Papers for Thursday, Sep 18 2025

We use artificial intelligence (AI) and supervisory adaptive control systems to plan and optimize the mission of precise spacecraft formation. Machine learning and robust control enhance the efficiency of spacecraft precision formation of the Virtual Telescope for X-ray Observation (VTXO) space mission. VTXO is a precise formation of two separate spacecraft making a virtual telescope with a one-kilometer focal length. One spacecraft carries the lens and the other spacecraft holds the camera to observe high-energy space objects in the X-ray domain with 55 milli-arcsecond angular resolution accuracy. Timed automata for supervisory control, Monte Carlo simulations for stability and robustness evaluation, and integration of deep neural networks for optimal estimation of mission parameters, satisfy the high precision mission criteria. We integrate deep neural networks with a constrained, non-convex dynamic optimization pipeline to predict optimal mission parameters, ensuring precision mission criteria are met. AI framework provides explainability by predicting the resulting energy consumption and mission error for a given set of mission parameters. It allows for transparent, justifiable, and real-time trade-offs, a capability not present in traditional adaptive controllers. The results show reductions in energy consumption and improved mission accuracy, demonstrating the capability of the system to address dynamic uncertainties and disturbances.

Precision cosmology with Type Ia supernovae (SNe Ia) requires robust quality control of large, heterogeneous datasets. Current data processing often relies on manual, subjective rejection of photometric data, a practice that is not scalable for forthcoming surveys like the Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST). We present a Bayesian framework that automates this step by integrating anomaly detection directly into the light curve fitting process. While the framework is model-agnostic and compatible with any spectral energy distribution (SED) model, here we demonstrate its application with the SALT3 model, implemented fully on GPU using \texttt{JAX-bandflux} for computational efficiency. Our method models the probability of each photometric measurement being anomalous with respect to the model, simultaneously inferring the physical supernova parameters and each data point's posterior probability of being a contaminant. Applying this framework to the Hawaii Supernova Flows dataset, we demonstrate its three principal capabilities: (i) robust mitigation of isolated outliers; (ii) automated identification and rejection of entirely corrupted bandpasses; and (iii) preservation of valid data by flagging only specific anomalous points within otherwise usable filters. We also find that contaminants are systematically brighter and bluer, which if uncorrected could bias subsequent cosmological inference.

Weak gravitational lensing observations of galaxy clusters are sensitive to all mass along the line-of-sight, introducing systematic and additional statistical uncertainties due to intervening structures. We quantify their impact on the recovery of mass density profile parameters using 967 clusters from the highest-resolution FLAMINGO simulation. We construct mock weak lensing maps, including both single source plane mocks and Euclid-like mocks with a realistic source redshift distribution. Applying Bayesian inference with Nautilus, we fit spherical and elliptical Navarro-Frenk-White models to recover the cluster mass, concentration, axis ratio, and centre, which we use to measure the brightest cluster galaxy (BCG) offset from the potential centre, or `BCG wobble'. We find that the spherical model fits clusters along under-dense sight-lines better than those along over-dense ones. This introduces a positive skew in the relative error distributions for mass and concentration, which increases with source redshift. In Euclid-like mocks, this results in a mean mass bias of $+5.3\pm1.4$% (significant at $3.5\sigma$) when assuming a spherical NFW model. We also detect a mean axis ratio bias of $-2.0\pm0.7$% ($2.9\sigma$), with no significant bias in concentration. We measure a BCG wobble of ~14 kpc in our Euclid-like mocks, with negligible contribution from line-of-sight structure. Furthermore, we predict the scatter in mass estimates from future weak lensing surveys that have mean source redshifts $z_\text s \gtrsim 1.2$ (such as the Nancy Grace Roman Space Telescope), will be dominated by line-of-sight structure and hence assuming a diagonal covariance matrix will lead to overestimating the precision. We conclude that cluster weak lensing pipelines should be calibrated on simulations with lightcone data in order to properly account for the significant impact of line-of-sight structure.

In the hierarchical assembly framework, the accretion history of the Milky Way is crucial to understand its evolution. However, in massive mergers, integrals of motion are not strictly conserved, redistributing accreted stars across dynamical spaces, such as energy-angular momentum ($E-L_z$). Additionally, the in situ disc becomes kinematically heated, acquiring halo-like orbits. Consequently, even for minor mergers, which should preserve dynamical coherence, we expect their kinematic-defined samples to be contaminated by both the massive merger(s) and the disc stars. This study aims at quantifying this contamination in known accreted halo substructures. As they are defined by kinematics, we aim at cleaning their samples analysing only chemical properties. We applied the kinematic selection criteria for the halo substructures to the Gaia EDR3 and APOGEE DR17 data. Then we adopted a Gaussian Mixture Model approach to chemically compare different substructures on a star-by-star basis, taking into account several abundances (Fe, Mg, Si, Ca, Mn, Al, and C). We argue that the chemical properties of Sequoia point towards a shared origin with GSE. Heracles, Thamnos and the Helmi Stream all likely comprise GSE and heated disc stars in a significant amount. Besides these two populations, we identified stars with chemical and orbital properties compatible with Sagittarius in the Helmi Stream and with $\omega$ Cen in Thamnos. Finally, GSE itself is contaminated by Sagittarius. Halo stars chemically compatible with GSE are spread throughout the $E-L_z$ space and considerably contaminate every halo substructure studied in this work. None of these substructures appears to be a unique population of stars with its own origin. In addition to GSE, they all appear to be mixtures of stars chemically compatible either with the metal-poor disc, Sagittarius, $\omega$ Cen, or with a combination of them.

We reconsider primordial black hole physics in Randall-Sundrum Type-II universes, focusing on constraints from cosmological and astrophysical observables. We pay particular attention to scenarios that allow the entirety of dark matter to be in the form of higher-dimensional primordial black holes. This is possible for a range of AdS radii and black hole masses. Observable constraints are generally modified due to the changes in the higher-dimensional gravitational sector, and come from low-energy $e^{\pm}$ emission, microlensing, and possibly from contributions to unresolved radiation backgrounds. We discuss constraints from the cosmic microwave background due to injection of Hawking quanta into the intergalactic medium. Finally, we comment on recent discussions on the compatibility of higher-dimensional black holes and the KM3-230213A event.

We present results from a deep, coordinated $XMM$-$Newton$ + $NuSTAR$ observation of the type 1 Seyfert PG 1426+015, a source of particular interest as the most massive reverberation-mapped black hole to date ($\log [M_{\rm{BH}}/M_{\odot}]$ = $9.01^{+0.11}_{-0.16}$). The high-resolution RGS data confirm the 'bare' nature of the source, showing no evidence for absorption beyond the Galactic column, while the broadband spectrum unambiguously reveals the presence of relativistic reflection from the innermost accretion disc (in the form of a relativistically broadened iron emission and associated Compton reflection hump) as well as confirming the presence of the strong soft excess reported previously. We explore whether relativistic reflection can successfully account for the soft excess along with the higher-energy reflection features, utilizing the two most-commonly used reflection codes (REFLIONX, XILLVER). Ultimately we find that both models are able to successfully reproduce the soft excess, though in the case of the XILLVER model this is contingent on reducing the strength of the O VIII line included in the model, as otherwise this feature prevents the model from reproducing the data. The reflection models that successfully reproduce the broadband data imply a relatively high density for the accretion disc of $\log [n_{\rm{e}} / \rm{cm}^{-3}] \sim 18$, consistent with the loose anti-correlation seen from other AGN in the $\log [n_{\rm{e}} / \rm{cm}^{-3}]$ vs $\log[m_{\rm{BH}} \dot{m}^2]$ plane, as well as a moderate-to-high black hole spin of $a^* \gtrsim 0.7$. This preliminary spin constraint is strongly dependent on the assumption that the soft excess is dominated by relativistic reflection.

Systems in which two oscillating stars are observed in the same light curve, so-called asteroseismic binaries (ABs), arise from either chance alignments or gravitationally bound stars. In the latter case, ABs offer a novel way to find binary systems and combine asteroseismology and orbital dynamics to determine precise stellar parameters for both stars. Such systems provide valuable tests to stellar models and scaling relations. While population synthesis studies predict approximately 200 ABs in the Kepler long-cadence data, only a few have been detected to date. In this work, we aim to (1) expand the sample of ABs in Kepler data, (2) estimate global asteroseismic parameters for both stars in each AB, and (3) assess whether these pairs are gravitationally bound. We analysed 40 well-resolved ABs identified in Kepler long-cadence data, and matched these solar-like oscillators with Gaia DR3 sources using spectroscopic estimates of $\nu_{\rm max}$. To assess whether each pair is gravitationally bound, we checked their projected separation and parallax consistency, and compared observed total orbital velocity differences from astrometry with theoretical predictions from Keplerian orbits. We find that most ABs appear to be chance alignments. However, two systems, KIC 6501237 and KIC 10094545, show orbital velocities, seismic masses, and evolutionary stages consistent with a wide binary configuration, with probabilities of ~50% and ~25%, respectively. Furthermore, eleven ABs are likely spatially unresolved binaries based on Gaia multiplicity indicators. Our findings suggest that most seismically resolved ABs in the Kepler field are not gravitationally bound, in contrast to earlier population synthesis predictions. Remarkably, the two wide binary candidates identified here are promising benchmarks for asteroseismic calibration. Spectroscopic follow-up is necessary to confirm their binary nature.

