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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.HE

Phase-Resolved Ultra-High-Energy Emission Defines an Energetic Boundary for Compact-Object Engines and Dense-Matter Structure

Marlon M. S. Mendes, Cesar H. Lenzi

We show that phase-resolved ultra-high-energy emission from LS I +61 303 defines a critical energetic boundary linking the compact-object engine, circumstellar interaction depth, and dense-matter structure. Combining the GeV-TeV-UHE spectral transition with an orbital acceleration-transparency sieve and branch-resolved stellar sequences for 116 certified EoS, we find that the measured 25-100 TeV tail primarily constrains the circumstellar environment, whereas a more demanding pure-hadronic > 1 T…

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astro-ph.GA

Virgo Filaments VII: MeerKAT HI-imaging of the VirgoIII filament

M. Ramatsoku, G. Nagaraj, P. Jablonka, R. A. Finn, B. Vulcani, G. Rudnick, F. Combes, G. De Lucia et al.

We present MeerKAT HI observations of galaxies in the nearby Virgo III filament. At a median distance of $\sim30$ Mpc, the filament extends over $\approx16$ Mpc across $\sim56$ deg$^2$. Our survey comprises 15 targeted MeerKAT pointings centred on HI deficient galaxies. Multi-resolution HI imaging at 8-90 arcsec with an rms of $\sim0.3$ mJy beam$^{-1}$ reaches column densities of $\sim4\times10^{20}$ to $\sim4\times10^{18}$ atoms cm$^{-2}$. This probes HI in galaxy discs at $\sim1.2$ kpc resolut…

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astro-ph.HEastro-ph.IMgr-qc

Enabling new sampling strategies for continuous-wave analyses by integrating Bilby into PyFstat

Maria-Antonia Ferrer-Martinez, David Keitel

Continuous-wave searches for rotating neutron stars usually cover wide parameter spaces and produce a large number of candidate signals. Stochastic sampling methods therefore play an important role in candidate follow-up and parameter estimation. We present the integration of the Bayesian inference library BILBY into the open-source continuous-wave analysis package PyFstat, enabling access to the broad range of stochastic samplers available through BILBY while preserving the existing PyFstat ana…

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astro-ph.HEastro-ph.IMgr-qc

Enabling new sampling strategies for continuous-wave analyses by integrating Bilby into PyFstat

Maria-Antonia Ferrer-Martinez, David Keitel

Continuous-wave searches for rotating neutron stars usually cover wide parameter spaces and produce a large number of candidate signals. Stochastic sampling methods therefore play an important role in candidate follow-up and parameter estimation. We present the integration of the Bayesian inference library BILBY into the open-source continuous-wave analysis package PyFstat, enabling access to the broad range of stochastic samplers available through BILBY while preserving the existing PyFstat ana…

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astro-ph.HEastro-ph.GA

Compton-induced HE -- VHE $γ$-rays from pair cascade emissions in the SEDs of radio galaxies: NGC 1275

Mfuphi Ntshatsha, Markus Böttcher, Soebur Razzaque

In the scheme of active galactic nuclei (AGNi), the blazar subclass is particularly bright in $γ$-rays. This is because of their emissions being beamed into our line of sight, as opposed to their misaligned parent population, radio galaxies. This work presents results of a Monte-Carlo code that propagates jet-collimated $γ$-rays through the magnetized AGN environment, leading to secondary cascade emissions from relativistic electron-positron pairs. The resulting multi-wavelength emissions are us…

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astro-ph.GA

Design and commissioning of a windowless gas-target system for high-current beams at JUNA

Xuyang Wanga, Fuqiang Cao, Weike Nana, Gang Lian, Wei Nan, Hongwei Huang, Yuchen Jiang, Jingyu Dong et al.

Windowless gas targets avoid the beam-energy loss and straggling introduced by entrance foils and are therefore well suited for direct measurements of low-energy nuclear reactions. A windowless gas-target system designed for operation with milliampere beams has been developed for the Jinping Underground Nuclear Astrophysics facility (JUNA). The system combines three-stage differential pumping, closed-loop gas recovery and purification, a constant-temperature power-compensation calorimeter, and a…

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astro-ph.GA

Design and commissioning of a windowless gas-target system for high-current beams at JUNA

Xuyang Wang, Fuqiang Cao, Weike Nan, Gang Lian, Wei Nan, Hongwei Huang, Yuchen Jiang, Jingyu Dong et al.

