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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.HEastro-ph.GA

Dissecting the variability of Sagittarius A* in the orbiting hotspot framework

Maciek Wielgus, Aristomenis Yfantis

Sagittarius A* (Sgr A*) exhibits intermittent flaring behavior, characterized by strong enhancements in high-energy emission (infrared and X-ray). These events have been interpreted as related to the coherent orbital motion of localized regions of energized plasma - hotspots. While this framework has been quite fruitful in constraining properties of Sgr A*, it is subject to important challenges and limitations. In this brief review we discuss the recent observational and theoretical developments…

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astro-ph.IMastro-ph.CO

PSFSim: PhySics First Simulations for the Point Spread Function of the Roman Space Telescope

Nihar Dalal, Chris Hirata, Charuhas Shiveshwarkar, Anthony Harbo Torres, Chun-Hao To, Elise Moore, Katherine Laliotis, David Kuhtenia et al.

We present a new tool for generating simulated point spread functions (PSFs) in the Wide Field Instrument (WFI) of the Nancy Grace Roman Space Telescope. The simulation tool is physics forward, and performs a raytrace of the optical system of the instrument to compute the PSF, while also accounting for various detector effects. The tool also has the capability to add perturbations to the optical system and detectors. We explore several applications of the tool that may arise during the commissio…

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hep-phastro-ph.HEhep-ex

Heavy Inert Doublet Reconciles LZ and IceCube

Hitoshi Murayama, Bea Noether

We show that the inert doublet dark matter can reconcile the purported LZ direct detection signal and IceCube constraints. The preferred dark matter mass is 11.3--20.3~TeV, an order of magnitude heavier than the standard higgsino target. The smaller number density at a high mass can reproduce the LZ event given the exponential sensitivity to the velocity, while suppressing the capture rate in the Sun because of the higher infall velocity. On the other hand, the high mass requires a large couplin…

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astro-ph.GA

Cluster Membership Probabilities: A Review of Methods and Gaia Applications

Tahereh Ramezani, Johana Balciráková, Prapti Mondal, Katerina Neumannova, Ernst Paunzen, Gabriel Szász

Reliable stellar-cluster membership is essential for deriving cluster ages, distances, reddenings, metallicities, mass functions, dynamical parameters, and Galactic-structure tracers. The Gaia era has produced a proliferation of membership and cluster-detection methods, but the resulting catalogues are not interchangeable. We review the historical development of membership assignment, compare the statistical assumptions of major methods, and explicitly examine the practical consequences of metho…

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

Metal-poor Brown Dwarf Kinematics from JWST NIRSpec Spectroscopy

Chih-Chun Hsu, Christopher A. Theissen, Adam J. Burgasser, Adam C. Schneider, Christian Aganze, Aaron M. Meisner, Jonathan Gagné, Nicolas Lodieu et al.

Galactic archaeology relies on stellar kinematics and chemical abundances to identify various stellar populations and associations. With JWST, Galactic archaeology of ancient metal-poor brown dwarfs is now possible through high-sensitivity, medium-resolution spectroscopy. We present the first metal-poor brown dwarf radial velocity (RV) survey using JWST/NIRSpec G395H spectra ($λ/Δλ\sim$ 3,000) for a sample of 23 LTY dwarfs across a wide range of temperatures and metallicities. We introduce a for…

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

Metal-poor Brown Dwarf Kinematics from JWST NIRSpec Spectroscopy

Chih-Chun Hsu, Christopher A. Theissen, Adam J. Burgasser, Adam C. Schneider, Christian Aganze, Aaron M. Meisner, Jonathan Gagné, Nicolas Lodieu et al.

