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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.HEgr-qchep-phnucl-th

General-purpose equations of state for hadron-quark matter: first application to accretion-induced phase transitions in neutron stars

János Takátsy, Henrique Gieg, Tim Dietrich

Strong first-order phase transitions in the cores of neutron stars (NSs) can have profound implications for astrophysical observables, however, their existence remains an open question. Since most NSs form in binary systems, they are expected to experience prolonged episodes of mass accretion that gradually increase their central density and can potentially trigger such a transition. This might, in turn, generate observable multi-messenger signals, as suggested by previous studies. Motivated by…

astro-ph.GA

Impact of Gaia-Sausage-Enceladus merger revealed by a single cosmic clock: thick-to-thin disc transition, gas disc shrinking and bar formation

Natsuki Funakoshi, Daisuke Kawata, Jason L. Sanders, Ioana Ciucă, Robert J. J. Grand, Noriyuki Matsunaga, Brian Thorsbro, HanYuan Zhang et al.

Whether the formation of the Galactic bar was connected to the Gaia-Sausage-Enceladus (GSE) merger, the last significant merger experienced by the Milky Way, remains an open question. The bar formation epoch has been inferred from the star formation history of the nuclear stellar disc (NSD) traced by Mira variables, and the GSE merger epoch from the age-metallicity relation of red giants. However, these epochs rest on different stellar tracers with different age scales and cannot be compared dir…

astro-ph.COastro-ph.GA

Optimal galaxy magnification: generalized fundamental-plane residuals and number counts are all you need

Kun Xu, Ravi K. Sheth

Weak-lensing magnification complements cosmic shear through its effects on galaxy fluxes, sizes, and number counts. We derive the optimal magnification statistics from galaxy properties and show that the optimal measurement can be decomposed into an optimal mean statistic and total number counts. The optimal mean statistic can be constructed from the residual distribution of a generalized fundamental plane (GFP), $F(i,\boldsymbol{X})$, which predicts galaxy size or, equivalently, flux from surfa…

astro-ph.SRastro-ph.IM

Analog Electronic Computation of Stellar Structure: Polytropic Benchmarks, Circuit Scaling, and Error-Controlled Verification

Zuhoor Elahi, Wafa Gull, Christopher Sirola

We present an electronic analog-computing framework for static stellar-structure equations and verify it using polytropic Lane-Emden benchmarks with known or high-accuracy reference solutions. Starting from an exploratory operational-amplifier and multiplier circuit, we identify sign, coefficient, central-regularity, and signal-conditioning problems that complicate direct electronic implementation. We develop dimensionless first-order formulations, derive regular finite-radius initial conditions…

astro-ph.EP

Predictions for an unseen third planet in the WISPIT 2 system

Amena Faruqi, Farzana Meru, Gabriel-Dominique Marleau, Pooneh Nazari, Andrew Swan, Ralph E. Pudritz, Thomas G. Wilson

We predict the mass and semi-major axis of a currently unseen but hypothesised planet in the WISPIT 2 system based on the location of the ring observed by ALMA at 144.4 au. Using findings from previous hydrodynamical models, we predict that a ~0.2-1 $M_{Jup}$ planet may exist at ~ 100-120 au. We also demonstrate that the ring seen in VLT/SPHERE observations at 96.7 au is consistent with the mass and semi-major axis of WISPIT 2b and confirm that WISPIT 2b cannot be the cause of the ALMA ring. We…

astro-ph.HE

Modeling MAD Sgr A* flares and their dependence on spin

Eleni Antonopoulou, Antonios Nathanail, Yosuke Mizuno, Foivos Zanias

Aims: This study aims to place constraints on the spin of Sgr A* from recent flare observations. It models the flare kinematics in the vicinity of a supermassive black hole, evaluates their dependence on black hole spin, and assesses the correlation between the spin of the black hole and the astrometric observations in the Galactic center. Methods: Our study extends the work of Antonopoulou et al. 2025 to a range of black hole spins. A prominent flux eruption is identified in the simulation, and…

astro-ph.HE

Extended vs. thin screen approximation in astrophysical settings

Manuel Adlberger, Tobias Kramer

Context: In the context of radio wave propagation through plasma concentrations and for gravitational lensing, the thin screen approximation often provides a suitable approximation for scattering and deflections caused by three-dimensional spatial structures. For scattering of electromagnetic waves from an extended medium, stochastic theories provide analytical bounds on ensemble averaged quantities, such as the scintillation index. If neither the conditions for a stochastic treatment nor the th…

physics.space-phastro-ph.SR

An Implicit Conservative Finite Volume Scheme with Poisson Brackets for the Steady-State Transport of Galactic Cosmic Rays

