach to describe heterogeneous cloud cover with pre-computed 1D grids. We present new Exo-REM grids, hereafter Exo-REM k26, featuring critical updates: (1) the incorporation of a cloud sedimentation parameter, $f_{sed}$, to govern cloud opacity, thereby enabling even the reddest of objects to be accessed on a CMD, revealing a trend of decreasing $f_{sed}$ along the L--T transition (2) the substantial update of molecular opacities and abundances used, including new experimentally validated alkali line lists, and (3) the implementation of strict convergence criteria that entirely avoid unstable model solutions. Correcting an erroneous $\text{CH}_3\text{D}$ abundance leads to spectral changes for low-$T_{eff}$ objects. Applying Exo-REM k26 to the cool GJ 504 b thus leads to a revision of its parameters ($T_{eff} = 473^{+14}_{-12}$ K, $\log g = 4.0 \pm 0.1$ dex). For the variable VHS 1256 b, a two-column framework that emulates cloud heterogeneities achieves an improved global fit over a single 1D model. A ~60-40% split of thick and thin clouds best describes its atmosphere, further confirming the presence of patchy clouds. This reproduces the strong $10 \mu$m silicate absorption in the JWST data of VHS 1256 b.

The polarimetry of recent pulsar observations has provided a wealth of observational data with which to test physical theories of emission mechanisms, radiative transfer and even theories that extend beyond the Standard Model. In this work, we have outlined the data analysis of the polarisation time series data of a population of 513 pulsars from the Thousand Pulsar Array observing programme, laying the foundation for building the MeerKAT Thousand-Pulsar Polarization Array as a probe for ultralight Axion-Like Dark Matter (ALDM). From this large dataset we have focused on the temporal trends in the observed polarisation angle (PA) through a measure we call the PA offset, and characterised the trends due to the effects of Faraday Rotation within the interstellar medium and the Earth's ionosphere, as well as generic white and red noise models that are estimated within a Bayesian MCMC analysis. Then, motivated by potential extra contributions to the rotation of the PA that may not be Faraday-like, arising from the proposed ALDM field, we have investigated a derived time dependence for the rotation measure (RM) required to explain the observed PA offset. Comparison of these estimates to RM values that are measured in typical pulsar studies, through a technique known as RM Synthesis, provides a probe of any wavelength-independent contribution to the rotation of the PA. Although we find no evidence for oscillatory behaviour within our dataset's observation timespan, we do find cases of deviation from the usual RM values in several `pulsars of interest', as well as long-term linear trends in the time evolution of Faraday rotation that have been presented in the literature before.

Hubble Space Telescope (HST) images are used to study the structure of the central regions of the luminous infrared galaxy (LIRG) IC 860. IC 860 is of special interest as a system due to its extreme central concentration of molecular gas cloaking its compact obscured nucleus (CON). The CON provides most of the 1.5E11 Lsun luminosity in IC 860 from an undetermined combination of stellar and AGN power sources. We mapped and photometered the central molecular zone (CMZ) of IC 860 motivated by a previous NIR detection of a luminous compact nuclear source. Our objective was to study properties of the CMZ and its relationship to the CON, that we identified as an opaque central region in archival near infrared (NIR) images. Coordinates of the compact NIR source, IC860-a, came from HST image coordinates calibrated with Gaia positions. Photometry of the HST images yielded magnitudes, colors, and high V-band dust optical depths based on foreground screen dust models. Photometry corrected for dimming by dust yielded NIR luminosities of IC860-a and the CMZ. We found IC 860 has distinct compact central luminosity sources: Most of the NIR luminosity is from the CMZ while the LIRG-CON is an obscured region centered in the CMZ. IC860-a, in the northeast side of the CMZ, is offset by about 0.2 arcsec from the CON, has a luminosity of approximately 1E9 Lsun, and may be a massive young stellar complex or intruding nucleus. We concluded that the inner CMZ in IC 860 contains two luminous compact objects: The CON is identified for the first time as an obscured central source while the structure of the CMZ and CON is complicated by the presence of the IC860-a compact object, possibly a massive young stellar system or second nucleus. The presence of IC 860-a in combination with the CON is a further signature of the unusual evolution of the gas-rich IC 860 CMZ.

Hydrodynamic shielding is a theoretically well-established but observationally elusive and experimentally difficult-to-replicate phenomenon with implications that extend far beyond meteor physics. Rare earthgrazing meteoroids with infrasound signatures that penetrate to the ground can be used to probe hydrodynamic shielding that leads to strong shock formation at high altitude. Here, we report the first coordinated optical and multi-station infrasound observations of a centimeter-scale earthgrazing fireball that generated sustained cylindrical line shock at thermospheric altitudes near 92 km. The event was recorded by numerous optical stations and three infrasound arrays, allowing trajectory reconstruction, ablation behavior, acoustic source localization, and shock characteristics. Optical observations indicate early mechanical erosion and ablation/evaporation at exceptionally low dynamic pressure, consistent with a cometary or a porous, volatile-bearing CM chondritic object. Independent infrasound detections localize shock generation to multiple points along a 164 km trajectory segment near perigee. Weak-shock modeling yields a consistent blast radius of ~30 m, implying an acoustic-equivalent source size far exceeding the physical dimensions of the ~45 g nucleus. We demonstrate that classical gas dynamics and ablation-driven hydrodynamic shielding alone cannot account for these observations under ambient thermospheric conditions. We show that volatile release provides the additional flow-field density enhancement required to amplify hydrodynamic shielding, reduce the effective local Knudsen number, and sustain a shock envelope capable of radiating detectable infrasound. These results demonstrate that small, volatile-rich meteoroids can transiently establish continuum-like flow in rarefied environments.

Neutron star mergers are amongst the most promising sources for the joint detection of gravitational waves and electromagnetic signals. They are also potential sites for the production of r-process elements and probes of the equation of state of matter above nuclear saturation density. Neutrino-matter interactions during and after merger strongly influence the thermodynamic evolution and composition of the remnant and its outflows, thereby affecting kilonova emission and nucleosynthesis yields. However, existing merger simulations remain limited by significant approximations in the treatment of neutrino transport and interaction rates. In this work, we assess the thermodynamic conditions under which neutrinos decouple from matter and show the effect of charged-current absorption, quasi-elastic scattering on nucleons and nuclei, pair-production processes, and inelastic neutrino-electron scattering for electron neutrinos, electron antineutrinos, and heavy-lepton neutrinos in the different thermodynamical conditions sampled by a simulation using an energy-dependent Monte Carlo neutrino transport. We first estimate opacities in the post-merger remnant assuming neutrinos in equilibria with the fluid, and find results consistent with previous studies performed on simulations using a gray two-moment scheme. We note the very distinct regions in which nucleon-nucleon Bremmstrahlung and electron-positron annihilation are active (high and low density regions, respectively). We then evaluate opacities using the actual distribution function of neutrinos within a Monte Carlo simulation. We show greatly increased pair annihilation rates in cold, low-density regions, especially for heavy-lepton neutrinos. We also show that inelastic scattering on electrons, which has not been included in merger simulations so far, makes important contributions to the thermalization of heavy-lepton neutrinos.

The recent detection of an atmosphere surrounding the trans-Neptunian object (TNO) 2002 XV$_{93}$ from stellar occultation measurements has challenged the longstanding view that only the largest TNOs can sustain an atmosphere. Atmospheric refraction modeling of the occultation light curves indicated a surface pressure of 100$-$200 nbar, despite 2002 XV$_{93}$'s relatively small size (~510 km in diameter) and weak surface gravity. Together with the detection of methane fluorescence on Makemake, this result suggests that tenuous atmospheres may be more common among TNOs than previously thought. We report JWST/NIRSpec observations acquired before and after the 2024 stellar occultation measurements, obtained with the PRISM and medium-resolution gratings at resolving powers of ~100 and ~1000, respectively. We detect no statistically significant emission features attributed to methane or carbon monoxide gas. By comparing the higher spectral resolution data with synthetic fluorescence models, we report upper limits for the methane and carbon monoxide surface partial pressures of $(3-10)\times10^{-6}$ and $(50-300)\times10^{-6}$ nbar, respectively, substantially below the atmospheric pressure inferred from the occultation measurements. Additionally, we report no evidence of an extended source of either methane gas or refractory material. Our results indicate that the atmospheric interpretation of the occultation measurements may require either a composition dominated by volatile species other than methane and carbon monoxide, with nitrogen and argon as possible candidates, or a methane-dominated atmosphere confined near the surface with a steeply decreasing vertical density profile.

The 21-cm emission line from neutral hydrogen during the cosmic Dark Ages can be a powerful probe of cosmological models and early universe physics. This work provides a quantitative forecast for the design requirements of a lunar far-side interferometer array aimed at measuring the 21-cm power spectrum and constraining inflationary models through the running of the spectral index $\alpha_s$. During the Dark Ages, larger collapsed objects have not yet formed, allowing linear perturbation theory to remain valid down to much smaller scales than is possible in current large-scale structure or CMB surveys. We first validate this linearity assumption by quantifying the contribution of minihalos to the 21-cm signal. We then establish a generalized and flexible analytical framework for the baseline density distribution of interferometers that may consist of an arbitrary number of stations or sub-arrays. Incorporating a realistic noise model, we determine the configurations necessary to reach the detection threshold and demonstrate that distributing the total collecting area into multiple stations can improve the signal-to-noise ratio of the power spectrum at a tunable small scale of interest by up to two orders of magnitude. We then show that a lunar array requires at least $\sim30,000$ probed Fourier modes to achieve a constraint on inflation of $\sigma(\alpha_s) = 0.034$, a result competitive with the Planck 2018 results and capable of distinguishing between different inflationary scenarios. We quantitatively explain how thermal noise severely erodes modes at high redshifts and small scales -- scales previously considered easily accessible to Dark Ages observations in the literature -- and discuss the prospects for Dark Ages observations as a new and independent probe despite this limitation.

