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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.IM

Silencing the stellar glare with kernel-nulling and active phase control on photonic chips

Marc-Antoine Martinod, Vincent Foriel, Nick Cvetojevic, Frantz Martinache, Jeronimo Calderon-Gomez, Roxanne Ligi, David Mary

Characterizing exoplanets and finding biosignatures are among the hottest topics in astronomy. This quest is challenged by the brightness contrast between the faint planet and the overwhelming glare of the host star, their small angular separation, and observing conditions degraded by optical aberrations. Nulling interferometry is a promising technique to achieve this goal by fulfilling requirements for both high contrast and high angular resolution. Photonic Integrated Circuits (PICs) provide c…

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

Premature re-entry of the FACSAT-2 nanosatellite: orbital decay and attribution to the maximum of solar cycle 25

Santiago Vargas Dominguez, Mara Valentina Angel, Brayan Nicolas Buitrago

FACSAT-2 Chiribiquete, the second satellite of the Colombian Aerospace Force and the first South American nanosatellite mission dedicated to greenhouse gases, re-entered on 27 October 2025, 926 days after its deployment into a Sun-synchronous orbit, against a declared service life of at least five years and an estimated orbital lifetime of fifteen. The orbital evolution was built from the epochs of the TLEs (two-line elements) of NORAD ID 56205. We reconstruct its decay using its 3696 orbital el…

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astro-ph.IMmath-phmath.ST

Natural coordinates for constrained correlation functions: Partial autocorrelations and the geometry of positive power spectra

Thomas Erben

Two-point correlation functions are a standard summary statistic in cosmic shear and large-scale-structure analyses. Their values are, however, constrained: non-negativity of the underlying power spectrum restricts any admissible sequence of correlation coefficients $(r_1,\ldots,r_N)$ to a bounded convex region, described in the one-dimensional case by the recursive interval geometry of Schneider & Hartlap (2009). Their formalism introduces an affine variable $x_n$ that maps the admissible inter…

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astro-ph.IM

Development of a Photonically Generated Frequency Reference for Space VLBI

Hannah Tomio, Kohei Yamamoto, Charlotte Zehnder, Guangning Yang, Kenji Numata, Andrew Attar, Henry Timmers, Holly Leopardi et al.

Space-based Very Long Baseline Interferometry (VLBI) can improve both the angular and temporal resolution of images over terrestrial VLBI techniques. Future space VLBI (sVLBI) missions are targeting higher observation frequencies than modern, terrestrial VLBI, and therefore these missions will require higher stability frequency references than standard hydrogen masers. While existing frequency references for space-based applications have concentrated on long-term stability, in this effort, we pr…

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astro-ph.SRphysics.plasm-ph

Oblique kink waves in solar coronal streamers

Aleksandr V. Rubtsov, Valery M. Nakariakov, Dmitri Yu. Klimushkin, Ding Yuan

Coronal streamer kink waves excited by an impact of coronal mass ejections (CMEs) are routinely used to estimate the coronal Alfvén speed. These estimates generally assume wave propagation parallel to the equilibrium magnetic field directed radially outward to the Sun, in the plane of the sky. However, the geometry of CME impacts naturally allows for oblique propagation. We investigate the properties of obliquely propagating kink waves guided by a plasma slab with a central current sheet represe…

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astro-ph.COastro-ph.HEgr-qc

Biases from Astrophysical Environmental Effects in Standard-Siren Cosmology

Ioannis Liodis, Rodrigo Vicente, Soumen Roy, Samaya Nissanke

Next-generation ground based gravitational wave detectors will enable precision standard-siren cosmology, making systematics increasingly important. We investigate how line-of-sight acceleration, as may arise for compact binaries in dense astrophysical environments, biases measurements of the Hubble constant $H_0$. We simulate a catalogue of 50 binary neutron star bright sirens with known host redshifts, assuming the signals have been impacted by line-of-sight acceleration and analysing them wit…

