UchUchU

Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.EP

Spectral Evolution of Ceres' Surface and Implications for Space Weathering

Qing Zhang, Jian-Yang Li, Yazhou Yang, Minge Liu, Yang Liu

The surface of Ceres exposed to the space environment will be gradually altered, but the evolution of its spectral properties remains poorly understood. Here we analyze visible and infrared spectra acquired by the Dawn mission to investigate spectral variations across different surface units. We identify local shifts of a few nm toward shorter wavelengths in the 2.7 $μ$m band center, predominantly associated with freshly exposed slumping and impact materials. Our analysis suggests that compositi…

Read →
astro-ph.GA

A comparative analysis of the long-term optical variability characteristics of narrow and broad-line Seyfert 1 galaxies at z > 0.8

Aratrika Dey, Stalin C. S., Akshith S., Suvendu Rakshit

We present the results on a comparative analysis of the long-term optical variability characteristics of high-redshift narrow-line Seyfert 1 (NLSy1) galaxies and broad-line Seyfert 1 (BLSy1) galaxies. Our sample spanning the redshift range of $0.8 < z < 2.6$, comprises 2490 NLSy1 and 2490 BLSy1 galaxies matched in the optical brightness$-$redshift plane. We used V-band data from the Catalina Real-Time Transient Survey covering a baseline of 5$-$9 years, and g, r, and i-band data from the Zwicky…

Read →
astro-ph.IMastro-ph.EPstat.CO

Nii-MALA: A Fast Metropolis-Adjusted Langevin Sampler with Radial Velocity Benchmarks

Jian Jiao, Sheng Jin, Wenxin Jiang, Dong-Hong Wu

Markov chain Monte Carlo is widely used for model assessment and parameter fitting in astronomy and astrophysics, leading to numerous ready-to-use packages implementing various sampling techniques. For large-scale analyses involving many individual targets, computational efficiency becomes paramount, as it dictates the overall runtime. We introduce Nii-MALA, a high-performance C implementation of the Metropolis-Adjusted Langevin Algorithm, which leverages Message Passing Interface for paralleliz…

Read →
astro-ph.HEquant-ph

Hardware-aware quantum attention for fast radio burst identification

Li He, Xuan Yang, Feng Xiong, Songbo Zhang, Qiuhao Chen, Yuchen He, Yunxiang Yang, Jun Lu et al.

Fast radio bursts (FRBs) are millisecond-duration extragalactic pulses whose discovery requires searches over large signal-parameter spaces and the rejection of candidate sets dominated by radio-frequency interference and noise. Integrating quantum processors into FRB searches requires a workflow connecting telescop data to hardware-compatible models. Here we develop a pipeline that converts raw search-mode PSRFITS data into dynamic-spectrum segments and identifies FRB-like signals using a hybri…

Read →
astro-ph.GAastro-ph.IM

The driving mode of turbulence in disc galaxy simulations with adaptive mesh refinement

James Watt, Christoph Federrath, Thorsten Tepper-Garcia, Oscar Agertz, Joss Bland-Hawthorn

Turbulence is a key ingredient in controlling the structure of the interstellar medium (ISM) and star formation, yet we still lack a detailed understanding of its drivers in galaxies. Previous idealised simulations of turbulence employ a stochastic forcing field to drive turbulence. The geometry of this forcing field - whether it is predominantly solenoidal or compressive - is a key parameter governing how turbulence shapes the ISM density distribution and regulates the star formation rate. The…

Read →
astro-ph.GA

Nexus-CDM: Isolated Galaxy Simulations with Cosmologically Evolving Dark-Matter Halos I. Method and Validation

Thor Tepper-García, Joss Bland-Hawthorn, Oscar Agertz, Christoph Federrath

Galaxy evolution can be modelled in two complementary ways. Standalone simulations place a single galaxy in isolation, evolving it under controlled initial conditions without the surrounding cosmic web. This approach offers high resolution and computational efficiency, making it well suited to disentangle specific physical processes (e.g. feedback and disc instabilities) and testing them cleanly, though at the cost of ignoring environmental context, gas accretion from the broader large-scale str…