Extreme mass-ratio inspirals (EMRIs) are among the primary targets of future space-based gravitational-wave observatories, such as LISA, TianQin, and Taiji. Active galactic nucleus (AGN) disks provide a gas-rich environment in which stellar-mass black holes can migrate toward central supermassive black holes and form EMRIs. Previous studies of this ``wet'' channel have largely neglected stellar interactions within the disk. Here we show that binary formation, hierarchical mergers, and recoil kicks fundamentally regulate wet EMRI formation in AGN disks. Using semi-analytical AGN disk models combined with Monte Carlo simulations across supermassive black hole masses of $10^5$--$10^7M_\odot$ and Eddington ratios of $10^{-3}$-1, we find that recoil kicks from mergers and binary--single interactions repeatedly lift stellar-mass black holes out of the disk plane, temporarily interrupting migration and strongly suppressing EMRI formation in much of parameter space. Detectable EMRIs are therefore preferentially produced in young AGNs, typically within $\sim$ 10-20Myr of disk formation, and often involve merger-grown secondary black holes. We predict LISA detection rates of $\sim$ 1-30yr$^{-1}$, with the observable population dominated by low-mass AGNs and sensitive to the poorly constrained demographics of faint active nuclei. Our results identify stellar interactions as a key ingredient in the evolution of compact objects in AGN disks and show that future EMRI observations can probe both AGN disk physics and the low-mass AGN population.

Shadows cast in the cosmic ray (CR) muon sky by the Sun were located using muon data from the MINOS far detector in Northern Minnesota. The shadows were observed independently across three time periods; near solar minimum, near solar maximum, and over the entire 13 year span of the data. A distribution of muon positions for each shadow was then sampled to simulate CR motions near the Sun using the Parker spiral model of the Heliospheric Magnetic Field (HMF) and a dipole model of the Geomagnetic Field (GMF). The resulting particle distributions were then compared to their position with respect to the Sun. Results show that the Parker spiral model is most consistent with the solar minimum shadow and least consistent with the solar maximum shadow, as expected. The simple Parker spiral is more consistent with the data for a harder CR spectrum than is actually present, indicating the need for a more detailed HMF model. Plausible modifications to the Parker spiral model which would affect the overall shift of the Sun's CR shadow are discussed.

The spaceflight environment presents unique physicochemical conditions, including microgravity, ionizing radiation, altered fluid transport, and confined engineered habitats, which influence biological systems and biomolecular assembly processes. These conditions also provide opportunities for orbital biomanufacturing and autonomous biofabrication that are difficult to reproduce under terrestrial gravity, motivating the development of compact autonomous experimental platforms for spaceflight research. Here, we present the Modular Astrobiology Experiment (MAEx) platform, a compact 3U spaceflight-compatible payload designed for autonomous multimodal biological characterization under space-relevant conditions. MAEx was engineered to operate within the constraints of orbital deployment, including limited volume, low power consumption, thermal regulation, and autonomous data acquisition. To demonstrate platform versatility, representative biological systems, including the electroactive bacterium Shewanella oneidensis MR-1, the radiation-resistant fungus Ustilago maydis FB1, and the human eye lens protein {\gamma}D-crystallin, spanning cellular and molecular scales were incorporated. MAEx platform integrates imaging, absorption and fluorescence spectroscopy, and electrochemical sensing within a modular architecture, enabling simultaneous monitoring of microbial growth, extracellular electron transfer (EET), and protein aggregation dynamics.

The cusp-core problem remains a challenge to the $\Lambda$CDM model, since dwarf galaxies often exhibit flat central density cores rather than the steep cusps ($\rho \propto r^{-1}$) predicted by collisionless $N$-body simulations. We model the dark-matter-dominated dwarf irregular galaxy DDO 168 within the Bose--Einstein condensate (BEC) or fuzzy dark matter (FDM) framework, in which ultralight bosons form a solitonic core governed by the Gross--Pitaevskii--Poisson (GPP) equations, with the soliton mass--radius relation enforced. We numerically validate the ground-state solution of the GPP system as a consistency check and fit the inner rotation curve of DDO 168 using SPARC data. Within this framework, the data are consistent with an axion mass \[ m = (1.3^{+0.3}_{-0.2}) \times 10^{-23}\,\mathrm{eV}, \] and yield a solitonic core with characteristic radius \[ R_c = 2.40^{+0.24}_{-0.22}\,\mathrm{kpc}, \] enclosing a mass \[ M(<2.47\,\mathrm{kpc}) \simeq (1.5 \pm 0.2)\times10^{9}\,M_\odot. \] The observed flat inner rotation curve is reproduced and the presence of a weak H\,I bar is compatible with multigigayear survival timescales, consistent with reduced Chandrasekhar dynamical friction in a shallow central potential. These results demonstrate that the BEC/FDM framework provides an internally consistent description of DDO 168, simultaneously reproducing the observed rotation curve, alleviating the cusp-core tension, and allowing long-lived weak bars under conservative dynamical assumptions.

We analyze the rest-frame optical (~8000 Å) morphologies and star formation activity of Ly{\alpha} emitters (LAEs) at redshifts $2.4$, $3.1$, and $4.5$, identified in the ODIN survey. To compare their physical properties with those of other galaxies, we construct a comparison sample of typical star-forming galaxies (SFGs) at similar redshifts from the COSMOS2025 catalog. Using the \textit{JWST}/NIRCam images from the COSMOS-Web survey, we measure the rest-frame optical sizes and Sérsic indices. We first examine their size-mass relations and find that LAEs at all three redshifts have smaller sizes than typical SFGs, with the size difference decreasing at higher redshifts. We also find that LAEs tend to have larger Sérsic indices at $z=2.4$ and $3.1$ than typical SFGs, but the difference becomes weaker at $z=4.5$. These trends are qualitatively reproduced in the Horizon Run 5 cosmological hydrodynamical simulation. We then investigate star formation activity and find that LAEs exhibit higher star formation rates than typical SFGs at all redshifts considered. Finally, we examine the connection between Ly{\alpha} emission and galaxy structure, finding that the rest-frame equivalent width (REW) of the Ly{\alpha} emission line has negative and positive correlations with size and Sérsic index, respectively. In addition, we find a strong positive correlation between the Ly{\alpha} REW and the ratio of the instantaneous star formation rate to that averaged over the last $100\;\mathrm{Myr}$ (i.e., $\mathrm{SFR_{inst}}/\mathrm{SFR_{100 Myr}}$). These results suggest the compact and starbursting nature of LAEs, and provide important constraints on the physical mechanism for the Ly{\alpha} photon escape from galaxies.

We present extensive, well-sampled multiwavelength photometric and low-resolution optical spectroscopic observations of the low-luminosity Type IIP supernova SN 2024abfl. SN 2024abfl is found to be at the faintest end of Type IIP supernovae with unprecedented flat (0.1 mag/ 100 day) plateau evolution and a mid-plateau absolute magnitude of Mv~-13.8 mag, placing it among one of the faintest Type IIP supernovae discovered to date. SN 2024abfl is adjacent to SN 2018zd in the same host NGC~2146. Using various SN distance measurement probes, we provide independent estimates of the debated distance to the host NGC 2146 (7-9 Mpc). Spectral evolution of SN 2024abfl is found to be similar to other SNe spectra of this subclass but with very narrow line profiles, indicating moderately low expansion velocities of the ejecta. Detailed 1-D hydrodynamical modeling suggests a compact progenitor with an upper limit of 10 Msun, fairly consistent with the directly detected progenitor estimates. It exploded with very low-energy 0.05 foe or less with a very low nickel mass of 0.003 Msun, consistent with the observed parameters. These parameters provide important constraints on the nature of low-energy core-collapse explosions. We discuss possible progenitor scenarios and compare SN 2024abfl with other low-luminosity Type IIP supernovae.

The diffuse $\gamma$-ray emission from short-lived radioactive $^{26}$Al and $^{60}$Fe provides a direct probe of ongoing nucleosynthesis in the Galaxy. However, theoretical models have long struggled to reproduce the observed $^{60}$Fe/$^{26}$Al flux ratio, typically predicting values significantly higher than constraints derived from INTEGRAL/SPI observations. In this work, we investigate the impact of the recently measured, temperature-dependent stellar $\beta^-$ decay rate of $^{59}$Fe on the nucleosynthesis of these isotopes. We compute a grid of non-rotating massive star models ($14$-$80$ M$_\odot$) at solar metallicity using the MESA code, coupled with a rigorous numerical resolution analysis. We find that the updated rate significantly suppresses the net production of $^{60}$Fe by approximately 0.28 dex ($\sim 47\%$) compared to models using LMP theoretical rates, while leaving $^{26}$Al yields virtually unchanged. This reduction is primarily driven by the enhanced $\beta^-$ decay during convective carbon shell burning. Integrating these yields over a standard Salpeter Initial Mass Function, we predict a Galactic flux ratio of $\sim 0.18$, which is in excellent agreement with the observed value of $0.184 \pm 0.042$. Furthermore, this ratio exhibits a weak dependence on the IMF slope. Our results indicate that the updated nuclear physics input significantly alleviates the long-standing $^{60}$Fe overproduction problem, bringing theoretical predictions into much closer alignment with current Galactic observations.

O-C timing analysis is a useful diagnostic tool for quasi-periodic eruptions (QPEs), but their interpretation depends sensitively on the integer cycle number assigned to each eruption. In this note, we show that even a small mismatch in the cycle number, $N_{\rm cyc}$, can produce large false signals in O-C diagrams, and \emph{a universal feature of these false signals is a large in-phase sinusoidal modulation between even and odd eruptions.} Therefore, uncertainties in $N_{\rm cyc}$ must be inferred or marginalized over before physical interpretations are attached to O-C. We then apply both O-C and EMRI+disk to GSN 069 and eRO-QPE2. For GSN 069, the timing data favor an anti-phase modulation in even and odd eruptions, consistent with apsidal precession in a low-eccetricity EMRI crossing an equatorial disk. For eRO-QPE2, the data are well described by a near-circular EMRI and a precessing disk.

We present DEtection in phase-folded Light curves with cOntrastive Scoring (DELOS), a contrastive-learning-based framework designed to search for shallow transits in Kepler photometry. DELOS combines GPU-accelerated phase folding, optimized phase binning, and a custom one-dimensional convolutional encoder to assign a transit-likeness score to each folded light curve, thereby producing a score periodogram over trial periods without relying on pre-detected threshold-crossing events. Focusing on intermediate-to-long-period signals with orbital periods of 100-150 days, DELOS was trained on 20 million synthetic light curves generated with realistic transit models and Kepler-like noise properties, achieving a validation accuracy of 99.3 percent on the synthetic validation set. In controlled injection-recovery experiments, DELOS improves the combined precision-recall performance by 15.5 percent relative to Box-fitting Least Squares (BLS) and 11.25 percent relative to Transit Least Squares (TLS) in the low Signal-to-Noise Ratios (low-SNR) regime. It also accelerates the search by factors of approximately 3-5 and 74-80 compared with BLS and TLS, respectively. Applied to a selected Kepler validation sample, DELOS recovered all known shallow intermediate-to-long-period transit signals in the tested period range. These results demonstrate that DELOS provides an efficient and sensitive framework for low-SNR transit searches and represents a practical step toward future searches for longer-period terrestrial planets in Kepler, K2, TESS, PLATO, and Earth 2.0 data. Accordingly, this work is intended as a methodological development and validation study, with the detailed astrophysical validation of newly identified candidates deferred to future work.