The recently identified Gaia population of main-sequence--white dwarf (MS+WD) binaries at separations of ${\sim}\,1~{\rm AU}$, often with moderate eccentricities, is not readily reproduced by binary population synthesis models. Barium stars represent a closely related population whose enrichment in $s$-process elements both confirms the presence of a WD companion and attests to past binary interaction. It also indicates that mass transfer occurred at least during the late- and post-AGB phases of the WD progenitor, when $s$-process elements are dredged up. In this work, we further explore the connection between the astrometrically identified Gaia MS+WD binaries and the classical barium star population. To achieve this, we used high-resolution FEROS spectroscopy to measure abundances for 30 Gaia DR3 non-single-star binaries, identifying 10 as Ba-enriched. Together with our recent analysis of archival GALAH data, this yields a sample of 38 barium dwarfs with dynamically measured WD masses, compared to only 6 previously known systems with known WD masses at these separations. We find that, in cases where metallicity is sufficiently low to facilitate efficient $s$-process production, barium and yttrium enrichment is often detected. This enrichment is also identified in eccentric systems, suggesting that post-AGB mass transfer mechanisms are capable of pumping eccentricity into the orbit or occur without erasing it. Our results indicate that the Gaia MS+WD binaries trace the population from which barium stars emerge. Treating the large Gaia-discovered population as an extension of known $s$-process enriched dwarfs opens an avenue to empirically constrain their formation and evolution.

Earthshine observations offer a unique opportunity to study Earth as an exoplanet seen from the Moon. As the Sun-Earth-Moon geometry changes, Earth can be observed as a spatially unresolved exoplanet at different phase angles, providing important context for future observations of Earth-like exoplanets. Here, we present a catalog of Earthshine polarization spectra obtained with FORS2 on the VLT, covering diverse scenes, surface conditions, cloud properties, and weather patterns for over a decade. For the first time, we model this extensive dataset in detail using a homogeneous modeling framework. Previous efforts to model some of these spectra struggled to reproduce the observed polarization continuum, even with advanced 3D radiative transfer models incorporating satellite-derived surface and atmospheric data. We improve upon this with a 3D model that includes subgrid cloud variability, wavelength-dependent surface albedo maps, and an accurate treatment of ocean glint. Our simulations successfully reproduce most observed spectra to a much higher precision than previously possible. Our statistical analysis reveals that the spectral slope in the visible can distinguish between ocean and mixed surfaces in both reflected and polarized light, which is not possible using broadband filters alone. Polarized light at large phase angles, beyond the Rayleigh scattering regime, is particularly effective in differentiating oceans from land, unlike reflected light. We also identify correlations between cloud optical thickness and the polarized spectral slope, and between cloud cover and broadband B-R differences in reflected light, demonstrating the diagnostic power of these observations. This work highlight the potential of polarization for characterizing Earth-like exoplanets. From polarization alone, we can infer oceans, vegetation, and an active water cycle, key indicators of a habitable planet.

The dust emission polarization spectrum -- how the polarization percentage changes with wavelength -- serves as a probe of dust grain properties in star-forming regions. In this paper, we present 89 $\mu$m - 214 $\mu$m polarization spectrum measurements obtained from SOFIA/HAWC+ for three star-forming clouds -- OMC1, M17, and W3. We find that all three clouds have an overall decreasing polarization percentage with increasing wavelength (i.e., a ``falling polarization spectrum''). We use SOFIA and Herschel data to create column density and temperature maps for each cloud. We fit for the slope of the polarization spectrum at each sky position in each cloud, and using the Pearson $r$ coefficient we probe each cloud for possible correlations of slope with column density and slope with temperature. We also create plots of slope vs. column density and slope vs. temperature for each cloud. For the case of OMC1, our results are consistent with those presented by J. Michail et al., who carried out a similar analysis for that cloud. Our plots of polarization spectrum slope vs. column density reveal that for each cloud there exists a critical column density below which a falling polarization spectrum is not observed. For these more diffuse sightlines, the polarization spectrum is instead flat or slightly rising. This finding is consistent with a hypothesis presented 25 years ago in a paper led by R. Hildebrand based on Kuiper Airborne Observatory data. This hypothesis is that regions shielded from near-IR radiation are required to produce a sharply falling polarization spectrum.

We use high-resolution cosmological zoom-in simulations to model mechanical and thermal feedback from AGN onto the evolution of Seyfert-type galaxies, studying the morphology of central galaxies growing within dark matter (DM) halos with masses logM/Mo ~11.8 at z=0. In Paper I, we focused on the end products at z=0, here we analyze evolution for z<10. Black holes (SMBHs) of ~10^6 Mo were seeded at z~9.1 and z~3.7, producing jets along their spin axes. Obtained SMBH accretion rates vary in the range ~0.3-10^(-4) of the Eddington rate. We compared the basic properties of galaxies, such as star formation rate, masses, gas and stellar fractions, bulge-to-disk mass ratios, SMBH masses, etc., over the range of redshifts. Our results indicate that jets and associated over-pressured bubbles have substantial effects on Seyfert galaxy evolution, including properties of the interstellar and circumgalactic medium (ISM and CGM), and even beyond. This feedback can suppress and even quench star formation, reduce stellar mass and gas fraction, modify the bulge-to-disk ratios, drive outflows from galaxies and host DM halos, and metal-enrich the CGM. The jets are largely but not exclusively contained within galaxies. However, over-pressured bubbles cross and modify the composition of the CGM and IGM, their thermodynamic and dynamic state, and generate vorticity. The CGM emerges as a complex region, where action of galactic outflows and jet-formed bubbles combines with the influx from cosmological filaments and diffuse accretion. Ultimately, the above processes affect the gas balance within the galaxy, its morphology, and gas supply to the SMBH, limiting its growth.

Extended periods of radio pulsations have been observed for six magnetars, displaying characteristics different from those of ordinary pulsars. In this Letter, we argue that radio emission is generated in a closed, twisted magnetic flux bundle originating near the magnetic pole and extending beyond 100 km from the magnetar. The electron-positron flow in the twisted bundle has to carry electric current and, at the same time, experiences a strong drag by the radiation field of the magnetar. This combination forces the plasma into a ``radiatively locked'' state with a sustained two-stream instability, generating radio emission. We demonstrate this mechanism using novel first-principles simulations that follow the plasma behavior by solving the relativistic Vlasov equation with the discontinuous Galerkin method. First, using one-dimensional simulations, we demonstrate how radiative drag induces the two-stream instability, sustaining turbulent electric fields. When extended to two dimensions, the system produces electromagnetic waves, including superluminal modes capable of escaping the magnetosphere. We measure their frequency and emitted power, and incorporate the local simulation results into a global magnetospheric model. The model explains key features of observed radio emission from magnetars: its appearance after an X-ray outburst, wide pulse profiles, luminosities $\sim 10^{30}{\rm{erg/s}}$, and a broad range of frequencies extending up to $\sim 100\, \mathrm{GHz}$.

White dwarfs accreting planetary debris provide detailed insight into the bulk composition of rocky exo-planetesimals. However, only one Kuiper-Belt analogue has been identified in that way so far. Here, we report the accretion of an icy extra-solar planetesimal onto white dwarf WD 1647+375 using ultraviolet spectroscopy from the Hubble Space Telescope. The accreted material is rich in the volatiles carbon, nitrogen, and sulphur, with a chemical composition analogous to Kuiper-belt objects (KBOs) in our solar system. It has a high nitrogen mass fraction ($5.1\pm1.6$ per cent) and large oxygen excess ($84\pm7$ per cent), indicating that the accreted planetesimal is water-rich (a water-to-rock ratio of $\simeq2.45$), corroborating a cometary- or dwarf planet-like composition. The white dwarf has been accreting at a rate of $\approx 2\times10^{8}$ g s$^{-1}$ for the past 13 years, implying a minimum mass of $\sim10^{17}$ g for the icy parent body. The actual mass could be several orders of magnitude larger if the accretion phase lasts $\sim10^5$ yr as estimated in the literature from debris disc studies. We argue that the accreted body is most likely a fragment of a KBO dwarf planet based on its nitrogen-rich composition. However, based on the chemical composition alone, it is difficult to discern whether this icy body is intrinsic to this planetary system, or may have an interstellar origin.

These lecture notes delve into field-level inference, a framework offering a robust way to extract more information and avoid biases compared to traditional methods for cosmological data analysis. The core idea is to analyse uncompressed maps to infer underlying physical fields and cosmological parameters. We introduce Bayesian hierarchical field-level models and discuss sampling techniques for exploring complex, high-dimensional posterior distributions. We review the framework that underpins field-level inference. Finally, we highlight some state-of-the-art applications across various cosmological probes, and the growing role of machine learning in enhancing field-level inference capabilities.

The source of high redshift dust has long been debated. One possible source are the ejecta of pair-instability and core collapse supernovae, but it is uncertain how much newly formed dust can survive the supernova reverse shock and be injected into the interstellar medium. We anticipate the structure of the pre-shocked dust to affect how much of it survives. Yet, the structure of dust formed in supernova is not well understood. We present three-dimensional soft-sphere, dust coagulation simulations aimed at studying the impact of temperature and particle size distribution on the structure of growing dust aggregates. Due to the qualitative nature of the concept of structure, there are many ways to define and quantify it, especially for an irregular aggregate. Thus, we test four metrics commonly used in the literature in order to compare the aggregate properties as well as the strengths and weaknesses of the metrics themselves. Our findings show that higher temperatures result in denser, more compact structures for all metrics tested. Additionally, we find that structures that coagulate from a distribution of particle sizes are denser and more compact than structures formed from identical particles under similar conditions. The latter finding, however, is true for three of the metrics except for the average number of contact points, which has proven to be the least reliable of the four considered metrics.

