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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

SMUDGes Below the Surface: Clusters Confirm the Diversity of Low-Surface-Brightness Galaxies

Donghyeon J. Khim, Dennis Zaritsky, Loraine Sandoval Ascencio, Michael C. Cooper, Richard Donnerstein

We use spatially resolved Keck Cosmic Web Imager spectroscopy to study high-surface-brightness stellar components and internal kinematics in 44 low-surface-brightness galaxies from the SMUDGes survey, including 30 ultradiffuse galaxies, spanning the red sequence, green valley, and blue cloud regions of the galaxy color-magnitude diagram. Although these galaxies appear largely smooth in survey imaging, we detect at least one cluster candidate in every galaxy. We identify clusters with nebular emi…

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astro-ph.EPastro-ph.GAastro-ph.SR

Flyby-induced high-eccentricity migration and the prevalence of hot Jupiters in M67

Mika V. Kontiainen, Cathie J. Clarke, Andrew J. Winter

Few planetary systems form in isolation. Rather, interactions in their birth environments may sculpt their architectures or drive them into unstable configurations. Here we study the role of environmental perturbations in triggering dynamical instabilities leading to hot Jupiter formation in dense clusters, focusing on whether the elevated occurrence rate of hot Jupiters in the open cluster M67 can be explained through flyby-induced high-eccentricity migration. We develop a hybrid method for mod…

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astro-ph.EP

Magnesium silicate condensation in sub-Neptune envelopes: the fundamental link between chemistry, structure, and observables

William Misener, Peter Gao, Nicole L. Wallack, Maggie A. Thompson, Anat Shahar

Chemical interactions between the hydrogen-dominated envelopes and silicate-rich interiors of sub-Neptunes likely play a key role in shaping their atmospheric structure, mass-radius relations, and upper atmosphere composition. While atmospheric abundances and structure deeply influence each other, many existing models have either considered the effects of chemical interactions without the structural implications or have modeled the envelope structure using oversimplified chemical networks. In th…

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astro-ph.EP

Magnesium silicate condensation in sub-Neptune envelopes: the fundamental link between chemistry, structure, and observables

William Misener, Peter Gao, Nicole L. Wallack, Maggie A. Thompson, Anat Shahar

Chemical interactions between the hydrogen-dominated envelopes and silicate-rich interiors of sub-Neptunes likely play a key role in shaping their atmospheric structure, mass-radius relations, and upper atmosphere composition. While atmospheric abundances and structure deeply influence each other, many existing models have either considered the effects of chemical interactions without the structural implications or have modeled the envelope structure using oversimplified chemical networks. In th…

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astro-ph.HE

The GPSP Atlas: High-resolution Galactic Photon Survival Probability Atlas for Very-High- and Ultra-High-Energy Gamma-Ray Astronomy

Ekrem Oğuzhan Angüner

The emergence of Galactic PeV astronomy makes photon--photon ($γγ$) absorption an increasingly important component of gamma-ray data analysis. In this work, the Galactic Photon Survival Probability (GPSP) atlas is presented as the first Galactic framework describing gamma-ray survival probabilities over the full parameter space $P(l,b,d,E_γ)$ between 1 TeV and 10 PeV. The atlas is constructed using two independent GALPROP-based interstellar radiation field (ISRF) models, allowing direct assessme…

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astro-ph.HE

Thermal Stability of Radiation-Pressure-Dominated Accretion Disks Threaded by Net Vertical Magnetic Flux

Shahram Abbassi, Armin Memarian, Samik Mitra

The classical radiation-pressure instability predicts strong thermal variability in luminous black-hole accretion disks, whereas most disk-dominated X-ray binary soft states remain comparatively stable. We examine whether net vertical magnetic flux can weaken this instability through its contribution to the radial stress. The stability depends not only on the equilibrium magnetic stress but also on how that stress changes during a thermal perturbation. We write the local stability condition in t…

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astro-ph.GA

The Mass Dependence of the Fundamental Metallicity Relation in Observations and Simulations

Laura Carnevale, Alex M. Garcia, Paul Torrey, Sara L. Ellison, Shweta Jain, Peixin Zhu, Kathryn Grasha, Ryan L. Sanders et al.