Transmission spectroscopy enables the characterization of exoplanet atmospheres by probing absorption features in their terminator regions. In the optical, it is particularly sensitive to metal oxides and atomic species that can strongly influence atmospheric energy balance and thermal structure. We aim to investigate the atmospheric properties of the hot Jupiter HAT-P-47b through optical transmission spectroscopy. Thirteen TESS transits were analyzed to refine the planetary ephemeris and system parameters. Two ground-based transits were observed with LBT/MODS and GTC/OSIRIS+. Chromatic transit light curves were modeled to derive instrument-specific transmission spectra and multiple Bayesian spectral retrievals were performed to characterize the atmospheric properties. The MODS transmission spectrum provides moderate Bayesian evidence ($\Delta\ln\mathcal{Z}=2.68$) for TiO absorption, whereas the OSIRIS+ spectrum does not yield statistically significant evidence for any specific opacity source. Both datasets exhibit a wavelength-dependent slope indicative of enhanced aerosol scattering. The MODS and OSIRIS+ joint free-chemistry retrieval, dominated by the higher signal-to-noise MODS data, yields moderate evidence ($\Delta\ln\mathcal{Z}=3.44$) for TiO with a log mass fraction of $-6.86^{+0.64}_{-0.63}$ dex. The same model indicates an aerosol contribution to the optical scattering opacity approximately $5000\times$ larger than pure H$_2$ Rayleigh scattering. HAT-P-47b appears to host a cloudy atmosphere with evidence for aerosols and tentative evidence for TiO absorption. Future high-precision observations will be essential to confirm the presence of TiO and further characterize its atmospheric structure.

Super-Eddington accretion onto compact objects is expected to produce optically thick outflows with a funnel-shaped cavity that may collimate the emission. At inclinations higher than the grazing angle of the funnel, the central source is obscured. Accordingly, the observed emission is dominated by scattered and reflected radiation, which can therefore be strongly polarized. The detection of strong X-ray polarization in the Galactic X-ray binary Cygnus X-3 provides the first direct probe of this geometry. In this work, we present a systematic study of the inclination-dependent radiative signatures of such systems using a combination of semi-analytical methods and Monte Carlo simulations. Our treatment explicitly accounts for multiple scatterings and demonstrates that both the polarization degree and the degree of collimation are highly sensitive to the albedo of the funnel surface. We find that a low albedo (significant absorption) is essential for producing high polarization, yet it simultaneously suppresses the collimation of the emission. Conversely, a high-albedo medium (nearly pure scattering) can modestly collimate radiation, but at the cost of substantially reducing the polarization degree. We discuss our results in the context of Imaging X-ray Polarimetry Explorer observations of Cygnus X-3 and propose a physical scenario for its spectral state transitions, considering a combination of reflection from the funnel surface and scattering by a diffuse medium above the funnel. Our model provides a general framework for interpreting X-ray polarimetric signatures of obscured accretors.

Multiple stellar populations (MPs), characterized by star-to-star light-element abundance variations, are ubiquitous in globular clusters (GCs). Spectroscopy directly reveals these anomalies, while photometric studies, especially with the \textit{Hubble Space Telescope} (\textit{HST}), have been essential for tracing MP sequences in colour-magnitude diagrams (CMDs). However, the limited field of view of \textit{HST} confines most studies to cluster centres. The upcoming \textit{Chinese Space Station Survey Telescope} (CSST), with its wide field of view and UV-optical coverage, will enable systematic MP studies over entire clusters. We assess the capability of the CSST wide-field camera to detect and characterize MPs in GCs using realistic simulations. Synthetic stellar population models with different helium abundances ($\Delta Y$) and CNO variations were used to simulate CSST observations of GCs at distances of 9.6 and 20~kpc under different exposure times. MP detectability was evaluated using CMDs in seven CSST bands and UV-optical pseudo-colour diagrams. For a GC at 9.6~kpc, the $NUV-u$ colour is highly sensitive to $\Delta Y$ and CNO variations, with separations of $\Delta(NUV-u)\approx0.16$ mag for red giants and up to 0.44 mag for dwarfs. MPs can be resolved when the total UV exposure exceeds $\sim1000$~s and the optical exposure exceeds $\sim300$~s. At 20~kpc, encompassing $\sim80\%$ of Galactic GCs, CSST still retains strong diagnostic power, resolving populations with $\Delta Y\geq0.06$ and $\delta[\mathrm{N/Fe}]\geq0.64$, and separating MPs down to $i\sim19.5$ mag in clusters with large chemical spreads. The $NUV$-$u$-$g$ combination provides diagnostic performance comparable to the \textit{HST} F275W--F336W--F438W system. CSST will enable homogeneous MP surveys across the full spatial extent of star clusters in the Milky Way and nearby galaxies.

As gravitational wave (GW) catalogs continue to expand, exhaustive Bayesian comparisons of candidate event pairs become increasingly computationally expensive, which motivates the development of fast prescreening methods for strongly lensed GW searches. We formulate lensed-pair identification as a binary verification problem using two preprocessed strain segments. To address this task, we propose Physics-Inspired ResNet (PI-ResNet), a Siamese one-dimensional residual network for pairwise GW candidate classification. Unlike spectrogram-based prescreening approaches, PI-ResNet operates directly on whitened time-domain strain data and avoids an intermediate time--frequency image representation. A shared residual backbone with Squeeze-and-Excitation (SE) modules encodes the two input segments, and the paired embeddings are compared through absolute feature differences and Hadamard-product interactions. We train and evaluate the model using simulated GW signals from binary black hole mergers lensed by point-mass (PM) and singular isothermal sphere (SIS) lenses, injected into simulated LIGO and Einstein Telescope (ET) detector noise. Under ET design noise, PI-ResNet achieves accuracies of $95.60\%$ for SIS lenses and $93.80\%$ for PM lenses, while maintaining $84.03\%$ and $78.25\%$ accuracy under simulated LIGO H1--L1 Gaussian noise. These results suggest that direct learning from 1D strain data provides an efficient and physically motivated preselection statistic for candidate lensed GW pairs, while also indicating the need for detector-domain adaptation.

We use Sun-as-a-star helioseismology data, collected by the Birmingham Solar-Oscillations Network (BiSON), to examine the relationship between the solar-cycle-induced frequency shifts of whole-Sun, low-angular degree solar p modes and well-known proxies of global solar activity. Changes in behaviour between the low-frequency modes and proxies, which in a previous study we found had occurred on the declining phase of Cycle 23, appear to have persisted into Cycle 25. More striking is a significant change in the relationship for higher-frequency modes, which the new Cycle 25 data now reveal. The observed mean frequency shifts in Cycle 25 are much stronger than one would expect for these modes based on the relationship between the frequencies and proxies seen in previous cycles, in particular Cycle 22. In sum, Cycle 25 is as strong as Cycles 22 and 23 when observed in this higher-frequency seismic band, in marked contrast to the relative sizes of the cycles seen in the global activity proxies, where Cycle 25 is noticeably weaker. When considered alongside a systematic reduction of the sensitivity of the mid-frequency modes to activity over the past three cycles, these results suggest that sub-surface structural changes associated with successive 11-year cycles are becoming ever more progressively confined just beneath the solar surface.

We present a comprehensive study of an infrared (IR) flare in the star-forming galaxy SDSS J010320.39+140152.5, which is selected from the sample of mid-IR (MIR) outbursts in nearby galaxies (MIRONG). Its MIR luminosity rose rapidly to a peak of $\sim5.4\times10^{43}$ \lum, maintained in the high state for about a year, and decreased continuously afterward. No optical variability was detected throughout the IR flare. Near-IR follow-up observations around the peak pinpointed the flare's location to spatially coincide with the galactic nucleus, with a $3\sigma$ upper limit of the offset of $\lesssim100$ pc. The IR spectral energy distribution (SED) of the flare is consistent with thermal emission of dust with temperatures of $\sim900$ K. Using a dust radiative transfer model, we inferred a peak UV luminosity of $\sim(4-10)\times10^{44}$ erg s$^{-1}$ and a total energy of $\sim(0.9-2)\times10^{52}$ ergs released. We ruled out the possibility of a supernova, and prefer that the IR flare originated from an obscured tidal disruption event (TDE) rather than a changing-look active galactic nucleus (AGN). This flare stands as one of the most compelling cases to date for the emerging class of dust-obscured TDEs in recent years. They are missed by optical surveys, partly accounting for the observed bias in TDE host galaxies, and represent a crucial, yet often overlooked, component for a complete understanding of the TDE population.

We report the discovery of a new Cartwheel-type collisional ring galaxy, PGC\,1112751, which we named ``Eridanus Wheel'' (EW). Such systems result from head-on collisions between galaxies and are of considerable interest as laboratories for studying star formation in propagating density waves and the response of the star-gas disk of galaxies to strong external perturbations. During a systematic visual inspection of fields from the DESI Legacy Imaging Surveys, we identified a galaxy at a redshift of $z=0.0856$ whose morphology closely resembles that of the famous Cartwheel Galaxy. EW exhibits a well-defined inner ring and a more diffuse outer ring, with so-called ``spokes'' visible in the region between them. The ring galaxy and its possible intruder are connected by a faint optical bridge. The projected distance between the centers of the galaxies is about 60 kpc. Using data from the DESI Legacy Surveys, we performed a photometric study of galaxies in the $griz$ filters. We conclude that the Eridanus Wheel is a giant late-type galaxy with a strong radial color gradient, whose observed morphology is most likely explained by a relatively recent head-on collision with an early-type galaxy. The further evolution of this object will most likely lead to the formation of a galaxy with a low surface brightness disk.

