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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.EPastro-ph.IM

Exoplanet Detection Techniques: Radial Velocity

Rafael Luque, Matthew R. Standing

The radial velocity (RV) technique enabled the discovery of the first exoplanets orbiting Sun-like stars. Since then, improvements in precision and sensitivity have enabled the detection of smaller planets, bringing us closer to the goal of discovering Earth analogs in the coming years. In this chapter, we provide an overview of the radial velocity method. We begin with a detailed description of the technique, including how precise radial velocities are measured and what limitations must be addr…

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astro-ph.EPastro-ph.IM

Exoplanet Detection Techniques: Radial Velocity

Rafael Luque, Matthew R. Standing

The radial velocity (RV) technique enabled the discovery of the first exoplanets orbiting Sun-like stars. Since then, improvements in precision and sensitivity have enabled the detection of smaller planets, bringing us closer to the goal of discovering Earth analogs in the coming years. In this chapter, we provide an overview of the radial velocity method. We begin with a detailed description of the technique, including how precise radial velocities are measured and what limitations must be addr…

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

JWST Observations of the Metal-poor T Dwarf WISEA J155349.96+693355.2: The First Brown Dwarf Associated with the Gaia-Enceladus Milky Way Substructure

Aaron M. Meisner, Adam J. Burgasser, Chih-Chun Hsu, Sherelyn Alejandro Merchan, Jacqueline K. Faherty, Genaro Suárez, ZengHua Zhang, Roman Gerasimov et al.

We present JWST NIRSpec and MIRI observations of the metal-poor T dwarf WISEA J155349.96+693355.2. The combined NIRSpec/prism plus MIRI/LRS spectrum (R ~ 100) provides 0.6-12 $μ$m spectroscopic coverage that reveals the presence of H$_2$O, CH$_4$, and NH$_3$ absorption features, enhanced collision-induced H$_2$ absorption, and weak or absent CO and CO$_2$ absorption, all indicators of a metal-poor low-temperature atmosphere. Comparison of the spectral data to a suite of atmosphere models yields…

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

JWST Observations of the Metal-poor T Dwarf WISEA J155349.96+693355.2: The First Brown Dwarf Associated with the Gaia-Enceladus Milky Way Substructure

Aaron M. Meisner, Adam J. Burgasser, Chih-Chun Hsu, Sherelyn Alejandro Merchan, Jacqueline K. Faherty, Genaro Suárez, ZengHua Zhang, Roman Gerasimov et al.

We present JWST NIRSpec and MIRI observations of the metal-poor T dwarf WISEA J155349.96+693355.2. The combined NIRSpec/prism plus MIRI/LRS spectrum (R ~ 100) provides 0.6-12 $μ$m spectroscopic coverage that reveals the presence of H$_2$O, CH$_4$, and NH$_3$ absorption features, enhanced collision-induced H$_2$ absorption, and weak or absent CO and CO$_2$ absorption, all indicators of a metal-poor low-temperature atmosphere. Comparison of the spectral data to a suite of atmosphere models yields…

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physics.comp-phastro-ph.HEhep-phphysics.plasm-ph

Monte Carlo sampling of first-order QED processes in laser and pulsar plasmas

Verneri Sarjomaa, Joonas Nättilä

Monte Carlo sampling of strong-field quantum electrodynamics processes underpins simulations of high-intensity laser experiments and of astrophysical compact-object magnetospheres. Sampling an event requires the total rate of the process together with the cumulative probability that determines how energy is partitioned between the produced particles. Simulations typically tabulate both in advance and invert the tabulated probability numerically. Here we replace this procedure with elementary-fun…

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astro-ph.HE

Comparative spectro-temporal study between 1A 1246$-$588 and 4U 0614$+$091 using AstroSat

