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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.EPastro-ph.IM

Resolving core-envelope degeneracies in giant planets and sub-Neptunes: constraining the equivalence in the presence of dilute gradients

Christian Wilkinson, Benjamin Charnay, Stéphane Mazevet, Baptiste Perrier, Anne-Marie Lagrange, Lukas Delay

The widespread recognition of dilute, "fuzzy" cores in giant planets and massive volatile mantles in sub-Neptunes has made interior modelling a highly degenerate, multi-dimensional problem. To map these degeneracies, we present fuzzycore, an open-source static structural integrator with a unified layered architecture spanning rock-water-envelope sub-Neptunes through volatile-rich gas giants. The framework supports dense parameter sweeps over compositional gradients at fixed observed $(M_p, R_p,…

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astro-ph.GA

Asymmetries in spatially unresolved 21-cm emission line profiles of isolated galaxies

Aditya Manuwal, H. M. Hernández-Toledo, J. A. Vázquez-Mata, Diana Serrato Barrajas, Aldo Rodríguez-Puebla, Vladimir Ávila-Reese, A. R. Calette

The origin of asymmetry in the ${\rm H}\,{\scriptsize{\rm I}}$ of galaxies remains an elusive problem, largely due to the difficulties associated with distinguishing between its secular and external contributors. We have compiled a sample of local isolated galaxies from the UNAM-KIAS and the latest AMIGA samples with near-complete beam coverage and robust estimates of ${\rm H}\,{\scriptsize{\rm I}}$ line asymmetry. The ${\rm H}\,{\scriptsize{\rm I}}$ measurements are based on single-dish spectra…

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astro-ph.EP

Distribution of Chemically-Processed Dust in a Viscously Evolving Protoplanetary Disk: Application to Crystalline Silicates in Comets

Lily Ishizaki, Shogo Tachibana, Shigeru Ida

Dust particles undergo chemical reactions in protoplanetary disks according to their environments, producing compositional diversity in planetary materials. Extraterrestrial records of irreversible reactions, such as crystallization of amorphous silicates, provide particularly strong constraints on the early evolution of the protosolar disk. In this study, we investigate such irreversible reactions and the spatiotemporal distribution of reacted dust in a viscously evolving disk using Monte Carlo…

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astro-ph.GA

Tidal Structures Around Edge-On Galaxies in Deep Imaging Surveys

Kyle R. Adams, Aleksandr Mosenkov, Jonah Seguine, Lydia Stacey, Thea Spigarelli, Jonah George

We present a statistical study of low-surface-brightness (LSB) tidal structures in two large samples of edge-on disk galaxies. Our primary sample comprises 5606 galaxies from the Edge-on Galaxies In SDSS (EGIS) catalog, analyzed using imaging from the DESI Legacy Imaging Surveys, supplemented by Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) data and deep Apache Point Observatory (APO) follow-up observations for selected objects. To assess the robustness of our results, we also examine an…

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astro-ph.SR

Effective temperatures estimation of low-mass stars and identification of T Tauri stars in LAMOST DR10 using machine learning

C. D. Millan-Valderrama, J. Hernandez, B. Sabogal, J. Muñoz

We present effective temperature (Teff) estimates of low-mass stars and T Tauri stars (TTS) candidate detections derived from automated spectroscopic measurements and low-complexity machine-learning models applied to the LAMOST DR10 V2 survey. Equivalent widths of key diagnostic spectral features, including the atomic lines Halpha, LiI 6708 AA and TiO/VO molecular bands, are automatically measured for all stars within 1 kpc observed by LAMOST. Using nine spectral features as inputs, we train a G…

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astro-ph.HEastro-ph.IMgr-qc

A Four-Dimensional Gaussian Random Field Generator for Modeling Spatiotemporal Variability in Astrophysical Sources

Alejandro Cárdenas-Avendaño, Diego Rubiera-Garcia, Frederic H. Vincent

Semi-analytic models of black-hole movies require both an emitting flow prescription and a time-dependent source variability. Existing prescriptions are often limited to either equatorial emission or time-independent sources. In this work we present a unified model for these two ingredients. First, we prescribe an off-equatorial, nongeodesic Kerr fluid rotation law by lifting an equatorial specific-angular-momentum profile to cylindrical surfaces, setting the polar component of the four-velocity…

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astro-ph.EP

Planet-wide, Concentric Density Waves in Venus's Upper Atmosphere Revealed through Polarimetry?