Weihao Liu, Igor V. Sokolov

Galactic cosmic rays (GCRs) pose a persistent radiation hazard to astronauts and spacecraft in the heliosphere. Modeling their transport is essential for understanding how the solar wind and heliospheric magnetic field shape their spatial distributions and energy spectra. Timely predictions require solving for the particle distribution function much faster than real time, but explicit numerical schemes are restricted by the stability limit on the time step. In this Letter, we present an implicit…

astro-ph.SR

Relation of Rotation and Pulsation Properties in $γ$ Doradus Stars

Á. Sódor, E. Plachy, Zs. Bognár

Connection between stellar rotation and pulsation amplitude has been proposed for several types of pulsating variable stars, but no such relation has been established for gamma Doradus stars from spectroscopic v sin i measurements. A high-amplitude gamma Dor subclass was also suggested recently, which had not been explored by spectroscopic means before. We investigate the connection between rotation and pulsational properties of gamma Dor stars using a homogeneous spectroscopic sample with avail…

astro-ph.IMastro-ph.EP

The Pandora SmallSat: Target Selection and Early Science

Emily A. Gilbert, Elisa V. Quintana, Jessie L. Dotson, Knicole D. Colón, Thomas Barclay, Pete Supsinskas, Jordan Karburn, Dániel Apai et al.

The Pandora spacecraft is a smallsat selected in NASA's inaugural class of Pioneers missions. The aim of the Pandora mission is to disentangle stellar activity signals from exoplanet atmospheric transmission spectroscopy measurements. Pandora accomplishes this goal with its combined visible photometry and NIR spectroscopy that observe each target in the prime mission for 10 separate transit observations, each spanning 24 hours at a time. Targets were carefully selected for the Pandora prime miss…

gr-qcastro-ph.HEhep-th

Local tests of Schwarzschild-Bertotti-Robinson spacetime

Fatma Kutlu, Livanur Çelik, Özgür Delice

We study weak field local tests of Schwarzschild-Bertotti-Robinson spacetime, which describes a static black hole embedded in an external magnetic field. Perihelion precession, deflection of light rays and time delay of radar echoes are the phenomena considered in this work to understand the possible effects of this external magnetic field on these observationally important tests. We not only derive weak field analytical results by employing appropriate methods, but also consider an exact approa…

astro-ph.GA

The Structural Anatomy of Galaxies: Environmental Dependence of Morphological and Quenching Evolution at 0.1 < z < 0.5

Can Xu, John D. Silverman, Qiusheng Gu, Daniela Galárraga-Espinosa, Andreas L. Faisst, Emanuele Daddi, Hassen M. Yesuf, Angelo George et al.

We investigate how cluster environments affect galaxy star formation, structure, and stellar populations using spectroscopically-confirmed galaxies in X-ray-selected eROSITA clusters, that have deep HSC-SSP imaging and DESI DR1 spectroscopy. At 0.1<z<0.5, we compare dust-corrected Ha star formation rates (SFRs), effective radii (Re), bulge-to-total light ratios (B/T), and Dn4000 between cluster satellites and a stellar-mass- and redshift-matched field control sample. We identify UVJ-quiescent ga…

astro-ph.SRastro-ph.HE

The diversity of late-time interaction in Type II supernovae

Luc Dessart, Wynn V. Jacobson-Galán, K. Azalee Bostroem

Studying core-collapse supernovae (SNe) beyond one year after explosion, when ejecta interaction with circumstellar material (CSM) progressively becomes the dominant power source, offers critical insights into the progenitor mass loss history. Using binary progenitors that underwent different levels of H-rich envelope stripping, we present radiative transfer calculations of the ejecta with CSM interaction in Type IIb, II-L and II-P SN scenarios covering epochs of 1.5 to 3-6yr, with a focus on th…

astro-ph.IM

A design concept for the High Resolution Imager on the Habitable Worlds Observatory

Vincent Van Eylen, Richard Massey, Alan Smith, Jerome Amiaux, Florence Ardellier, Saeeda Awan, Patrick Curry, Daniel Dicken et al.