The metal content of galaxies provides direct insight into the underlying physical processes that drive galaxy evolution. An example of this is the three-parameter relationship between stellar mass, gas-phase metallicity, and star formation rate, commonly referred to as the Fundamental Metallicity Relation (FMR). Previous studies have suggested that the FMR is redshift-invariant (at $z \lesssim 4$) and fully accounts for the scatter in the mass-metallicity relation (MZR). In this work, we test t…

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astro-ph.HE

Measurement of spin-orbit misalignment in binary black holes via the total spin

Charles F. A. Gibson, Isha Anantpurkar, Javier Roulet

The degree of spin-orbit alignment in merging binary black holes is a powerful probe of their formation history. However, assessing spin-orbit misalignment in individual events remains challenging, as most parameters commonly used to characterize precession tend to be poorly constrained. In this work, we introduce the angle between the total spin and orbital angular momentum, $θ_{LS}$, as an alternative measure of spin-orbit misalignment. Using synthetic observations, we show that $θ_{LS}$ retai…

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astro-ph.EP

Atmospheric Retrieval of Combined JWST, HST, and Ground-Based Observations Reveals a Featureless Transmission Spectrum for GJ 1132 b

Mohammad Senobar, Sareh Ataiee

We present a panchromatic transmission spectrum of GJ1132b spanning $0.71$--$5.16~μ$m, combining published transit observations from Magellan/LDSS3C, HST/WFC3 G141, and JWST/NIRSpec (G395H and G395M). Using petitRADTRANS and PyMultiNest, we perform Bayesian atmospheric retrievals, comparing a flat-line, Gaussian-feature models, and clear and cloudy atmospheric scenarios, including tests with and without the first JWST visit flagged as a potential outlier in a previous study. The inclusion of sho…

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astro-ph.HE

Supernova 1987A was a "failed supernova" twenty thousand years before its jet-driven explosion

Noam Soker

I show that the progenitor of supernova (SN) 1987A faded substantially and became red for hundreds of years to observers in and near the plane of the equatorial ring, because the equatorial ring, which was formed by a binary interaction between the SN 1987A progenitor and a main-sequence companion that ejected material about 20,000 years before the explosion, obscured the progenitor. For a few hundred years, the luminosity for such hypothetical observers was mainly light scattered by the two out…

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astro-ph.HE

Supernova 1987A was a "failed supernova" twenty thousand years before its jet-driven explosion

Noam Soker

I show that the progenitor of supernova (SN) 1987A faded substantially and became red for hundreds of years to observers in and near the plane of the equatorial ring, because the equatorial ring, which was formed by a binary interaction between the SN 1987A progenitor and a main-sequence companion that ejected material about 20,000 years before the explosion, obscured the progenitor. For a few hundred years, the luminosity for such hypothetical observers was mainly light scattered by the two out…

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gr-qcastro-ph.HE

Dynamical Friction as Environmental Gravitational Self-Force

Sayak Datta

Dynamical friction (DF) and gravitational-wave radiation reaction are conventionally treated as distinct dissipative mechanisms acting on a compact object inspiraling through a matter environment. We show that DF is not an additional force but a term at order $q^2ε$ in a covariant multiparameter expansion of the MiSaTaQuWa force equation that vanishes identically in the absence of a particle-induced perturbation of the environment's matter fields, where $q$ and $ε$ are respectively the mass rati…

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astro-ph.HE

Quantum-Gravity-Inspired Effects in Neutron Stars: A Critical Map from Microscopic Assumptions to Observables

Randall Hell Vargas Pradinett

Claims that neutron stars constrain quantum gravity often compare models whose new physics enters at different stages of the stellar calculation. This article provides a critical map of three representative routes: generalized-uncertainty-principle deformations of microscopic thermodynamics, noncommutative-inspired modifications of the effective matter source, and higher-curvature or scale-dependent modifications of gravitational dynamics. For each route we identify the quantity that is changed,…

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astro-ph.SRphysics.plasm-ph

Calculation of Field Line Slippage Rates in Coronal Simulations

Valentin Aslanyan, David MacTaggart, Roger B. Scott, Chloe P. Wilkins, David I. Pontin, Anthony R. Yeates, Peter F. Wyper, Karen A. Meyer et al.