Environment plays a crucial role in shaping galaxy formation, yet the impact of overdensities on the internal chemical structure of galaxies at cosmic noon is still under debate. Here, we present spatially resolved gas-phase metallicity gradients for 42 star-forming galaxies in three massive protoclusters at $z \sim 2.3$, derived fromHubble Space Telescope (HST) slitless grism spectroscopy from the MAMMOTH-Grism survey. We find that the majority (29 of 42, $\sim$69%) of these protocluster members exhibit positive (inverted) metallicity gradients, a fraction significantly higher than observed in field galaxies of similar mass and redshift. By examining correlations with global properties, we show that these positive gradients are strongly associated with galaxies that are metal-deficient relative to the field mass-metallicity relation, particularly among the massive population ($\log(M_*/M_\odot) > 9.95$). These trends suggest that galaxies in dense protocluster environments experience substantial, enhanced inflows of pristine gas toward their central regions, which dilute the central metallicity and produce the observed inverted gradients. Our results provide observational evidence that environmental effects actively regulate gas accretion and chemical redistribution during the peak epoch of cosmic star formation.

Long-term observations indicate that the relative intensity of cosmic-ray anisotropy remains below $0.1\%$ for energies less than $\sim 1$ PeV. Measuring such faint signals poses a significant challenge in data analysis, requiring careful removal of instrumental and atmospheric artifacts. The all-distance equi-zenith angle method is widely employed to extract cosmic-ray anisotropies, as it effectively suppresses the instantaneous variations arising from the instrument and atmosphere. \textcolor{black}{However, instability in the detector efficiency makes precise measurements of anisotropy challenging with this method.} In this work, we present an enhanced all-distance equi-zenith angle method for cosmic-ray anisotropy measurement. Unlike previous implementations, our improved approach enables the simultaneous measurement of anisotropies over multiple time frames and allows the detection efficiency to be determined directly from the data. This feature makes the method especially suitable for applications where the detector array does not operate with long-term stability\textcolor{black}{, and thus allows for the measurement of anisotropy with high-precision}. Moreover, our enhanced method is also feasible when the data do not span complete tropical years.

Aims. Our main aim with this work was to enlarge the pool of open clusters with determined carbon, nitrogen, and oxygen abundances in evolved giants to further advance chemical clocks in stellar age determinations. Methods. High-resolution spectra were analysed using a differential model atmosphere method. Carbon abundances were derived using spectral synthesis of the C2 band heads at 5135 and 5635.5 Å. The CN features at 6470-6490 Å were analysed to determine the abundances of nitrogen. The oxygen abundances were determined from the [O I] line at 6300 Å. Results. We provide abundances of C, N, and O for 88 giants in 28 open clusters and in two stars of the association Theia 1214. The results were compared with theoretical predictions and used for the analysis of the [C/N] relations with age, and we investigated the origin of the two Theia 1214 stars. Conclusions. Precise age dating requires separate age calibrations of [C/N] ratios for the first-ascent giants of the lower part of the red giant branch and for the red clump stars to account for the additional abundance alterations during the post-red giant branch luminosity bump evolution. In the first-ascent giant stars with larger turn-off masses, the observed C/N ratios are slightly higher than those predicted by standard models, and the obtained [C/N] versus age relation is flatter in the young age regime than in previous studies. We doubt that the two stars we investigated in the Theia 1214 association belong to the tail of NGC 752. Most probably, they are field stars.

Cosmic opacity may vary spatially due to the inhomogeneous distribution of dust, its grain properties, and the efficiency of photon attenuation. In this work, we present a model independent method to investigate the variation of cosmic opacity with redshift. Using strong gravitational lensing data we construct the opacity independent comoving distance function and we use latest supernovae type Ia (SNe Ia) Pantheon+ data to estimate the opacity dependent comoving distances. Using the distance duality equation, opacity parameter is constrained. Our analysis indicates a transparent Universe on average over the redshift range ($0.01 \leq z \leq 2.26137$) of Pantheon+ sample. However, if we split the dataset into subsamples with redshift bins of width $\bigtriangleup z = 0.1$, we find appreciable deviation from the transparency in several redshift intervals. Particularly, in the redshift range $0.3 < z \leq 0.4$, the opacity parameter is $\epsilon = -0.4283^{+0.1914}_{-0.2027}$. The current SNe Ia observations indicate the variation of opacity parameter with redshift. These results may have a significant impact on the values of the cosmological parameters deduced from the SNe Ia observations.

The statistics of large-scale structure are naturally described by power spectra in Fourier space. For fields on spatial hypersurfaces, translational invariance makes different Fourier modes uncorrelated and the power spectrum diagonal. Cosmological observables, however, are measured on our past lightcone, where wide-angle effects, radial evolution and integrated effects such as lensing break this symmetry: Fourier-space statistics become non-diagonal, with mode-mixing generated by the geometry of the lightcone itself. We define a more natural observer power spectrum by Fourier transforming over observer positions on a spatial hypersurface with fixed lightcone coordinates, rather than over source positions on a single lightcone. This forms a field on the observer hypersurface with a moveable light-ray leg. Statistical homogeneity of the observer hypersurface implies that this spectrum is diagonal for any observable, whether local or integrated and does not suffer from mode-mixing. We show how the various two-point statistics used in large-scale structure analysis are each recovered as projections of the observer spectrum. This extends directly to higher-order statistics. We illustrate it by constructing the relativistic kernel for the observed galaxy number count fluctuation, including density, redshift-space distortions, Doppler, lensing magnification, and integrated Sachs-Wolfe contributions.

We present a meteorite-calibrated Bayesian framework for searching archival abundance records for chemical technosignatures--operationally, compositional patterns better explained by an idealised "processed" template (endmember) than by the empirical distribution of natural rocks. We fit a multi-modal natural-composition reference using 3,493 whole-rock meteorite analyses, and for each of 697 star-paper abundance sets--spanning at least 397 distinct objects once Gaia-designated repeats are consolidated--we compare the Bayesian evidence for (i) natural material and (ii) a mixture of natural material with a fixed siderophile-enriched template, parameterised by a Ca-normalized mixing fraction alpha. Strong support for the processed template is uncommon: in the photospheric compilation (atm) 8/697 records have BF > 10 (4/697 have BF > 100), and in the diffusion-adjusted steady-state subset (acc ss; 148 records spanning at least 94 objects) 6/148 have BF > 10. We report the highest-evidence candidate records and infer the fraction of records detectably favoring the mixture model, with posterior medians pi-tilde = 0.011 (atm) and pi-tilde = 0.041 (acc ss). We calibrate the analysis with end-to-end injection-recovery experiments matched to each record's coverage and censoring. The calibration shows that discrimination is driven mainly by chemical information, typically requires greater-than-or-similar-to 5 detected elements for decisive support, and--for the siderophile template--is strongest for exact five-element panels that include Fe, Mg, Cr, and Ti together with Ni, Si, or Na. These results constrain the detectable incidence of the tested processed-composition class in current data and set observational requirements for future multi-element surveys and expanded template families.

The planet-forming disk of HD 142527 is known for its azimuthally asymmetric dust trap, shadows, and spiral arms. We use new ALMA observations to investigate the molecular composition and to determine the ongoing chemical processes and the origin of its asymmetric molecular emission. The observations cover a wide variety of molecular species, enlarging the known molecular inventory of this system. Strikingly, the emission of H$_2$CO, CN, and C$_2$H is dominated by spiral-like features peaking in the southern region of the disk, opposite to the large dust trap, while no relation is found between the observed asymmetries and the shadows seen in the scattered light. We attribute these features to low-density, late infalling, atomic carbon-rich material that locally enhances the C/O-ratio and, subsequently, facilitates the gas-phase formation of these species. The emission of C$^{17}$O and the HCO$^+$ $J$=1-0 transition is aligned with the large dust trap, likely due to an azimuthal enhancement in the surface density. Differences between the two observed C$^{17}$O transitions may be due to dust obscuration effects. This is not expected to affect molecular emission at 3 millimetres, given the lower optical depth of the dust trap. The four observed transitions of CS display different azimuthal extents and strengths, with the lines with lower upper level energies appearing more ring-like. An analysis of the $^{13}$CO brightness temperature yields no significant azimuthal temperature variations. Therefore, we propose that the observed CS transitions trace two different reservoirs: a cold reservoir that resides on a Keplerian orbit and a second, hotter reservoir of CS that is facilitated by the infalling material. A single weak transition of SO is observed, which may be explained by weak shocks induced by the spirals observed in the scattered light that liberate sulphur.

We present a novel, self-consistent, semi-numeric Cosmic Dawn (CD) simulation in which small-scale star formation (SF) is calibrated to the \emph{AEOS} and \emph{Renaissance} hydrodynamic simulations. SF proceeds within dark matter (DM) halos via neural network emulation while considering large-scale fluctuations in density and feedback. We translate the resulting 3D distribution of galaxies into predictions for the 21-cm brightness temperature, \Tb, and power spectrum, \PS. We simulate several unique realizations to study the impact of varying astrophysics on \Tb, finding that more efficient Population II (PopII) SF largely yields stronger Lyman-$\alpha$ coupling, resulting in a shallower and wider absorption trough. However, we find that PopII SF dominates \PS\ at $z \lesssim 20$ and on smaller scales at intermediate redshifts ($k \gtrsim 0.2\ \mathrm{Mpc^{-1}}$ at $z \simeq 34-20$) while Population III (PopIII) SF dominates \PS\ at $z\gtrsim34$ and on larger scales at intermediate redshifts. Compared with previous works, we find that the combination of hydrodynamic SF calibration, a critical halo mass for SF considering \Htwo\ self-shielding, and stochastic DM halo merger histories results in both earlier SF and higher SF rates across CD. Further, we find that the delay period separating PopIII and PopII SF (\tdelay) significantly impacts \Tb, and that one must include DM halo merger histories to properly account for this transition. Finally, we find our fiducial \Tb\ to be detectable at $z\lesssim25$ with 1080 hours of HERA observations under moderate foreground assumptions, and the lack of such a detection at $z \gtrsim 20$ would suggest \tdelay\ $\gtrsim$ 30 Myr.

Little red dots (LRDs) are compact high-redshift objects, newly discovered by the James Webb Space Telescope. Although LRDs exhibit broad Balmer emission lines suggestive of the presence of active galactic nuclei (AGN), their spectral features differ significantly from those of ordinary AGN. Recent studies suggest that their characteristics can be explained if accreting supermassive black holes (SMBHs) are embedded within dense gaseous envelopes and surrounded by compact stellar clusters. In this scenario, stars in the cluster can scatter onto plunging orbits that intersect the envelope and collide with its surface. Here we investigate the observational properties of such star-envelope collisions as luminous transient events. We find that collisions involving red supergiants with radii of $\sim 10^{3}~R_\odot$, together with gaseous envelopes whose masses are comparable to those of the central SMBHs, are the most promising targets due to their high luminosities and long durations. For compact clusters with sizes of $\lesssim 10~{\rm pc}$, such massive stars can participate in star-envelope collisions within their lifetimes at event rates reaching $\sim 0.3~{\rm yr}^{-1}$ per LRD. We show that these transients are detectable with future wide-field surveys such as the Nancy Grace Roman Space Telescope if they occur at relatively low redshifts ($z \lesssim 1$). Detection of such transients would provide strong evidence for the envelope+stellar-cluster scenario of LRDs and offer a unique probe of the envelope mass, which is otherwise difficult to constrain from LRD spectra alone.