Suchismito Chattopadhyay, Soma Mandal, Ranjeev Misra

We present a comparative broadband spectro-temporal study of the ultra-compact X-ray binary (UCXB) candidates 1A 1246$-$588 and 4U 0614$+$091 using AstroSat observations. Spectral modelling shows that the spectrum of 1A 1246$-$588 is well described by thermal Comptonization and a soft thermal disk component. We identify a candidate narrow quasi-periodic oscillation (QPO) at $993\pm4$ Hz with a single-detector significance of $ ~ 3.7σ$, tentatively consistent with the upper kHz QPO previously rep…

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astro-ph.IM

GIMLI: a toolkit connecting linear and non-linear magnetohydrodynamic regimes

Jordi De Jonghe, Nicolas Brughmans, Rony Keppens

In this work, we present the General Interface for MPI-AMRVAC / Legolas Interconnection (or GIMLI, for short) as a toolkit for in-depth (magneto)hydrodynamic studies combining linear and non-linear methods. Acting as a bridge between the linear (M)HD spectroscopy code Legolas and the non-linear simulation code MPI-AMRVAC, GIMLI facilitates the initialization of non-linear MPI-AMRVAC simulations with linear solutions. We showcase this functionality on both Cartesian and cylindrical setups, coveri…

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hep-phastro-ph.COastro-ph.HE

Metastable Neutron Stars as Transient-Rate Detectors of Heavy Dark Matter

Ziwen Yin, Hong-Yi Zhang

Metastable neutron stars can undergo catastrophic conversion to quark-containing stars when a localized energy deposition nucleates a critical bubble. We show that dark-matter-induced conversions can be constrained by the present transient rate of the neutron star population, rather than by the survival of any individual hadronic star as often assumed in previous literature. Population depletion makes the present transition rate nonmonotonic: weak triggering produces few transitions, whereas suf…

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

A Census of Stellar-mass Black Holes in the Milky Way with POPKIN. I. Isolated Black Holes

Jian-Guo He, Yong Shao, Yu-Dong Nie, Gui-Yu Wang, Xiao-Tian Xu, Chen Wang, Xiao-Jie Xu, Xiang-Dong Li et al.

Gravitational-wave observations have revealed hundreds of stellar-mass black holes, yet only about two dozen are known in the Milky Way, almost all in binaries. We present POPKIN, a Python framework that couples single- and binary-star evolution with Galactic orbital dynamics to trace black-hole progenitors from the zero-age main sequence to the present-day isolated black-hole (IBH) population. Across ten models varying the supernova (SN) prescription, mass-transfer efficiency, and common-envelo…

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

Metal-Poor Stars as Metal-Rich Impostors via Planet Engulfment

Zongheng Li, Shi Jia, Jie Su, Shang-Fei Liu, Jianheng Guo

Planet engulfment leads to planetary mass accretion and angular momentum deposition into the stellar envelope. This study uses MESA models to investigate the long-term impact of engulfment on stellar metallicity and rotational velocity, as well as the effect of rotational mixing on metal enrichment. Our models show that engulfment occurring during the late main-sequence (MS) stage yields significantly higher surface enrichment than at the ZAMS. Rotational mixing generally suppresses enrichment;…

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

Metal-Poor Stars as Metal-Rich Impostors via Planet Engulfment

Zongheng Li, Shi Jia, Jie Su, Shang-Fei Liu, Jianheng Guo

Planet engulfment leads to planetary mass accretion and angular momentum deposition into the stellar envelope. This study uses MESA models to investigate the long-term impact of engulfment on stellar metallicity and rotational velocity, as well as the effect of rotational mixing on metal enrichment. Our models show that engulfment occurring during the late main-sequence (MS) stage yields significantly higher surface enrichment than at the ZAMS. Rotational mixing generally suppresses enrichment;…

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astro-ph.GA

Optical spectropolarimetry of extreme H$α$ line profiles in seven active galactic nuclei

J. Biedermann, F. Marin, D. Hutsemékers, C. M. Gaskell

Some active galactic nuclei (AGNs) are known to show extremely asymmetric broad Balmer lines, with their main peak redshifted or blueshifted by thousands of km s$^{-1}$, severely challenging our understanding of the standard AGN paradigm. We wanted to explore the causes of such asymmetric features by carrying out a spectropolarimetric study of a sample of bright AGNs with known extreme Balmer line profiles. We present optical spectropolarimetry of seven bright (V $<$ 17.5) Seyfert-1 galaxies obt…