We present the first observations of chromospheric swirls using the Hydrogen-alpha Rapid Dynamics camera and Rapid Oscillations in the Solar Atmosphere imaging instruments at the Dunn Solar Telescope. These vortices contribute to heating and dynamics across the solar atmosphere. We analyze the morphology and evolution of 34 swirls and their cospatial bright points (BPs) from the photosphere to the mid-chromosphere. To examine swirl-BP interactions and temporal behavior, we use image segmentation, Fourier and spectral analysis, and local correlation tracking. The observed swirls have an average lifetime of 7.9$\pm$5 min and diameter of 3.6$\pm$1 Mm, with a positive correlation indicating smaller swirls tend to be short-lived. 76$\%$ are associated with a compact BP appearing 12 s to 9 min after swirl formation. Swirl motion is also closely linked to their BP(s) global motions. The swirls exhibit a mean angular speed of 0.04 rad s$^{-1}$, radial speed of 17.7 km s$^{-1}$, and period of 180 s. We observe the formation of a spiral-shaped swirl driven by a BP interacting with a large photospheric vortex. The BP is dragged toward the vortex centre, after which the swirl forms. The BP undergoes changes in orientation and elongation that mirror the swirl's chromospheric development. A time lag of -42.5 s between the sudden change in the BP's orientation and the peak of the swirl's intensity variation suggests torsional Alfven waves may contribute to swirl evolution. Our results support a magnetic origin for swirls rooted in motions of photospheric BPs.

The Lyman-alpha (Ly$\alpha$) forest at $z \sim 5$ offers a primary probe to constrain the history of the Epoch of Reionization (EoR), retaining thermal and ionization signatures imprinted by the reionization process. In this work, we present a new inference framework based on JAX that combines forward-modeled Ly$\alpha$ forest observables with differentiable neural emulators and Hamiltonian Monte Carlo (HMC). We construct a dataset of 501 low-resolution simulations generated with user-defined reionization histories and compute a set of 1D Ly$\alpha$ power spectra and model-dependent covariance matrices. We then train two independent neural emulators that achieve sub-percent errors across relevant scales and combine them with HMC to efficiently perform parameter estimation. We validate this framework by applying it to a suite of mock observations, demonstrating that the true parameters are reliably recovered. While this work is limited by the low resolution of the simulations used, our results highlight the potential of this method for inferring the reionization history from high-redshift Ly$\alpha$ forest measurements. Future improvements in our reionization models will further enhance its ability to extract constraints from observational datasets.

Nearby giant exoplanets offer an opportunity to search for moons (exomoons) orbiting them. Here, we present a simulation framework for investigating the possibilities of detecting exomoons via their astrometric signal in planet-to-star relative astrometry. We focus our simulations on $\alpha$ Centauri A, orbited by a hypothetical giant planet consistent with candidate detections in Very Large Telescope and James Webb Space Telescope observations. We consider a variety of observatory architectures capable of searching for exomoons, including upcoming facilities and also a hypothetical dedicated facility $-$ e.g., a purpose-built space telescope with diameter = 3m, central observing wavelength of 500 nm, and contrast-limited performance of $\sim$10$^{-9}$ in 1 hr observations. We find that such a facility would be capable of detecting $\sim$Earth-mass moons in a five year campaign, assuming a Saturn-mass planet. More generally, we simulate expected detection limits for a variety of levels of astrometric precision. We find that moons as small as $\sim$0.2 M$_\oplus$ on orbital periods of 4$-$30 days can be detected with astrometric precision of 0.1 mas and observing cadence of 1 hr over a five year campaign. Additionally, we find that a 39m ground-based telescope can detect Earth-sized exomoons orbiting the same hypothetical planet with a more modest observing cadence of one day. We discuss these results as motivation for a dedicated space observatory as well as a more detailed study of the physical parameters of a greater variety of star-planet-moon systems.

The architecture of planetary systems is a key piece of information to our understanding of their formation and evolution. This information also allows us to place the Solar System in the exoplanet context. An important example is the impact of outer giant planets on the formation of inner super-Earths and sub-Neptunes. Radial velocity (RV) surveys aim at drawing statistical insights into the (anti-)correlations between giants and inner small planets, which remain unclear. These surveys are limited by the completeness of the systems, namely, the sensitivity of the data to planet detections. Here, we show that we can improve the completeness by accounting for orbital stability. We introduce the Algorithm for the Refinement of DEtection limits via N-body stability Threshold (ARDENT), an open-source Python package for detection limits that include the stability constraint. The code computes the classic data-driven detection limits, along with the dynamical limits via both analytical and numerical stability criteria. We present the code strategy and illustrate its performance on TOI-1736 using published SOPHIE RVs. This system contains an eccentric cold giant on a 570-day orbit and an inner sub-Neptune on a 7-day orbit. We demonstrate that no additional planet can exist in this system beyond 150 days due to the gravitational influence of the giant. This outcome allows us to significantly refine the system completeness and also carries implications for RV follow-ups. ARDENT is user-friendly and can be employed across a wide variety of systems to refine our understanding of their architecture.

Large-scale galaxy redshift surveys conducted over the last couple of decades have proven crucial in deepening our understanding of structure growth in the Universe and galaxy evolution. While there have been several such surveys, until now those that achieve the high completeness and precision necessary to probe the low-mass end of galaxy groups have been limited to relatively low redshifts ($z\lesssim0.3$), with surveys exploring the more distant Universe being constrained by small sample sizes and/or low redshift completeness. The recent Deep Extragalactic VIsible Legacy Survey (DEVILS) aims to explore galaxy environment over the last $\sim6$ Gyr with a completeness level comparable to the most complete local Universe surveys ($>85\%$). In this work, we present the galaxy group catalogue for the D10-COSMOS field from DEVILS, which achieves a redshift completeness of $90\%$ for galaxies with $Y<21.2$ mag. We showcase the science potential by exploring the impact of environment on the fraction and power of active galactic nuclei (AGN), finding that satellites in galaxy groups show no evidence of altered AGN properties, while satellites in clusters exhibit increased AGN fractions but decreased AGN luminosities.

We study the dark matter (DM) annihilation signals from the Large Magellanic Cloud (LMC) and the impact of the LMC on the DM annihilation signals from the Milky Way (MW) halo, using a MW-LMC analogue from the Auriga magneto-hydrodynamical simulations. We find that the gamma-ray signals from DM annihilation from the LMC rises above the MW foreground by a factor of greater than 100 for the s-wave velocity-independent annihilation model, as well as for the Sommerfeld, p-wave, and d-wave velocity-dependent models. We derive upper limits on the annihilation cross section of DM particles in the LMC using Fermi-LAT data for all velocity-dependent cross section models. Bounds for d-wave annihilation are more stringent by $\sim 4-6$ orders of magnitude relative to previous bounds from dwarf galaxies, and for p-wave emission our bounds are $\sim 2-3$ orders of magnitude more stringent. We also demonstrate that the impact of the LMC on the DM annihilation signals from the MW halo is greatest for the p-wave and d-wave models towards the outer MW halo, while the impact is minimal for Sommerfeld and s-wave models. The LMC boosts the DM density and velocity distribution in the outer MW halo, both by bringing in high-speed DM particles and by accelerating the DM particles of the MW, affecting the DM annihilation signals from the MW for the p-wave and d-wave models.

We present JWST NIRSpec/PRISM IFU time-resolved observations of 2M1207 A and b (TWA 27), a $\sim 10$ Myr binary system consisting of a $\sim 2500$ K sub-stellar primary hosting a $\sim 1300$ K companion. Our data provide 20 time-resolved spectra over an observation spanning 12.56 hours. We provide an empirical characterization for the spectra of both objects across time. For 2M1207 A, non-linear trend models are statistically favored within the ranges 0.6-2.3 $\mu$m and 3.8-5.3 $\mu$m. However, most of the periods constrained from sinusoidal models exceed the observing window, setting a lower limit of 12.56 hours. We find the data at H$\alpha$ and beyond 4.35 $\mu$m show a moderate time correlation, as well as a pair of light curves at 0.73-0.80 $\mu$m and 3.36-3.38 $\mu$m. For 2M1207 b, light curves integrated across 0.86-1.77 $\mu$m and 3.29-4.34 $\mu$m support linear trend models. Following the interpretation of Zhang et. al. (2025), we model the 2M1207 b data with two 1D atmospheric components, both with silicate and iron condensates. The model of time variability as changes to the cloud filling factor shows broad consistency with the variability amplitudes derived from our data. Our amplitudes, however, disagree with the models at $\approx$0.86-1 $\mu$m. While an additional model component such as rainout chemistry may be considered here, our analysis is limited by a low signal-to-noise ratio. Our results demonstrate the capability of JWST to simultaneously monitor the spectral variability of a planetary-mass companion and host at low contrast.

We present a multi-wavelength analysis of the dust of BP Tau's protoplanetary disk. We use new optical spectra of BP Tau, taken with the Magellan/MIKE spectrograph in tandem with archival UV and mid-infrared observations. We use the magnetospheric accretion model to analyze the Ca II K and Mg II 2796.4 Å emission lines and derive the abundance of Ca and Mg in the accretion flows as a proxy for the refractory abundance in the innermost gas disk. Furthermore, we used irradiated accretion disk models to compare the spectral energy distribution (SED) to observations and model in detail the 10$\mu$m and 20$\mu$m silicate features to obtain the spatial distribution and stoichiometry of the dust in which the refractories are locked in the disk. We find a significant degree of depletion of refractory material in the innermost gas disk with median abundances of $\rm [Ca/H] = -2.0^{+0.1}_{-0.0}$ and $\rm [Mg/H] = -1.30^{+0.2}_{-0.3}$ and attribute this to both radial drift and dust trapping due to a pressure bump/gap. Our SED modeling recovers the inner cavity that extends up to 8 AU, consistent with sub-mm observations. We found a significant decrease of the Mg-to-Fe ratio with decreasing radius, with Mg-rich silicates in the outer wall and Fayalite in the inner wall, consistent with the Mg depletion inferred from the emission lines.