Superluminous supernovae (SLSNe) are a rare class of transients with peak luminosities 10-100 times greater than those of standard core-collapse supernovae (SNe). The mechanisms powering their extreme brightness remain debated, with circumstellar medium (CSM) interaction, or energy injection from a central engine like a magnetar wind nebula being the most plausible scenarios. To further constrain the underlying mechanism, we carried out a systematic search for GeV gamma-ray emission using the Fermi-LAT telescope from a sample of nearby hydrogen-poor (Type I) and hydrogen-rich (Type II) SLSNe over the past 16 years. Among the sample, only SN 2017egm shows significant gamma-ray emission, with likelihood test statistic (TS) values of 26-33 (i.e., >5$\sigma$) depending on the adopted time window. The signal arises between 50 and 160 days after explosion and is well described by a power-law spectrum with index $\Gamma=2.17 \pm 0.23$. The emission is consistent both in terms of its light curve and its spectrum, with predictions from magnetar models requiring either low nebular magnetization or faster spin-down than dipole losses. The CSM shell interaction scenario can reproduce the observed flux level but not the observed timing of the gamma-ray signal. In addition, the observed ratio, $L_{\gamma}/L_{opt} \sim 1$, is inconsistent with theoretical expectations and not in line with ratio measurements in other interacting CSM-dominated objects (e.g., novae or SNe) where this ratio is less than $10^{-2}$. Our study strongly suggests that a central engine like a magnetar plays a key role in this SLSN and could explain the bulk of the optical and gamma-ray light curves properties. Finally, simulations of 50 hours of CTAO observations indicate that a SN 2017egm-like event would be detectable up to 140 Mpc in the magnetar model but not in the CSM model due to strong gamma-gamma absorption.

The thermochemical evolution of planetesimals is an underprobed stage of volatile delivery to terrestrial planets during their formation, and may contribute to the volatile depletion of the Earth relative to primitive chondrites. We have developed a model of C outgassing from porous, chondritic planetesimals. Our model tracks the thermal evolution and the production of CO/CO2 gas using the redox states of ordinary and enstatite chondrites (OC and EC, respectively, collectively the "NCs"), and CI and CV carbonaceous chondrites ("CCs"). We posit the formation of global fractures when local gas pressure exceeds confinement levels, which vent the excess directly to space, leading to efficient C depletion. We also account for sintering and the enthalpy of dehydration from wet carbonaceous chondrite bodies. We find that C depletion is more efficient on CC planetesimals than NCs due to the former's oxidized environment: for 10-100 km planetesimals formed at 2 Myr after CAI formation, > 50% of C is depleted in almost all CC bodies while < 50% is depleted in almost all NC bodies. Both the largest and the smallest bodies tend to preserve more C, the former due to sintering locking condensed C in against escape, while the latter due to efficient conductive cooling. Earlier accreted planetesimals deplete more C: bodies formed before ~ My deplete most of their C. Our results favor NC planetesimals as the C carriers during terrestrial planets' accretion. Terrestrial planets likely accreted from a mix of C-depleted and C-rich bodies from both CC and NC reservoirs.

Hubble is still in prime observing condition for making transformative discoveries in UV astronomy. In this white paper we describe the science case for a deep (S/N>30) UV spectroscopic survey with HST/COS targeting approximately 20 QSOs at 0.5<z<1.5 at good resolution (20 km/s). This survey would capitalize on our current UV capability, produce a legacy dataset enabling community science in many areas of galactic and extragalactic research, and pioneer a path for future UV science with the Habitable Worlds Observatory. Such high-S/N spectra are largely missing from the MAST archives, and would be analogous to the deep Hubble imaging fields (HDF, UDF, Frontier Fields) that have been enormously successful and far-reaching in their science impact. This legacy dataset would enable frontier science programs in several areas, including (1) studies of the CGM and IGM at unparalleled sensitivity, covering a wide range of UV metal lines and reaching very low H I column densities of log N=12.6 and low metallicities near [Z/H]=-2, enabling precision studies of the chemical abundances, ionization, temperature, and baryon and metal budgets of the CGM and IGM; (2) diffuse gas in the Milky Way and Local Group, including high-velocity clouds and gas streams from satellite mergers; (3) AGN outflows, which would be probed in the rest-frame extreme ultraviolet (EUV), covering continuum-generation mechanisms and diagnostics of gas in accretion-disk outflows.

The streaming instability is the leading model for planetesimal formation in protoplanetary disks, but it typically operates within the first ~Myr. In the Solar System, however, some planetesimals (the chondrite parent bodies) formed 2-4 Myr after disk formation, implying that dust must have been retained for extended periods. Pressure bumps efficiently trap dust, but trapping alone does not guarantee planetesimal formation: even modest gas turbulence can inhibit vertical settling and radial concentration, preventing dust density from reaching Hill density. This motivates the study of alternative dust-gas instabilities, such as the Dusty Rossby Wave Instability (DRWI). We investigate the viability of such instabilities in global disk simulations using the multi-fluid code fargOCA. We first reproduce previous 2D shearing-box results in a global 2D viscous disk and characterize the dust clumping produced by the DRWI. We find that the instability is suppressed in fully 3D viscous disks by unperturbed high-z gas layers caused by dust settling near the midplane. We then explore the inviscid limit and find that multiple dust sub-rings form, concentrating solids into thin ring structures. These would appear observationally as a single radially broad, vertically thin ring, explaining observed protoplanetary disk rings without invoking anisotropic turbulence. Dust concentrations in the sub-rings may remain below the threshold for gravitational collapse, but gas photoevaporation enhances dust settling and radial concentration, eventually forming dense dust clumps in both viscous and inviscid cases. We conclude that planetesimal formation within dust-trapping pressure bumps is favored in very low-viscosity disks at late evolutionary stages, after sufficient gas removal by photoevaporation. This is consistent with the inferred late formation of chondrite parent bodies in the Solar System.

Full-disk observations of the Sun in the Ca II K line have been carried out since the late 19th century at various observatories worldwide. These long-term records of solar activity are crucial for reducing discrepancies among solar irradiance reconstructions and for advancing our understanding of the solar dynamo. To construct a consistent composite record, data from different observatories must be cross-calibrated to account for variations in spectral passband and spatial resolution, which are the primary sources of discrepancies between archives. In this study, we use high spectral and spatial resolution observations in the Ca II K line from the state-of-the-art Sunrise III mission to emulate different passbands and derive empirical contrast-contrast relationships between them. We find that these relationships are well described by a power law and provide coefficients for different combinations of passband widths in the range 0.1--9 Angstroms and spatial resolutions between 1 arcsec and 6 arcsec. Applying such a relationship to observations from two major Ca II K archives demonstrates its potential to improve their cross-calibration. The results provide a foundation for the construction of a consistent, century-long time series of solar activity from historical and modern Ca II K observations.

Molecular emission is observed in a wide variety of astrophysical environments, yet a substantial fraction of spectral features detected at mm wavelengths remains unidentified. Identifying these features is essential for constraining the inventory of interstellar and circumstellar molecules and for understanding the chemical pathways operating in evolved stars. In this study, we investigate a set of weak unidentified molecular features detected in the C-rich PN IC 418. We aim to constrain the nature of their molecular carriers and assess their possible connection to fullerene-related chemistry. High-sensitivity observations at 2, 3, and 7 mm were carried out using the RT40m and IRAM 30m radio telescopes. The spectral features found in these data sets were compared with public molecular spectroscopic databases. Spectral-pattern searches and line fits were performed under linear, symmetric, and asymmetric rotor approximations to estimate rotational constants of potential molecular carriers. We report the detection of 20 weak (SNR~2-13) unidentified features (UFs), none of which can be attributed to mm radio recombination lines, instrumental artifacts, or known molecular species. The observed features are inconsistent with the regular line spacing expected from linear molecules or symmetric rotors, although a recurrent doublet-like pattern is identified. The estimated rotational constants (B~2 500-3 660 MHz) suggest carriers with 4-13 atoms and are incompatible with those expected from C60 derivatives (B~100 MHz). Non-planar carbonaceous molecules produced during the destruction/processing of hydrogenated amorphous carbon (HAC) grains are suggested as promising candidates. The catalog of UFs presented here is made publicly available to facilitate future comparisons with laboratory measurements and theoretical calculations aimed at identifying their molecular carriers.

The most promising candidate for short-duration gamma-ray bursts (GRBs) is the merger of two neutron stars (NSs), which produces kilonovae (KNe) in the aftermath. This merging can result in a fast-spinning, highly magnetic NS, known as a millisecond magnetar, whose accretion processes can explain different phases in GRBs. The identification of a KN associated with the atypical long-duration GRB 211211A contradicted the classification schemes of the GRB progenitors. This study presents a comprehensive analysis of gamma- and X-ray observations, focusing on modeling X-ray data from a long-lived magnetar with two distinct fallback accretion rates ($\dot{M}\propto t^0$ and $\propto t^{\frac12}$) during the initial phase. The internal energy dissipation of the magnetar spin-down power, through the magnetization parameter, accounts for the long duration of the prompt gamma-ray episode observed in GRB 211211A. Furthermore, we provide a satisfactory explanation for the precursor and extended emissions following the prompt episode within the magnetar model with two fallback accretion rates. Although these accretion rates explain different characteristics, the model that incorporates a variable accretion rate offers a more accurate description. The current scenario for the GRB 211211A observations aligns with a compact binary merger that produces a long-lived magnetar instead of an immediate black hole.

Current observations with the James Webb Space Telescope (JWST) suggest that star-forming galaxies produce enough ionizing (LyC; $\lambda < 91.2$ nm) photons to drive cosmic reionization, but the efficiency with which these photons escape their host galaxies remains uncertain. Absorption by the neutral intergalactic medium progressively suppresses direct LyC detections above redshift $z\sim3$, forcing astronomers to rely on indirect diagnostics of LyC escape calibrated at low redshift. Low-resolution ultraviolet observations of high-redshift analogs obtained with the Cosmic Origins Spectrograph onboard the Hubble Space Telescope (HST) have been critical for developing these diagnostics. These studies suggest that stellar feedback plays a central role in regulating LyC escape, although the role of galactic winds and the underlying physical mechanisms remain poorly constrained. High-resolution spectroscopy blueward of 160.0 nm (rest-frame) is required to resolve the kinematic structure of the winds and reveal the physics governing LyC escape. Such observations are currently only possible with HST and represent a major science driver for the future Habitable Worlds Observatory (HWO). Extending the lifetime of HST and prioritizing ultraviolet observations are essential for interpreting current JWST studies of the early Universe and important preparatory science for HWO.