We present the Universal Slippage calculator (\texttt{USlip}), an extension of the Universal Fieldline Tracer (\texttt{UFiT}), that computes magnetic field line slippage rates from an input magnetic field defined on a structured grid. The slippage rate provides a local, physically grounded diagnostic of non-ideal evolution, directly quantifying departures from ideal frozen-in motion. We outline the theoretical formulation and describe an efficient numerical implementation. The method is validate…

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astro-ph.SRphysics.space-ph

Photospheric index of geomagnetic activity

Ismo Tähtinen, Timo Qvick, Timo Asikainen, Kalevi Mursula

Geomagnetic indices quantify the disturbances of the Earth's magnetic field. They form an important space weather and space climate record that tracks solar-terrestrial effects on the Earth. Although geomagnetic activity has its origins in the photospheric magnetic fields, the two have so far not been directly related. We develop a photospheric index of geomagnetic activity (PIGA) that measures the geoeffectiveness of the Sun based on photospheric magnetic field as presented in synoptic magnetog…

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astro-ph.EPq-bio.PE

Potential survivable niches for microbial life on the lunar south pole

Prabal Saxena, Stefano Bertone, Heather V. Graham, Natalie M. Curran, Aaron B. Regberg, Andrew Needham, D. E., Pugel et al.

Most lunar surface conditions are incredibly harsh for microbial survival. High ultraviolet radiation, temperatures, and energetic particle radiation limit survival over most unprotected lunar surfaces, particularly in equatorial regions where all previous crewed exploration occurred. However, whether these harsh conditions are widespread at lunar poles has not been examined considering topographical effects. Here, we show that recent microorganism survivability data and lunar surface remote sen…

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hep-exastro-ph.IM

Cosmic muon arrival directions as a source of entropy

Deepak Samuel

We demonstrate, for the first time, that the arrival directions of cosmic-ray muons from a muon telescope provide a measurable source of physical entropy. Using six months of data collected from a muon telescope, the local zenith and azimuth angles were used for randomness extraction. The result of this study show that each cosmic muon track from our detector can generate upto 4 bits with an entropy of 0.999182 bits/bit with a maximum bit rate of roughly 650 bits/s which can possibly be enhanced…

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astro-ph.SRastro-ph.GAastro-ph.IM

Improving the Physical Interpretability of Gaussian Processes in Stellar Activity Modeling: A Study Case on Photometric Variability Among Stellar Clusters

Leslie Moranta, Jonathan Gagné, Jacqueline K. Faherty, Mark Popinchalk, Jason Lee Curtis, Johanna M. Vos, Alexandrine L'Heureux, Andrew Ayala et al.

Gaussian Processes (GPs) are widely used to model stellar variability in photometric surveys, but a statistically successful fit does not guarantee that the inferred hyperparameters correspond to physically meaningful stellar properties. This is especially important for young, active stars, whose TESS light curves contain evolving spots, harmonics, and non-sinusoidal variability. We use stellar rotation as a case study to examine when the period hyperparameter of a quasi-periodic GP can be inter…

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gr-qcastro-ph.IM

Unsupervised Deep Learning Method for Clustering KAGRA O3GK Transient Noise Data

Yubin Kim, Kihyun Jung, Kyujin Kwak

The advent of ground-based gravitational wave detectors has significantly improved the detection of faint gravitational wave signals. However, these detectors are affected by various types of transient noise, known as glitches, which can mimic true gravitational wave signals and limit detector sensitivity. Classifying glitches according to their time-frequency characteristics not only facilitates a deeper understanding of their origins, but also supports their mitigation on data to maintain data…