Type II Cepheids are pulsating stars that can be used as standard candles for old stellar populations due to their characteristic Period-Luminosity and Period-Luminosity-Colour relations. They are traditionally divided in 3 sub-classes, namely BL Her, W Vir and RV Tauri. In this paper we focus on the first two sub-classes, to provide a new theoretical scenario and develop tools and relations to be adopted in distance scale and old stellar populations studies. We have built new nonlinear convective pulsation models of Type II Cepheids, computed along selected stellar evolution tracks and spanning a wide range of pulsation period and stellar parameters. Three chemical compositions have been taken into account. For each assumed Z and Y, models have been computed following stellar evolution predictions for off Zero Age Horizontal Branch evolution of stellar masses lower than typical RR Lyrae stars, crossing the classical instability strip as BL Her or W Vir pulsating stars. A new theoretical prediction for the instability strip boundaries of these classes of variable stars has been obtained together with their dependence on metal abundance. The predicted light and radial velocity curves have been computed along the evolution inside the strip, showing how the amplitude and the morphology are affected by the position relative to the edges and by the luminosity and mass values. The transformation of bolometric light curves into various photometric systems allowed us to provide new theoretical Period-Luminosity and Period-Wesenheit relations for BL Her and W Vir. These relations are consistent with previously published RR Lyrae model results but with a smaller metallicity dependence. Moreover, the application of the inferred theoretical relations to Magellanic and Galactic Type II Cepheid data provides results in good agreement with some independent distance estimates in the literature.

Coronagraphic observations enable direct monitoring of coronal mass ejections (CMEs) through scattered light from free electrons, but determining the 3D plasma distribution from 2D imaging data is challenging due to the optically-thin plasma and the complex image formation processes. We introduce SuNeRF-CME, a framework for 3D tomographic reconstructions of the heliosphere using multi-viewpoint coronagraphic observations. The method leverages Neural Radiance Fields (NeRFs) to estimate the electron density in the heliosphere through a ray-tracing approach, while accounting for the underlying Thomson scattering of image formation. The model is optimized by iteratively fitting the time-dependent observational data. In addition, we apply physical constraints in terms of continuity, propagation direction, and speed of the heliospheric plasma to overcome limitations imposed by the sparse number of viewpoints. We utilize synthetic observations of a CME simulation to fully quantify the model's performance for different viewpoint configurations. The results demonstrate that our method can reliably estimate the CME parameters from only two viewpoints, with a mean velocity error of $3.01\pm1.94\%$ and propagation direction errors of $3.39\pm1.94^\circ$ in latitude and $1.76\pm0.79^\circ$ in longitude. We further show that our approach can achieve a full 3D reconstruction of the simulated CME from two viewpoints, where we correctly model the three-part structure, deformed CME front, and internal plasma variations. Additional viewpoints can be seamlessly integrated, directly enhancing the reconstruction of the plasma distribution in the heliosphere. This study underscores the value of physics-informed methods for reconstructing the heliospheric plasma distribution, paving the way for unraveling the dynamic 3D structure of CMEs and enabling advanced space weather monitoring.

This work explores the morphology and dynamical properties of cores within rich superclusters, highlighting their role as transitional structures in the large-scale structure of the Universe. Using projected and radial velocity distributions of member galaxies, we identify cores as dense structures that, despite being gravitationally bound, are not yet dynamically relaxed. However, they exhibit a tendency toward virialisation, evolving in a self-similar manner to massive galaxy clusters but on a larger scale. Morphological analysis reveals that cores are predominantly filamentary, reflecting quasi-linear formation processes consistent with the Zeldovich approximation. Our estimates of the entropy confirm their intermediate dynamical state, with relaxation levels varying across the sample. Mass estimates indicate efficient accretion processes, concentrating matter into gravitationally bound systems. We conclude that cores are important environments where galaxy evolution and hierarchical assembly occur, bridging the gap between supercluster-scale structures and virialised clusters.

Stellar surface abundances are records of the state of the gas from which stars formed, and thus trace how individual elements have mixed into the surrounding medium following their ejection from stars. In this work, we test the common assumption of instantaneous and homogeneous metal mixing during the formation of the first Population II stars by characterizing the chemical homogeneity of the gas in simulated star-forming environments enriched by Population III stellar feedback. Testing the homogeneity of metal mixing in this time period is necessary for understanding the spread of abundances in the most metal-poor stars, and the (in)homogeneity of individual sites of star formation. Using Aeos, a suite of star-by-star cosmological simulations, we quantify how gas abundances change over space and time relative to Population II stellar abundances using Mahalanobis distances, a measure of covariance-normalized dissimilarity. We find that the homogeneous mixing assumption holds only within $\sim100$ pc of a star-forming region and $\sim 7$ Myr following the star formation event. Beyond this regime, deviations between stellar and gas abundances increase until they become indistinguishable from assuming a homogeneous mix of metals averaged over the initial mass function. This highlights the limited applicability of assuming instantaneous and homogeneous mixing in realistic halo environments at high redshift. We identify critical mixing scales that are necessary to explore chemical evolution in the early Universe. These scales can be applied to determine the precision needed for accurate chemical tagging of observed data and to explore parameter space with analytical models.

We report the discovery of a new directly-imaged brown dwarf companion with Keck/NIRC2+pyWFS around a nearby mid-type M~dwarf LSPM~J1446+4633 (hereafter J1446). The $L'$-band contrast ($4.5\times10^{-3}$) is consistent with a $\sim20-60\ M_{\rm Jup}$ object at 1--10~Gyr and our two-epoch NIRC2 data suggest a $\sim30\%$ ($\sim3.1\sigma)$ variability in its $L'$-band flux. We incorporated Gaia DR3 non-single-star catalog into the orbital fitting by combining the Subaru/IRD RV monitoring results, NIRC2 direct imaging results, and Gaia proper motion acceleration. As a result, we derive ${59.8}_{-1.4}^{+1.5}\ M_{\rm Jup}$ and $\approx4.3~{\rm au}$ for the dynamical mass and the semi-major axis of the companion J1446B, respectively. J1446B is one of the intriguing late-T~dwarfs showing variability at $L'$-band for future atmospheric studies with the constrained dynamical mass. Because the J1446 system is accessible with various observation techniques such as astrometry, direct imaging, and high-resolution spectroscopy including radial velocity measurement, it has a potential as a great benchmark system to improve our understanding for cool dwarfs.

The Data Release 1 (DR1) of the Dark Energy Spectroscopic Instrument (DESI) is the largest sample to date for small-scale Ly$\alpha$ forest cosmology, accessed through its one-dimensional power spectrum ($P_{\mathrm{1D}}$). The Ly$\alpha$ forest $P_{\mathrm{1D}}$ is extracted from quasar spectra that are highly inhomogeneous (both in wavelength and between quasars) in noise properties due to intrinsic properties of the quasar, atmospheric and astrophysical contamination, and also sensitive to low-level details of the spectral extraction pipeline. We employ two estimators in DR1 analysis to measure $P_{\mathrm{1D}}$: the optimal estimator and the fast Fourier transform (FFT) estimator. To ensure robustness of our DR1 measurements, we validate these two power spectrum and covariance matrix estimation methodologies against the challenging aspects of the data. First, using a set of 20 synthetic 1D realizations of DR1, we derive the masking bias corrections needed for the FFT estimator and the continuum fitting bias needed for both estimators. We demonstrate that both estimators, including their covariances, are unbiased with these corrections using the Kolmogorov-Smirnov test. Second, we substantially extend our previous suite of CCD image simulations to include 675,000 quasars, allowing us to accurately quantify the pipeline's performance. This set of simulations reveals biases at the highest $k$ values, corresponding to a resolution error of a few percent. We base the resolution systematics error budget of DR1 $P_{\mathrm{1D}}$ on these values, but do not derive corrections from them since the simulation fidelity is insufficient for precise corrections.

The extended main-sequence turn-offs (eMSTOs) and extended red clumps (eRCs) observed in intermediate-age star clusters challenge the traditional understanding of clusters as simple stellar populations. Recently, eMSTOs have been interpreted as signatures of stellar rotation. In this work, we test the effectiveness of rotational mixing in shaping the color-magnitude diagram (CMD) of star clusters. We computed a set of separate single-age synthetic stellar populations, referred to as "Base Stellar Populations" (BSPs), including stellar rotation. These BSPs were generated from two grids of stellar models that share the same input physics but differ in the efficiency of rotational mixing. We used an optimization algorithm to determine the best combination of BSPs to fit the CMDs of two star clusters: the Small Magellanic Cloud cluster NGC 419 and the Milky Way cluster NGC 1817. The synthetic clusters with weak rotational mixing provide the best fit to both the eMSTO and eRC features for both clusters, and are consistent with the luminosities and asteroseismic masses we derived for eRC stars in NGC 1817. In contrast, synthetic clusters with strong rotational mixing result in overly bright post-main-sequence stars, inconsistent with observations. This suggests that, for intermediate-mass stars, the influence of rotational mixing of chemical elements on stellar evolution cannot be so strong as to significantly increase the post-main-sequence luminosity. A simple test suggests that accounting for self-extinction by decretion discs in equator-on fast rotators could influence inferred rotation distributions and help reconcile the projected rotational velocity discrepancy across the eMSTO between models and observations.

We present a non-parametric reconstruction of the three-dimensional velocity field of the Scorpius-Centaurus OB association (Sco- Cen). Using Gaia DR3 astrometry and radial velocities, we infer the velocity field using information field theory on a 70 x 70 x 50 grid at 3 pc resolution. Our model suggests the existence of a primary stellar velocity field with a secondary field that accounts for an additional young kinematic component in Upper Scorpius and Lupus. We find clear tracers of a feedback-driven expansion of the association, while Galactic rotation appears to play a subordinate role. The results confirm the existence of cluster chains and reveal coherent large-scale expansion with characteristic speeds of 1-2 km s$^{-1}$ and local maxima of about 10 km s$^{-1}$. Power spectra indicate an excess of small-scale structure and slopes shallower than Kolmogorov, consistent with energy injection from stellar feedback. Maps of the divergence reveal net positive values, implying an approximate dispersal timescale of 10-15 Myr. A comparison with molecular gas in Lupus and Ophiuchus shows broadly consistent patterns but systematic velocity offsets of several km s$^{-1}$, suggesting partial decoupling for optically visible young stars and gas. The framework presented provides a physically motivated description of the Sco-Cen velocity field and a basis for quantifying the dynamical state and feedback history of OB associations in the local Galaxy.