Gourav Mahapatra, Michiel Rodenhuis, Frans Snik, Daphne M. Stam, Loïc Rossi, Christoph Keller

We report observations of faint ($10^{-6}$), concentric, planet-wide rings in the polarized flux of sunlight that is reflected by Venus, obtained during a serendipitous, 36-minute run in 2010, with the highly sensitive Extreme Polarimeter (ExPo) on the William Herschel Telescope. The rings appear to be centered slightly downwind of the sub-solar point, are visible in different filters across the visible, and are not obvious in the simultaneous total flux observations. ExPo's dual-beam exchange a…

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physics.ed-phastro-ph.IMphysics.soc-phphysics.space-ph

A First Africa Wide Amateur Radio Contact Experiment with the International Space Station

Domingos Barbosa, Miracle Chibuzor Marcel, Declan Kirrane, Miguel Avillez, Amare Abebe Gidelew, Carla Sharpe Mitchell, Vidvuds Beldavs, Claudio Ariotti et al.

The Amateur Radio on the International Space Station (ARISS) program is recognized by its great Science, Technology, Engineering, and Mathematics (STEM) impact: it brings space science to education and outreach initiatives by enabling direct contact with astronauts in orbit and other space savvy professionals. Strategic partnerships between ARISS and digital platforms for citizen science act as a powerful real-world STEM motivator and can overcome logistical barriers, demonstrating a scalable mo…

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astro-ph.GAastro-ph.SR

Fragmentation of massive clumps: constant mass fraction and growing mass inequality of cores

Zu-Jia Lu, Qi-Tian Chen

The fragmentation of massive molecular clumps into dense cores sets the initial conditions for stellar clusters, yet how core mass distributions evolve remains unclear. Using the ALMAGAL survey (1,013 clumps and 6,348 cores), we analyze the Gini coefficient of core mass distributions for the 514 clumps containing at least four cores ($N_{\rm frag} \ge 4$), which host 5,728 cores in total. We find that the most massive core consistently accounts for $\sim 38\%$ of the total core mass ($f_{\rm cor…

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astro-ph.EP

The Polana-Eulalia Complex with JWST NIRSpec: Connections to Bennu, Ryugu, and Outer Solar System Bodies

Lucas McClure, Joshua Emery, Driss Takir, Julia de Leon, Mario de Pra, Brittany Harvison, Bryan Holler, Javier Licandro et al.

Carbon rich [C complex] asteroids provide insight into the early Solar System, and families of C complex asteroids serve as robust samples for learning about the internal structure of planetesimals and the materials of the protoplanetary disk. This work investigates the compositions of asteroids within the Polana Eulalia Complex [PEC] through analyses of JWST NIRSpec. Obtained as part of the Spectral Analysis of Main Belt Asteroids in the 3 um Region [SAMBA3] project. NIRSpec observations were c…

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astro-ph.COastro-ph.GA

Origin of the Sloshing Spiral in the Abell 2107 Galaxy Cluster

Muhammed Kıyami Erdim

We present a detailed thermodynamic analysis of a sloshing spiral discovered in the intracluster medium (ICM) of the galaxy cluster Abell 2107, based on deep Chandra X-ray Observatory observations. Spectral analysis reveals that the spiral arm is significantly cooler and exhibits lower entropy and higher metallicity compared to the surrounding ICM, consistent with an origin in the cool, dense cluster core. We detect three cold fronts at the edges of the spiral, roughly aligned along an east-west…

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physics.space-phastro-ph.EPphysics.plasm-ph

Electron Temperature Gradients Regulate the Duration of Two-Stage Plasmasphere Refilling

Jaden Fitzpatrick, Kausik Chatterjee, Naomi Maruyama, Xiangning Chu, Jacob Bortnik, Jerry Goldstein, Lauren Blum, Tyler Bishop et al.