Read →
astro-ph.HEastro-ph.CO

Optical spectroscopy of the VHE flat-spectrum radio quasar PKS 0903-57

E. Kasai, P. Goldoni, C. Boisson, S. Pita, W. Max-Moerbeck, F. D'Ammando, B. Rajput, M. Backes et al.

We report new optical spectroscopic results for the gamma-ray blazar PKS~0903$-$57. The optical properties of this source have historically been complicated to establish, due to a bright foreground star separated from the blazar by only 0.67$^{\prime\prime}$. During its strong high-energy (HE) and very high-energy (VHE) gamma-ray flaring period between 2020 and 2022, the Southern African Large Telescope and Very Large Telescope (VLT) took spectra of its optical counterpart. Photometric monitorin…

Read →
astro-ph.HE

Measurement of Cosmic-Ray Density in the Spiral Arms toward Galactic Anticenter

Jia-hao Liu, Bing Liu, Rui-zhi Yang

Using nearly 17 years of Fermi-LAT data, we analyzed the diffuse gamma-ray emission associated with different spiral arms of the Milky Way in the ranges $l = 105^\circ$ to $145^\circ$ and $b = -5^\circ$ to $5^\circ$. The gamma-ray emissions from these spiral arms all exhibited clear pion-bump features, which can be well explained by a power-law spectrum of cosmic-ray protons. The spectral indices corresponding to the three distinct spiral arms -- the Local Arm, the Perseus Arm, and the Outer Arm…

Read →
astro-ph.GAastro-ph.SR

Tracing Stellar Populations through the Mg-Al Anti-Correlation in Gaia-ESO Globular Clusters

H. Sinclair-Wentworth, C. C. Worley, P. Jofre, J. Schiappacasse-Ulloa, L. Magrini

Context. Globular clusters (GCs) are fragments of the chemical history and evolution of the Milky Way. Their notable intra-cluster abundance variations have been used to characterise chemical trends and stellar populations. However, the origins of these populations and GCs in general are still largely unknown. Aims. Our aim is to explore the origin of the stellar populations belonging to 14 GCs making use of their abundances derived from the Gaia-ESO Survey (GES) spectra. In particular, we use t…

Read →
astro-ph.COastro-ph.IM

Field-Level Baryon Acoustic Oscillation Reconstruction of the DESI DR1 Luminous Red Galaxies with Linear Field Transformer (LiFT)

Liam Parker, Uroš Seljak, Adrian E. Bayer, Richard Feder, David Valcin

We present the first application of neural field-level baryon-acoustic oscillation (BAO) reconstruction to real spectroscopic survey data. We develop Linear Field Transformer (LiFT), a 3D vision transformer that takes as input the observed galaxy field, its standard reconstruction, and a set of context channels encoding local line of sight, survey coverage, and redshift, and learns to correct standard reconstruction toward the linear density field. We construct a forward-modeling pipeline to pro…

Read →
astro-ph.EPastro-ph.SR

Second Generation Planet Formation in Post-AGB Discs - II: Dust Coagulation and Core Accretion

Ali Pourmand, Orsola De Marco, Devika Kamath, Daniel J. Price

Observations have established that the circumbinary discs formed around post-asymptotic giant branch (post-AGB) binaries have striking similarities to protoplanetary discs around young stars. In this study, we examine the feasibility of the different stages of growth in the core accretion framework of planet formation in post-AGB discs, in order to assess whether planet formation is possible in these systems. We find that dust coagulation up to mm sizes is possible within the lifetimes of post-A…

Read →
nucl-thastro-ph.HEhep-ph

Stability and Structural Properties of Hot Quark Stars within Perturbative QCD

Tousif Raza, Tyler Gorda

The hypothesis of strange quark matter (SQM) and the possible existence of strange stars have been extensively investigated within the thermodynamic bag model, typically employing the free Fermi gas approximation with or without perturbative QCD corrections at zero temperature, where quark confinement is modeled by the bag pressure. In this work, based on the perturbative inclusion of quark mass effects, we develop a thermodynamically consistent equation of state (EOS) for SQM at finite temperat…

Read →
astro-ph.HEnucl-th

Bayesian Inferences on Analytical Equations of State Approximations of Neutron Stars