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astro-ph.GAastro-ph.EPastro-ph.HE

Binary-pulsar Timing: A 3D Solar-System Accelerometer and Unknown-Source Probe

Zheng-Long Wang, Zi-Qing Xia, Bo Zhang, Yi-Zhong Fan

The acceleration of the Solar System barycenter (SSB) offers a unique precision probe of the local gravitational environment, enabling searches for otherwise invisible gravitating sources such as Planet Nine and nearby (primordial) black holes. Using the binary-pulsar timing measurements, we develop an analysis framework that combines the line-of-sight differential accelerations of 26 binary pulsars to jointly reconstruct the three-dimensional acceleration of the SSB and place directional upper…

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astro-ph.HEastro-ph.SR

SN 2025aedz: A typical short-plateau type IIP supernova with rapid post-peak decline

Bo Wang, Luhan Li, Chengyuan Wu, Jujia Zhang, Yongzhi Cai, Yize Dong, Xuefei Chen, Zhanwen Han et al.

Type IIP supernovae (SNe IIP) are the most common subclass of core-collapse SNe in observations. However, SNe IIP with short plateaus of the order of tens of days are rarely observed. The progenitors for this kind of SN can help to address the red supergiant issue in stellar evolution. In this article, we report optical photometry and spectroscopy of SN\,2025aedz, a rapidly post-peak declining SN IIP with a typical short plateau. It exhibits a peak absolute magnitude of $M_r=-17.16\pm0.03$\,mag.…

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astro-ph.GAastro-ph.HE

Stellar Collisions from Self-consistent Stellar Dynamics Around Growing Supermassive black Holes

Fupeng Zhang, Pau Amaro Seoane

The centers of galaxies harbor the densest stellar environments, where a massive black hole (MBH) accelerates stars to such high velocities that direct collisions can result in high-energetic phenomena, such as gravitational wave sources, kilonovae, and supernova-like transients. These collisions can reshape the cluster's density profile and release gas that can be subsequently accreted by the MBH. However, the evolving rates of such phenomena from self-consistent dynamics around mass-growing MB…

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gr-qcastro-ph.HE

Learning Inspiral-Merger-Ringdown Waveforms from a Post-Newtonian Baseline

Arghya Chattopadhyay, Shilpa Kastha

Modeling the full inspiral-merger-ringdown signal requires combining analytically controlled inspiral physics with the nonlinear strong-field information supplied by numerical relativity. We represent the numerical relativity contribution beyond an analytic inspiral waveform as residual amplitude and phase corrections. Retaining the leading-order frequency-domain amplitude and the $3.5$ Post-Newtonian TaylorF2 phase, we use a Kolmogorov-Arnold network to learn these residual corrections from SXS…

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astro-ph.GAhep-ph

Mass-Dependent Dark Matter Deficit from Inelastic Scattering

Daneng Yang, Yi-Zhong Fan

Recent stellar-kinematic and neutral-hydrogen observations indicate a dark matter deficit within the central tens of kiloparsecs of nearby galaxies that grows systematically with stellar mass relative to hydrodynamical simulations. We show that this mass dependence can arise from exothermic inelastic dark matter with strongly velocity-dependent scattering. Two nearly degenerate dark matter states interact through vector and scalar mediators with opposite-sign contributions and unequal ranges. Th…

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astro-ph.SRastro-ph.EP

On the altitude profile of lower ionospheric D-region response time delay during solar flares

Sayak Chakraborty, Rakhi Paul, Tamal Basak

The D-region ionosphere is sluggish in nature while responding to the incoming solar radiation. We study the altitude (h) profile of mid-latitude D-region response time delay (Delta t) during three chosen solar flares, namely, C5.2, M5.2, and X2.2 classes. We solve "electron continuity equation" numerically at each and every h to obtain Delta t-h profile. We investigate the 1) latitudinal variation (over both Northern and Southern hemispheres) and 2) seasonal variation (throughout the year) of D…