The Habitable Worlds Observatory (HWO) will be NASA's next flagship astrophysics mission, designed to search for signs of life on planets around nearby stars and conduct transformational science across astrophysics. Its High Resolution Imager (HRI) is not only the observatory's main imaging camera, but also provides grism spectroscopy and sub-microarcsecond astrometry, as well as the observatory's fine guidance, wavefront sensing and pupil imaging. We present a design concept for HRI, developed…

gr-qcastro-ph.HE

Rotation slows the instability of Ellis-Bronnikov wormholes

Nikita M. Shirokov, Ilya Nachevsky

We present nonlinear 3+1 evolutions of rotating Ellis-Bronnikov wormholes. We construct stationary rotating drainhole solutions with a spectral solver up to an equatorial rotation velocity of 99% of the speed of light, validate the solver against published symmetric solutions, and correct an inconsistency in a published field equation. Perturbed only by truncation error, the evolutions show that rotation slows the radial instability of the static wormhole. Near 30% of the extremal angular moment…

astro-ph.HEhep-ph

PBR sensitivity to boosted dark matter explanation for the KM3-230213A event

M. H. Reno, T. Venters, M. Abrate, J. Adams, J. Alfaro, D. Allard, P. Alldredge, R. Aloisio et al.

POEMMA-Balloon with Radio (PBR) is a hybrid fluorescence and optical Cherenkov telescope that is a pathfinder instrument for a future Probe Of Extreme Multi-Messenger Astrophysics (POEMMA), together with a radio instrument, to be flown on a super pressure balloon in Spring 2028. One of its science objectives is follow up of astrophysical event alerts via signals of tau decays in the atmosphere, sourced by Earth-skimming tau neutrinos. The recent report of the KM3NeT Collaboration's muon event wi…

astro-ph.EPphysics.ao-ph

Topographically Forced Stationary Waves Can Explain the Near-Surface Zonal Winds Observed by Huygens on Titan

Sooman Han, Scot Rafkin, J. Michael Battalio, Bowen Fan, Juan M. Lora

Titan's equatorial superrotation is associated with climatological retrograde (westward) near-surface winds at low latitudes, as consistently simulated by Titan general circulation models. However, the Huygens probe measured prograde (eastward) near-surface winds, contrary to the expected circulation. We investigate whether these observations reflect localized forcing by large-scale topography, using paired three-dimensional dry simulations with and without topography in the Titan Atmospheric Mo…

astro-ph.IMastro-ph.HE

Cosmic Ray Observations using Coincident Scintillator and Radio Signals with the Beamforming Elevated Array for COsmic Neutrinos (BEACON)

Zachary Martin, Jackson Hinkel, Kira Perna, Andrew Zeolla, Jaime Alvarez-Muñiz, Sergio Cabana-Freire, Washington Carvalho, Austin Cummings et al.

At energies above 100 PeV, coherent radio frequency (RF) emission across the 10 -- 1000 MHz band from cosmic particle-induced atmospheric showers becomes increasingly dominant, making radio detection a powerful probe at ultrahigh energies. The Beamforming Elevated Array for COsmic Neutrinos (BEACON) considers mountaintop phased radio arrays to monitor large areas at the horizon for upward-going geomagnetic emission in the 30 -- 80 MHz band produced as a consequence of Earth-skimming tau neutrino…

astro-ph.IMastro-ph.HE

In-orbit anomaly and recovery of IXPE detector 2

Fabio Muleri, Luca Baldini, Sudip Chakraborty, Chien-Ting Chen, Enrico Costa, Ettore del Monte, Alessandro Di Marco, Kurtis L. Dietz et al.