After geomagnetic storms erode the plasmasphere, cold ionospheric plasma flows along magnetic field lines to refill the depleted flux tubes. Previous studies have suggested that refilling undergoes two stages characterized by their distinct refilling rates; however, not all observations or models exhibit this feature, and a recent analysis indicates that only a subset of refilling events display two clear stages. In this study, we show that the magnitude of the field-aligned electron temperature…

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astro-ph.HEastro-ph.CO

Gas Motions in Hydra-A: XRISM Constraints on ICM Kinematics Across Jet-Inflated Cavities

Anwesh Majumder, B. R. McNamara, P. E. J. Nulsen, H. Russell, T. Rose, T. Heckman, A. Simionescu, A. Fabian et al.

We report on two deep XRISM observations of the central and northern regions of Hydra-A's X-ray atmosphere covering the bubbles inflated by jets from the central galaxy's active galactic nucleus (AGN). We use spatial-spectral mixing that combines Chandra's high spatial resolution with XRISM's high spectral resolution to investigate atmospheric kinematics. The atmospheric velocity dispersion in the northern region, $σ_v = 140^{+30}_{-20}$ km s$^{-1}$, is comparable to that in the central region (…

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astro-ph.GAastro-ph.CO

The size of the HI disk across different environments: isolated, compact groups, clusters, and pairs

R. Ianjamasimanana, L. Verdes-Montenegro, K. M. Hess, P. Kamphuis, M. G. Jones, J. Garrido, S. H. A. Rajohnson, A. Sorgho et al.

The 21 cm line of atomic hydrogen (HI) is a sensitive tracer of the outer disk of galaxies, where environmental signatures are most apparent. The relative extent of HI disks compared to optical disks ($D_{\rm HI}$ vs $D_{25}$) is thought to provide a quantitative measure of such imprint, yet systematic comparisons between extreme environments remain scarce. We quantify the relative extent of HI disks in Hickson Compact Groups (HCGs) and in the Analysis of the interstellar Medium in Isolated GAla…

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gr-qcastro-ph.HE

Biases in Tests of General Relativity from Microlensed Gravitational-Wave Signals

Anirban Kopty, Apratim Ganguly, N. V. Krishnendu, Anuj Mishra

Gravitational-wave (GW) observations of compact binary mergers enable precision tests of general relativity (GR) in the strong-field regime, but their reliability depends on accurate waveform modeling. Unmodeled physical effects can induce systematic biases that mimic deviations from GR. Here we study the impact of GW microlensing on standard LIGO-Virgo-KAGRA tests of GR using GW150914-like simulated signals lensed by isolated point-mass objects with masses in the range $10-10^{5}M_\odot$. We pe…

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astro-ph.GA

VAR-PZnn: A machine-learning framework for AGN photometric redshifts using color and variability-based features

S. Satheesh-Sheeba, P. Sánchez-Sáez, R. J. Assef, T. Anguita, R. Shirley, M. Salvato, P. Arévalo, T T. Ananna et al.

Photometric redshift estimation for active galactic nuclei (AGNs) remains a fundamental challenge for current and upcoming large-scale photometric surveys. Traditional spectral energy distribution (SED) fitting suffers from color-redshift degeneracies, particularly for AGNs whose power-law continua hide the strong spectral features required to anchor redshift estimates. While AGN variability provides additional constraining power, existing frameworks require multi-band light curves that are not…

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astro-ph.HEastro-ph.GA

Simultaneous radio, optical and X-ray monitoring of hard X-ray selected AGN: a variability study

L. Hernández-García, F. Panessa, D. Williams-Baldwin, P. Arévalo, A. M. Muñoz Arancibia

AGN emission is intrinsically variable across the electromagnetic spectrum. Mapping the coupling between the accretion disk, the X-ray corona, and ejection flows is key to understanding the energy flow within the central engine. We characterize the multi-wavelength variability of 14 hard X-ray selected AGN from the INTEGRAL/IBIS catalog in the radio, optical, and X-ray bands, to determine the coupling between these frequencies and how variability relates to the physical properties of the central…

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astro-ph.SRastro-ph.EPastro-ph.GA

Dynamical friction in stratified stellar envelopes

Damien Gagnier

Dynamical friction prescriptions used for common-envelope and planetary engulfment inspirals often assume a homogeneous medium and/or rectilinear perturber motion. A gravitating object embedded in a giant-star envelope instead excites an orbit-scale wake while moving on a curved orbit through a finite, radially stratified medium. We formulate the linear barotropic acoustic response of a weak point perturber on a circular orbit in a hydrostatic, spherically stratified gaseous medium. We apply the…

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astro-ph.HE

Detectability of Gravitational-wave counterparts of EP-FXTs observed during the O4b LIGO-Virgo-KAGRA Observing Run

Ansh Chopra, Samuele Ronchini, Biswajit Banerjee, Marica Branchesi, Stefano Ascenzi, Maria Edvige Ravasio, Peter Jonker, Andrew Levan et al.

