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宇宙工学・惑星科学・宇宙物理の最新プレプリント。

astro-ph.HEhep-ph

Emission and cooling of a newborn quark star

Mikalai Prakapenia, Gregory Vereshchagin

It has long been believed that newborn quark stars are inefficient emitters because the quark plasma frequency is so high that it suppresses electromagnetic radiation across the entire spectrum up to energies of several tens of MeV. Here, we show that significant electromagnetic emission can instead originate from the electrosphere of a quark star, where the plasma frequency is much lower, approximately 40 keV. As a result, the cooling of a newborn quark star is expected to proceed through two d…

astro-ph.HE

Prompt and Afterglow Constraints on the Central Engine of GRB 240825A

Daban Mohammed Saeed, Rahim Moradi, Chen-Wei Wang, Brwa Shukur Ismael, Marco Muccino

GRB 240825A shows unprecedented temporal and spectral features that constrain the properties of its inner engine: (1) a prompt emission three-component spectrum consisting of a Band function continuum, a quasi-thermal bump, and a hard MeV tail; and (2) an X-ray afterglow fitted by a power-law decay with index $1.29 \pm 0.02$; and (3) a $6.37 \pm 0.05$ Hz quasi-periodic oscillation (QPO) identified in the 100-300 keV band during the 2.07-3.25 s time interval, coinciding with the photospheric radi…

astro-ph.EPphysics.space-ph

The precipitation of protons and electrons in Jupiter's auroral regions: a statistical comparison based on Juno/JEDI data

B. Benmahi, N. André, V. Hue, Z. -Y. Liu, G. Gronoff, B. Mauk, B. Bonfond, T. Stallard et al.

Energetic electrons dominate the energy precipitated into Jupiter's auroral regions, but protons precipitate along the same field lines, with a contribution that remains poorly constrained. We statistically compare the precipitating energy flux of protons and electrons in two of Jupiter's auroral sub-regions, the polar (PE) and main (ME) emission regions. We use Juno/JEDI data from PJ3 to PJ66. The magnetic footprint of the spacecraft, computed with the JRM33 and CON2020 field models, is assigne…

astro-ph.GA

Before fragmentation: from uniform clouds to stellar clusters

A. Giannetti, T. Pillai, J. Kauffmann, A. Palau, E. Vazquez-Semadeni, K. Morii, P. Sanhueza

Our study of the early stages of fragmentation in massive clumps has revealed a striking anomaly: $\sim15\%$ of the CoCoA sample exhibit no fragmentation at all. These sources could represent the initial conditions before core formation. We investigate whether these sources are indeed at the onset of core formation, and whether gravity or turbulence dominates their early fragmentation. We study the transition from uniform gas to active cluster formation, and compare contrasting predictions of tu…

astro-ph.SRastro-ph.HE

Limits on eccentricity excitation by tidally enhanced mass loss in Wolf-Rayet binaries

Viktória Fröhlich, Zsolt Regály

Wolf--Rayet (WR) binaries frequently display high orbital eccentricities, and their eccentricity distributions are inconsistent with that of high-mass Galactic field binaries at high significance. This raises the question of whether these eccentricities are primordial or generated during the WR phase. We test whether a tidal enhancement of the mass-loss rate can pump the eccentricity of a WR binary on a sample of 14 WR systems. We model each system as a variable-mass two-body problem and integra…

astro-ph.SR

Doppler Velocity Variation near the Solar Limb in the Solar Photosphere Observed with Hinode

Akie Moritsuka, Yukio Katsukawa, Ryohtaroh T. Ishikawa

The Doppler velocity and bisector of photospheric lines show significant center-to-limb variation. This variation has been considered to be caused by the projection angle of the granular convection which has a corrugated surface. This study aimed to show the spectral line shifts up to limb and investigate how these shifts are caused by granular convection. We analyzed the Fe I 630.15 nm absorption line by spatially resolving the granulation very close to the limb using datasets of polar observat…

astro-ph.EPphysics.space-ph

Energy distributions of precipitating electrons in Jupiter's auroral regions from combined Juno/JADE and Juno/JEDI measurements