Windowless gas targets avoid the beam-energy loss and straggling introduced by entrance foils and are therefore well suited for direct measurements of low-energy nuclear reactions. A windowless gas-target system designed for operation with milliampere beams has been developed for the Jinping Underground Nuclear Astrophysics facility (JUNA). The system combines three-stage differential pumping, closed-loop gas recovery and purification, a constant-temperature power-compensation calorimeter, and a…

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astro-ph.GAastro-ph.CO

Weak cool core, weak turbulence: XRISM, XMM-Newton and Chandra spectroscopy of the core of Abell 1413

Egemen Gormez, Murat Hudaverdi

We present the first XRISM spectroscopy of the core of Abell 1413 (z = 0.143), combining 104.7 ks of Resolve with archival XMM-Newton and Chandra spectra of a matched sky region. A1413 is hot, massive and relaxed but lacks a strong cool core (t_cool = 6.4 Gyr), a regime in which the low turbulence reported to date has been tested only once, in A3571. The Resolve spectrum requires a single velocity-broadened component with kT = 7.06 (+0.33, -0.43) keV and a line-of-sight velocity dispersion sigma…

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astro-ph.GAastro-ph.CO

Detection prospects for heavy WIMP dark matter around M31* in microwave band

Andrei E. Egorov

This work analyzes the detection prospects for weakly interacting massive particles (WIMPs) in dark matter (DM) density spike around the supermassive black hole (SMBH) in Andromeda galaxy M31 in microwave band. WIMP annihilation produces relativistic electrons and positrons, which generate the synchrotron emission in strong magnetic field of the accretion flow medium at microwave frequencies. Properties of this emission, as well as their dependence on DM and medium parameters, were modeled. Atac…

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astro-ph.HEhep-phnucl-th

A Two-Parameter Framework for the Diffuse Supernova Neutrino Background

Cecilia Lunardini, Xingyun Yang

Following important experimental developments, tests of the Diffuse Supernova Neutrino Background (DSNB) are entering a new phase that might lead to a discovery. This motivates the development of simple and broadly applicable tools for comparing theoretical predictions and interpreting experimental results. We show that, over the energy range relevant to current detectors, the DSNB is well described by an exponential spectrum, characterized by the differential flux at 20 MeV, $φ_{20}$, and a spe…

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astro-ph.HE

A Unified Timescale Relation for Quasi-Periodic Eruptions and Repeated Nuclear Transients

Shifeng Huang, Tinggui Wang, Ning Jiang, Yibo Wang, Zhenfeng Sheng, Tian-Yu Xia, Jiazheng Zhu, Zheyu Lin et al.

Quasi-periodic eruptions (QPEs) and recurrent nuclear transients (RNTs) exhibit recurrent high-amplitude flares from galactic nuclei, yet their characteristic timescales remain poorly understood. In this work, we compile a sample of these systems and investigate empirical scaling relations between flare timescales and black hole masses. We find that the recurrence timescale exhibits a positive but highly scattered dependence on black hole mass in the combined QPE and RNT sample, approximately fo…

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astro-ph.HE

Stratified Wind Geometries of GRS 1915+105: Density Profiles and Radii

Noa Keshet, Ehud Behar, Jon M. Miller, Joey Neilsen

The low-mass X-ray binary GRS 1915+105 exhibits dramatic spectral and flux variability, often accompanied by highly ionized outflows. In this work, we analyze four archival Chandra/HETG observations spanning over a decade, which vary greatly in their ionizing spectrum from soft (low inner disk temperature) to hard (high inner disk temperature). We measure the wind properties, using the insightful tool of the absorption measure distribution (AMD, a distribution of column density with ionization).…

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astro-ph.EP

Centaur Longevity Revisited: Reclassification of the Bailey and Malhotra Sample with Modern Orbital Solutions and Astrometric Constraints