The atmospheres of hot rocky exoplanets (HREs), should they persist, are products of interactions with underlying magma oceans. Spectra collected by the James Webb Space Telescope (JWST) hint at a CO/CO$_2$-rich atmosphere on the HRE 55 Cancri e, indicative of such a process. Here, we aim to identify diagnostic features that can be used to infer the composition and geochemical state of HREs. We construct a coupled atmosphere-interior model that computes the equilibrium gas speciation in the atmosphere in the system Si-Mg-Fe-O-C-H-S-N-He. The model accounts for both the equilibrium vaporisation of mineral gases and the partitioning of volatile species between the magma ocean and atmosphere. Using a fiducial planet with the properties of 55 Cancri e, we explore a parameter space that spans volatile mass fractions from 0.1 to 10 times that of the Earth, solar- to Earth-like metallicities, and 12 orders of magnitude in oxygen fugacity fO$_2$. We find fO$_2$ to be the major control of the shape of emission and transmission features. The presence of species such as SO$_2$ and the relative intensities of H$_2$O and CO$_2$ features allow to distinguish the origin of the gas, accreted or outgassed, while the atmospheric mass is more challenging to constrain. Inflated HREs, whose densities are compatible with a nebular atmosphere are rare, but a viable explanation for the planet TOI-1408 c. The majority of HREs, including 55 Cancri e, are too dense to be dominated by H$_2$-rich nebular gas yet too puffy for an Earth-like volatile budget, implying modest atmospheres of mixed heritage that are degenerate in fO$_2$, volatile mass and composition. The MIRI observation of 55 Cancri e disfavours oxidised Earth-like and reduced primoridal atmospheres alike, while the NIRCam data remain inconclusive. Future observations at wavelengths beyond 8 $\mu$m are key to discerning between potential scenarios.

We use the TNG50 simulation to explore the possible existence of satellite galaxy sets, with fixed-in-time identities, forming kinematically-persistent planes (KPPs) along cosmic time around 190 MW/M31-like galaxies. This is the first study to assess their frequency within the $\Lambda$CDM framework. We identify KPPs around 46 of these host galaxies, with at least 25\% of their satellites in such configurations. Thereby, KPPs appear more frequent than previously reported, appearing in $\sim24\%$ of MW/M31-like systems, and in $\sim40\%$ of those populated with $N_{\rm sat}\geq9$. We find a dependency of the former frequency on the minimum satellite stellar mass cut, suggesting that it would increase with higher mass resolution. KPP satellite members form a distinct set compared to satellites outside KPPs, located at further distances from the center of their host and maintaining higher specific angular momentum since high redshift. KPP satellites form thin and oblate planes in positional space during long periods of cosmic time. We statistically confirm that KPPs form a kind of backbone of observationally-detected positional planes, and that, in velocity space, KPPs behave as kinematic morphological disks. We show that KPP formation, defined as the time when satellite orbital poles align around a specific, fixed direction (occurring at Universe age $\sim4$ Gyr), predates the end of halo's fast-phase of mass assembly, indicating that halo processes do not drive this clustering. Finally, our results are broadly consistent with the MW's kinematic plane at $z=0$ concerning its morphological properties and degree of satellite orbital poles clustering, mitigating the tension between the existence of these structures and the $\Lambda$CDM paradigm.

We introduce Nessie, a galaxy group finder implemented in Rust and distributed as both a Python and R package. Nessie employs the friends-of-friends (FoF) algorithm and requires only on-sky position and redshift as input, making it immediately applicable to surveys that lack a well-defined luminosity function. We implement several algorithmic optimizations including binary search and k-d tree pre-selection that significantly improve performance by reducing unnecessary galaxy pair checks. To validate the accuracy of Nessie, we tune its parameters using a suite of GALFORM mock lightcones and achieve a strong Figure of Merit. We further demonstrate its reliability by applying it to both the GAMA and SDSS surveys, where it produces group catalogues consistent with those in the literature. Additional functionality is included for comparison with simulations and mock catalogues. Benchmarking on a standard MacBook Pro (M3 chip with 11 cores) shows that version 1 of Nessie can process about 1 million galaxies in around 10 seconds, highlighting its speed and suitability for next-generation redshift surveys.

The polarized light of the cosmic microwave background is sensitive to new physics that violates parity symmetry. For example, the interaction of photons with the fields of elusive dark matter and dark energy could cause a uniform rotation of the plane of linear polarization across the sky, an effect known as cosmic birefringence. We extract the cosmological rotation angle, $\beta$, using Bayesian analysis of parity-violating correlations, $EB$ and $TB$, of polarization data from the Atacama Cosmology Telescope (ACT) Data Release 6. We use prior probabilities for instrumental miscalibration angles derived from the optics model for the ACT telescope and instruments, and marginalize over a residual intensity-to-polarization leakage. We measure $\beta = 0.215^\circ\pm 0.074^\circ$ (68\% confidence level), which excludes $\beta=0$ with a statistical significance of $2.9\sigma$. Although there remain systematics in the ACT data that are not understood and do not allow us to draw strong cosmological conclusions, this result is consistent with previous independent results from the \wmap\ and \planck\ missions. It is suggestive that independent data sets and analyses using different methodologies have yielded the same sign and comparable magnitudes for $\beta$.

Predicting the statistical properties of the neutral hydrogen (HI) density field during reionization is an important step in using upcoming 21 cm observations to constrain models of reionization. Semi-numerical models of reionization are often coupled with the collapse fraction field $f_{\text{coll}}(\mathbf{x})$, which determines the fraction of dark matter within halos. In this work, we improve upon earlier prescriptions that compute $f_{\text{coll}}$ based on the dark matter overdensity $\delta(\mathbf{x})$ alone, to include more information about the environment in the form of eigenvalues of the tidal tensor. We compute the mean of the $f_{\text{coll}}$ conditioned on these eigenvalues from a set of high-resolution, small-volume simulations and use them to sample the $f_{\text{coll}}$ field of a low-resolution, large-volume simulation. We subsequently use a semi-numerical code for reionization to compute the HI density field and its power spectrum, and benchmark our results against a reference high-resolution, large-volume simulation. Across variations in redshift, ionized fraction, grid resolution, and minimum halo mass, our method recovers the large-scale HI power spectrum with errors at the $\lesssim 2\%-5\%$ level for $k \lesssim 0.5~ h~ \text{Mpc}^{-1}$, providing a substantial improvement over the $\sim 10\%$ results previously obtained using density-only conditioning. Overall, this makes our method a simple yet efficient tool for forward modeling HI maps during reionization.

Ultraluminous X-ray pulsars (ULXPs) serve as unique astrophysical laboratories, offering critical insights into accretion physics under extreme conditions, such as strong magnetic fields and super-Eddington accretion rates. Additionally, the nature of pulsars, i.e., the equation of state of supranuclear matter, is still a matter of intense debate, basing on either conventional neutron stars or strange stars in the litterateurs. In this work, we investigate accretion columns of ULXPs based on the strangeon-star model, focusing on the thermal mound at the column base. Accounting for Coulomb and strangeness barriers of the strangeon stars, we find that the mound can reach $0.7-0.95\,\rm km$ in height with temperatures above $10^9\, \rm K$, enabling substantial neutrino emission via electron-positron annihilation. Heat transport along the strangeon star surface contributes a luminosity of $10^{36} \, \rm erg\, s^{-1} $, independent of the accretion rate. At low accretion rates ($< 10^{20}\, \rm g\,s^{-1}$), photons dominate the luminosity, while at higher rates ($> 10^{21}\, \rm g\, s^{-1}$), photon trapping makes neutrino emission the main cooling channel, with total luminosity exceeding photon emission, which saturates near $10^{41}\, \rm erg\,s^{-1}$. Estimating neutrino fluxes at Earth, we find that only the nearest ULXP, Swift J0243.6$+$6124, could produce a marginally detectable signal, while most extragalactic sources remain well below background levels. These results emphasize the key role of the thermal mound and strangeon star properties in determining accretion luminosities and neutrino emission, offering insights for future modeling and observations of ULXPs.

Carbon-oxygen (C-O) shell mergers in massive stars play a crucial role in both nucleosynthesis and the final stages of stellar evolution. These convective-reactive events significantly alter the internal structure of the star shortly before core collapse. We investigate how the enhanced production of light particles (especially protons) during a C-O shell merger, relative to classical oxygen shell burning, affects the energy balance and evolution of the convective shell. We derive the budget for direct and reverse nucleosynthesis flows across all relevant nuclear reactions from stellar evolution models, and we assess the relative energy produced. We find that proton capture reactions on 32,34S, 31P, and 38Ar (SPAr) dominate the nuclear energy production in typical C-O shell mergers as predicted by 1D stellar models. Their combined energy output is approximately 400 times greater than that of C and O fusion under the same conditions. Our results highlight the critical importance of including these proton-capture reactions in simulations of convective-reactive burning. Excluding their contribution can lead to inaccurate modeling of the dynamics and nucleosynthesis in advanced stellar evolutionary phases. Such results will need to be confirmed by 3D hydrodynamics models.

The Effective Field Theory of Dark Energy (EFTofDE) provides a systematic and model-independent framework to study dark energy (DE) and modified gravity (MG) with one additional scalar degree of freedom. It can describe the known models such as Quintessence, k-essence, DGP, $f(R)$, and Horndeski theories. In this work, we update constraints on EFTofDE by utilizing the most up-to-date public data including the BAO (DESI DR2), CMB (Planck 2018 \& ACT DR6), SNIa (DESY5), weak lensing (DESY3) and full-shape galaxy power (BOSS DR12). We find with the $\Lambda$CDM background, general relativity (GR) is favored by the data, while with the $w0wa$CDM background, slight modification to GR is favored, but still consistent with GR within $1.5\sigma$. We also find the significance level for dynamical DE is greatly reduced within EFTofDE compared to within GR, indicating the degeneracy between dynamical DE and MG.