B. Benmahi, V. Hue, N. André, B. Bonfond, M. Blanc, Z. -Y. Liu, B. H. Mauk, F. Allegrini et al.

Jupiter's auroras are produced by magnetospheric electrons precipitating into its atmosphere. Juno/JADE and Juno/JEDI together measure these electrons from 100 eV to 1 MeV. However, their auroral spectra are poorly reproduced by the widely used kappa distribution, hereafter the classical single-kappa distribution. We aim to statistically characterize the energy flux distributions of precipitating auroral electrons and to derive a new phenomenological 4-kappa distribution better suited to JADE+JE…

physics.space-phastro-ph.EPastro-ph.SR

P2D - A Two-Dimensional Multi-Spacecraft Solar Wind Persistence Model

Daniel Milošić, Manuela Temmer, Stephan G. Heinemann, Mathew Owens, Stefan J. Hofmeister

The background solar wind is a key component in space weather forecasting, as it contains geoeffective high-speed streams and provides the medium through which coronal mass ejections propagate and evolve in interplanetary space. Due to the solar rotation and the slow evolution of large-scale solar wind structures, solar wind properties exhibit an autocorrelation with a period of roughly 27 days, particularly at solar minimum. We made use of this property to develop a solar wind persistence model…

astro-ph.EP

Hybrid worlds are the commonest outcome among the M-dwarf sub-Neptunes characterised with JWST

Juan F. Pagés Navarrete

The sub-Neptunes orbiting M dwarfs are usually assigned to one of two classes: rocky cores beneath primordial hydrogen, or volatile-rich bodies formed beyond the water-ice line. Bulk density cannot distinguish them, the two being degenerate in mass and radius once envelope evolution is modelled self-consistently (Rogers et al. 2023); the atmospheric mean molecular weight μ is the route past it. We compile the eight M-dwarf sub-Neptunes with published JWST spectra and a constrained μ, and combine…

astro-ph.SR

Power balance and anomalous exchange in post-AGB pulsations

Jan Zalewski

We develop a complex balance relation for stellar pulsations whose real and imaginary parts give paired relations for the excitation rate and oscillation frequency. The formulation includes thermodynamic exchange, boundary power, and the inertial, compression, horizontal-area, and gravitational-stratification terms, without assuming weak nonadiabaticity. Applied to portions of an envelope, it provides cumulative diagnostics evaluated using the eigenfrequency and eigenfunctions of the complete pu…

astro-ph.GAastro-ph.CO

KiDS-DR5: Exploring dust transport in dark matter halos of galaxies

Eray Genc, Angus H. Wright, Hendrik Hildebrandt, Dian P. Triani, Dominik J. Bomans, Benjamin Stölzner, Marika Asgari, Henk Hoekstra et al.

We analyse a well-defined sample of galaxies from the final data release of the Kilo-Degree Survey (KiDS-DR5), selected using magnitude, photometric redshift, and stellar mass cuts, to measure their mean halo mass and circumgalactic dust content as a function of stellar mass. Our goal is to provide empirical constraints on dust transport mechanisms, such as stellar- and AGN-driven outflows, operating in galaxy halos. We develop and validate a new measurement and modelling framework using the MIC…

astro-ph.HE

Unexpected Gamma-ray Outburst from the CSS Radio Galaxy 3C 216

Stefano Ciprini, Federica Giacchino

While compact steep-spectrum (CSS) radio galaxies, genuine young/intermittent-jet or frustrated-jet radio galaxies trapped in gas-rich environments, are rarely detected in GeV gamma-ray energy bands, 3C 216 is an interesting exception. In 2023, the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope detected an unexpected, rapid, and powerful GeV gamma-ray outburst from this CSS radio galaxy, which was followed up by UV and X-ray observations from the Neil Gehrels Swift Space…

astro-ph.EPastro-ph.SR

Resolved Structure and Orbital Motion of a Localized 1 au-scale Dust Accumulation in the Protoplanetary Disk around TW Hya

Takashi Tsukagoshi, Takayuki Muto, Hideko Nomura, Ryohei Kawabe, Satoshi Okuzumi, Shigeru Ida, Jun Hashimoto, Taichi Uyama et al.