Arijit Das, Sourav Roy Chowdhury

Equations of state (EoS) for dense matter are commonly provided in tabulated pressure-energy density relations, complicating numerical implementation and potentially compromising thermodynamic consistency. In this work, we propose a universal, piecewise-continuous functional form with a common parametrization capable of representing a broad class of dense matter EoSs. We validate this parametrization against tabulated EoSs from the CompOSE and LALSimulation repositories. Following the initial de…

Read →
astro-ph.EP

WINERED Detects a Strong Atmospheric Outflow on the Sub-Neptune GJ 3090b

Shreyas Vissapragada, Zifan Lin, Annabella Meech, Collin Cherubim, Leonardo A. Dos Santos, Aaron Householder, Krishna Kanumalla, Mercedes Lopez-Morales et al.

Sub-Neptunes are the most common short-period ($P<100$ d) planets known. A major goal for the field is to build a comprehensive understanding of their compositions and evolutionary histories, and an important tool for achieving this goal is metastable helium (He$^*$) transmission spectroscopy, which traces atmospheric escape. In this paper, we report the detection of He$^*$ in the atmosphere of the sub-Neptune GJ 3090b at high spectral resolution. We observed two consecutive transits of this pla…

Read →
gr-qcastro-ph.HEhep-th

Full set of scenarios of high energy collision in the Schwarzschild background and kinematic censorship

A. V. Toporensky, P. Gusin, A. Radosz, O. B. Zaslavskii

We consider collisions between particles moving freely in the Schwarzschild background. We suggest classification of scenarios that lead to unbounded energy output in the center of mass frame. Although this is forbidden in the exterior of a black hole, the phenomenon becomes possible with account of white hole region and mirror universe in the complete space-time diagram. Also, we scrutinize collisions in the vicinity of the bifurcation point and reveal the role of resting observers in the inner…

Read →
astro-ph.COastro-ph.GA

Bayesian Inference of the Tip of the Red Giant Branch: I. One-Dimensional Analysis

James D. Gibbon, Daniel J. Mortlock

The tip of the red giant branch (TRGB) can be used as a relative distance measure as part of the cosmic distance ladder to infer the Hubble constant. We present a Bayesian framework for TRGB inference that incorporates selection effects and propagates per-star uncertainties, modelling the observed catalogue as a realisation of an inhomogeneous Poisson point process which includes the RGB and contamination from the asymptotic giant branch (AGB). We derive expressions for the predicted TRGB uncert…

Read →
astro-ph.GA

PRISMS. GHZ1. A standard tale of galaxy evolution with atypical ionizing conditions at $z=9.878$

Borja Pérez-Díaz, Marco Castellano, Javier Álvarez-Márquez, Luis Colina, Lorenzo Napolitano, Sarah Kendrew, Alejandro Crespo Gómez, Stefano Carniani et al.

[Abridged] The first operating years of the James Webb Space Telescope (JWST) have revealed a surprising number of $z \gtrsim 10$ UV-bright objects, many of them characterized by their compactness, anomalous chemical abundance patterns and complex ISM physics (e.g. N-enhanced systems). To assess whether these objects are a phase of early galaxy evolution or a peculiar population, it is essential to understand the physics of systems without anomalous abundance patterns in this epoch. We present a…

Read →
astro-ph.HE

First results on the search for the Galactic Center Excess in the sub-GeV band with the emulsion telescope in GRAINE 2023

Yuya Nakamura, Shigeki Aoki, Takashi Azuma, Hirotaka Hayashi, Yudai Isayama, Atsushi Iyono, Takumi Kato, Tsuyoshi Kawahara et al.

Please check the paper for full abstract. The Galactic Center Excess (GCE) is an unexplained excess of gamma-ray emission from the Galactic Center. The GRAINE experiment aims to reveal the origin of the GCE using an emulsion gamma-ray telescope with high angular resolutions of 1 deg at 100 MeV and 0.1 deg at 1 GeV. In this study, we search for the GCE in a small region near the Galactic Center using the GRAINE 2023 flight data. In particular, rather than focusing on the spectral peak of the GCE…

Read →
astro-ph.GAastro-ph.IM

Euclid: Data Release 1 (DR1) -- Fornax-7, an ultra-faint companion to the Fornax dwarf spheroidal galaxy? A remote star cluster or dwarf satellite of the Fornax dSph