The outer rings (ORs) of Supernova (SN) 1987A were ejected ~20000 years before the explosion. Their characterisation is crucial for constraining the properties of the progenitor of this famous SN. While numerous studies investigated in detail the ejecta, equatorial ring (ER), and reverse shocks, few were dedicated to the ORs. We fill this gap and investigate the ORs physical properties. We analyse data obtained over a long temporal period, from multiple instruments, and over a wide wavelength range from optical to mid-infrared of the northern and southern ORs (NOR and SOR). We combine observations taken with HST between 1994 and 2022, VLT/MUSE in 2023, and JWST in 2022 and 2024. We measure emission flux in the ORs in HST and JWST/NIRCam images. We extract optical and mid-infrared spectra for the ORs in MUSE and JWST/MIRI/MRS data and measure line emission fluxes. We analyse the evolution of the ORs clumps' morphology over time with HST. The optical lightcurves of the ORs have shown a steady decline with time over the last 30 years. It is expected as the ORs were ionised by the initial SN UV-flash and are since then fading. The observations do not show any sign of interaction of the SN ejecta with the ORs. We estimated the decay times for [O III] to be 900 and 680 days for the NOR and SOR, and for Halpha+[N II] to be 15870 and 7160 days for the NOR and SOR. We constrained the temperature from the optical [N II] lines to 13400-16900K and 11800-14500K for the NOR and SOR. We constrained the electron density from the optical [S II] lines to 610-670cm-3 and 720-790cm-3 for the NOR and SOR. The spectra of the ORs differ significantly from the spectrum of the ER in lines detected and line ratios. The ORs will likely keep on fading for the next years, until the SN ejecta sweep them up. Continued monitoring of SN1987A and its ring system at all wavelengths is essential to capture this instant.

Here we present an updated shape model of (486958) Arrokoth, the bilobate Kuiper Belt Object (KBO) which the NASA New Horizons spacecraft flew past in 2019. This updated shape model uses all of the resolved images of Arrokoth obtained by the New Horizons LOng Range Reconnaissance Imager (LORRI). We developed an updated shape modeling algorithm which allowed the shape and rotational pole of Arrokoth to be fit to much better quality with an efficient use of GPU-accelerated features. The resulting model of Arrokoth's contact binary shape is significantly thicker and of larger volume than the one previously published immediately after the flyby by Spencer et al (2020). We show that Arrokoth's smaller lobe Weeyo is roughly spherical in shape, while the larger lobe Wenu is more flattened, with the volume ratio between the lobes being roughly 2:1. Owing to Wenu's oblate shape, Arrokoth's rotational lightcurve would have significantly lower mean reflectance when viewed from subobserver latitudes that would have shown lightcurve variation. We discuss the impact this may have on estimates of the frequency of contact binaries in the Kuiper Belt. We also discuss the implications of this shape for the formation of Arrokoth, particularly in the context of the Streaming Instability.

Sub-Neptunes and Neptunes are often modeled with distinct, fully convective layers. Yet, there are several arguments for compositions gradients that can inhibit convection. In these regions, energy transport depends on the thermal conductivity and radiative opacity. We compare three thermal conductivity models and investigate their impact on planetary evolution accounting for the possibility of convective mixing eroding composition gradients. Using a modified version of MESA, we model the evolution of planets with masses of Mp=5, 10, 15 Mearth and three initial entropies. We implement thermal conductivities for: pure water, fully ionized matter, and constant electron conductivity. Convective mixing complicates the relation between conductivity, evolution, and radius. For hot forming planets with a large composition gradient, where the heavy-element mass fraction changes gradually from the core to the envelope, convective mixing has a large impact on the radius evolution. In this case, the thermal conductivity is less relevant and the radii converge to similar values after billions of years. For cold forming planets or narrow composition gradients, convective mixing is less efficient. If the composition profile is not altered significantly, the thermal conductivity becomes critical. It determines how much energy can be trapped beneath stable composition gradients. For intermediate initial entropies, high thermal conductivity inhibits convection. Further work is required to determine the thermal conductivity for various mixtures expected in sub-Neptune and Neptunes at high densities and temperatures. In addition, further constraints on the entropy and composition profile after formation can reduce the degeneracy of the planetary evolution, in particular, the dependence of the radius with time.

We introduce Cosmo-PINN, a Physics-Informed Neural Network for reconstruction of the cosmological theory. In this work we demonstrate the application of the Cosmo-PINN in the reconstruction of the dark energy equation of state parameter $w_{DE}\left( z\right) $ directly from late-time cosmological observations. This framework overcomes the main limitation shared by Gaussian Process and Artificial Neural Network reconstruction approaches, where the recovered solution is driven by the data and it is not necessarily true that it is physically consistent, by embedding the cosmological constraints directly into the loss function as hard constraints, ensuring that the reconstructed quantities satisfy the physical laws at every point during the training. For the training of the network, we employed background data, and specifically the Baryon Acoustic Oscillation from DESI DR2, the Cosmic Chronometers and three different Supernova compilations, while we simultaneously introduce the cosmological parameters $H_{0},~\Omega _{m0}$ and $r_{\mathrm{drag}}$ as trained parameters. The reconstruction shows that the trained $w_{DE}\left( z\right) $ crosses the phantom divide within the redshift range $z=0.27-0.42$ in agreement with the value obtained by the Chevallier-Polarski-Linder model. In the quintessence scenario, for large redshifts the dark energy $\Omega _{DE}\left( z\right) $ provides a pressureless nonzero contribution to the cosmological fluid suggesting a unified scenario. Finally, we demonstrate the significance of imposing the physical constraints within the loss function by comparing the Cosmo-PINN reconstruction against a purely data-driven neural network with the same architecture.

delta Scuti stars are pulsating stars constituting the delta Scuti instability strip in the HR diagram, which consists of A and F stars of various evolutionary stages. They are in the transition region between high-mass hot stars and low-mass solar-like stars, making it essential to understand their magnetic properties to understand magnetism across the HR diagram. Also, discovering magnetic delta Scuti stars allows for magneto-asteroseismology, which can determine the internal rotation profile, internal magnetic field strength, and the efficiency of mixing and transport processes more accurately than classical asteroseismology. To date, magnetic fields have been detected at the surface of 13 delta Scuti stars. However, the overall incidence rate of magnetism in these stars remains unknown. Fossil magnetic fields are detected in 10\% of OBA stars. In this work, we investigated the incidence rate of surface magnetic fields among delta Scuti stars using photometric data from the CoRoT space mission. We analyzed long-duration (~5-month) light curves of ~1750 delta Scuti stars to search for pulsations and rotational modulation - a photometric signature that indicates chemical or temperature spots at the stellar surface, usually caused by magnetic fields. We have identified 147 rotational variables, which we designate as magnetic candidates, potentially drastically increasing the known population of magnetic delta Scuti stars, suggesting an incidence rate of fossil magnetic fields in delta Scuti stars similar to the incidence rate in OBA stars in general. Our analysis has also revealed a few delta Scuti - gamma Dor hybrid stars and four binary stars in the sample. We have determined rotation periods and projected rotation velocities of the magnetic candidates to select suitable targets for follow-up spectropolarimetric observations to confirm and characterize their magnetic fields.

Cluster analysis is a widely applied machine learning technique to understand the existing patterns in the population of gamma-ray bursts (GRBs), in order to explore their physical sources. In the present scenario, the number of clusters corresponding to differentiable groups is still under conflict, in spite of numerous attempts with the state-of-the-art clustering procedures. This crucial unknown parameter needs to be evaluated, either directly or indirectly in terms of other tuning parameters, to produce the clusters in GRBs through implementation of an appropriate clustering algorithm. While most of the applied algorithms reached two physically explained groups of merger and collapsar predominated by the short and long bursts respectively, other statistical approaches violated this binary partition. However, physical establishment of any additional cluster(s) is not yet confirmed. Therefore, we propose a new algorithm, from a different stream of clustering referred to as `completely parameter-free', which carries out the classification of GRBs in a manner that has not been tried so far. It indicates two main groups, of short and long duration bursts from the BATSE sample, compatible with the merger-collapsar theory.

The 14 Herculis system hosts two super-Jupiters on eccentric, significantly misaligned orbits. This orbital architecture represents a dynamical puzzle that demands explanation. In this work, we reproduce the system's dynamical history and current architecture using a large suite of N-body simulations of planet-planet scattering. Our results demonstrate that planet-planet scattering is able to reproduce 14 Her's peculiar orbital architecture, but only if additional massive bodies were initially present in the system that were subsequently ejected. The mass of any such ejected planet can in turn constrain the system's initial configuration. We also analyze the present-day secular evolution of the system and conclude that while there are most likely nontrivial eccentricity and inclination oscillations currently occurring, the magnitudes of these oscillations are not strong enough to allow tidal forces to meaningfully alter the system's architecture. Finally, we discuss how forthcoming observations from future Gaia data releases and the Roman mission may situate 14 Her's dynamical history within a broader, population-level framework.

Fast radio bursts (FRBs) are bright (Jansky-level) and short-duration ($\sim 1$ ms) flashes of extragalactic origin. Observations of single events have now been complemented by large-area surveys, delivering FRB catalogues and enabling the first population studies. The Northern Cross (NC) radio interferometer is one of the instruments performing observations of FRBs. In this work, we present the Italian Northern Cross Atlas of Radio Transients ({\tt INCART}), a public platform for the distribution of data products from the NC. {\tt INCART} makes available to the community the FRBs observed by the NC through manageable frequency-time series datasets and catalogues with best-fit physical parameters. The design of {\tt INCART} guarantees the possibility of scientific re-analysis of the FRB properties, in view also of future releases of the processing pipeline. Furthermore, {\tt INCART} focuses on long-term storage optimisation, which is a key aspect of state-of-the-art instrumentation. Public access to the FRB data from the NC maximises the legacy value of the collection, facilitates the synergy with other publicly-available catalogues, and fosters research group collaborations.

