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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.GA

Star Formation in the H II Region Sh 2-205: 3D Morphology and Kinematics from Young Stars and Molecular Gas

Yiwei Dong, Chaojie Hao, Ye Xu, Yingjie Li, Zehao Lin, Dejian Liu, Yan Sun, Longhui Yang et al.

Using Gaia astrometry of young stars combined with CO observations, we present the first systematic three-dimensional (3D) analysis of the structure, kinematics, and evolutionary history of the star-forming regions in the environs of the H II region Sh 2-205 (S205). S205 exhibits a complex morphology and coherent expansion on both global and subregional scales. We identify several O9-B1 stars and a 0.56 Myr old pulsar that are likely associated with the region. A momentum estimate suggests that…

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astro-ph.GAastro-ph.SR

Catalytic formation of H_2 on carbonaceous dust grains - implications for interstellar observations

Aryav Das, Julia Gao, Daniel Vrinceanu, H. R. Sadeghpour

We use kinetic Monte Carlo (KMC) simulations to study molecular hydrogen formation on carbonaceous dust grain surfaces, validated against recent laboratory measurements of H$_2$ formation on coronene films at temperatures from 10 to 250 K. The model uses a three-dimensional amorphous carbon lattice with heterogeneous physisorption ($45 \pm 5$ meV) and chemisorption ($1.75 \pm 0.25$ eV) sites, and tracks both Langmuir--Hinshelwood (LH) and Eley--Rideal (ER) formation channels within a stochastic…

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astro-ph.GA

The H$α$ specific angular momentum of dwarf galaxies

Simon Deeley, Sarah Sweet, Dilyar Barat, Matthew Colless, Luca Cortese, Francesco D'Eugenio

The relationship between a galaxy's specific angular momentum $j$ and its mass $M$, parameterised by $j \propto M^α$ and known as the Fall relation, has emerged as a fundamental scaling relation reflecting key physical and morphological properties of galaxies. This relation has been well studied for galaxies with masses above $10^{9}$ $M_{\odot}$. However, whether or not it holds for the low-mass dwarf galaxies, especially given their varied morphologies, remains uncertain. Here we use H$α$ obse…

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astro-ph.EP

Stability Mapping of the New Uranian Moon S/2025 U1 with Updated Masses for Cordelia, Ophelia, and Cressida

J. Xavier, A. Amarante, S. Giuliatti Winter, A. Ferreira

We investigate the dynamics of Uranus's inner satellite system considering three recent updates: the inclusion of the new moon S/2025~U1, revised mass estimates for Cordelia, Ophelia, and Cressida, and updated zonal harmonic coefficients (J$_2$, J$_4$, and J$_6$). Using numerical integrations, mean-motion resonance analysis, and Frequency Map Analysis (FMA), we explore their impact on orbital stability. For the first time, we analyze the dynamics of the newly discovered moon S/2025~U1 and find t…

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astro-ph.GAastro-ph.SR

Gaia DR3 Limits on Stellar Engine Technosignatures in Nearby Stars

Bo-Lun Huang, Zhen-Zhao Tao, Tong-Jie Zhang, Zhi-E Liu

An operating stellar engine that transfers momentum to its host star could produce an approximately persistent transverse acceleration during the Gaia Data Release 3 (DR3) observing epoch. We search for such accelerations among 406,984 quality-selected Gaia DR3 stars with nominal distances below 200 pc (about 650 light-years), using 8,890 published Acceleration7 solutions. Because long-period binaries and astrometric systematics can produce similar sky-plane curvature, we model these conventiona…

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astro-ph.IMastro-ph.EPastro-ph.SR

TomoSphero: Fast Differentiable Projector for Planetary and Solar Tomography on Spherical Grids

Evan Widloski, Lara Waldrop

Computational tomography is a tool for determining the internal structure of objects from a set of projections, typically taken along some regular path. In recent years, methods and GPU-accelerated libraries have emerged that allow for fast reconstruction from projections along more complicated paths. Most of these libraries rely on a Cartesian discretization of the object, which is not appropriate for all scenarios. We present TomoSphero, a differentiable tomographic projector over spherical gr…

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astro-ph.HEastro-ph.GAastro-ph.SR

SN 2023gfo: A Peculiar Type IIP Supernova with High Luminosity and Normal Plateau Duration

Riko Namba, Masayuki Yamanaka, Keiichi Maeda, Avinash Singh, Kenta Taguchi, Takahiro Nagayama, Miho Kawabata, Koji S. Kawabata et al.