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astro-ph.SR

Streamer slab eigenmode analysis with the Legolas code

Jordi De Jonghe, Daria Sorokina, Tom Van Doorsselaere

Context. Helmet streamers are large ray-like structures extending from the solar corona that thin further away from the solar surface, forming an extended current sheet. These structures are quasi-stable, and are observed to support kink waves travelling outward from the Sun, called helmet streamer waves. Aims. Limited analytical models identify streamer waves as fast body kink eigenmodes of the streamer slab. To bridge the gap between analytical models and numerical simulations, we investigate…

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nucl-thastro-ph.HE

Universal $Z^{2/3}/\sqrt{Q_α}$ Scaling Law in Alpha Decay from Nuclei to Neutron-Star Mergers

Hisham Anwer, B. Salah, A. R. Abdulghany

We establish a universal scaling law for $α$-decay half-lives based on the variable $X_a = Z^a/\sqrt{Q_α}$, which collapses experimental and theoretical data spanning over twenty orders of magnitude onto a single linear correlation. Global optimization over the complete set of even-even $α$ emitters reveals a uniquely sharp optimum at $a \simeq 2/3$. This exponent is theoretically motivated by the leading geometric scaling of heavy nuclei and emerges quantitatively from the correlated nuclear sy…

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astro-ph.EPastro-ph.SR

How dust particles orbiting white dwarfs can reveal undetected co-orbiting exoplanets I. Exoplanet on a circular orbit

Kyriaki I. Antoniadou, Dimitri Veras

Abridged. Mounting observations of transiting dusty debris orbiting WDs display complex signatures that often feature orbital period drifts. The asteroid or planet progenitor of this debris might still be partly intact on a near-circular orbit that is inclined or coplanar, with a period that is similar to that of the dust. Alternatively, the debris could persist concurrently with other intact asteroids or planets that had tidally circularised around the WD at a later time, but still remain direc…

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astro-ph.IMastro-ph.HE

IceCube Upgrade status and perspectives

Anna Eimer

The IceCube Neutrino Observatory instruments one cubic kilometer of deep-glacial ice between 1450 m and 2450 m below the surface at the geographic South Pole to detect neutrinos via Cherenkov radiation of relativistic charged particles produced in their interactions. This detector is responsible for a number of key observations in neutrino astrophysics, which include the discovery of a high-energy astrophysical neutrino flux and, more recently, the galactic plane. During the austral summer of 20…

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astro-ph.SR

Stellar flare detection and characterization in ZTF High-cadence light curves

Aratrika Ghosh, Shravan Hanasoge, Matthew J. Graham, Ashish Mahabal

Stellar flares are brief, intense increases in brightness resulting from magnetic reconnection events in stellar atmospheres. In this paper, we have developed a pipeline to detect and characterize flares in short-duration (approximately 6.2-hour) light curves from the Zwicky Transient Facility (ZTF) Extended Deep-Drilling survey. This method involves robust detrending with Tukey's biweight estimator, followed by sigma-based thresholding and visual scrutiny to identify flare candidates. It is app…

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astro-ph.EPastro-ph.SR

Impact of accretion variability on the CO emission of a disk around a very-low-mass star with JWST

C. Bergez-Casalou, B. Tabone, Y. Aoyama, G. Herczeg, A. Caratti o Garatti, E. Habart, E. F. van Dishoeck, I. Chemerynska et al.

Studying the structure of very-low-mass stars ($M_\star<0.2M_\odot$) protoplanetary disk is crucial to understand the formation of Earth-like planets. In this paper, we characterize the innermost regions of the disk around a known very-low-mass star, 2MASS J16053215-1933159 (J1605 hereafter), by analyzing new JWST/NIRSpec observations taken in 2024, 2 years after a first observation with JWST/MIRI. We find that between the two epochs (2022 \& 2024), the CO flux is reduced by a factor $\sim 3$, t…

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astro-ph.SRastro-ph.GAastro-ph.HE

Companion masses of Gaia DR3 AstroSpectroSB1 binaries: a Bayesian forward-modelling framework