We investigate the presence of primordial oscillatory features in measurements of CMB anisotropies through a systematic comparison of phenomenological templates. Building upon previous searches for primordial features using Planck data, we compare the full PR3 legacy release with the PR4 (NPIPE) processing to assess how the results depend on the choice of CMB maps and likelihood framework. To maximise our sensitivity to rapidly varying oscillatory signals, we employ unbinned likelihoods. We find that several previously reported indications of oscillatory structure persist across different analyses, although none attains global statistical significance. Furthermore, some anomalies reported in earlier studies are substantially reduced when updated to the new versions of the CamSpec likelihood using Planck PR4 products. For all templates considered, we identify a small number of frequencies in the range $\omega \sim 10-100$ that improve the fit to the CMB data by up to $\Delta\chi^2 \simeq -10$ to $-15$ relative to the featureless reference model. However, this improvement is not supported by a Bayesian model comparison. The inclusion of three or four additional parameters can reduces the overall predictability of the feature models and leads to an Occam penalty. Finally, after properly accounting for the look-elsewhere effect, the significance of the preferred frequencies is reduced, corresponding to a global statistical significance of at most $2.6\sigma$. We present forecasts for forthcoming CMB experiments, highlighting the decisive role of next-generation polarisation measurements in distinguishing genuine primordial oscillations from statistical fluctuations and modelling systematics. The upper bounds or uncertainties on the feature amplitudes, expected from the combination of SO and LiteBIRD, improve by more than one order of magnitude.

Efficient computation of the angular bispectrum is an essential part of modelling large-scale structure observations, but it still remains an extremely challenging task. In this work, we compute the tree-level, unequal-time angular bispectrum in both real and redshift space. By deriving full-sky results, we show that the bispectrum can be expressed as a sum of products of two angular power spectra, enabling the use of our recently developed flat-sky approximation to enhance computational efficiency significantly. This flat-sky formalism preserves key line-of-sight mode information while discarding extraneous full-sky contributions. We validate our approach by comparing it with direct full-sky integration, finding excellent agreement across a wide range of scales and redshifts for all bispectrum configurations. At redshift $z = 1$, we achieve sub-percent agreement (for multipoles $\ell \gtrsim 5$) between full-sky and flat-sky results for equilateral, squeezed, and folded configurations, using narrow Gaussian radial window functions ($\sigma_z = 0.01$) in both equal-time and unequal-time scenarios. On small scales, where direct full-sky integration becomes computationally prohibitive, our results align with the Limber approximation (where applicable), confirming the robustness and accuracy of our implementation. To facilitate future studies, we provide a \texttt{Python} implementation of our results, which is publicly available on \texttt{GitHub}.

The most irreplaceable capability of HST in the 2030s is not only its angular resolution or its UV--optical sensitivity, but its accumulated time baseline. We recommend a Hubble Local Group Astrometric Legacy that would obtain matched 2030s ACS/WFC and WFC3/UVIS imaging of selected M31 and M33 star cluster fields, combine those observations with a careful astrometric audit of the existing archive, and deliver public transverse velocity products through MAST. PHAT and PHATTER already provide exceptional first epochs across the nearest large external spirals, resolving tens to hundreds of millions of stars and identifying thousands of star clusters and compact background reference objects. Earlier targeted HST programs, dating back to the mid 90's, can extend the temporal baseline in selected cases, but only after camera, chip, filter, dithering, crowding, and reference-frame triage. A coherent 2030s repeat campaign would turn the best of this archive into bulk cluster motions, enabling the first systematic orbital mapping of star cluster populations beyond the Milky Way. These measurements would constrain disk heating, cluster disruption, accretion histories, stream associations, the M31--M33 interaction, and the mass distributions of Local Group spirals. The same program would also preserve and stress-test the calibration infrastructure needed for high-stability optical/UV astrophysics in the HWO era: geometric-distortion solutions, PSF and CTE modeling, matched-epoch observing strategies, long-term reference frames, and durable public high-level products.

The existence of a landscape of metastable vacua raises the possibility that our Universe may have undergone quantum vacuum decay at late times. This work explores how such a transition can be tested with cosmological observables, focusing on precision distance measurements and cosmic microwave background (CMB) anisotropies. A set of phenomenological models is constructed in which late-time quantum tunneling changes the vacuum energy and may convert a subcomponent of dark matter into dark radiation, possibly accompanied by domain-wall production. The resulting expansion histories are compared with DESI DR2 baryon acoustic oscillation data; supernova distance measurements from DES-Dovekie, Pantheon+, and Union3; and a compressed CMB likelihood. For quantum-tunneling models, current cosmological distance measurements still allow a 50% decrease in the total vacuum energy for a transition redshift $z_t<1$. The model with dark-matter conversion and domain-wall production provides a good fit to resolve the tension between cosmological observables and the $\Lambda$CDM model, with a preferred transition around $z_t \sim 7$ and about 10% of dark matter participating in the transition. Additionally, CMB anisotropy constraints from bubble nucleation and the associated domain-wall network are derived and shown to strongly restrict slow or sparse late transitions. Applied to the minimal quantum-tunneling model, these constraints allow an $\mathcal{O}(10\%)$ decrease in the total vacuum energy for a transition redshift $z_t$ of order unity. For nonminimal models, dark-matter-density-dependent tunneling can proceed rapidly enough to evade such bounds. These results demonstrate that late-time quantum vacuum decay is a testable cosmological phenomenon and provide a concrete observational handle on metastable-vacuum physics motivated by landscape scenarios.

Galaxy redshift surveys encode a wealth of information generated by nonlinear gravitational evolution, galaxy bias, and redshift-space distortions, only part of which is accessible through standard two-point statistics. Motivated by the need for flexible and computationally efficient alternatives, we introduce the augmented correlation function, a general framework in which an arbitrary transformation of the galaxy field defines additional ``latent'' dimensions that extend the standard two-point correlation function and isolate clustering properties averaged out in conventional analyses. As a proof of concept, we study a latent variable constructed from the pairwise gradient of the inverse Laplacian of the galaxy density field, showing that the resulting statistics naturally distinguish clustering regimes associated with infalling and outflowing pairs. Using Fisher forecasts based on $z=1$ halo catalogues from the Quijote simulations within $\nu\Lambda\mathrm{CDM}$ cosmology, we find that the augmented correlation systematically yields tighter constraints on all cosmological parameters considered. Although these improvements should be regarded as indicative given the exploratory nature of the analysis and the limitations of Fisher forecasts and simulations, our results demonstrate the potential of augmented correlations as a flexible framework for extracting additional information from spectroscopic galaxy surveys.

In cosmological models, the Hubble parameter is determined by the time evolution of the scale factor, and current observations reveal a persistent tension between its values inferred from different probes, such as Cepheid variable stars and the cosmic microwave background. Within Tsallis' statistical framework, we identify two distinct definitions of fugacity associated with relativistic and non-relativistic regimes. For the non-relativistic sector, we introduce an effective chemical potential and establish its connection with the Gibbs free energy. We then explore a phenomenological correspondence between this effective chemical potential and an Unruh-like temperature associated with accelerated trajectories in an expanding cosmological background. As an application, we derive an effective expression for the Hubble parameter that includes a statistics-dependent contribution arising from the non-relativistic matter sector. This contribution suggests that non-Gaussian statistical effects, when consistently incorporated in the non-relativistic matter sector, can enhance the sensitivity of the expansion rate to underlying thermostatistical assumptions, achieving a substantial increase in sensitivity by approximately ten orders of magnitude when compared with previous relativistic constructions that investigated, at a phenomenological level, the discrepancy observed in current determinations of the Hubble constant.

We propose a gauge-symmetry origin of a rank-two Dirac neutrino mass matrix that enforces one exactly massless neutrino, while being consistent with the oscillation data, as well as cosmological constraints. The mechanism relies on a minimal dark $SU(2)_D$ gauge symmetry under which one right-handed-neutrino-like Weyl fermion is charged, thereby forbidding its Standard Model Yukawa coupling. Quantum consistency then fixes the minimal dark-sector completion: Cancellation of the Witten anomaly requires a second fermionic $SU(2)_D$ doublet, while a discrete $Z_4$ symmetry that forbids Majorana masses allows the two dark doublets to form a vectorlike pair. This anomaly-free completion gives rise to a secluded, confining dark sector with a viable dark matter candidate, linking the protected neutrino texture to dark infrared dynamics.

We extend the frequency-domain analysis of quasinormal modes in a dynamical, spherically symmetric black hole spacetime undergoing constant-rate mass evolution. In particular, we report a novel feature of the spectrum: the presence of purely imaginary eigenvalues in addition to the usual light-ring modes. We study the frequencies of these modes both analytically and numerically. The analytical calculation uses a novel formalism based on recent advances in connection coefficients of Heun functions. We then compute the frequencies numerically using a spectral method on hyperboloidal slices and find excellent agreement between the two approaches. Finally, we validate the frequency-domain results against an independent set of time-domain simulations. Our analysis shows that the purely imaginary modes govern the late-time signal through exponentially decaying tails. In the Schwarzschild limit, both frequency- and time-domain studies consistently show that the purely imaginary modes give rise to the familiar Schwarzschild power-law tail.

The possibility that Dark Matter (DM) is partially or totally constituted by stable Planckian remnants of light Primordial Black Holes (PBHs), suggested for instance by Loop Quantum Gravity (LQG), is investigated. Distinct phenomenological regimes are identified, including scenarios that trigger an early matter-dominated epoch. New constraints are derived on the initial PBH and final remnant abundances. We show that a significant initial abundance of PBHs lighter than $10^3$ kg would overproduce Planckian relics, implying that any observational evidence for such PBHs would challenge models with quasi-stable remnants. Conversely, the products of Hawking radiation from PBHs with masses between $10^3$ and $10^{12}$ kg impose that Planckian relics could only be a highly subdominant DM component. We identify a PBH mass around $10^3$ kg for which Hawking evaporation naturally reheats the Universe while the remnants entirely constitute the present-day DM. Such a scenario does not require fine-tuning the initial abundance of PBH of this mass, which could range from $10^{-10}$ to order one. These early-Universe cosmologies yield distinct observational signatures: scalar-induced gravitational waves sourced by primordial or Poisson fluctuations that are amplified by the early PBH-dominated era. Current and future observations of LIGO/Virgo/KAGRA, the Einstein Telescope and LISA, as well as probes of the effective number of relativistic degrees of freedom, can be used to probe and constrain the initial PBH abundance and the present-day abundance of Planckian relics.