We present the results of high-resolution ($\sim1$~au) Atacama Large Millimeter/submillimeter Array (ALMA) observations of the TW~Hya protoplanetary disk in the Band 6 dust continuum, as well as the \ce{^13CO} and \ce{C^18O} J=2--1 emission lines. The primary focus of this study is to investigate the kinematics, internal morphology, and local gas environment of the prominent dust blob at a radius of 52~au. By comparing our 2021 data with archival observations from 2017, we detect the proper moti…

astro-ph.GA

Discovery of Kolmogorov-like turbulence in the inner shell of SNR HB 9

Li Xiao, Ming Zhu, Xiao-Hui Sun, Wolfgang Reich, Patricia Reich

We investigated the scaling relation of the magnetohydrodynamic turbulence in the inner and outer shells of the supernova remnant HB 9 using multi-tracers. For the eastern inner shell section, one-dimensional structure function and power spectrum analyses of the radio total intensity, H-alpha emission, and polarized intensity consistently show a Kolmogorov-like scaling of l^2/3 over the inertial range. The two-dimensional power spectrum for the entire inner region follows k^-8/3 of all tracers,…

astro-ph.EPastro-ph.SR

Planets Around Solar Twins/Analogs (PASTA) III: Chemical Clock Relations in Planet-Hosting Solar Analogs

Qinghui Sun, Serat M. Saad, Yuan-Sen Ting, Jiayue Zhang, Chenyang Ji, Fei Dai, Sharon Xuesong Wang, Bryant Randolph et al.

Context. Abundance ratios between elements synthesized on different nucleosynthetic timescales provide empirical chemical clocks for estimating stellar ages, but robust calibrations require homogeneous samples with precise stellar parameters and elemental abundances. Aims. We aim to investigate whether the presence of planets modifies empirical chemical clock relations. Methods. We present high-precision stellar parameters and elemental abundances for 52 new planet-hosting targets observed with…

astro-ph.HE

Gravitational Waves from Core-Collapse Supernovae: Dependence on the Progenitor Star, Rotation Rate and Nuclear Equation of State

Jade Powell, Bailey Sykes, Bernhard Müller

We simulate 137 axisymmetric core-collapse supernova explosions to systematically investigate the impact of different progenitor properties, rotation rates, and equations of state on the supernova gravitational-wave emission. We use 15 different progenitor stars, with masses ranging from $9.71\,\mathrm{M}_{\odot}$ to $36.61\,\mathrm{M}_{\odot}$, three equations of state, and three rotation rates, with durations extending up to 5.5\,s after bounce. We find substantial differences in the gravitati…

astro-ph.SRastro-ph.EPphysics.space-ph

Numerical analysis of electron density and response time delay during solar flares in mid-latitudinal lower ionosphere

Sayak Chakraborty, Tamal Basak

Impacts of solar flare vary at different parts of the lower ionosphere depending on its proximity to the direct exposure of incoming solar radiation. The quantitative analysis of this phenomenon can be attributed to the solar zenith angle (chi(t)) profile over the ionosphere. We numerically solve the electron continuity equation to obtain the lower ionospheric electron density profile (Ne(t)). The electron production rate (q(t)) is governed by the (i) X-ray profile (phi(t)) of the flare, (ii) ch…

astro-ph.GAastro-ph.SR

R Coronae Borealis fadings: a dusty gas cloud eclipse model

Mark A. Walker, Artem V. Tuntsov, Arthur G. Suvorov

R Coronae Borealis stars (RCBs) are hydrogen-deficient supergiants that undergo deep fading events due to transient extinction by dust. First observed over two centuries ago, that behaviour remains poorly understood. Our aim is to investigate the possibility that the fading events are eclipses by orbiting, dusty gas clouds. We construct a simple physical model of the dust wind that is driven from the cloud surface by the stellar radiation field, and we calculate the extinction and scattered ligh…

nucl-thastro-ph.HE

Medium effects on neutron star modified and direct Urca cooling rates

B. X. Zhou, Jin-Biao Wei, Z. H. Li, G. F. Burgio, H. -J. Schulze

We study the effects of in-medium modification of the elementary cooling processes on observable properties of isolated neutron stars. We then deduce the neutron star mass distributions compatible with the cooling analysis and compare with current theoretical models. We conclude that current cooling data require fast direct Urca (DU) cooling, moderated by proton superfluidity, to be active in most neutron stars, and that the DU onset threshold must lie below canonical masses. In that case medium…

astro-ph.GA

Toward Resolution Convergence for Star Formation and Galactic Winds in Galaxy Simulations