Prasid Sandave, Raghuveer Garani

Gaia Data Release 3 (DR3) has substantially expanded the study of unresolved binaries by providing combined astrometric and spectroscopic orbital solutions for a large sample of non-single stars. We present a Bayesian forward-modelling framework for estimating companion masses in Gaia DR3 \texttt{AstroSpectroSB1} systems. The method samples the physical parameters of each binary, predicts the corresponding astrometric Thiele-Innes constants and spectroscopic orbital coefficients, and evaluates t…

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astro-ph.GA

Gravity-driven Emergence of Multi-fractal Density Structure in the Orion A Integral Shaped Filament

Mengke Zhao, Guang-Xing Li, Keping Qiu, Guangya Zeng

Molecular clouds are often described as self-similar structures, although spatially averaged measures do not retain local variations in density scaling. We use the density exponent $κ_ρ$ ($ρ\propto r^{κ_ρ}$) to characterize the density structure of the Integral Shaped Filament (ISF) in Orion\,A. Applying the Multiscale Decomposition Reconstruction method to the Herschel column-density map, we find distinct density--scale relations across the connected filament. Their slopes steepen from $κ_ρ\app…

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astro-ph.IM

Fast and accurate astronomical source deblending with Density-Peak Clustering

M. D. Lepinzan, F. Tomba, E. Romelli, A. Rodriguez, L. Tornatore

Source deblending is a fundamental challenge for current and forthcoming astronomical surveys, where increasing source density and image depth lead to a growing number of overlapping detections. Accurate deblending is essential for reliable measurements of source morphology and photometry, as well as for cosmological analyses. We present a redesign of the Advanced Density Peak (ADP) clustering algorithm, tailored to the identification and separation of blended astronomical sources within detecti…

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astro-ph.IMastro-ph.GAcs.CVphysics.comp-ph

Scale-Vector Alignment: A Scale-Aware Framework for Spatially Resolved Morphological Similarity in Astronomical Images

Mengke Zhao, Guang-Xing Li, Keping Qiu, Shanghuo Li

Astronomical maps made with different tracers are not expected to have identical morphology. Excitation, optical depth, chemistry, radiation, and ISM phase alter the response of a tracer, and the resulting differences can depend on both position and spatial scale. We propose scale-vector alignment, a scale-aware method based on Constrained Diffusion Decomposition (CDD). CDD decomposes an image into localized scale components; at each position, their amplitudes define a scale vector that describe…

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astro-ph.HE

Rotating Radio Transient Phases of Isolated Neutron Star Systems and Descendants of Central Compact Objects

Ş. Demirok, Ü. Ertan, A. A. Gençali

Rotating radio transients (RRATs) form an isolated neutron star (INS) population characterized by their sporadic and short radio bursts. In the fallback disc model, it was suggested that most INS populations pass through an RRAT phase during their evolution, and the mechanism producing these bursts could be the enhancement of the flux of open magnetic field lines through the poles of dead pulsars due to penetration of the inner disc into the light cylinder. To test this idea, we determine the RR…

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astro-ph.GA

Gas phase Elemental abundances in Molecular cloudS (GEMS) XII. First look into the para-to-ortho ratio of c-C3D2 towards prestellar cores

J. Ferrer Asensio, A. Fuente, E. Roueff, K. Furuya, B. Tercero, N. Sakai

Symmetric molecules with identical nuclei form distinct nuclear spin isomers (ortho and para) that cannot interconvert via radiative or inelastic transitions, preserving clues about formation conditions. In the interstellar medium, cyclopropenylidene (c-C3H2) and its doubly-deuterated isotopologue (c-C3D2) provide a prime laboratory for studying these ratios. While measured for the main species, spin ratios for c-C3D2 remain unavailable. We present new detections of ortho and para transitions of…

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astro-ph.EP

Feasibility of the Phobos 1 Hypothesis for Dark Comet 1998 KY$_{26}$

Adam Hibberd, Adam Crowl, Abraham Loeb

The asteroid 1998 KY$_{26}$ has been the subject of thorough observation, both optical and radar, from shortly following its discovery on 28 May 1998, through 2 further close apparitions in 2020 and 2024. This has previously allowed an accurate characterization of the object, including an unusually rapid spin-rate with period 5.3516 $\pm$ 0.0001 minutes, a diameter of 11 $\pm$ 2 m, and a high albedo of $\sim{0.52}$. Furthermore, the presence of significant nongravitational accelerations (NGAs),…