Naresh Prasannaa, Chrisphin Karthick

Bailey & Malhotra (2009; BM09) assigned dynamical classes to individual Centaurs using 2007 Minor Planet Center orbital elements. They classified 2005 TH173 as quasi-stable (Q) from a 17-day observational arc. We revisit this scheme using modern JPL Small-Body Database elements (2026-07-26), REBOUND WHFast integrations, and diagonal clone ensembles to separate orbital uncertainty from intrinsic chaotic divergence in dynamical lifetimes. For Centaurs with observational arcs >=30 d, the within-obj…

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astro-ph.HEastro-ph.IM

Supermassive black hole binaries in the multi-messenger context of ground and spaceborne VLBI

B. Hudson, L. I. Gurvits, D. J. D'Orazio, C. Tiede, T. M. Eubanks, E. Mooij

Evidence of a gravitational wave background suggests the existence of a population of sub-parsec supermassive black hole binaries (SMBHBs), with characteristic angular separations on the order of 1-10 $μ$as. Spaceborne extensions of Very Long Baseline Interferometry (VLBI) and the next generation ground arrays introduce the possibility of directly imaging these SMBHBs. In this work, a binary Spectral Energy Distribution (SED) model is used to predict the detectability of SMBHBs with ground and s…

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astro-ph.IMeess.SPmath-phphysics.comp-phphysics.ins-det

Full Characterisation of the Polarisation Primary Beam of the GRAO 32-m Telescope

Theophilus Ansah-Narh, Nia Imara, Benedicta Woode, Joseph Bremang Tandoh, Emmanuel Proven Adzri, Diana Klutse, Evaristus Uzochukwu Iyida

Direction-dependent instrumental polarisation is a major systematic limitation in high-fidelity single-dish radio polarimetry, yet a unified characterisation of beam leakage and the conditioning of polarisation recovery is lacking for the Ghana Radio Astronomy Observatory (GRAO) 32-m telescope. We aim to establish a quantitative, direction-dependent polarimetric beam model at 5.0 and 6.7 GHz. High-resolution \texttt{GRASP} electromagnetic simulations of the nominal telescope configuration are us…

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astro-ph.IMgr-qc

A Content-Addressed Workflow for Reproducible DANTE Gravitational-Wave Anomaly Analysis

Luca Cirfeta

Unsupervised analysis of gravitational-wave detector data combines expensive scientific stages with data acquisition, provenance checks, statistical calibration, follow-up products, and reporting. Reproducing such an analysis requires more than preserving model weights or a final candidate table: the execution graph, scientific contracts, retry semantics, and verification boundary must also be explicit. We present a local workflow layer for the Domain-Adaptive Network for Transient Evaluation (D…

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astro-ph.HE

Constraints on the Low-frequency Radio Emission of the Galactic FRB Source SGR 1935+2154

Chen-Ran Hu, Jinhuang Cao, S. A. Tyul'bashev, Pei Wang, Yong-Feng Huang, E. A. Brylyakova, G. E. Tyul'basheva, Jin-Jun Geng et al.

We present a search for radio pulses from the Galactic magnetar SGR 1935+2154, a well-known source of fast radio bursts (FRBs), at $\sim$110 MHz using the Large Phased Array (LPA) of the Pushchino Radio Astronomy Observatory. Data from two active periods in 2020 (March -- May and September -- November, with $\sim 3.5$ minutes of daily coverage) were analyzed with new methods tailored to both FRB-like single pulses and pulsar-like periodic signals. No significant FRB-like pulses were found. Using…

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astro-ph.GA

The environmental dependence of the circumgalactic medium in a high-resolution cosmological simulation

Georg Herzog, Rajeshwari Dutta, Michele Fumagalli

There is increasing evidence from observations that the circumgalactic medium (CGM) of galaxies depends on the large-scale structure in which they are embedded. When probing the CGM in absorption using quasar sightlines, studies find an enhanced sky coverage in the CGM of galaxies in overdensities compared to galaxies in isolation. However, the exact reason for this environmental dependence is still unclear. In this work we aim to model for the first time the influence of the large-scale structu…

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astro-ph.EPastro-ph.SR

XUE. ProDiMo models of internally and externally irradiated planet-forming disks around 0.3-4.0 solar mass stars (The IRIS project I)

Jenny Frediani, Konstantin V. Getman, Peter Woitke, Bayron Portilla-Revelo, Eric D. Feigelson, Christian Rab, Arjan Bik, María Claudia Ramírez-Tannus et al.