Galactic archaeology relies on stellar kinematics and chemical abundances to identify various stellar populations and associations. With JWST, Galactic archaeology of ancient metal-poor brown dwarfs is now possible through high-sensitivity, medium-resolution spectroscopy. We present the first metal-poor brown dwarf radial velocity (RV) survey using JWST/NIRSpec G395H spectra ($λ/Δλ\sim$ 3,000) for a sample of 23 LTY dwarfs across a wide range of temperatures and metallicities. We introduce a for…

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

Triggering star formation by free-floating planets

Yu. N. Eroshenko

Recently, a population of free-floating planets has been discovered in the Galaxy. This paper examines the influence of the planets trapped within a protostellar hydrogen clouds on the processes of gravitational instability in the gas. A sufficiently massive planet can become an alternative dynamic center for the contracting cloud. This occurs due to rapid mass growth from accretion onto the planet within the cloud. Owing to residual velocity and density gradients in the cloud, the planet that t…

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astro-ph.SRastro-ph.HE

A comprehensive multi-wavelength study of two X-ray emitting Be stars

Hema Anilkumar, Blesson Mathew, Savithri H. Ezhikode, Sreeja S. Kartha, Suman Bhattacharyya, Sneha Nedhath, Ajith N

We present a multi-wavelength study of two X-ray-emitting Be stars, CXOU J052218.4+332820 (Star 1) and CXOU J052304.2+332846 (Star 2), identified from the LAMOST DR5 Hot emission-line stars catalog. Our spectroscopic and photometric analyses indicate that Star 1 is a main-sequence B5e star, whereas Star 2 is a pre-main-sequence B7e star. The LAMOST spectrum of Star 1 exhibits shell-type Feii, Paschen, and Oi emission from circumstellar regions extending to ~ 3 - 5Rstar. TESS period analysis reve…

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astro-ph.HEastro-ph.SR

Tomography analysis of the intermediate-luminosity Type Iax SN 2024pxl

Barnabás Barna, Mridweeka Singh, Lindsey A. Kwok, Saurabh W. Jha, R. Dastidar, Conor Larison, Alexei V. Filippenko, J. P. Anderson et al.

We present an abundance tomography analysis of SN 2024pxl, an intermediate luminosity Type Iax supernova ($M_{r}=-16.82 \pm 0.19$ mag), with the most-detailed follow-up in the Type Iax subclass to-date. As one of the few intermediate luminosity Type Iax objects, SN 2024pxl may link the two extremes of the peculiar thermonuclear supernova subclass. To test this hypothesis, we analyze its spectral evolution through the first 100 days after the explosion and aim to probe the structure of its ejecta…

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astro-ph.HEhep-phnucl-th

Stability of hybrid stars via catastrophe theory

Eduardo S. Fraga, Sergio E. Jorás

We discuss the possible topologies of the mass-radius relation for hybrid stars in light of catastrophe theory. We show that different branches of compact stars emerge or disappear depending on the bifurcation structure of the underlying catastrophe potential function, the mathematical analog of an effective potential. For that we assume a single first-order phase transition between nuclear and quark matter. After a warm up with incompressible fluids, we present a qualitative discussion explaini…

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hep-phastro-ph.HEphysics.plasm-ph

Plasma instability splits axion-photon conversion lines

Elizabeth A. Tolman

The axion coupling to electromagnetism may leave signatures of uncertain nature in astrophysical spectra; one is thought to be a single line centered at the axion frequency $ω= \sqrt{\left(m_a c^2/\hbar\right)^2 + c^2 k_a^2}$, with $m_a c^2/\hbar$ the axion Compton frequency and $\hbar k_a$ its momentum. If a parametric plasma instability is excited, this signature is transformed into a set of lines, which may be proportionally spaced and linearly polarized. A Crab pulsar signal at a frequency n…

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astro-ph.HE

Composition-dependent acceleration of UHE Cosmic Rays in AGN electric fields

E. Koutsoumpou, I. Contopoulos, A. Nathanail, A. Loules, D. Kazanas

The origin of ultra-high-energy cosmic rays (UHECRs) remains elusive, as proposed acceleration mechanisms are rarely connected directly to composition-sensitive air-shower observables. We establish such a connection for voltage-drop acceleration in near-horizon current sheets of magnetically arrested disks around supermassive black holes. Fragmentation is represented by a log-normal distribution of effective potential-sampling factors $η$, with $μ_η=\langle\lnη\rangle$, $σ_η=[\mathrm{Var}(\lnη)]…