Xue-Fu Li, Weishan Zhu, Tian-Rui Wang, Huan Chen, Long-Long Feng

The predictive power of hydrodynamic simulations of galaxies is often hampered by the resolution dependence of sub-grid models for star formation (SF) and stellar feedback. We present three-dimensional hydrodynamic simulations of an M82-like low-mass starburst galaxy at resolutions of 4, 8, 16, 32 pc and develop optimized sub-grid prescriptions to mitigate these numerical inconsistencies. For star formation, we adopt a $\sim20$ pc physical-scale control volume, corresponding to the typical size…

astro-ph.GAastro-ph.SR

A Study on the Evolution of NGC6822. I. Investigating the Star Formation History through Evolved Stellar Populations

Fatemeh Khatamsaz, Mahdi Abdollahi, Atefeh Javadi, Hamidreza Mahani, Jacco Th. van Loon, Hedieh Abdollahi, Sepideh Ghaziasgar

NGC6822 is an isolated dwarf irregular galaxy in the Local Group at a distance of $\sim$ 490 kpc . In this paper, we derived the star formation history (SFH) of NGC6822 employing a method based on evolved asymptotic giant branch (AGB) stars, known as long-period variable (LPV) stars. We utilized a dataset of 329 LPVs in JHK$_s$ bands to estimate the star formation rate (SFR) over time and reconstructed the SFH of the galaxy. In addition to obtaining the SFH assuming constant metallicity values w…

astro-ph.GAastro-ph.IM

Improving Lens Modelling from Ground-Based Imaging with Deconvolution

Eric Paic, Kenneth C. Wong, Anupreeta More, Anton T. Jaelani

Accurate and precise mass modelling of strong lensing systems is essential for extracting insights into cosmology, galaxy environments, and the nature of dark matter. The Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP), which has mapped $\sim$1000 square degrees of the sky, discovered over 1000 definite or probable galaxy-scale gravitational lens candidates. As the resolution of ground-based imaging poses challenges for accurate lens modelling, high-resolution imaging is traditionally sough…

astro-ph.GA

Trigonometric Parallaxes of Maser Sources toward the Far Side of the Milky Way

Z. H. Lin, Y. Xu, M. Reid, J. J. Li, S. B. Bian

We present trigonometric parallaxes and proper motions for eight maser sources associated with high-mass star-forming regions. Four 22 GHz H$_2$O masers and four 6.7 GHz CH$_3$OH masers were observed over eight epochs between 2024 and 2025. Combining parallax, proper-motion, and radial-velocity information, we determine distances and spiral-arm assignments for these sources. The newly measured far-side masers extend the known distributions of the Sagittarius and Perseus arms toward Galactic long…

astro-ph.GA

Large-Scale Spiral Structure of the Milky Way Traced by Young Classical Cepheids

Z. H. Lin, C. J. Hao, D. J. Liu, Y. J. Li, J. J. Li, Y. W. Dong, Y. X. He, Jarken Esimbek et al.

Using 985 classical Cepheids younger than 100 Myr, we investigate the large-scale spiral structure of the Milky Way by comparing their spatial and kinematic distributions with the R19 (four-arm) and X23 (multiple-arm) spiral-arm models. Both models provide reasonably good descriptions of the current sample: R19 yields slightly smaller point-to-arm distances, whereas X23 has a higher supported-arm fraction, but the descriptive statistics do not provide a decisive preference between them. Model-de…

astro-ph.GA

Morphological Statistic of Milky Way-like Galaxies

Zehao Lin, Junye Wei, Ye Xu, Yingjie Li, Chaojie Hao, Dejian Liu, Yiwei Dong, Zhen-yu Wu et al.