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astro-ph.GA

High-z galaxies with the JWST and the ELT: Toward Ever-finer Detail

Eros Vanzella

The exploration of the early Universe is being transformed by the James Webb Space Telescope (JWST), which delivers unprecedented angular resolution at infrared wavelengths and opens a unique window redward of the K band (2um). Thanks to NIRCam, NIRISS, NIRSpec, and MIRI instruments, which provide both imaging and spectroscopy with exquisite efficiency, new classes of sources have emerged within the first years of operations. The first half-Gyr of cosmic time is now routinely probed, revealing m…

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astro-ph.IMastro-ph.GAastro-ph.SR

Uber-calibration-based Two-level Radial-velocity Zero-point Correction for APOGEE

Jinming Zhang, Haibo Yuan, Zhijia Tian

APOGEE delivers high-resolution, near-infrared spectroscopy and highly precise radial velocities (RVs), with extensive repeat observations spanning more than a decade. Long-term RV repeatability is nevertheless limited by instrumental zero-point systematics: exposure-to-exposure drift and fiber-dependent offsets that are only partially tracked by lamp-based wavelength calibration, and that can evolve as fibers are serviced or replaced. We infer and remove these zero points directly from the publ…

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astro-ph.EP

A Possible Complication of Using the 4.14 μm band to Assess D/H Ratios on Icy Bodies

Mark J. Loeffler, Rebecca A. Carmack, Stephen C. Tegler

Determining isotopic ratios on the surfaces of extraterrestrial objects can provide insight into their formation conditions and evolution. Recently, remote-sensing detections of the 4.14 μm HDO absorption band have enabled astronomers to estimate the D/H ratio on several icy objects in the outer solar system. Here, we quantify how ice phase and radiation processing affect the 4.14 μm absorption band. While the band is visible in H2O-ice samples with a crystalline component, we cannot detect it i…

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gr-qcastro-ph.HE

Constraining the Quadratic-mode Amplitude Coupling in GW250114

Yuxin Yang, Changfu Shi, Yi-Ming Hu

Detecting quadratic quasi-normal modes in black hole ringdowns would provide evidence for nonlinear gravitational dynamics, while measuring their properties would enable tests of the corresponding predictions of general relativity. Specifically, second-order black hole perturbation theory predicts that their amplitudes scale with the product of the amplitudes of their parent linear modes, with a coupling coefficient that depends on the spin of the remnant black hole. This mode-specific coupling…

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astro-ph.HEastro-ph.COastro-ph.IM

DETECT: Real-Time Identification of Transients with DESI Spectroscopic Redshift

Yu-Hsing Lee, Ting-Wan Chen, Ze-Ning Wang, Sheng Yang, Limeng Deng, Chuan-Jui Li, K. C. Chambers, Thomas de Boer et al.

Wide-field surveys now report thousands of transients per month, while spectra are obtained for only a few per cent of them. We present DETECT (DESI--Transient Event Cross-matching Tool), a pipeline that turns each Transient Name Server (TNS) alert into a distance-informed candidate within an hour by placing it in the context of the Dark Energy Spectroscopic Instrument (DESI) archive. DETECT cross-matches every new report against the 22 million spectra of DESI EDR and DR1 through a HEALPix index…

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astro-ph.EPastro-ph.SR

A Collisional Origin for Ice-rich Iapetus and Titan's Anomalous Eccentricity

Ignacio Mosqueira

We test whether collisions involving Titan can eject enough water-rich material onto sufficiently distant Saturn-bound orbits to form Iapetus, while also accounting for Titan's orbital eccentricity. Three-dimensional impact calculations and post-impact trajectories examine initially Saturn-unbound and bound impactors. In the oblique unbound case with a differentiated impactor roughly a tenth the mass of Titan at a speed of 10 km s\(^{-1}\), outgoing predominantly icy material from a selected pop…