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astro-ph.SR

The physics of deep-interior convective shell boundaries in a massive pre-supernova star: Internal gravity wave mixing at the $N^2$ peak

Praneet Pathak, Falk Herwig, Simon Blouin, Paul R. Woodward, Joshua Issa

The physics of convective boundary mixing involves concepts such as penetration and overshooting and has been mostly characterized for envelope and core convection. For the burning shells deep inside massive stars in their final stages, the convective boundary remains poorly understood. 1D stellar-evolution codes typically place a steep entropy gradient and the corresponding narrow \brunt{} ($N^2$) peak at a lower convective shell boundary. Based on high-resolution 3D hydrodynamic simulations of…

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astro-ph.SRastro-ph.HE

3D Radiation Hydrodynamics of Blue Supergiant Envelopes

Linhao Ma, Lars Bildsten, Yan-Fei Jiang

We present the first 3D radiation hydrodynamical simulation of the outer envelope of a blue supergiant. These near Eddington limited massive stars in the Hertzsprung gap exhibit substantial photometric variability and have spectroscopic line widths indicating unexplained macroturbulent velocity fields. Our Athena++ simulations find that the convection associated with the opacity peak from iron directly extends to the photosphere, as found in previous 3D simulations of massive main sequence stars…

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astro-ph.GA

Mapping the Milky Way in Six Dimensions: A contiguous, homogenised, phase-space catalogue of \textit{Gaia} DR3 tracers up to 250 kpc

Sutirtha Mukherjee, Amogh Srivastav, Subhabrata Majumdar

We present a comprehensive, homogenised catalogue of $32{,}552{,}876$ stellar sources with full 6D phase-space information, spanning Galactocentric distances from the inner galaxy ($\gtrsim 5$\,kpc) to the outer halo ($\sim\!250$\,kpc). By cross-matching \textit{Gaia} DR3 astrometry with spectrophotometric distances and line-of-sight velocities from 14 surveys (including \textsc{desi}, \textsc{sdss-boss}, \textsc{apogee}, \textsc{lamost}, \textsc{galah}, and \textsc{ges}), we achieve median frac…

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astro-ph.HE

Dynamically Stable Magnetic Fields in Relativistic Neutron Stars: A Diverse Landscape of GRMHD Equilibria

Mai Li, Vasileios Paschalidis, Antonios Tsokaros, Maria Mutz, Koji Uryu

Neutron stars endowed with purely poloidal or purely toroidal magnetic fields are known to be unstable, and settle into mixed poloidal-toroidal configurations. The end state of these instabilities is still poorly understood. It is unclear whether this state is unique or whether the dynamically stable configuration has memory of the initial conditions. In this work, we perform long-term, fully general relativistic magnetohydrodynamic simulations of equilibrium configurations of slowly rotating ne…

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astro-ph.SRastro-ph.EP

External photoevaporation in the center of Tr14

Katia Gkimisi, Da Eun Kang, Dominika Itrich, Rossella Anania, Eleonora Fiorellino, Sacha Gavino, Ralf S. Klessen, Victor F. Ksoll et al.

Most stars form in massive stellar clusters, where intense far-ultraviolet (FUV) radiation from OB stars can accelerate the dispersal of protoplanetary disks through external photoevaporation. Quantifying the impact of this process on disk evolution remains challenging, particularly in distant and crowded star-forming regions. We investigate the low-mass stellar population in the highly irradiated center of Trumpler 14 and examine how the local FUV radiation field influences circumstellar disk e…

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astro-ph.SR

Detection of new Galactic Wolf-Rayet stars with SPHEREx

Paul A. Crowther, Erin L. Smith

We assess the potential for the NASA Explorer SPHEREx mission in adding to the Milky Way census of Wolf-Rayet (WR) stars by extracting 0.75--5micron spectrophotometry of 30 candidate WR stars previously identified using Gaia XP spectra. We confirm an additional Galactic 13 WR (8 WN and 5 WC) stars, identify 3 probable [WC]-type central stars of Planetary Nebulae, plus 2 He emission line sources. SPHEREx has the potential to detect additional relatively isolated WR stars on the far size of the Mi…