T. Saifollahi, A. Lançon, A. M. N. Ferguson, P. Boldrini, M. Gatto, J. M. Howell, N. F. Martin, A. C. Robin et al.

We report the discovery of an ultra-faint stellar system in the vicinity of the Fornax dwarf spheroidal (dSph) galaxy in Euclid DR1. This system, which we designate Fornax-7, is located $1.1$ deg from the centre of the Fornax dSph at about $145$ kpc, corresponding to a projected distance of $\sim 2.8$ kpc assuming the distance of the Fornax dSph. We characterise Fornax-7 using constraints from its colour-magnitude diagram (CMD), luminosity function (LF), and integrated optical colours from groun…

Read →
astro-ph.SRastro-ph.GA

Stripped helium stars in UV

L. R. Yungelson, A. G. Kuranov, A. V. Mishakina

The model of Galactic population of stripped helium stars, the remnants of $5 \lesssim M/M_\odot \lesssim 24$ primary components of close binaries after RLOF is presented. These stars emit in the UV range of the spectrum and may be observed by detectors aboard planned "Spektr-UV" (WSO-UV) space telescope. For the current star formation rate in the Galaxy 2$\mathrm {M_\odot yr^{-1}}$, the estimate of the number of 1 to 7 $M_\odot$ objects with $T_{\rm eff} \gtrsim$25,000\,K ranges from 14700 to 2…

Read →
astro-ph.HE

First Light of Neutron Star Mergers: Off-axis Cocoon Cooling X-ray Emission from Short Gamma-Ray Burst Jets

Jian-He Zheng, Wenbin Lu

Neutron star mergers (NSMs) are confirmed gravitational wave sources. Identifying an early electromagnetic counterpart for these events is therefore crucial for rapid localization and multimessenger follow-up. However, the associated Gamma-Ray Bursts (GRBs) are highly collimated and are therefore easily missed by off-axis observers. An early, less beamed counterpart is essential for identifying the majority of mergers. In this Letter, we investigate the cooling emission from jet-driven cocoons p…

Read →
astro-ph.HEastro-ph.COastro-ph.SRhep-phnucl-th

NICER neutron stars with dark energy and dark matter: effects on the inferred equation of state

Nathan Rutherford, Chanda Prescod-Weinstein, Anna Watts

[Abridged] In this work, we compare neutron stars where dark energy or dark matter are present in the core, contrasting them against purely baryonic stars with the same central energy density. From this comparison, we find that the dark energy models are more constrained by neutron star observations than the dark matter models, suggesting that neutron stars can place strong constraints on dark energy parameters. We consider four configurations: purely baryonic neutron stars described by a piecew…

Read →
astro-ph.GAastro-ph.CO

The Connection between Halo Assembly History and the Stellar Distribution I: The Central Stellar Mass - Richness Plane

Shuo Xu, Song Huang, Alexie Leauthaud, Benedikt Diemer, Katya Leidig, Conghao Zhou, Carlo Cannarozzo

Recent observations suggest intrinsic links between the stellar components of massive halos and their assembly histories. Using massive halos with $\log[M_{\rm halo}/M_\odot] \geq 13.0$ from the IllustrisTNG-300 simulation, we explore differences in secondary halo properties between samples selected by central galaxy stellar mass and satellite richness. For group-like masses, we find that halos selected by the outskirts stellar mass of their central galaxies between 50 and 100 kpc ($M_{\star,[50…

Read →
astro-ph.GA

Nitrogen-Loud Quasars from the Dark Energy Spectroscopic Instrument. II. Broad-Line Region Metallicity and Relative Nitrogen Enrichment

Shuo Zhai, Wei-jian Guo, Yong-Jie Chen, Haining Li, Jian-Min Wang, Gang Zhao

Whether the unusually strong nitrogen emission in nitrogen-loud (N-loud) quasars reflects high overall metallicity, enhanced nitrogen abundance relative to other elements, or both has long been debated. We analyze the broad-line region (BLR) abundances of 121 N-loud quasars at $2.13 \leq z \leq 3.90$ selected from the Dark Energy Spectroscopic Instrument Data Release 1 and construct a control sample of normal quasars matched in redshift, continuum luminosity, and virial black hole mass. Within t…