Fast X-ray transients (FXTs) detected by the Einstein Probe mission have emerged as a rapidly growing class of extragalactic transients, whose physical origin remains uncertain. Compact binary coalescence (CBC) systems have been proposed as one possible progenitor for at least a subset of these events, making FXTs promising targets for multi-messenger studies with gravitational-wave (GW) observations. This work presents the first systematic investigation of GW counterparts to FXTs observed by Ei…

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astro-ph.GAastro-ph.CO

LoVoCCS. III. Third Generation Pipeline & The Hercules Supercluster

Anthony M. Englert, Shenming Fu, Ian Dell'Antonio, Mohamed H. Abdullah, Shrouk Abdulshafy, Eddie Aljamal, William K. Black, Nicole Chidester et al.

The Local Volume Complete Cluster Survey (LoVoCCS) is a volume-complete survey of over one-hundred nearby ($0.03 10^{44} \text{ erg s}^{-1}$) galaxy clusters in the southern sky. Observations for the survey concluded in December 2025, reaching Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) Year 1-2 depth in each field and providing observations with $\lesssim 1"$ seeing for weak lensing science. In this paper, we present the latest pipeline for reducing observations using the…

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astro-ph.EP

Case Study of a Super-eccentric Warm Jupiter Migrating via Equilibrium and Dynamical Tides

Donald Liveoak, Sarah Millholland, Michelle Vick

A leading theory for hot Jupiter formation is high-eccentricity migration, in which planets are born at large separations and excited to near-unity eccentricities, creating extreme tidal dissipation that shrinks and circularizes their orbits. The most direct evidence for this scenario is the detection of highly eccentric planets caught in the act of migrating. Although such planets are rare, the recent discovery of TIC 241249530 b - a super-eccentric ($e = 0.94$) and retrograde hot Jupiter proge…

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astro-ph.GA

Cosmological simulations of the high-redshift galaxy population adopting a variable stellar initial mass function

Anna Durrant, Robert A. Crain, Cedric G. Lacey, Joop Schaye, Renske Smit, Andrea Gebek, Matthieu Schaller, Shengdong Lu et al.

JWST surveys reveal a greater space density of high-redshift UV-bright galaxies than predicted by conventional galaxy formation models. We present results from a $L=100$ cMpc cosmological simulation evolved to $z=5$ with a variation of the COLIBRE galaxy formation model that adopts a density-dependent stellar initial mass function (IMF), such that stellar populations formed from dense gas are born with a top-heavy IMF. Crucially, heavy element and dust yields, and supernova feedback energetics,…

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astro-ph.EP

Planet-moon ejections in close stellar encounters

Yannick Badoux, Simon Portegies Zwart

Free-floating planet-moon pairs (FFPMs) may form when planetary systems experience close stellar encounters. We quantify moon-retention probabilities and ejection cross sections for planets and planet-moon systems subject to close stellar encounters, and to dentify the orbital conditions most favorable for forming FFPMs. We conducted extensive numerical scattering experiments to compute ejection cross-sections on a grid in the orbital separation of the planet ($a_p$) and the moon ($a_m$), margin…

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astro-ph.HEastro-ph.SR

Superorbital variability in the quiescent black hole X-ray transient A0620-00

Enzo A. Saavedra, Roi Alonso, Teo Muñoz-Darias, Jorge Casares, Manuel A. P. Torres, Montserrat Armas Padilla, James F. Steiner, David M. Russell et al.