We analyze the spiral morphology of 1,738 nearby galaxies with similar Hubble type of the Milky Way ($i<60^\circ$, $z<0.048$) using multi-band optical images from the Sloan Digital Sky Survey and Digitized Sky Survey. Multiple-arm systems dominate, comprising $\sim$50-60% of the sample and $\sim$75% of large galaxies ($d_{\rm max} \geqslant 18~\mathrm{kpc}$). In $90\pm3$% of multiple-arm galaxies, two inner arms extend into multiple outer arms; three-arm inner structures occur in $9\pm2$%, and f…

astro-ph.HEastro-ph.GAhep-ph

Comment on "Fermi-LAT Galactic Center Excess Morphology of Dark Matter in Simulations of the Milky Way Galaxy"

Kevork N. Abazajian, Jason Kumar, Oscar Macias

Muru et al. [Phys. Rev. Lett. 135, 161005 (2025)] conclude from the HESTIA constrained simulations that the $γ$-ray morphologies of the Galactic Center Excess predicted by dark matter annihilation and by an old stellar population are essentially indistinguishable. Their "quadratic dark matter" maps, however, show the square of the mass projected along the line of sight, $\bigl[\intρ\,s^{2}\,ds\bigr]^{2}$, rather than the annihilation integral $\intρ^{2}\,ds$. Squaring a nonnegative map preserves…

astro-ph.GA

PEGASUS (Pfs Emission-line GAlaxy SUrvey with Subaru): II. Metal Poor AGNs in High Equivalent-Width Narrow-Band Emitters

Hisakazu Uchiyama, Tohru Nagao, Mariko Kubo, Tadayuki Kodama, Rhythm Shimakawa, Akio Inoue, Masayuki Tanaka, Jialai Wang et al.

We present Subaru 'Ōnohi'ula Prime Focus Spectrograph (PFS) optical--NIR spectroscopic follow-up of high-equivalent-width (EW) narrow-band (NB) emission-line galaxies selected from Hyper Suprime-Cam Subaru Strategic Program, to assess whether high-EW sources preferentially host low-metallicity AGNs. PFS spectroscopy yielded secure identifications for 583 targets, including 581 sources with reliable PFS redshift solutions and two manually identified $z\sim4$ interlopers. We construct BPT diagnost…

astro-ph.EP

A JWST Study of Stardust. II. Polycyclic Aromatic Hydrocarbons in Comet 81P/Wild 2 and Implications for Primitive Solar System Carbon

Nathan X. Roth, Stefanie N. Milam, Diane H. Wooden, Els Peeters, Charles E. Woodward, Dominique Bockelee-Morvan, Michael S. P. Kelley, Steven B. Charnley et al.

We report observations of comet 81P/Wild 2, target of the Stardust sample return mission, on UT 2023 March 20 and 24 at a heliocentric distance ($r_H$) of 1.85 au using the NIRSpec and MIRI integral field unit spectrographs on board the James Webb Space Telescope (JWST). This study is the first compositional comparison between JWST remote-sensing spectroscopy of a solar system object against terrestrial analysis of its returned samples. Recent work determined contributions of molecular emission…

astro-ph.EPastro-ph.SR

Dynamical Impacts of Accretion Streamers on Protoplanetary Disks

Han-Gyeol Yun, Jeong-Eun Lee, Jaehan Bae, Woong-Tae Kim

Recent observations suggest that accretion streamers are common in protoplanetary disks, yet their dynamical impact on disk evolution remains poorly understood. Using three-dimensional hydrodynamic simulations with mass infall rates of $10^{-8}$--$10^{-6} \ M_{\odot}\ \mathrm{yr}^{-1}$, we investigate how streamer accretion influences the structure and evolution of protoplanetary disks. We find that a prograde streamer can excite disk eccentricity globally to values as high as $\sim0.4$. The res…

astro-ph.IMastro-ph.GAcs.AIcs.MA

Reconstructing Implicit Scientific Knowledge: Evaluating LLM Agents through End-to-End Reproduction of Astronomy

Yuehui Wang, Xinyu Qi, Guirong Xue, Cheng Wang, Yangbin Xie, Xiaoyu Tang, Cong Sun

The integration of large language models (LLMs) into scientific workflows is accelerating, yet their ability to reconstruct the reasoning underlying published research remains unexplored. Papers specify explicit procedures while leaving many methodological dependencies-data selection, calibration corrections, priors, and domain assumptions-implicit. This ambiguity complicates the evaluation of LLM-based agents, since a failure to reproduce a result may reflect either limitations of the agent or…