Magnetic field extrapolation from the solar photosphere to the corona plays an important role in solar physics research. In this work, we present a fully-implicit viscous-relaxation nonlinear force-free field (FIVR-NLFFF) extrapolation code based on a viscous magnetohydrodynamic relaxation model. The method solves the magnetic induction equation alongside a simplified momentum equation, which assumes a balance between the Lorentz force and the viscous force. Under this assumption, the velocity field driving the magnetic field evolution is determined instantaneously by the Lorentz force distribution. Through viscous dissipation, the system relaxes toward a minimum-energy state, consistent with the vector magnetogram prescribed at the lower boundary. To enhance numerical stability, we adopt a fully implicit time integration scheme and employ central finite differences for spatial discretization. The resulting system of nonlinear algebraic equations is solved using the Jacobian-free Newton-Krylov method, as implemented in the Portable, Extensible Toolkit for Scientific Computation (PETSc). We validate the code using three benchmark models: the Low and Lou force-free solution, the Titov-Démoulin magnetic flux rope model, and a strongly sheared arcade configuration containing a current sheet. Quantitative comparisons demonstrate good agreement with the reference solutions. Notably, the code's ability to handle discontinuities and reconstruct coronal current sheets makes it a promising tool for studying magnetic fields that may directly trigger solar eruptions.

Space missions offer unique opportunities for studying ultra-high-energy (UHE) cosmic rays and neutrinos by leveraging secondary emissions generated by extensive air showers (EAS) resulting from their interactions with the atmosphere or Earth's crust. Detecting UHE neutrinos associated with transient sources holds great potential for unraveling the origins of UHE cosmic rays and the physical processes driving their production. Stratospheric balloon missions, illustrated recently by the Extreme Universe Space Observatory on a Super Pressure Balloon II Mission, serve as crucial precursors to space missions. Due to slewing abilities of their telescopes, they can perform follow-up observations of transient sources foreseen as potential candidates for detectable UHE neutrino emissions. Strategies tailored to stratospheric and space missions are essential for optimizing follow-up observations aimed at detecting these elusive neutrinos for the first time. To address this challenge, we have developed a flexible software dedicated to scheduling transient source observations. The software comprises three main modules: a listener module that aggregates alerts from existing alert systems to construct a comprehensive source database, an observability module that factors in the detection system's properties and trajectory to determine a list of observable sources during a specific timeframe, and a scheduler module that prioritizes observations and proposes an optimized observation schedule. The initial release of the neutrino target scheduler software is tailored to the requirements of stratospheric balloon missions, with mock observation examples provided for various flight scenarios. This version will be employed for the upcoming PBR flight in 2027. Future developments will extend its capabilities, and ensure its relevance for various types of missions.

Polycyclic aromatic hydrocarbons (PAHs) are widespread in the interstellar medium (ISM) of Solar metallicity galaxies, where they play a critical role in ISM heating, cooling, and reprocessing stellar radiation. The PAH fraction, the abundance of PAHs relative to total dust mass, is a key parameter in ISM physics. Using JWST and MUSE observations of 42 galaxies from the PHANGS survey, we analyze the PAH fraction in over 17 000 H II regions spanning a gas-phase oxygen abundance of 12+log(O/H) = 8.0-8.8 (Z ~ 0.2-1.3 Zsun), and ~400 isolated supernova remnants (SNRs). We find a significantly lower PAH fraction toward H II regions compared to a reference sample of diffuse ISM areas at matched metallicity. At 12+log(O/H) > 8.2, the PAH fraction toward H II regions is strongly anti-correlated with the local ionization parameter, suggesting that PAH destruction is correlated with ionized gas and/or hydrogen-ionizing UV radiation. At lower metallicities, the PAH fraction declines steeply in both H II regions and the diffuse ISM, likely reflecting less efficient PAH formation in metal-poor environments. Carefully isolating dust emission from the vicinity of optically-identified supernova remnants, we see evidence for selective PAH destruction from measurements of lower PAH fractions, which is, however, indistinguishable at ~50 pc scales. Overall, our results point to ionizing radiation as the dominant agent of PAH destruction within H II regions, with metallicity playing a key role in their global abundance in galaxies.

The timing (cross-)calibration of astronomical instruments is often done by comparing pulsar times-of-arrival (TOAs) to a reference timing model. In high-energy astronomy, the choice of solar system ephemerides and source positions used to barycenter the photon arrival times has a significant impact on the procedure, requiring a full reprocessing the data each time a new convention is used. Our method, developed as part of the activities of the International Astronomical Consortium for High Energy Calibration (IACHEC), adapts an existing pulsar solution to arbitrary JPL ephemerides and source positions by simulating geocentric TOAs and refitting timing models (implemented with PINT). We validate the procedure and apply it to thousands of observations of the Crab pulsar from 14 missions spanning 2002--2025, demonstrating inter-ephemeris TOA consistency at the $\lesssim5\,\mu$s level, using the DE200/FK5-based Jodrell Bank Monthly Ephemeris as a reference. We release open-source tools (TOAextractor) and a TOA database to support future calibration and scientific studies. Instrument timing performance is broadly consistent with mission specifications; the X-ray-to-radio phase offset varies with energy and time at a level that is marginally compatible with the uncertainties of the radio ephemeris, motivating coordinated multiwavelength follow-up.

The gravitational wave equation of motion includes direct coupling to the Riemann tensor. The curvature terms are usually neglected, but they can be large at the location of matter particles and impact the angular diameter distance. We apply the recently introduced post-geometrical optics approximation that includes curvature to gravitational wave propagation. Assuming that particles are localised within their Compton wavelength, the curvature due to electrons leads to a large effect on the angular diameter distance, but caustic formation invalidates the post-geometrical optics approximation. We conclude that the interesting regime of validity of the approximation is limited, as it ceases to apply when the curvature effects become large. Other methods are needed to evaluate the effect of curvature spikes, and the localisation of particles due to decoherence also needs further work.

Ultra-diffuse Galaxies (UDGs) are a subset of Low Surface Brightness Galaxies (LSBGs), showing mean effective surface brightness fainter than $24\ \rm mag\ \rm arcsec^{-2}$ and a diffuse morphology, with effective radii larger than 1.5 kpc. Due to their elusiveness, traditional methods are challenging to be used over large sky areas. Here we present a catalog of ultra-diffuse galaxy (UDG) candidates identified in the full 1350 deg$^2$ area of the Kilo-Degree Survey (KiDS) using deep learning. In particular, we use a previously developed network for the detection of low surface brightness systems in the Sloan Digital Sky Survey \citep[LSBGnet,][]{su2024lsbgnet} and optimised for UDG detection. We train this new UDG detection network for KiDS (UDGnet-K), with an iterative approach, starting from a small-scale training sample. After training and validation, the UGDnet-K has been able to identify $\sim3300$ UDG candidates, among which, after visual inspection, we have selected 545 high-quality ones. The catalog contains independent re-discovery of previously confirmed UDGs in local groups and clusters (e.g NGC 5846 and Fornax), and new discovered candidates in about 15 local systems, for a total of 67 {\it bona fide} associations. Besides the value of the catalog {\it per se} for future studies of UDG properties, this work shows the effectiveness of an iterative approach to training deep learning tools in presence of poor training samples, due to the paucity of confirmed UDG examples, which we expect to replicate for upcoming all-sky surveys like Rubin Observatory, Euclid and the China Space Station Telescope.

We present the first near-infrared interferometric data of a QSO at z=4. The K-band observations were performed with GRAVITY+ on the VLTI using all 4 UTs, detecting a differential phase signal that traces the spatially resolved kinematics for both the H$\beta$ and H$\gamma$ lines in the broad line region. We fit the two lines simultaneously with an updated model that includes distinct rotating and conical outflowing components. We find that more than 80\% of the HI line emission from the BLR originates in an outflow with a velocity up to $10^4$ km s$^{-1}$. This is oriented so that our line of sight is along an edge of the conical structure, which produces the prominent blue wing on the line profile. A combination of anisotropic line emission and mid-plane opacity lead to the single-sided phase signal. The model is able to qualitatively match both the outflowing CIV line profile and the systemic OI fluorescent emission. The derived black hole mass of $8\times10^8$ M$_\odot$ is the highest redshift black hole mass measurement to date obtained directly from BLR dynamics. It is an order of magnitude lower than that inferred from various single epoch scaling relations, and implies that the accretion is highly super-Eddington. With reference to recent simulations, the data suggest that this QSO is emitting close to its radiative limit in a regime where strong outflows are expected around a polar conical region.

The 21 cm brightness temperature during the Epoch of Reionisation is widely modelled using semi-numeric simulations, used for their computational speed and flexibility in testing astrophysical and cosmological parameters. However, it is common practice to simulate coeval brightness temperature boxes, and then apply post-processing algorithms that treat the lightcone effect and redshift-space distortions separately, assuming they can be added in sequence. We instead model them together, allowing for partial coeval cell contributions, and ensuring that velocity-induced frequency shifts are computed at the correct cosmic time for every position along the line of sight. We show that considering these effects simultaneously creates a difference in the shape of the power spectrum over all Fourier scales, and remains recoverable after semi-blind foreground removal. We show that our lightcones consist of an average of 8% and maximum of 120% of a coeval cell length. These contributions to a 21cm brightness temperature lightcone voxel are shifted from within a +/- 0.5 MHz range of the emitted frequency. The boost in the power spectrum seen over small scales (k>1.5 Mpc) of our robust 21 cm lightcone method compared to basic methods is recoverable after the addition and removal of diffuse radio foregrounds. The largest differences during the Epoch of Reionisation lie in the k-space, where the noise sensitivity for a 1000-hour SKAO-low observation is greater than the signal. However, in the cosmic dawn, we have shown that the major differences lie outside of this noise-dominated region.