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astro-ph.HEastro-ph.GA

Probing the Metallicity Dependence of Fast Radio Burst Progenitors with CHIME/FRB Outrigger Dwarf Host Galaxies

Y. Dong, W. Fong, K. Nimmo, N. Loudas, B. C. Andersen, S. Andrew, A. Cai, S. Chatterjee et al.

Using the fast radio bursts (FRBs) localized with the CHIME/FRB Outriggers between February and October 2025, we conduct a systematic search for dwarf host galaxies. We identify and characterize eight host galaxies for one repeating and seven apparently non-repeating FRBs, newly classifying five hosts as dwarfs with stellar masses of $\log(M_\ast/M_\odot) \approx 8.1-9.1$. We measure their gas-phase metallicities and, when combined with hosts from the literature, finding that repeating and non-r…

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astro-ph.GA

The quest for high-redshift radio galaxies II. Discovery of the most powerful known radio galaxy at z=4.946

B. Balmaverde, A. Capetti, M. Chiaberge, F. Massaro, M. Coloma Puga, A. Jimenez-Gallardo

As part of our quest for high-redshift radio galaxies (HzRGs), we present the results obtained from optical spectroscopy leading to the confirmation of one HzRG candidate selected using the Lyman break technique. The optical emission, associated with the radio source TXS 2354+015, exhibits a prominent drop in the r band, which is characteristic of sources at z~5. The optical spectrum shows a bright asymmetric emission line, with a large equivalent width of ~900 Angstrom. Its identification with…

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astro-ph.IM

A Practical Primer on Software Citation in Research

Floor S. Broekgaarden, Phil R. Van-Lane, Sasha Levina, Ahmed Bello, Sandra Gesing, Daniel S. Katz, Bhavesh Patel, Pengyin Shan et al.

Software underlies virtually all modern research, yet citation practices for software remain inconsistent and often inadequate. This short primer offers practical guidance in two directions: how to properly cite the software you use in your research, and how to make your own software easy for others to cite. We describe a seven-step workflow for citing software and a five-step workflow for making your software citeable, along with the community tools and resources that support each step. We also…

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astro-ph.EP

Just a Phase? Weakening Vertical Shear Instability Explains Class II Disk Morphologies: Simulations with dust coagulation, sedimentation, thermal relaxation, and backreaction

Thomas Pfeil, Alexandros Ziampras, Shangjia Zhang, Philip J. Armitage, Yan-Fei Jiang

The Vertical Shear Instability (VSI) is known to create turbulence and strong vertical mixing in protoplanetary disks if thermal relaxation is sufficiently fast. In simulations where this condition is met, VSI can loft dust particles to large altitudes, creating a vertically extended appearance in mock millimeter-wavelength observations, which is inconsistent with the morphology of the majority of observed class II disks. We present simulations of protoplanetary disks with VSI that are consisten…

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astro-ph.GA

A sub-100 pc view at z~5 of a Multiply-Imaged Massive Quiescent Galaxy

Richard Pan, Danilo Marchesini, Joseph F. V. Allingham, Seiji Fujimoto, Adi Zitrin, Dan Coe, Vasily Kokorev, Lukas J. Furtak et al.

Recent James Webb Space Telescope spectroscopic surveys reveal an abundance of rapidly assembled early galaxies in the first billion years. Cosmological simulations struggle to reproduce this population because models require a rapid, highly efficient conversion of baryons into stars followed by an abrupt cessation of star-formation, known as quenching, in the early Universe. Testing these theoretical models remains difficult because high-redshift field galaxies appear compact and unresolved. Th…

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astro-ph.HE

First Pre-peak Ultraviolet Spectrum of a Tidal Disruption Event: A Fast Outflow Revealed Prior to Maximum Light in TDE2025aarm

Erica Hammerstein, Ryan Chornock, Jean Somalwar, Raffaella Margutti, Brenna Mockler, Olivia Aspegren, Itai Sfaradi, Natalie LeBaron et al.