We present near-infrared (NIR) and optical observations of the highly reddened Type IIP supernova (SN) 2023gfo in the nearby galaxy NGC 4995 ($d = 26.4 \pm 3.2$ Mpc), which reached a high peak luminosity of $M_V = -18.6$ mag. The SN was initially detected as a faint red event, with $B-V = 0.8$ mag at the beginning of the plateau phase. By comparison with template, we estimate a total extinction of $A_V = 2.1$ mag. After correcting for this extinction, we derive a peak quasi-bolometric luminosity…

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astro-ph.GA

The Koi Pond: A Strongly Lensed Protocluster Core hosting a Diverse Population of DSFGs

Nicholas Foo, Kevin C. Harrington, Brenda L. Frye, Patrick S. Kamieneski, Melanie Kaasinen, Rafael Ortiz, Alex Pigarelli, Gibson B. Bowling et al.

We present James Webb Space Telescope (JWST) and Atacama Large Millimeter Array (ALMA) observations of PJ0846+15, \textit{The Koi Pond}, a strongly lensed protocluster core at Cosmic Noon. This field offers a magnified view of 11 dusty star-forming galaxies (DSFGs) all at $z=2.67$ (within $ΔV=800$ km s$^{-1}$) spanning a projected extent of $>300$ kpc lensed by a $z=0.77$ foreground cluster. NIRCam and ALMA Band 6 continuum measurements map the stellar distribution and thermal dust emission resp…

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astro-ph.IMastro-ph.HEhep-exphysics.class-phphysics.ins-det

Exact spherical-wave forward model for radio reflection from stratified media

Paramita Dasgupta

Radio detection of ultra-high energy particles ($\gtrsim10^{18}$ eV) depends on how broadband radio pulses reflect from natural media boundaries. We extend the spherical-wave (Sommerfeld--Weyl) treatment of a single homogeneous interface to stratified media by replacing the Fresnel coefficient of each plane-wave component with the characteristic-matrix reflection coefficient of a layered medium, evaluated in the local tangent plane on the spherical surface. The calculation reduces to the single-…

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astro-ph.HE

A statistical relation of energy injection plateaus in multi-band afterglows of gamma-ray bursts

Xiao-Yan Li, Tong Liu, Bao-Quan Huang

The origin of the plateau phase in gamma-ray burst (GRB) afterglows remains under debate, with the energy injection model being one of the most competitive explanations. If the plateau is truly driven by energy injection, the average X-ray and optical luminosities during the plateau phase, $L_{\rm X, plat, ave}$ and $L_{\rm opt, plat, ave}$, should naturally be correlated. Moreover, under this scenario, the scaling relations between the luminosities during the plateau and the normal decay phase…

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astro-ph.EPastro-ph.SR

A High-Resolution Spectroscopic Survey of Directly Imaged Companion Hosts: III. Characterization of the Cold Imaged Planet Hosts AF Lep A and $ε$ Indi A

Aneesh Baburaj, Quinn M. Konopacky, Christopher A. Theissen, Jerry W. Xuan, Roman Gerasimov, Kielan K. W. Hoch

JWST has enabled the measurement of carbon, oxygen, and sulfur abundances in the atmospheres of directly imaged planets. Interpretation of these abundances from a planet formation standpoint requires the corresponding abundances for the host star. In this work, we present detailed characterizations of the cold imaged planet hosts AF Lep A and $ε$ Indi A using high-resolution Gemini/GHOST spectra. We derive the atmospheric parameters $T_{\rm eff}$ and $\log{g}$ using two different approaches, rev…