The Imaging X-ray Polarimetry Explorer (IXPE) is a joint NASA-ASI mission launched in December 2021 to measure the linear polarization of celestial X-ray sources in the 2-8 keV energy range. The payload comprises three identical telescopes, each combining grazing-incidence X-ray optics with a focal-plane photoelectric polarimeter based on the Gas Pixel Detector technology. On 14 April 2025, the second detector experienced an anomaly that significantly altered the electrical behavior of the ASIC…

astro-ph.IM

In search of the third dimension in Compton X-ray polarimeters

Fabio Muleri, Riccardo Campana, Edoardo Borciani, Lorenzo Amati, Enrico Costa, Nicolas De Angelis, Ettore Del Monte, Alessandro Di Marco et al.

Compton polarimeters are typically designed to be sensitive only to the azimuthal angle of the scattered photon, ignoring the scattering angle. Such a 2-dimensional reconstruction of the event is pursued for both simplicity and because the polarization of the incident photon influences only the azimuthal response of the instrument. While this is true for on-axis sources, when the source starts to be off-axis of several degrees the azimuthal response of the instrument is effectively a convolution…

astro-ph.GA

A Little Red Dot emerging from a nitrogen-rich UV-luminous galaxy with Very Massive Stars

Alberto Torralba, Jorryt Matthee, Rui Marques-Chaves, Fabrice Martins, Benjamín Navarrete, Gabriele Pezzulli, Edoardo Iani, Rohan P. Naidu et al.

JWST is revealing abundant populations of high-$z$ galaxies with unforeseen properties: UV-luminous galaxies with high nitrogen enrichment, populations of very massive stars (VMSs; $>100\ M_\odot$), and early forms of massive black hole growth such as the Little Red Dots (LRDs). Here we present all these phenomena appearing simultaneously in COLA1, a luminous ($M_{\rm UV}=-21.3$) galaxy at $z=6.6$. New NIRSpec medium-resolution data reveal a blue UV continuum ($β_{\rm UV}=-2.5$) with strong emis…

astro-ph.GA

Evaluating Zero-Shot Anomaly Detection for Identifying Unusual Galaxy Morphologies in CEERS and NGDEEP

T. B. Surakan, J. S. Kartaltepe, R. Pattnaik, C. K. Binu, I. G. Cox, T. Y. Hsiao, R. A. Lucas, F. Pacucci et al.

Galaxy morphology out to $z\sim 6$ provides insight into galaxy formation and evolution, but identifying rare or structurally complex systems is difficult due to observational limits and the scale of modern imaging surveys. Here, we apply AdaCLIP, a Zero-Shot Anomaly Detection (ZSAD) model built upon the Contrastive Language-Image Pretraining (CLIP) model and adapted using non-astronomical anomaly-detection datasets, to identify structurally unusual galaxies without galaxy-specific anomaly-detec…

gr-qcastro-ph.IMphysics.ins-det

A Broadband Room-Temperature Design for the Einstein Telescope

Teng Zhang, Amit Singh Ubhi, Huan Yang, Alan V. Cumming, Mark Barton, Angus Bell, Fabio Bergamin, Giacomo Bruno et al.

The unique underground location of the Einstein Telescope (ET) is expected to substantially suppress seismic and gravity-gradient noise, providing a favorable environment for gravitational-wave detection at low frequencies compared with surface-based observatories. The baseline ET design aims to achieve broadband sensitivity through a xylophone configuration, in which separate cryogenic and room-temperature interferometers are optimised for low- and high-frequency gravitational-wave detection. H…

astro-ph.HE

PSR J0653+0443: An Eclipsing Millisecond Pulsar in an Extremely Eccentric Double Neutron Star System

Z. L. Yang, J. L. Han, L. G. Hou, Z. W. Chen, Y. G. Gong, Y. L. Guo, Y. J. Lu, C. Zhang et al.

Double neutron star (DNS) systems emit gravitational waves (GW) as they orbit each other, with waveforms dependent on their orbital properties \cite{Poisson+2014grav.book.....P}. The number of DNS systems surviving binary star evolution in the Milky Way and the distribution of their orbital parameters are fundamental questions for GW astronomy and binary evolution studies. Here, we report the discovery of a new Galactic field DNS system, PSR J0653+0443, comprising two ~1.4 $M_\odot$ components i…

astro-ph.SRastro-ph.HE

Neutron Star-Main-Sequence Star Collision: Formation and Long-Term Evolution of Thorne-Żytkow Objects