Read →
hep-phastro-ph.SR

Probe of Solar Neutrino Magnetic Moments through Spin-Flavor Precession: Resonance Structure and Antineutrino Appearance

Pouya Bakhti, Sudip Jana, Chui-Fan Kong, Seodong Shin, Seokhoon Yun

We investigate solar-neutrino spin--flavor precession (SFP) induced by magnetic moments in the three-active-flavor framework. For Majorana neutrinos, SFP can convert solar neutrinos into antineutrinos of different active flavors. In the Dirac case, SFP instead produces sterile right-handed states and can lead to the disappearance of active neutrinos. Using the full $6\times6$ Hamiltonians and GS98 and AGSS09 solar profiles, we examine propagation-eigenvalue crossings at $B_\perp=0$ and the proje…

Read →
astro-ph.HE

Evolution of the High-Energy Excess in Swift J1727.8-1613 during Its 2023 Flare State

Xiao Fan, Bei You, Yi Long, Han He, Liang Chen

We investigate the evolution of the high-energy excess in Swift J1727.8-1613 during its 2023 flare state using joint Insight-HXMT and INTEGRAL/ISGRI observations covering 2-500 keV. Fits to the broadband spectra with a model including thermal Comptonization and disk reflection leave systematic positive residuals above ~150 keV. Adding a power-law component improves the fits and yields photon indices of 2.08-2.61, demonstrating that the high-energy excess beyond the thermal Comptonization continu…

Read →
astro-ph.HE

Evolution of the High-Energy Excess in Swift J1727.8-1613 during Its 2023 Flare State

Xiao Fan, Bei You, Yi Long, Han He, Liang Chen

We investigate the evolution of the high-energy excess in Swift J1727.8-1613 during its 2023 flare state using joint Insight-HXMT and INTEGRAL/ISGRI observations covering 2-500 keV. Fits to the broadband spectra with a model including thermal Comptonization and disk reflection leave systematic positive residuals above ~150 keV. Adding a power-law component improves the fits and yields photon indices of 2.08-2.61, demonstrating that the high-energy excess beyond the thermal Comptonization continu…

Read →
astro-ph.HE

High-energy spectral cutoffs in the prompt emission of Fermi gamma-ray bursts: bulk Lorentz factors, emission radii, and a cutoff-peak energy relation

Yuan-Yuan Zuo, Yuan-Chuan Zou

The high-energy end of the gamma-ray burst (GRB) prompt spectrum carries information on the physical conditions of the relativistic outflow, but the number of well-characterized spectral cutoffs is small. We present a systematic search for high-energy spectral cutoffs in the time-integrated prompt spectra of 139 GRBs observed by Fermi between 2008 July and 2025 December, selected to have broadband coverage either through a LAT detection or through bright BGO emission. Joint GBM, LLE, and LAT spe…

Read →
astro-ph.SR

Presence of Solar Neutral Atom Corona and Coronal Heating

Z. Q. Qu, R. Y. Zhou, H. Su, Y. Liang, L. Chang, X. M. Cheng

By analyzing slit scanning spectral data obtained during 2024 total solar eclipse, presence of neutral atom corona is revealed along with a hidden inner F-corona detected within heights below half a solar radius. The inner F-corona is found to be essentially different from the Fraunhofer corona formed by dust scattering beyond about 2.3 solar radius heights. The two new kinds of the solar corona are deduced from the intensity difference between the spectral line intensity distribution and their…

Read →
astro-ph.SRastro-ph.GAastro-ph.HE

Thermodynamic exchange and mode stability in strongly nonadiabatic radial pulsations

Jan Zalewski

We apply the quadratic balance relation for linear nonadiabatic pulsations to radial modes of a sequence of post-AGB envelope models covering $3.52\leq\log(T_{\rm eff})\leq4.6$. The relation separates the thermodynamic exchange power $\mathcal{P}_{\rm ex}$, response power $\mathcal{P}_{\rm rsp}$, and surface contribution $ΔB$, and introduces an effective norm through $\mathcal{P}_{\rm ex}+ΔB=2γχ_{\rm eff}\mathcal{E}_{\rm kin}$, where $γ$ is the mode growth rate. For nearly adiabatic modes $χ_{\r…

Read →