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astro-ph.HE

A NuSTAR Reflection-Spectroscopy Survey of Cygnus X-1

Kshitij Duraphe, Kartik Mandar, Chooda Khanal, Gopal Bhatta

Relativistic-reflection measurements of Cygnus X-1 disagree on the extent of disk truncation and commonly infer supersolar iron abundances. We analyze a selected sample of 26 archival NuSTAR observations obtained between 2012 and 2024 using two configurations from one reflection-model family, with posterior modes sampled by preconditioned sequential Monte Carlo. In the baseline recovered modes, disk-surface ionization increases with photon index (Pearson r = +0.59), with state medians rising fro…

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astro-ph.HE

A NuSTAR Reflection-Spectroscopy Survey of Cygnus X-1

Kshitij Duraphe, Kartik Mandar, Chooda Khanal, Gopal Bhatta

Relativistic-reflection measurements of Cygnus X-1 disagree on the extent of disk truncation and commonly infer supersolar iron abundances. We analyze a selected sample of 26 archival NuSTAR observations obtained between 2012 and 2024 using two configurations from one reflection-model family, with posterior modes sampled by preconditioned sequential Monte Carlo. In the baseline recovered modes, disk-surface ionization increases with photon index (Pearson r = +0.59), with state medians rising fro…

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astro-ph.HE

A Population View of the Cosmic-Ray Knee: The Role of Variance in Supernova Maximum Rigidities

Carmelo Evoli

The broad shape of the Galactic cosmic-ray knee challenges source models in which all supernova remnants share a nearly universal, sharp maximum rigidity. We investigate whether the knee can instead arise as a population effect, produced by source-to-source variations in the maximum energy of Galactic supernova remnants. We derive the population-averaged spectrum for sources with sharp individual cutoffs and distributed $E_{\max}$, showing that it is given by an underlying propagated power law m…

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astro-ph.IM

A Social Network Analysis of JWST General Observer Programs: The Emergence of a Decentralized Heterarchy

Christopher Williams

Developing proposals to execute programs on space telescopes involves networks of astronomers coalescing around ideas and plans for observations. When aggregated, these program level networks allow a collective structure of the overall social network of astronomers using a telescope to be created and analysed. We do this using program level investigator data over the first five cycles of accepted General Observer (GO) programs on the James Webb Space Telescope (JWST). The aggregate network conta…

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astro-ph.SRastro-ph.EP

Planetary systems in the light of asteroseismology: metallicity threshold for the planetary systems and age-metallicity relation

M. Yıldız, A. Demirkol, S. Örtel, T. Çakır Alsaç, T. Daylan

We compiled data for 127 hosts (plus six candidates) and used them as constraints to construct interior models of the hosts using the {\small MESA} code. Two significant conclusions emerge from these models. First, except for a few stars, the hosts' metallicity ($Z_0$) is greater than 0.007. This suggests a possible suppression of the occurrence of planets below $Z_0\approx0.007$. Second, it concerns how chemical evolution unfolds in the galactic disc. For a given $Z_0$ value, considering the ol…

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astro-ph.GA

The Low-Mass Baryon Cycle in QUEST Dwarf Galaxies I: Sample definition and first results

Ava Polzin, Hsiao-Wen Chen, Zhijie Qu, Erin Boettcher, Allison Strom, Tsang Keung Chan

We introduce the QUEST Dwarfs program, which connects low-mass galaxies' stellar populations, interstellar medium, and circumgalactic medium in a large and coherently analyzed sample using a combination of optical spectroscopy, broadband imaging, and FUV absorption spectra of bright background sources .We present initial results from the first-release sample, comprising 14 galaxies with stellar mass $M_\mathrm{star} \leq 10^9 M_\odot$ at $z\approx0.001-0.017$, each with at least one CGM absorpti…

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gr-qcastro-ph.HE

Effective metric for bound state in an effective-one-body theory based on the third-post-Minkowskian approximation

Hanjun Zou, Sheng Long, Xiaokai He, Zhoujian Cao

The effective-one-body (EOB) framework, originally formulated within the post-Newtonian (PN) expansion, is central to modeling and interpreting gravitational-wave signals. Recent developments have incorporated the post-Minkowskian (PM) expansion into EOB theory. In this work, we focus on the bound state dynamics in the PM approximation up to the third order and construct the core ingredients of EOB: the effective metric. We examine two correspondence strategies, one based on the radial action va…