Yuhao Guo, Xiao-Tian Xu, Dong Lai

Thorne-$\dot{\mathrm{Z}}$ytkow objects (T$\dot{\mathrm{Z}}$Os) are stars containing a neutron-star (NS) or black-hole (BH) core embedded in a stellar envelope and powered primarily by mass accretion onto the core. Classical evolution models of T$\dot{\mathrm{Z}}$Os begin with an assumed equilibrium configuration and predict chemical anomalies in the stellar envelope resulting from nuclear burning in the vicinity of the NS core. Here we connect dynamical formation to long-term evolution by combin…

astro-ph.EP

The morphology of contact binary objects in the Solar System

Richard E. Cannon, Agata Rożek, Colin Snodgrass

Contact binaries, appearing as two objects stuck together, are prevalent throughout the Solar System, making up between 30- 50% of asteroids and comets. Despite this, detailed shape models of contact binaries are hard to obtain remotely, requiring rare occultation events or close approaches to Earth (< 0.1 au) to observe with ground-based radar systems. Despite only 16 contact binary models being published, there already exists a wide variety of different arrangements of the two lobes relative t…

gr-qcastro-ph.HEastro-ph.IM

SpinOctopus: A Versatile, User-Friendly, and Extensible Public Code for General-Relativistic Ray-Tracing in axisymmetric spacetime

Shiyang Hu, Dan Li, Chen Deng, Lina Zhang, Wenfu Cao

Relativistic ray-tracing algorithms serve as indispensable numerical tools for investigating gravitational theories and high-energy astrophysics. In this paper, we develop and release SpinOctopus, a versatile relativistic ray-tracing code tailored for arbitrary axisymmetric spacetimes, powered by a Fortran/Python hybrid architecture and OpenMP multi-threading acceleration. This numerical toolkit is capable of simulating timelike orbits and their corresponding light curves, null geodesics, as wel…

astro-ph.SR

Coronal spectroscopy - Past, Present and Future

Jagdev Singh, R. Ramesh, V. Muthu Priyal

After the beginning of photography of solar corona during the eclipses in the year 1860, efforts began to carry out spectroscopic observations of solar corona. During the total solar eclipse of 1868 August 18 at Guntur, Madras state, the observation of emission line 5875Å by Janssen lead to the discovery of Helium. Next year, during the eclipse of 1869 August 7, Charles Young and William Harkness discovered green emission line around 5310Å (later measured as 5303Å). It was interpreted as due to…

astro-ph.SRastro-ph.GA

Stellar Loci X: Selection of Nitrogen-Rich Giants Using GALEX NUV and Synthetic SDSS Photometry

Liangyu Yu, Haibo Yuan, Baitian Tang, Kai Xiao, Xue Lu, José G. Fernández-Trincado

Nitrogen-rich (N-rich) field stars (likely second-generation escapees from globular clusters) provide a powerful, but currently sample-limited, probe of globular-cluster disruption in the Galactic halo. We exploit the fact that enhanced NH, CN absorption depresses optical u band flux, while the near-ultraviolet (NUV) band is largely insensitive to nitrogen enhancement while remaining sensitive to overall metallicity. Combining GALEX NUV photometry with (synthetic) SDSS optical photometry, we con…

astro-ph.GA

Euclid Quick Data Release (Q1). The metallicity of the intracluster light

Euclid Collaboration, J. B. Golden-Marx, N. A. Hatch, S. P. Bamford, H. Gao, T. Kolcu, M. Montes, H. J. Brown et al.

Colour provides key information to constrain the stellar population of the intracluster light (ICL), the diffuse light within galaxy clusters. We derive radial colour profiles ($Y_\mathrm{E}-H_\mathrm{E}$, $J_\mathrm{E}-H_\mathrm{E}$, $I_\mathrm{E}-H_\mathrm{E}$) of the brightest central galaxy (BCG) and ICL for 168 galaxy clusters from the Dark Energy Survey redMaPPer catalogue within the redshift range $0.1 10^{14.05}M_\odot/h$, within the Euclid Quick Data Release (Q1). By stacking the light…