The tidal disruption and eventual accretion of a star by a massive black hole can lead to the launching of outflows and winds that encode important information about the tidal disruption and accretion processes. However, little is known about the existence and behavior of these outflows before optical light-curve peak, when processes such as stream-stream collisions and disk formation may be important. Here, we present the first pre-peak ultraviolet (UV) spectrum of a tidal disruption event (TDE…

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astro-ph.IMastro-ph.COastro-ph.GAgr-qcphysics.comp-ph

Differentiable astrophysics at scale: solving and differentiating ODE ensembles on the GPU

A. Spurio Mancini

Astronomers increasingly fit their models with gradient-based methods, such as Hamiltonian Monte Carlo, which need the derivatives of the model with respect to its parameters. In many analyses a prediction requires solving a small system of ordinary differential equations (ODEs) for thousands to millions of parameter sets, and this ensemble of integrations often sets the cost of the analysis. We introduce to the astronomical community GRADSOLVE, a JAX library that moves this computation to graph…

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astro-ph.IM

The shell around VY Canis Majoris in SPHEREx is likely an artifact

Viraj Karambelkar, Yashvi Sharma, Kishalay De

Recently, the presence of a large shell around the bright hypergiant star VY Canis Majoris was reported in images from the SPHEREx mission. We report similar shells around other bright stars at similar locations in SPHEREx Band 1 images, suggesting that this shell is not astrophysical but instead a detector artifact.

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astro-ph.HEphysics.comp-phphysics.plasm-ph

Performance-portable GPU acceleration of the hybrid particle-in-cell code dHybridR

Bricker Ostler, Miha Cernetic, Damiano Caprioli

Hybrid particle-in-cell simulations are widely used to study kinetic processes in collisionless astrophysical and space plasmas, yet the high computational cost of large-scale three-dimensional runs has largely confined production studies to two dimensions or restricted domains. To address this challenge, we present a performance-portable GPU implementation of the hybrid particle-in-cell code dHybridR. The implementation combines OpenMP target offloading with specialized SYCL kernels for the mos…

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astro-ph.SRastro-ph.GA

A Search For Stellar-mass Black Holes Via Astrometric Microlensing II: 2012-2015 Keck Candidates

Mace J. Huston, Jessica R. Lu, Casey Y. Lam, J. Nijaid Arredondo, Natasha S. Abrams, Shep Brooke, Sage H. Remulla, Eran Ofek et al.

The Milky Way is expected to host $\sim$10$^8$ stellar-mass black holes with an uncertain binary fraction. The only proven method to detect isolated stellar mass black holes is gravitational microlensing. Here we report the results of a microlensing search for black holes with photometry and astrometry. By combining 10 years of seeing-limited photometry from OGLE and MOA with diffraction-limited photometry and astrometry from adaptive optics imagers at the W.~M.~Keck Observatory, we constrain le…

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stat.APastro-ph.IM

Multivariate Continuous-Time Autoregressive Moving Average Processes for Astronomical Multiband Time Series

Izak Schmidlkofer, Zhirui Hu, Lishan Shi, Weixiang Yu, Hyungsuk Tak

Large-scale astronomical surveys provide unprecedented volumes of multivariate time-series observations obtained through multiple optical filters. We develop a structured multivariate continuous-time autoregressive moving average (MCARMA) framework for multi-band time series with irregular sampling, heteroscedastic measurement errors, and partially observed bands. The framework allows band-specific stochastic dynamics while modeling cross-band dependence through correlated Brownian driving proce…

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nucl-thastro-ph.HE

Strange Quark Stars and Spontaneous Scalarization

Mina Mehraeen Nazdik, Zeinab Rezaei

Strange quark matter, as one of the most extreme dense states in astrophysics, can be explored through relativistic compact objects. Hypothetical relativistic stars composed of dense strange quark matter are characterized by the equation of state of that matter. The spontaneous scalarization of strange quark stars is influenced by the equation of state of strange quark matter. Here, we investigate how the equation of state of strange quark matter influences the spontaneous scalarization of these…

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