Most stars and planets form in massive star-forming regions, where disks are exposed to external far-ultraviolet (FUV) radiation from nearby O- and B-type stars. The combined effects of stellar irradiation and external FUV fields on terrestrial planet-forming regions (< 10 au) across stellar masses remain unclear. We investigate how internal UV and X-ray irradiation and external FUV fields affect mid-infrared (mid-IR) gas emission and the atmospheric carbon-to-oxygen (C/O) ratios inferred in T T…

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astro-ph.HEgr-qchep-phnucl-th

Decoding the Imprints of Energy-Momentum Squared Gravity in Neutron Stars with Machine Learning Analysis

Sayantan Ghosh, Premachand Mahapatra, Dipti Deb

Neutron stars (NSs) provide a unique laboratory for testing gravity in the strong-field regime and for searching for deviations from General Relativity (GR). In this work, we investigate the effects of Energy-Momentum Squared Gravity (EMSG) on NS structure and examine whether its signatures can be identified from observable stellar properties using supervised machine learning (ML). We solve the modified Tolman-Oppenheimer-Volkoff equations for approximately $10^{4}$ nuclear equations of state (E…

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astro-ph.IMastro-ph.COastro-ph.HEastro-ph.SR

A Missing Tool for Calculating Auto/Cross-correlation Function under Nonuniform Sampling Observations

Chen-Ran Hu, Yong-Feng Huang, Jin-Jun Geng, Orkash Amat, Ze-Cheng Zou, Chen Deng, Fan Xu, Xiao-Fei Dong et al.

Nonuniform sampling presents a long-standing challenge in astrophysical time-domain analysis, invalidating the standard autocorrelation and cross-correlation functions and forcing researchers to adopt ad-hoc methods like interpolation or binning, which introduce unquantified biases and lack rigorous error estimation. Here we introduce a new method for calculating the nonuniform autocorrelation function (NUACF) and nonuniform cross-correlation function (NUCCF) for irregularly sampled time series.…

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astro-ph.EPastro-ph.GAastro-ph.SR

Radial velocity follow-up of \textit{Gaia} astrometric substellar companions: six confirmed brown dwarfs and 13 impostor binaries

Marcus L. Marcussen, Simon H. Albrecht, Kamil K. Kalinowski, Joshua N. Winn, Guðmundur Stefánsson, Jens Reersted Larsen, Julie Gadeberg, Evan Fitzmaurice et al.

With microarcsecond precision, \textit{Gaia} has made the astrometric discovery of substellar companions feasible. However, follow-up observations are needed to check on orbital solutions and rule out astrophysical false positives. We validate and characterise a sample of 20 \textit{Gaia} Data Release 3 (DR3) astrometric candidates for substellar companions, with the dual goal of identifying false positives and deriving robust physical parameters for genuine companions. We performed high-resolut…

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astro-ph.EPastro-ph.IMcs.DB

MAD-LEO: A Maneuver-Annotated Orbital Dataset for LEO Satellites with Tiered Multi-Source Evidence

Zhixin Guo, Qi Shi, Xiaofan Xu, Linqiang Ge, Hua Zhu, Liyan Ben, Bendian Nie, Yuanrui Zhao et al.

With the rapid development of aerospace technology and the large-scale deployment of low Earth orbit (LEO) constellations, the risk of orbital collisions has increased, creating a growing demand for reliable observations of satellite maneuvers. However, public datasets containing real maneuver records remain scarce. We present MAD-LEO, a Maneuver-Annotated orbital Dataset for LEO satellites. The mission-reported subset contains 1,134 maneuver events from eleven geodetic and altimetry satellites…

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cs.SCastro-ph.GAphysics.comp-ph

Physical Law Ecology: mapping multi-mechanism ecologies as the zeroth step of data-driven scientific discovery

Xiongheng Bian, Xiangyu Cui, Ma Feng, Xiaoyan Shen

Every data-driven equation discovery method assumes (implicitly and without verification) that the target system obeys a single governing law ($K{=}1$). Here we show that this assumption is the primary bottleneck limiting scientific discovery in multi-mechanism systems, and introduce Physical Law Ecology, a framework that makes $K^*$ (the number of coexisting independent mechanisms) itself the first quantity to be determined from data. The framework automatically mines a pool of topologically di…