Astrophysical neutrinos provide a unique probe of neutrino flavor changes over cosmological baselines. While the tau component of the neutrino flux is expected to arise almost entirely from mixing, current measurements rely primarily on rare double-cascade signatures. We investigate a complementary method to measure the tau fraction using the visible inelasticity of starting track events in neutrino telescopes. Muonic decays of tau leptons produce tracks with systematically larger visible inelasticity than those from muon neutrino interactions, potentially enabling statistical separation of the two flavors. Using realistic IceCube exposures and detector performance, we show that this observable already yields competitive sensitivity to the tau-to-muon flux ratio, $R_{\tau\mu}$, achievable with existing data. This approach may further enable flavor measurements of individual sources and the selection of tau-enhanced source catalogs. Starting-track inelasticity thus provides a powerful and immediately accessible probe of astrophysical neutrino flavor and of potential physics beyond standard neutrino mixing.

In this work we generalize the thermal decoupling, or freeze-out, of weakly interacting massive particle dark matter within the Tsallis nonextensive formalism. The generalization is implemented through $q$-deformed distribution functions obtained from the maximum entropy principle with Curado-Tsallis constraints. The Tsallis parameter $q$, which measures deviations from extensivity with respect to the limit $q=1$, is promoted to a dynamical quantity depending on the dimensionless variable $x=m_\chi/T$, where $m_\chi$ is the dark matter mass. This dynamical evolution is characterized by a relaxation toward extensivity, while requiring that the nonextensive deformation is not completely erased before freeze-out. We solve the Boltzmann equation assuming a sectorial deformation, where only the dark matter equilibrium abundance is generalized and the radiation background remains extensive. The relic abundance is computed for different dark matter masses and initial values of the Tsallis parameter. From this evolution, we extract the residual value $q_\chi^{\rm fo}$ at freeze-out, which is then used as the initial input for a phenomenological memory channel. This channel propagates the residual nonextensivity into the radiation sector, specifically into the electron-positron plasma and neutrinos, while photons are kept extensive in order to avoid direct tensions with CMB physics. The resulting deformation modifies the neutrino energy density and the photon reheating contribution, producing a correction to $N_{\rm eff}$. We compare the predicted values with the compressed CMB+BAO constraint on $N_{\rm eff}$ and find that the residual-memory scenario can remain phenomenologically compatible with current bounds.

We develop a theoretical framework to describe the full interaction between vector vortex light fields and gravitational waves (GWs). Using perturbation theory and the canonical quantization of the electromagnetic field, we calculate the quantum transition probabilities of vector Bessel beams propagating through GWs. We demonstrate that GWs induce fourteen different quantum transition channels across orbital angular momentum (OAM) $l$ and spin angular momentum (SAM) $\sigma$, mapping initial states $\ket{\sigma,l}$ to $\ket{\sigma+\Delta \sigma,l+j-\Delta \sigma}$, where $\Delta\sigma \in \{-2, 0, 2\}$ represents the change in SAM and $j \in \{-3, \dots, 3\}$ denotes the change in total angular momentum. Among these channels, SAM-conserving transitions between OAM states, specifically $\ket{\sigma, l}\rightarrow \ket{\sigma, l\pm 1}$, provide the most viable mechanism for experimental detection. Conversely, spin-flip transitions are shown to be heavily suppressed relative to OAM transitions. Additionally, the reversal of SAM induces an asymmetric shift in the OAM transition channels, reflecting the underlying coupling between SAM and OAM during the gravitational interaction. Based on these transition channels, we propose a new cavity-based GW detection configuration. By relying on quantum transitions rather than macroscopic arm-length changes, this scheme is inherently insensitive to displacement-based disturbances like seismic noise, offering a new paradigm and frequency bands for GW observation.

Six challenges for the standard cosmological model $\Lambda$CDM are listed, which arise when comparing theoretical predictions with observational data on scales of ~1 Mpc. Different parameters of luminous and dwarf galaxies in the local sphere with a radius of 12 Mpc are presented. The average densities of stellar matter and dark matter are reproduced depending on a distance in the Local volume. Observational data on distribution of angular momentum of nearby galaxies are considered. A comparison of the dark matter mass estimates for systems of galaxies based on motions of their internal (virialized) members and neighboring galaxies is given. The reasons for the low derived value of the dark matter density, $\Omega_m = 0.08\pm0.02$, in the Local Universe with respect to the global value $\Omega_m = 0.30\pm0.02$ are discussed

We study the quantum chaos bound in the photon ring region surrounding black holes. By evaluating the Lyapunov exponent associated with unstable null geodesics in a broad class of generalized Kerr geometries, as well as the temperature induced by a string probe, we show that the quantum chaos bound is exactly saturated on equatorial circular orbits of the photon ring. We confirm our result by deriving the same exponent from out-of-time-order correlators in the near ring region. As a byproduct, we show that the photon ring saturation of the quantum chaos bound implies the saturation of the Bekenstein bound on the rate of information emission from the ringdown phase through the quasi-normal modes in the eikonal limit. Our results extend the known correspondence between black hole thermodynamics and chaotic dynamics, highlighting the role of the photon ring as a probe of the fundamental limits on thermalization and information scrambling in black holes.

Weakly ionized plasmas can be found in the lower layers of the solar and stellar atmospheres and in structures such as prominences and spicules. A variety of density perturbations and bulk flows detected in these environments have been explained as the result of the ponderomotive force generated by nonlinear Alfvénic waves. In addition, the dissipation of the energy carried by these waves leads to heating of the plasma. Here, we use a two-fluid model to study the combined influence of Hall's current and elastic collisions between ions and neutrals on the propagation of linearly and circularly polarized transverse waves in weakly ionized plasmas. We derive analytical expressions for the damping and heating rates, showing their dependence on the strength of the collisional coupling and on the polarization state. We also perform numerical simulations to investigate the nonlinear generation of density perturbations and bulk flows related to the ponderomotive force and the energy dissipation by the ion-neutral interaction. We find that the nonlinear perturbations associated with the circularly polarized eigenmodes do not show the oscillatory motions typically caused by linearly polarized eigenmodes, but they retain the non-oscillatory bulk flows. We also briefly discuss how in weak coupling conditions the nonlinear dynamics of the neutral fluid is mainly driven by the wave energy dissipation while the ponderomotive force only directly acts on the charged fluid, resulting in different amplitudes of the longitudinal motions and the perturbations of density and temperature.

We study black hole (BH) formation from the nonlinear growth and collapse of primordial perturbations during the matter-dominated era. Modelling cold dark matter (CDM) as pressureless dust, we describe the collapse in a fully nonlinear relativistic framework using the Lemaître-Tolman-Bondi (LTB) and quasi-spherical Szekeres solutions as exact perturbations of a spatially-flat Friedmann-Lemaître-Robertson-Walker (FLRW) $\Lambda$CDM background. At first order in relativistic scalar perturbation theory, the growing mode of any relevant quantity can be expressed in terms of the conserved gauge-invariant curvature perturbation $\mathcal{R}_c$, which acts as a potential for the 3-curvature of hypersurfaces orthogonal to the matter 4-velocity. We use this result to express the active gravitational mass and curvature functions of the LTB and Szekeres models in terms of the initial values of $\mathcal{R}_c$ and its spatial derivatives. From these initial curvature data we derive: (i) the turn-around, collapse, and apparent-horizon formation times, and (ii) the regularity conditions required for BH formation. We show that sinusoidal and Gaussian profiles do not provide viable BH-forming channels, whereas broad compensated curvature peaks, naturally predicted by peak theory, do. We then estimate the formation times of $10^{3}-10^{6}~\mathrm{M}_\odot$ massive BH seeds produced by the direct collapse of primordial CDM curvature peaks, finding full BH formation at redshifts $z>5$, with core collapse beginning at $10 \lesssim z \lesssim 16$. Finally, we characterize the local dynamics and singularity type of the collapse (point-like, cigar-like, or pancake-like) directly from the initial comoving curvature data, clarifying the role of the initial shear in selecting the collapse end-state.

Skipper Charge-Coupled Devices (Skipper-CCDs) are a leading technology in the search for sub-GeV dark matter and coherent elastic neutrino-nucleus scattering. A key background for rare-event searches with these detectors arises from "spurious charge" -- single-electron events generated when charges are transferred through the active region to the serial register, and across the serial register to the readout stage. We present a characterization of spurious charge in both the active region and the serial register of SENSEI Skipper-CCDs, and show that, in a well-shielded low-background environment, the dominant contribution originates in the serial register during Skipper readout, when horizontal clocks are held at constant voltage between pixel transfers. Motivated by this finding, we develop a "tri-level" clocking scheme in which the held-low phase is raised to an intermediate voltage during readout to suppress trap-mediated charge generation. Using the SENSEI detector near the MINOS cavern, we measure a serial-register single-electron density of $(2.9 \pm 0.1) \times 10^{-5}$ electrons/pixel/image under standard SENSEI readout conditions, reduced to $(4.0 \pm 0.4) \times 10^{-6}$ electrons/pixel/image with tri-level clocking -- a factor of $\sim$7 improvement. This technique offers a promising path to lower backgrounds in current and future Skipper-CCD experiments.

Are AI agents tools, co-authors, or researchers? We present a quantified case study ($N=1$): a physicist supervising an AI coding agent (Claude Code, Sonnet and Opus models) over 12 work days and 57 sessions to build CLAX-PT, a differentiable one-loop perturbation theory module in JAX. We documented and classified 15 supervision events by intervention level. The agent resolved ten autonomously by iterating against oracle tests. Two more by the physicist's domain knowledge. The three it could not -- all evaded oracle detection -- share a common property: the agent treated symptom reduction as root-cause resolution. It spent 33 of the 57 sessions adjusting coefficients within a code architecture that could not represent the target physics, and could not re-evaluate its CLASS-PT branch choice even when prompted to reconsider; only an injected physics concept (anisotropic BAO damping) triggered the redesign. Separately, the agent committed a calibrated correction that passed all oracle tests but corresponded to no quantity in the theory, predicting wrong values at any other cosmology. The fudge factor was caught and replaced within the same session. Three supervision practices proved critical for catching what oracle tests missed: testing at diverse parameter points beyond the fiducial calibration; shared changelogs that surfaced stalled exploration across sessions; and an explicit rule against unphysical numerical patches. In this case, supervision design, not model capability, determined whether the agent's output was trustworthy. Closing the gap would require agents that propose architectural alternatives rather than optimize within a given structure, and distinguish predictive adequacy from explanatory correctness -- capabilities not exhibited here, not obviously addressed by scaling alone. [Abridged.]