Recent JWST observations of the temperate sub-Neptune K2-18 b with NIRISS SOSS/NIRSpec G395H and MIRI LRS have yielded apparently inconsistent results: the MIRI spectra exhibit spectral features nearly twice as large as those seen at shorter wavelengths, challenging the high-metallicity, CH4-rich non-equilibrium model that fits the NIRISS/NIRSpec data. We perform a suite of atmospheric retrievals on both datasets, including free-chemistry, non-equilibrium, and aerosol models, using laboratory-derived complex refractive indices for a variety of photochemical haze analogues. Free retrievals systematically return lower metallicities than inferred by self-consistent chemical disequilibrium models, and the inclusion of absorbing aerosols, especially CH4-dominated, nitrogen-poor tholins, can further reduce the inferred metallicity by over an order of magnitude. These hazes reproduce the observed NIRISS slope through scattering and match MIRI features via C-H bending absorption near 7 um, while yielding particle properties consistent with photochemical production in H2-rich atmospheres. Although their inclusion improves the joint fit and reduces tension between datasets, it also significantly lowers the retrieved CH4 abundance, highlighting degeneracies between metallicity, composition, and aerosol properties. Our results underscore the importance of aerosol absorption in interpreting temperate sub-Neptune spectra, and motivate future JWST observations and laboratory work to break these degeneracies.

The quest to uncover periodic patterns within the $\gamma$-ray emissions of jetted active galactic nuclei (AGN) has recently emerged as a focal point in astrophysics. One of the primary challenges has been the necessity for prolonged exposures in the $\gamma$-ray energy band. In our investigation, we leverage 12 years' worth of observations from the \textit{Fermi}-LAT to systematically explore periodicity across 1492 jetted AGN cataloged in 4FGL, representing the largest sample analyzed to date. Our analysis involves a robust pipeline employing nine distinct techniques designed to detect potential periodic emissions within their $\gamma$ rays. We note that 24 objects with previous hints of periodicity are deliberately excluded in the present work since they were reanalyzed in a dedicated paper using a similar methodology. Using this thorough approach, we do not find any evidence for periodic signals in the 1492 jetted AGN $\gamma$-ray light curves analyzed here.

Improved low-frequency sensitivity of gravitational wave observatories would unlock study of intermediate-mass black hole mergers, binary black hole eccentricity, and provide early warnings for multi-messenger observations of binary neutron star mergers. Today's mirror stabilization control injects harmful noise, constituting a major obstacle to sensitivity improvements. We eliminated this noise through Deep Loop Shaping, a reinforcement learning method using frequency domain rewards. We proved our methodology on the LIGO Livingston Observatory (LLO). Our controller reduced control noise in the 10--30Hz band by over 30x, and up to 100x in sub-bands surpassing the design goal motivated by the quantum limit. These results highlight the potential of Deep Loop Shaping to improve current and future GW observatories, and more broadly instrumentation and control systems.

With the rise of the integral field spectroscopy, we are currently dealing with large amounts of spatially resolved data, whose analysis has become challenging, especially when observing complex objects such as nearby galaxies. We aim to develop a method to automatically separate different physical regions within the central parts (1"~160 pc, on average) of galaxies. This can allow us to better understand the systems, and provide an initial characterisation of the main ionisation sources affecting its evolution. We have developed an unsupervised hierarchical clustering algorithm to analyse data cubes based on spectral similarity. It clusters together spaxels with similar spectra, which is useful to disentangle between different physical processes. We have applied this method to a sample of 15 nearby (distances <100 Mpc) galaxies, 7 from the Galaxy Activity, Torus, and Outflow Survey (GATOS) and 8 archival sources, all observed with the medium resolution spectrometer (MRS) of the Mid-Infrared Instrument (MIRI) on board of the JWST. From the clusters, we computed their median spectrum and measured the line and continuum properties. We used these measurements to train random forest models and create several empirical mid-IR diagnostic diagrams for the MRS channel 3 wavelength range, including among others the bright [Ne II], [Ne III], and [Ne V] lines, several H2 transitions, and PAH features. The clustering technique allows to differentiate emission coming from an AGN, the disc, and star forming regions in galaxies, and other composite regions, potentially ionised by several sources simultaneously. This is supported by the results from the empirical diagnostic diagrams, that are indeed able to separate physically distinct regions. This innovative method serves as a tool to identify regions of interest in any data cube prior to an in-depth analysis of the sources. [abridged]

Stellar substructures within tidal debris preserve information about their progenitor galaxies' properties, offering insights into hierarchical mass assembly. We examine a compact stellar system (CSS) around the nearby spiral galaxy NGC 7531, including the shell-like tidal debris. Our goals are to determine the nature of the CSS, reconstruct the accretion history, and understand how the large, diffuse shell-like structure formed. We present photometric measurements of the shell-like debris and CSS using DESI Legacy Imaging Survey (LS) data. We obtained Keck/LRIS spectroscopic data for the CSS to confirm its association with NGC 7531 and to derive its star formation history (SFH). Deep ($\sim$27.9 mag/arcsec$^{2}$) amateur telescope images enabled complete characterization of the tidal debris structure. We confirm the CSS is associated with NGC 7531. We rename it NGC 7531-UCD1, since its stellar mass ($3.7_{-0.7}^{+1.0}\times 10^6$ $\mathrm{M}_\odot$), half-light radius ($R_{h} = 0.13 \pm 0.05$ arcsec) and SFH place it as an ultra-compact dwarf galaxy (UCD). NGC 7531-UCD1 was likely a nuclear star cluster (NSC) that was tidally stripped into a UCD- this is further supported by the presence of tidal tails. We quantify the shell-like debris' mass as $M_\star\sim 3$--$11\times 10^8 M_\odot$, implying a merger mass ratio of ~300:1 to 10:1. Our amateur telescope images confirm new pieces of debris, previously unclear in the DESI LS images. N-body simulations reproduce the tidal features, requiring a near radial orbit of the progenitor with two pericentric passages. The first passage coincides with the measured star formation enhancement ~1 Gyr ago. Our findings agree with predictions about the NSC to UCD formation pathway via tidal stripping, and further confirm the presence of these objects outside of our Milky Way.

Magnetars occupy the neutron star population, with magnetic field strengths of more than 10e12 G. They have been proposed as one of the most likely progenitor models for the phenomenon of energetic, ms-duration, extragalactic radio bursts (FRBs) intensively since FRB-like bursts emitted from the galactic Magnetar SGR 1935+2154. Only a low fraction of the magnetars (six in total) has been detected in the radio regime and most magnetars are radio quiet. We conducted regular observations of 13 radio quiet magnetars to probe the long term radio quietness using MeerKAT. These provide deep constraints on the radio emission of magnetars, relevant for the progenitor models of FRBs Given that MeerKAT is an interferometer, we probe the magnetars for radio emission in both imaging and time domain. We search in the time domain in a DM range of 20 pc/cm^3 to 10000 pc/cm^3 for single pulses using a TransientX based search pipeline (FRB perspective) as well as from a pulsar perspective by folding the data using the X-ray ephemeris. We use the imaging domain to search for radio emission in Stokes I and V as well as to create light curves using snapshot imaging having the long transient perspective as well. We find no radio emission in the time domain for any of the observed magnetars but provide deep limits of the mean flux density 60 uJy and the single pulse fluence of 39 mJy. From the image domain, we provide upper limits on the persistent radio radio emission and the light curve for the 13 magnetars. Additionally, an ULPT and an additional magnetar were observed in the images. We provide an extensive series of deep upper limits in the time domain but also as a novelty limits from the imaging domain for the magnetars. We encourage monitoring of radio quiet magnetars independent of their X-ray flux with high cadence for further insights in their potential for emitting in the radio regime.

We present first detailed maps of the thermal Sunyaev-Zel'dovich (tSZ) effect on a $z = 0.89$ cluster with the NOrthern Extended Millimeter Array (NOEMA). The high sensitivity of these observations enabled the effective identification and removal of the millimetre-wave sources contaminating the tSZ signal, thus isolating the influence of the cluster's hot electron gas on the cosmic microwave background radiation from other emissions. The tSZ observed with success by NOEMA is modelled together with previous single dish (IRAM 30-metre, Green Bank Telescope, and Caltech Sub-millimeter Observatory) observations to obtain the first core to outskirts (from $\sim$ 15 to $\sim$ 1500 kpc) pressure profile reconstruction on such a high redshift galaxy cluster. High angular resolution NOEMA observations have shown that the pressure profile is flat in the core of the cluster. These observations confirm the disturbed nature of CL J1226.9+3332 and map for the first time the distribution of its thermal gas at arcsecond scales, in the environments of the central cluster galaxy. Our results showcase NOEMA's excellent capabilities to complement and enhance the data provided by other millimetre-wave instruments in resolving the core of high-redshift clusters via tSZ emission.

"Pebble snow" describes a planet formation mechanism where icy pebbles in the outer disk reach inner planet embryos as the water ice line evolves inward. We model the effects pebble snow has on sculpting planetary system architectures by developing "The PPOLs Model". The model is capable of growing any number of protoplanet seed masses by pebble accretion simultaneously and accounts for differences in rocky and icy pebble composition, the filtering of pebbles by other protoplanets, the pebble isolation mass, and a self-consistently evolving snow line. The growth and bulk composition are recorded across a grid of protoplanetary disks with stellar masses ranging from 0.125 - 2.0${M_{\odot}}$ (M to A stars) and disk masses ranging from 1 - 40 % of the stellar mass. Three system architectures emerge following a low-, mid-, and high-disk mass fraction that remains consistent across stellar mass. The low-mass architecture is the only one to yield short period Mars-Earth mass cores with bulk water content spanning orders of magnitude and may be prelude to observed "peas in a pod" systems. The high-mass architecture produces proto-gas giant cores in the outer disk. The middle-mass architecture produces a bimodal peak in mass within a system, with the outer protoplanet mass at the snow line growing to an order of magnitude larger, resembling the Solar System. Solar system-like architectures appear for a small range of initial disk masses around F and G stars, but are not a common feature around K and M stars.