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astro-ph.EP

Giant exoplanets are not fully mixed

Chantal Hemmann, Simon Müller, Ravit Helled

The interior structure and bulk composition of giant planets are not directly observable and must be inferred from models. Under the common assumption of a well-mixed, adiabatic envelope, the measured atmospheric metallicity is taken as a proxy for the metallicity of the entire envelope, and hence for the planet's heavy-element budget. JWST now provides precise atmospheric metallicities for a growing number of warm giants, allowing this assumption to be tested for the first time. We quantify the…

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astro-ph.HE

Year-timescale changes in AGN radio luminosity as seen by the ASKAP Variables and Slow Transients Survey

Chloe Klare, Charlotte Ward, Dougal Dobie, David Kaplan, Akash Anumarlapudi, Tara Murphy, Joshua Pritchard, Laura N. Driessen et al.

A few dozen previously radio-quiet active galactic nuclei (AGN) have been observed to transition to radio-loud at 1-3 GHz frequencies over timescales of more than a decade, and this has has been interpreted to be due to newly launched jets. We identified 101 compact radio sources out of a sample of 64,972 non-blazar AGN which increased in flux density by 80-1800% over 1-6 years in the 887.5 MHz Australian SKA Pathfinder Variables and Slow Transients survey. We obtained optical spectra and radio…

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astro-ph.EP

The Viability of Life in Helium-Dominated Exoplanet Atmospheres

Sara Seager, Janusz J. Petkowski

Helium is the second most abundant element in the Universe, yet helium-dominated atmospheres are rarely considered as environments for life. Two assumptions have contributed to this neglect: helium is expected to escape from rocky planets together with hydrogen, and Earth itself lacks a substantial helium envelope. Recent observations and atmospheric evolution models, indicate that rocky exoplanets can retain helium-dominated atmospheres. Here we make the case for life in such environments by sy…

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astro-ph.GA

The reddening of NGC 7469 and evidence for variable extinction

C. Martin Gaskell, Ananya R. Kamath, Emily I. Kwan, Divya G. Subramonian

We estimate the reddening of the broad-line region and continuum of the active galactic nucleus NGC 7469 during the 1996 International AGN Watch multi-wavelength monitoring campaign using seven different reddening indicators. As was found for NGC 5548, these indicators support velocity-integrated broad hydrogen line ratios being close to Case B values. All the indicators point to substantial reddening of E(B-V) = 0.44 +/-0.03 for NGC 7469 during mid-1996. We find evidence for a gradual increase…

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astro-ph.GA

Multiphase turbulence as the origin of OH+, H2O+ and H3+ column density scatter in the local ISM

Uri Malamud, Shmuel Bialy, Benjamin Godard, David Neufeld, Blakesley Burkhart

Observations of the reactive ions OH+, H2O+ and H3+ in the Galactic interstellar medium reveal large sight-line-to-sight-line scatter in their column densities, commonly interpreted as evidence for substantial variations in the cosmic-ray ionization rate (CRIR). We revisit this interpretation using high-resolution three-dimensional magneto-hydrodynamic simulations of the multiphase ISM with time-dependent chemistry for H, H2, H+ and electrons, building on the fiducial model of Godard et al. (202…

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gr-qcastro-ph.GA

Nonlinear Density Waves and a Galactic-Scale Estimate of the Graviton Mass

Miroslava Vukcevic

In February 2016 the LIGO and Virgo collaborations reported the discovery of gravitational waves in merging black holes, with the conclusion that their observational data did not show any violation of general relativity. The joint LIGO and Virgo team presented an upper limit on the graviton mass, using tests of modified gravitational dynamics. Yukawa-type gravitational potential corrections are often used as generic finite-range parametrisation in modified gravity contexts, including massive-gra…

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astro-ph.GA

Theoretical emission lines and metallicity calibrations of H II regions in ASTRID simulation

Yao Yao, Kathryn Grasha, Stuart Wyithe, Enci Wang, Nianyi Chen, Patrick Lachance, Tiziana Di Matteo, Yihao Zhou et al.