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astro-ph.EP

Feasibility of the Phobos 1 Hypothesis for Dark Comet 1998 KY$_{26}$

Adam Hibberd, Adam Crowl, Abraham Loeb

The asteroid 1998 KY$_{26}$ has been the subject of thorough observation, both optical and radar, from shortly following its discovery on 28 May 1998, through 2 further close apparitions in 2020 and 2024. This has previously allowed an accurate characterization of the object, including an unusually rapid spin-rate with period 5.3516 $\pm$ 0.0001 minutes, a diameter of 11 $\pm$ 2 m, and a high albedo of $\sim{0.52}$. Furthermore, the presence of significant nongravitational accelerations (NGAs),…

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astro-ph.HEastro-ph.GA

Fast Radio Bursts Associated with Persistent Radio Sources Prefer Hydrogen-poor Superluminous Supernova Host Environments

Fujia Li, Fei Liu, Di Li, Dongzi Li, Ziheng Ding, Ran Gao

A subset of repeating fast radio bursts (FRBs) is associated with compact persistent radio sources (PRSs). The FRB-PRS hosts differ dramatically from the general FRB host population: they do not follow the distribution of localized non-PRS FRB hosts, nor the SFR-weighted or mass-weighted mock host distributions expected for the general star-forming galaxy population, instead occupying the extreme low-mass, high-sSFR, and low-metallicity end of host-galaxy parameter space. We compare these hosts…

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astro-ph.GAastro-ph.CO

StAGE: Stellar Archaeology-driven Galaxy Evolution II. Binary Black Hole Mergers in Quiescent Galaxies and their Star-forming Progenitors

Irene Iorio, Andrea Lapi, Lumen Boco, Giovanni Antinozzi, Michele Bosi, Cecilia Sgalletta, Mario Spera, Luigi Danese et al.

We apply StAGE, a data-driven galaxy-evolution framework based on stellar archaeology, to study binary black hole (BBH) mergers in quiescent galaxies (QGs) and their star-forming progenitors. We combine StAGE star-formation and chemical-enrichment histories with pre-computed SEVN binary population-synthesis catalogs to derive the BBH merger-rate density, its dependence on intrinsic binary and host-galaxy properties, and the associated stochastic gravitational-wave (GW) background. We assess unce…

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astro-ph.COastro-ph.IM

Sound-Horizon-Independent Test of Cosmic Distance Duality Relation Using Artificial Neural Networks and Gaussian Processes

Bo-Hao Jiang, Guo-Jian Wang, Tao Yang

The cosmic distance duality relation (CDDR), $D_L(z)(1+z)^{-2}/D_A(z) \equiv 1$, is a fundamental relation in modern cosmology linking luminosity distance $D_L$ and angular diameter distance $D_A$. We define $η(z) \equiv D_L(z)(1+z)^{-2}/D_A(z)$ and reconstruct the relevant quantities over $0 < z < 2.5$ using two independent non-parametric methods: Gaussian processes (GP) and artificial neural networks (ANN). Specifically, we reconstruct $D_L$ from three different Type Ia supernovae (SNe$~$Ia) c…

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gr-qcastro-ph.HE

Event Detection and Finite-Grid Effects at an Imposed Absorbing Boundary in Newtonian Black Hole Orbit Integrations

Gregory M Davis

Numerical classification of black-hole orbits can depend on how prescribed inner capture or absorbing boundaries are implemented. This study investigated how discrete evaluation of such a boundary affects orbit classification. Massless particles were integrated about an isolated Newtonian point mass and initialized at periapsis with an absorbing boundary at rsink = 104RS. Because the Keplerian periapsis q is constant, the expected classification can be analytically determined. A classifier omitt…

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astro-ph.HEhep-ph

Constraints on Axion-like Dark Matter from Cosmic Birefringence with a Polarization Array of Repeating Fast Radio Bursts

Xiaohui Liu, Zi-Yan Yuwen, Yun-Long Zhang, Zerui Liu, Shiqian Zhao, Shuai Feng, Wei-Yang Wang, Xuelei Chen et al.