In this letter, we present a systematic search for the electromagnetic counterparts of binary neutron star (BNS) merger candidate GW231109_235456 by examining all transients reported within the 90% probability region and detected within four days of the merger. While non-detection in $\gamma$-ray, we identify two optical candidates, each associated with and residing in a host galaxy, which locate within 330 Mpc from earth; notably, one of them, AT2023xqy, is located at a distance of $178.6$ Mpc, in good agreement with the estimated distance of the GW candidate ($\sim165^{+70}_{-69}~\mathrm{Mpc}$). Near the trigger time of GW231109_235456 (MJD 60257.996), AT2023xqy showed evidence of a $\sim$15-day rise, first detected at $3\sigma$ significance on MJD 60259.097 and confirmed above $5\sigma$ on MJD 60262.088. This was followed by a rapid $\sim$5-day decline and a plateau lasting at least 50 days, with the subsequent decay unobserved due to a data gap. The spatiotemporal coincidences indicate that AT2023xqy could be a candidate for the EM counterpart of BNS merger candidate GW231109_235456, though its lightcurve is difficult to reconcile with a standard kilonova. We examine two possible scenarios to explain the origin of AT2023xqy, a BNS merger-irrelevant scenario involving a peculiar supernova or a BNS merger-relevant scenario involving a magnetar-powered kilonova under extreme conditions. Follow-up radio observations are strongly encouraged, as they may provide critical insights into the nature of AT2023xqy.

In multiple-planet systems, gravitational interactions of exoplanets could lead to transit timing variations (TTVs), whose amplitude becomes significantly enhanced when planets are in or near mean-motion resonances (MMRs). In cases where both TTVs and radial velocity (RV) measurements are available, combined analysis can break degeneracies and provide robust planetary and system characterization, even detecting non-transiting planets. In this context, HIP 41378 hosts five confirmed transiting planets with periods ranging from 15 to over 542 days, providing a unique dynamical laboratory for investigating wide multi-planet systems analogous to the Solar System. In this study, we present an intensive space-based photometric follow-up of HIP 41378, combining 15 new CHEOPS observations with eight TESS sectors, alongside data from K2, Spitzer, HST, and HARPS. We dynamically modeled the TTVs and RV signals of the two inner sub-Neptunes via N-body integration. These planets, HIP 41378 b ($P_{b}$ = 15.57 days) and HIP 41378 c ($P_{c}$ = 31.71 days), are close to ($\Delta\sim1.8$ %) a 2:1 period commensurability. We report a clear detection of TTVs with amplitudes of 20 mins for planet b and greater than 3 hrs for planet c. We dynamically confirm the planetary nature of HIP 41378 g, a non-transiting planet with a period of about 64 days and a mass of about 7 $M_{\oplus}$, close to a 2:1 commensurability with planet c, suggesting a possible MMR chain in the inner system. Our precise determination of the masses, eccentricities, and radii of HIP 41378 b and c enabled us to investigate their possible volatile-rich compositions. Finally, by leveraging on the last TESS sectors we constrained the period of HIP 41378 d to three possible aliases ($P_{d} =$ 278, 371, and 1113 days) suggesting that the system could be placed in a double quasi resonant chain, highlighting its complex dynamical architecture.

As old stellar systems, globular clusters (GCs) are key fossil tracers of galaxy formation and interaction histories. This paper is part of the LEWIS project, an integral-field spectroscopic survey of ultra-diffuse galaxies (UDGs) in the Hydra I cluster. We use MUSE spectroscopy and new VIRCAM $H$-band imaging data to study the GC populations and dark matter content in four dwarf galaxies. We retrieved line-of-sight velocities for all sources in the observed MUSE fields. Since the spectroscopic measurements are limited to relatively bright sources, we developed a multi-band photometric procedure to identify additional GC candidates too faint for spectroscopic confirmation. GC candidates were selected using a combination of photometric properties and morphometric criteria. Additionally, the $H$-band observations were used to constrain the stellar masses of the studied galaxies. Based on the spectroscopic classification, we confirm one GC in UDG3, two in UDG7, and four in UDG11, while UDG9 has no spectroscopically confirmed bright GCs. We identify four intra-cluster GCs in the vicinity of UDG3 and UDG11, and one ultra-compact dwarf with a radial velocity only $\Delta v = -85 \pm 10\mathrm{km\ s^{-1}}$ relative to UDG7, suggesting it may be bound to it. Considering completeness corrections and accounting for possible contamination, from photometry we estimate that the number of GCs ranges between 0 and $\sim40$ for the investigated UDGs. Their specific frequencies suggest that three out of four UDGs are either GC-rich, similar to those in the Coma cluster, or belong to an intermediate population as seen in the Perseus cluster. Dark matter content estimates, inferred from GC counts and stellar mass, indicate that these galaxies are dark-matter dominated, with dynamical-to-stellar mass ratios of $M_{\mathrm{dyn}} / M_\star \sim 10-1000$.

The search for atmospheres on rocky exoplanets is a crucial step in understanding the processes driving atmosphere formation, retention, and loss. Past studies have revealed the existence of planets interior to the radius valley with densities lower than would be expected for pure-rock compositions, indicative of the presence of large volatile inventories which could facilitate atmosphere retention. Here we present an analysis of the JWST NIRSpec/G395H transmission spectrum of the warm ($T_\mathrm{eq,{A_B}=0}$ = 569 K) super-Earth TOI-270 b ($R_\mathrm{p}$ = 1.306 $R_\oplus$), captured alongside the transit of TOI-270 d. The JWST white light-curve transit depth updates TOI-270 b's density to $\rho_\mathrm{p}$ = 3.7 $\pm$ 0.5 g/cm$^3$, inconsistent at 4.4$\sigma$ with an Earth-like composition. Instead, the planet is best explained by a non-zero, percent-level water mass fraction, possibly residing on the surface or stored within the interior. The JWST transmission spectrum shows possible spectroscopic evidence for the presence of this water as part of an atmosphere on TOI-270 b, favoring a H$_2$O-rich steam atmosphere model over a flat spectrum ($\ln\mathcal{B}$ = $0.3-3.2$, inconclusive to moderate), with the exact significance depending on whether an offset parameter between the NIRSpec detectors is included. We leverage the transit of the twice-larger TOI-270 d crossing the stellar disk almost simultaneously to rule out the alternative hypothesis that the transit-light-source effect could have caused the water feature in TOI-270 b's observed transmission spectrum. Planetary evolution modeling furthermore shows that TOI-270 b could sustain a significant atmosphere on Gyr timescales, despite its high stellar irradiation, if it formed with a large initial volatile inventory.

We extend analytic formulas for the gravitational-wave (GW) spectrum from first-order phase transitions to include cosmic expansion under the thin-wall and envelope approximations. We demonstrate that even for strongly supercooled transitions the GW amplitude is bounded from above. Moreover, the spectral shape, amplitude, and peak frequency remain largely unaffected by the details of the nucleation rate once expressed in terms of the comformal variables.

The rapidly increasing sensitivity of gravitational wave detectors is enabling the detection of a growing number of compact binary mergers. These events are crucial for understanding the population properties of compact binaries. However, many previous studies rely on computationally expensive inference frameworks, limiting their scalability. In this work, we present GWKokab, a JAX-based framework that enables modular model building with independent rate for each subpopulation such as BBH, BNS, and NSBH binaries. It provides accelerated inference using the normalizing flow based sampler called flowMC and is also compatible with NumPyro samplers. To validate our framework, we generated two synthetic populations, one comprising spinning eccentric binaries and the other circular binaries using a multi-source model. We then recovered their injected parameters at significantly reduced computational cost and demonstrated that eccentricity distribution can be recovered even in spinning eccentric populations. We also reproduced results from two prior studies: one on non-spinning eccentric populations, and another on the BBH mass distribution using the third Gravitational Wave Transient Catalog (GWTC-3). We anticipate that GWKokab will not only reduce computational costs but also enable more detailed subpopulation analyses such as their mass, spin, eccentricity, and redshift distributions in gravitational wave events, offering deeper insights into compact binary formation and evolution.

We revisit string theoretic derivations of black hole entropy and argue that their enabling structures do not persist in realistic cosmologies. We formalize this as the Thermodynamic Split Conjecture (TSC) which is the statement that in any UV complete quantum gravity, black hole and cosmological horizon thermodynamics are generically inequivalent. The BKE criterion is then formulated to formalize this approach while we also discuss ways to falsify the conjecture. Finally, we propose an observational scaling test which is centered around comparisons of data native entropy proxies from tomographic maps to the Bekenstein Hawking prediction. The framework both sharpens when and why the area law holds and provides a roadmap towards a UV complete description of cosmological horizon entropy.

We propose a machine learning-based approach for parameter estimation of Massive Black Hole Binaries (MBHBs), leveraging normalizing flows to approximate the likelihood function. By training these flows on simulated data, we can generate posterior samples via Markov Chain Monte Carlo with a relatively reduced computational cost. Our method enables iterative refinement of smaller models targeting specific MBHB events, with significantly fewer waveform template evaluations. However, dimensionality reduction is crucial to make the method computationally feasible: it dictates both the quality and time efficiency of the method. We present initial results for a single MBHB with Gaussian noise and aim to extend our work to increasingly realistic scenarios, including waveforms with higher modes, non-stationary noise, glitches, and data gaps.