We present a theoretical framework to derive redshift-dependent metallicity calibrations for galaxies at $z$=2-7. The ionization parameter ($U$) and gas pressure ($P$) in our approach are not assumed, but are predicted self-consistently. By combining the ASTRID cosmological simulation with stellar population synthesis (SPS) and MAPPINGS V photoionization modeling, we evolve young star clusters under an analytic wind-driven bubble model. This directly couples stellar feedback to the local ISM den…

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astro-ph.HEgr-qc

Strangeness Transport in Binary Neutron Star Mergers

Melvin Storbacka, Jiaxi Wu, Alexander Haber, Elias R. Most, Jacquelyn Noronha-Hostler, Mateus Reinke Pelicer, Nikolas Cruz-Camacho, Veronica Dexheimer et al.

The presence of hyperons in the cores of neutron stars opens fast strangeness equilibration channels that can produce bulk-viscous dissipation during binary inspiral. Because these reactions coexist with electron $β$-equilibration, tidal compression can drive the two coupled chemical imbalances far beyond linear response. We construct the first reaction network that self-consistently evolves the electron and strangeness fractions with a four-dimensional strangeness-dependent chiral mean-field (C…

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astro-ph.EPphysics.space-ph

Plasma Turbulence in the Lunar Environment Across Solar Wind and Magnetotail Conditions: Observations from Chandrayaan-2 Radio Science experiment

Keshav Aggarwal, R. K. Choudhary, Abhirup Datta, Anshuman Sharma

The Moon's transit between the solar wind and Earth's magnetotail exposes the near-lunar environment to large and rapid variations in plasma density and flow structure. Two-way coherent S-band radio occultation measurements from Chandrayaan-2 were used to quantify electron-density fluctuations integrated along the Earth-Moon line of sight. Observed frequencies were processed to remove geometric Doppler contributions derived from relativistic light-time modeling. The remaining frequency residuals…

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astro-ph.HE

Polarization of GRB standard X-ray afterglow and its detection prospects by eXTP

Jun-Xi Lin, Zelin Ren, Mi-Xiang Lan, Ming-Yu Ge, Zi-Gao Dai, Xue-Feng Wu, Shuang-Nan Zhang

The polarization signatures of Gamma-ray Burst (GRB) afterglows serve as a powerful diagnostic tool for studying their environments and jet physics. This work systematically investigates the X-ray (2--8~keV) polarization properties of standard GRB afterglows and assesses their detectability with the Polarimetry Focusing Array aboard the enhanced X-ray Timing and Polarimetry (eXTP) satellite. A Morris global sensitivity analysis is first conducted to identify the dominant parameters, which are th…

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astro-ph.HE

Jet Power, Bulk Lorentz Factor, Black Hole Spin, and Magnetic Field of Accretion Disk in Jetted Active Galactic Nuclei: A Large Gamma-Ray Emission Sample

Dingrong Xiong, Junhui Fan, Feng Yuan, Jun-Xian Wang, Minfeng Gu, Yongquan Xue, Jirong Mao, Liang Chen et al.

We present a catalog of physical parameters for powerful jet-accretion disk-black hole systems in one of the largest samples of gamma-ray emitting jetted active galactic nuclei (AGNs), including jet kinetic and radiative powers, jet radiative efficiencies, bulk Lorentz factors, black hole spins, accretion-disk magnetic fields and Compton dominance. Comparing jet kinetic power estimators for blazars, values derived from spectral energy distribution (SED) fitting tend to exceed those estimated via…

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astro-ph.HE

Interpretations of the $10\%$ polarization observed in the early forward-shock afterglow of GRB 091208

Yang liu, Mi-Xiang Lan

The $\sim10\%$ optical polarization observed at the early stage of GRB 091208B comes from the forward shock emission, which is higher than the conventionally predicted value. Polarizations of the forward shock radiation would depend on the observational geometry and the post-shock magnetic field structure. This magnetic field could arise either from the compression of a pre-existing magnetic field (i.e., the magnetic field in the outer medium) or from the shock-generated instabilities. In this p…

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