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astro-ph.COastro-ph.IMphysics.comp-ph

Chebyshev interpolation in Einstein-Boltzmann codes

Herman Sletmoen

Einstein-Boltzmann codes compute theoretical predictions of cosmological models and rely heavily on interpolation in their independent variables: time $τ$, wavenumber $k$ and multipole $\ell$. We give a practical summary of interpolation with Chebyshev polynomials, which converges rapidly for smooth functions and thus pairs naturally with approximation-free Einstein-Boltzmann codes. By solving the perturbations and line-of-sight integrals at Chebyshev nodes in $k$ and $\ell$, we show that Chebys…

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astro-ph.GA

Spatially resolved molecular gas conditions in the circumnuclear disc of 3C 84

Bin Jia, Tom Oosterloo, Serena Viti, Raffaella Morganti

The brightest cluster galaxy NGC 1275, at the centre of the Perseus cluster, hosts the radio-loud AGN 3C 84 and a circumnuclear disc (CND) of cold molecular gas onto which large-scale CO filaments accrete, yet the physical and chemical conditions of the gas in the CND remain poorly constrained. We present a spatially resolved analysis of ALMA CO(2-1), HCN(3-2), and HCO$^+$(3-2) observations at 72 pc. The data are partitioned into beam-sized hexagonal regions and modelled with a Bayesian framewor…

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astro-ph.IMastro-ph.EP

NIRC2-Pol: First Light of Near-Infrared Polarimetry on Keck II

Briley L. Lewis, Manxuan Zhang, Maxwell A. Millar-Blanchaer, Eduardo Marin, Jayke S. Nguyen, Carlos Alvarez, Jaren N. Ashcraft, Mahawa Cisse et al.

NIRC2, the Near Infrared Camera 2 on the Keck II telescope, was recently upgraded with a new suite of polarimetric observing modes. The new polarimetry modes (referred to as NIRC2-Pol) open up a wide range of new studies, including investigations of exoplanets, the Galactic center, active galactic nuclei, and solar system objects. The new modes enabled by the upgrade span the 1.1 to 4.1 micron range (i.e. J through L' bands) and include imaging polarimetry, coronagraphic imaging polarimetry, and…

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gr-qcastro-ph.HE

Global uniqueness of Kerr black hole spin and inclination from a segment of the critical curve

Kenta Hioki

High-resolution observations are expected to probe the photon-ring structure of black hole images. The critical curve is the geometrically defined limiting locus on the observer's screen toward which successive higher-order photon subrings accumulate. For a Kerr black hole, the shape of this limiting curve depends on the dimensionless spin parameter $a$ and the inclination angle $i$. We investigate whether these parameters can be determined uniquely from a connected positive-length segment of th…

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astro-ph.SRastro-ph.HE

The Interplay of Magnetic Fields, Turbulence and Vorticity in Core-Collapse Supernovae

David Calvert, Michael Redle, Bibek Gautam, Carles J. Stapleford, Carla Frohlich, James P. Kneller, Matthias Liebendoerfer

The convective turbulent motion of the fluid below the shock in a core-collapse supernova stretches and amplifies the magnetic field of the progenitor star. The energy contained in the field is sourced from the work done by the fluid on the field which comes at the expense of the fluid's kinetic and internal energy. In addition to the energy exchange with the fluid, the magnetic field also has a back-reaction upon the fluid via a contribution to the baroclinic vector and thus affects the fluid v…

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gr-qcastro-ph.HE

The Bondi Dipole in Full Numerical Relativity: a Self-Accelerating Positive-Negative Mass Binary