Quiescent black hole low-mass X-ray binaries provide a key setting for probing accretion physics at low luminosities. A0620-00, the archetypal system in this class, has remained in X-ray quiescence for decades and exhibits complex optical variability, yet the long-term behaviour of its accretion flow remains poorly understood. Here, we report an analysis of long-term optical monitoring of A0620-00 from ZTF, LCO, and ATLAS. The full dataset spans nearly two decades, with the ZTF light curve provi…

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astro-ph.GA

Morphologies of SAGAbg low-mass galaxies in Legacy Survey multi-band imaging: dependence on stellar masses, star-formation rates and low-redshift evolution

Joy Bhattacharyya, Guinevere Herron, Yasmeen Asali, Abby Mintz, Mithi A. C. de los Reyes, Yao-Yuan Mao, Annika H. G. Peter

The optical morphologies of low-mass galaxies can be used to directly trace their assembly and constrain models of galaxy evolution. We select a sample of 6211 low-mass ($7\lesssim {\rm log}(M_{\ast}/M_{\odot})\lesssim 10$) star-forming galaxies from the SAGAbg catalog that has high-completeness at low-redshifts ($z<0.1$). We obtain their galaxy maps in the $griz$ - bands of the Legacy Surveys and apply STATMORPH to calculate non-parametric morphological measures including the Gini index, $M_{20…

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astro-ph.GA

Euclid: Calibrating distances from surface brightness fluctuations with Early Release Observations of the Fornax cluster

R. Habas, M. Cantiello, G. Riccio, G. Raimondo, N. Hazra, S. Mei, A. Lançon, G. D'Ago et al.

Surface brightness fluctuations (SBF), the pixel-to-pixel variations in flux that arise from the statistical distribution of stars in galaxy images, provide a powerful tool to measure redshift-independent distances from photometric data alone. This method is particularly important in the era of large imaging surveys, such as those carried out during the Euclid mission. Here we present the first application of SBF to Euclid data, using the FAST-SBF code to measure stellar fluctuation amplitudes i…

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astro-ph.SR

SEP-PRISM Data: A multi-source dataset for solar energetic particle forecasting

Yian Yu, Yang Chen, Lulu Zhao, Kathryn Whitman, Ward Manchester, Tamas Gombosi

Solar energetic particle (SEP) event forecasting often involves integrating heterogeneous observations that differ in cadence, temporal coverage, format, and historical availability, posing challenges for reproducible analysis of data-driven approaches. This paper presents SEP-PRISM Data, a curated multi-source dataset designed for 24-hour ahead forecasting of operational SEP events, defined by proton flux exceeding 10 pfu in the GOES > 10 MeV channel. SEP-PRISM Data integrates flare records, ac…

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astro-ph.HE

X-ray polarization of Z-type neutron star low-mass X-ray binaries -- II. Spectropolarimetric analysis

Andrea Gnarini, Francesco Ursini, Giorgio Matt, Stefano Bianchi, Fiamma Capitanio, Massimo Cocchi, Sergio Fabiani, Ruben Farinelli et al.

IXPE has provided for the first time detailed energy- and time-resolved X-ray polarimetry of Z-type neutron star low-mass X-ray binaries (NS-LMXBs) as they move along their color-color diagrams (CCDs). These sources can reach the highest polarization observed for NS-LXMBs in the 2-8 keV range when they move along the horizontal branch. In a previous paper, we characterized the spectral state of a sample of Z-sources using the CCD and estimated the polarization with model-independent analysis. He…

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astro-ph.HE

Eccentricity as a Magnifying Glass: Precision Population Inference Enabled by Eccentric Neutron Star-Black Hole Mergers

Alberto Salvarese, Hsin-Yu Chen, Aaron Zimmerman, Snehal Tibrewal

The formation history of compact binary systems remains one of the key open questions in astrophysics. Theoretical studies generally favor isolated binary evolution for neutron star-black hole (NSBH) systems, which tends to produce nearly circular orbits. However, recent analyses of the gravitational-wave event GW200105 indicate that its source has measurable eccentricity, suggesting that alternative formation channels may also contribute. It has been shown that the intrinsic parameters of eccen…

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astro-ph.HE

Impact of eccentricity and higher-modes on neutron star-black hole parameter estimation

Snehal Tibrewal, Aasim Jan, Aaron Zimmerman, Hsin-Yu Chen

Detections of gravitational waves from neutron star-black hole systems provide avenues for studying extreme matter, constraining binary formation channels, and testing the nature of compact objects in strong gravity. Eccentric signatures in the signal further enhance this potential by improving parameter estimation and offering clues about binary formation. Because eccentricity is primarily imprinted during the inspiral phase, it is often weakly constrained or missed entirely in binary black hol…

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