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astro-ph.HE

Nuclear equation-of-state effects on the two-dimensional post-outburst thermal evolution of magnetized neutron-star crusts

Wei-Feng Zhang, Zhi-Fu Gao, Wen-Qi Ma, Na Wang, Yan-ling Liu

We present a controlled two-dimensional study of nuclear-equation-of-state (EOS) effects on the post-outburst thermal relaxation of magnetized neutron-star crusts. Six EOS models are evolved at a fixed gravitational mass of $1.4 M_{\odot}$ with EOS-specific TOV backgrounds, crust compositions, and transport inputs under identical magnetic-field and heating prescriptions. Our analysis combines self-consistent multi-EOS evolution with a BSk-family factorization that separates structural, microphys…

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astro-ph.GA

J023721.13$-$010528.5: A Giant $S$-shaped Radio Galaxy Showing Four Episodes of Jet Activity

Pavan Vijay Khadekar, Dharam Vir Lal, Ramana Athreya

We present high-sensitivity, high-resolution radio observations of J023721.13$-$010528.5 using the upgraded Giant Metrewave Radio Telescope in band-3 (250--500\,MHz) and band-4 (550--950\,MHz), along with MeerKAT (1280\,MHz) and VLA (3\,GHz) survey images. The radio source, hosted by a bright cluster galaxy at redshift $z=0.372$, is a giant radio galaxy with a projected linear size between the outermost hotspots of 1.2~Mpc and is one of the largest $S$-shaped radio sources known. Its radio morph…

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hep-phastro-ph.SR

A distance-independent constraint on the axion-electron coupling from RGB stars

Thomas Levasseur, Oscar Straniero, Andrea Caputo

Interest in axions and axion-like particles has resurged, driven by their role in solving the strong CP problem and their appeal as dark matter candidates. The luminosity of the tip of the red giant branch (TRGB) offers a key observable for probing these particle properties. This work aims to improve existing bounds on the axion-electron coupling by adopting a differential observable that is less sensitive to distance, interstellar extinction, the zero-point of bolometric corrections (BCs), and…

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astro-ph.SR

Magnetic Signatures in Merger Products

Nicolas Muntean, Lisa Bugnet, Lynn Buchele, Debasish Dutta, Lukas Einramhof, Paul G. Beck, Lucas Barrault, Bastien Liagre et al.

Asteroseismic estimates of the magnetic field strength in the radiative interior of red giant stars depend strongly on the internal stellar structure derived from models. Since red giant branch merger products have been shown to be able to possess a different core structure than single stars of the same mass, we investigate how a mass-gain history influences our estimates of an internal magnetic field strength. We construct stellar models with and without a mass-gain event after the onset of the…

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astro-ph.HE

Sharpening the Mass Measurement of PSR J1048+2339 via High-Cadence Photometry

Kwan-Lok Li, Ka-Yui Au, Lupin C. C. Lin, C. Y. Hui, Albert K. H. Kong, Jumpei Takata

Neutron stars are among the densest objects in the universe, and the mass measurements are crucial to the understanding of their equation of state. Pulsars in tight binaries can be weighed dynamically, but accurate mass estimates are often hampered by uncertainties in orbital inclinations. In this paper, we report on multi-epoch optical monitoring of the pulsar binary, PSR J1048+2339, using the 0.5-m RIFT telescope at Lulin Observatory. Our observations reveal frequent optical flares with eclips…

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astro-ph.HEgr-qc

Near-Horizon Tidal Disruption Events

Yang Yang, Xian Chen

Tidal disruption events (TDEs) offer a unique dynamical probe of the spacetime geometry around supermassive black holes (SMBHs). While conventional TDEs occur around SMBHs of $M_\bullet \sim 10^6 - 10^7 M_\odot$, where stars are disrupted far from the event horizon, here we identify a special class of TDEs around rapidly spinning SMBHs with masses $M_\bullet \gtrsim 10^8 M_\odot$, where the tidal-disruption radius approaches the gravitational radius. We term these events "near-horizon TDEs" and,…

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