Nikita M. Shirokov

Bondi showed in 1957 that bodies of opposite active gravitational mass self-accelerate: the negative chases the positive it repels, and the pair runs off together. We evolve this "Bondi dipole" in $3+1$ numerical relativity: two complex scalars share identical Klein-Gordon dynamics; only the phantom enters Einstein's equations with a minus sign -- inertial and passive masses positive, active mass negative. Across a matrix of thirty-four evolutions -- runaway pairs, controls, and parameter scans…

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astro-ph.GA

Estimator forensics for the wide-binary gravity test: the eccentricity-triple coupling manufactures a pseudo-signal, and a pre-registered protocol for Gaia DR4

Hicham Boufourou

Analyses of Gaia DR3 wide binaries reach opposite verdicts on a claimed low-acceleration anomaly: gamma = Geff/G ~ 1.4 (Chae 2023-2026; Hernandez et al. 2024) versus Newtonian at high significance (Banik et al. 2024; Pittordis et al. 2025), from the same catalogue. We localize the disagreement experimentally. A generative model -- Keplerian binaries plus hierarchical triples with photocentre and time-averaging effects -- is validated without tuning against Pittordis et al. (2025). Synthetic cata…

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astro-ph.HE

A Broadband X-ray Analysis and Optical Counterpart Search of IC5052 ULX

Nabil Brice, Dominic J. Walton, Felix Fürst, Daniel Stern, Amy H. Knight, Matteo Bachetti, Matthew J. Middleton, Alistair Pagan et al.

We present broadband X-ray spectral and timing analysis of the Ultra-luminous X-ray source (ULX) in IC5052 using simultaneous XMM-Newton and NuSTAR observations from 2022, supplemented by archival 2013 XMM-Newton data. A two-thermal component model, often interpreted as radially-segregated emission from a super-Eddington inner disc and its associated wind, provides a statistically acceptable fit but yields an implausibly high inner disc temperature of $k T_\mathrm{in} \approx 6.4$ keV, inconsist…

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astro-ph.HE

Assessing the Credibility of Gamma-Ray QPO Candidates in 41 TeV-Selected Blazars

Wen-Xin Yang, Yi Liu, Hong-Guang Wang, Denis Bastieri, Jun-Hui Fan

We analyze quasi-periodic oscillation (QPO) candidates in the 0.1-100 GeV Fermi-LAT light curves of 41 TeV blazars with a conservative, multi-stage timing analysis combining FFT power spectra, red-noise Monte Carlo simulations, false-discovery-rate control, bootstrap period uncertainties, split-sample cross-validation, Lomb-Scargle and WWZ diagnostics, a detection-only sensitivity test, observingwindow checks, and injection-recovery experiments. A first-pass FFT search flags 16 sources above a r…

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nucl-exastro-ph.HE

Cluster emission and its impact on the r-process nucleosynthesis

Natalia Thomas, Silvia Bara, Thomas Elias Cocolios, Stephane Goriely, Boris Andel, Andrei N. Andreyev, Alberto Camaiani, James G. Cubiss et al.

Cluster emission is an exotic decay mode between alpha-decay and fission, in which a parent nucleus emits a cluster of nucleons heavier than an alpha-particle, but lighter than what is usually considered a fission fragment. The properties of cluster emission were investigated by analyzing five high-energy events detected in a spectrum of a mass A = 230 beam produced at ISOLDE (CERN). Under the assumption that these events were caused by cluster emission, the most likely parent-cluster pair respo…

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astro-ph.HEastro-ph.GA

Probing the Three-Dimensional Structure of a Jet with Faraday Tomography

Sawera Gull, Masaya Kurogi, Keitaro Takahashi

Magnetic fields play a fundamental role in the dynamics and radiation of jets associated with active galactic nuclei (AGNs), where they accelerate and collimate the relativistic plasma and produce the observed synchrotron emission. Faraday tomography is a powerful technique for probing the three-dimensional distribution of magnetic fields and synchrotron-emitting plasma along the line of sight, by reconstructing the Faraday Dispersion Function (FDF) from the observed polarization spectrum. To ex…

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