Axion-like dark matter (ALDM) is a well-motivated dark matter candidate whose Chern-Simons coupling to photons can induce cosmic birefringence, producing temporal oscillations and spatial correlation in polarization angle (PA) signals from different sources. Hyperactive repeating fast radio bursts (FRBs) with high linear polarization are a particularly promising probe of such signatures. We develop a Bayesian framework to search for PA oscillations caused by ALDM in individual repeating FRBs, an…

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astro-ph.GAastro-ph.CO

A Sample of 459 Galaxy Groups Identified from the FAST All Sky HI Survey DR2

Z. S. Yuan, Z. L. Wen

Groups of HI-rich galaxies are key laboratories for understanding galaxy evolution and environmental effects, constructing samples of such groups is fundamental for relevant studies. Using the FAST All Sky HI Survey (FASHI) Data Release 2 (DR2), currently the largest and deepest HI catalog available, we identify galaxy groups directly from HI signals, without relying on optical pre-selection. A group-finding algorithm with a density contrast criterion and a minimum membership of five yields a ca…

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astro-ph.SR

The Common Envelope Evolution Outcome. III. the Improvement of Stellar Binding Energy with the Envelope Residual

Lifu Zhang, Hongwei Ge, Dylan Hebrail, Ross Church, Mingkuan Yang, Zhenwei Li, Hailiang Chen, Dengkai Jiang et al.

Common-envelope evolution (CEE) is a key process in the evolution of close binary systems. Many important astrophysical objects and evolutionary stages are closely related to CEE, including white dwarf binaries, hot subdwarfs, and gravitational wave mergers. In the standard energy formalism of CEE, the binding energy of the donor envelope plays a crucial role, as it directly affects the final orbital period after CEE and serves as a key physical parameter in binary population synthesis studies.…

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astro-ph.HEastro-ph.GA

AT2019aalc: An obscured tidal disruption event candidate in an active galactic nucleus revealed by its first flare?

Ying Gu, Xiao Li, Xue-Guang Zhang, En-Wei Liang

AT2019aalc is considered a repeating tidal disruption event (TDE) candidate occurring in an active galactic nucleus (AGN). In this paper, we highlight previously unnoticed but intriguing features that include a brief optical dimming prior to the rise of the main flare and a significantly lower post-flare luminosity compared to the pre-flare level. By applying a time-dependent obscured TDE model to AT2019aalc, we successfully reproduce its light curves with the tidal disruption of a $1.122_{-0.17…

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astro-ph.GAastro-ph.CO

The CAMELS-CROCODILE Simulation Suite: A New Cosmology--Astrophysics Playground for Machine Learning

Kentaro Nagamine, Yuri Oku, Atsushi J. Nishizawa, Jun-Young Lee, Francisco Villaescusa-Navarro, Shy Genel, Daniel Anglés-Alcázar

We present CAMELS-CROCODILE, a suite of cosmological hydrodynamic simulations that extends the CAMELS framework with the \gadget{} smoothed particle hydrodynamics code and the Osaka feedback model. As a companion to the IllustrisTNG-based second-generation CAMELS suite, it provides an independent implementation of the baryonic physics that shapes galaxies, the intergalactic medium, and large-scale structure, broadening the range of subgrid models over which machine-learning (ML) inference can be…

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astro-ph.EPastro-ph.SR

Satellite Survival through Gas Redistribution in a Low-viscosity Disk

Ignacio Mosqueira

We investigate satellite survival through gas redistribution in a dense circumplanetary disk with a low dimensionless viscosity parameter $α\sim 10^{-6}$. The model combines modal Lindblad excitation, launch-dependent shock deposition, 3D effects, and a conservative, instantaneous Rayleigh adjustment that prevents sharp gas density gradients. An isolated Ganymede-mass satellite depletes the disk outside its orbit and stalls, even in the presence of a calibrated three-dimensional Lindblad torque.…

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