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astro-ph.HEastro-ph.GA

Recurrent double-peaked $γ$-ray sub-flares in PKS 1424-418

Na Wang, Tong Liu, Jingran Xu

We report a hint of recurrent double-peaked $γ$-ray sub-flares in PKS~1424--418 during two similar major active epochs, MJD 56117--56498 and MJD 59669--59978. The candidate double-peaked sub-flares show a characteristic intra-subflare peak separation of $\sim 11.8$ d and a neighbouring-subflare spacing of $\sim 67$ d. Red-noise Monte Carlo tests indicate that the candidate recurrent double-peaked morphology is not easily reproduced by stochastic variability alone, with false-alarm probabilities…

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astro-ph.HE

Radiative properties and optical appearance of a thin accretion disk around a charged-PFDM black hole

Taiyang Zhang, Zongyuan Qin, Qian Feng, Zheng-Wen Long

Accretion onto magnetically charged black holes in a perfect fluid dark matter (PFDM) background opens a new window for testing strong-field gravity. This paper investigates the radiative properties and optical appearance of a thin accretion disk surrounding a charged-PFDM black hole. We numerically compute the radiative energy flux, temperature distribution, and radiative efficiency, and employ a ray-tracing method to construct the direct images, secondary images, redshift distribution, and obs…

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astro-ph.SR

Study of Chromospheric Global-Scale Flows using Local Correlation Tracking Across the past 10 Solar Cycles

Qin Li, Yan Xu, Keiji Hayashi, Chunlei Liang, Haimin Wang

Global-scale solar surface flows, including differential rotation and meridional circulation, provide key observational constraints on the solar dynamo. We investigate these flows using local correlation tracking (LCT) of chromospheric intensity structures in digitized \ion{Ca}{2}~K observations from the Kodaikanal Solar Observatory covering Solar Cycles (SC) 14 to 23 (1907 -- 2007). The most valuable data coverage are from cycles 14 to 19 for two reasons: (1) it provided record for early cycles…

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astro-ph.SR

Central stars of newly discovered infrared nebulae: eruptive Be stars PY Gem and HD253659

Olga Maryeva, Julieta Sánchez Arias, Sergey Karpov, Michaela Kraus, Michalis Kourniotis, Sabina Mammadova

The presence of a nebula around massive hot stars often works as an indicator that the object is either in an advanced evolutionary stage or a rare product of close binary interaction. Here, we focus on two Be stars - PY Gem and HD253659 - whose nebulae were detected with the Wide-field Infrared Survey Explorer. We estimated their basic physical parameters from modelling the spectral energy distribution and examined their variability. We combined archival photometric data from several ground-bas…

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cs.LGastro-ph.IMastro-ph.SR

Image Fidelity is Not Field Fidelity: Joint Thermodynamic Reconstruction and Error Localization in Neural Tomography

Alan Hsu, Jenna Samra, Alin Razvan Paraschiv, Liam Connor

Neural fields for scientific tomography are optimized from 2D images, but the actual quantity of interest is often a latent 3D physical field. Because the forward map is many-to-one, low 2D image error need not certify a correct 3D field. Moreover, the latent field is not directly supervised during training, and its error cannot be evaluated against truth at deployment. We develop CoroNeRF to jointly optimize 3D electron density and temperature fields directly from multiview, multiline intensiti…

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astro-ph.EP

On the Long-Term Orbital Behaviour of Hilda Asteroids - I. Global Stability Patterns and Catalogue

Cristian F. Chavez, Jonathan Horner, Patryk Sofia Lykawka, Timothy R. Holt, Brad Carter

The Hildas are objects trapped in 3:2 mean-motion resonance (MMR) with Jupiter, and are a fascinating window into the Solar system's formation and evolution. We present the results of detailed dynamical integrations of 2,699 numbered asteroids in the Hilda region, following 243 clones of each Hilda for 1 Gyr under the influence of the giant planets and the Sun; 54.7% of our sample exhibit extreme dynamical stability, with all clones of 1,475 Hildas remaining trapped in the 3:2 MMR for the full 1…

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