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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.HEastro-ph.COastro-ph.GA

Tightening Bounds on Warm Dark Matter with High-Redshift Gamma-Ray Bursts

Jun-Jie Wei, Jing-Meng Hao, Ding-Fang Hu, Yang Liu, Bao Wang, Xi Kang, Xue-Feng Wu

The cold dark matter paradigm successfully explains large-scale structure but faces persistent tensions on small scales. Warm dark matter (WDM) with $\mathrm{keV}$-scale particles can alleviate these issues by suppressing small-scale structure formation. The presence of collapsed structures at high redshifts places strong lower limits on the WDM particle mass $m_x$. Gamma-ray bursts (GRBs) are ideal high-redshift probes due to their extreme brightness. Using the most recent \emph{Swift} GRB data…

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astro-ph.EPastro-ph.GA

KMT-2025-BLG-0975Lb and KMT-2025-BLG-1160Lb: Two Uranus-Mass Planets Beyond the Snow Line Discovered by Microlensing

Cheongho Han, Chung-Uk Lee, Andrzej Udalski, Andrew Gould, Michael D. Albrow, Sun-Ju Chung, Youn Kil Jung, Kyu-Ha Hwang et al.

We present the analysis of two planetary microlensing events, KMT-2025-BLG-0975 and KMT-2025-BLG-1160, discovered during the 2025 Galactic bulge microlensing season through high-cadence survey observations. In both events, short-duration anomalies near the peaks of the lensing light curves reveal the presence of planetary companions. Light-curve modeling yields planet-to-host mass ratios of $q = 8.6 \times 10^{-4}$ for KMT-2025-BLG-0975 and $1.3 \times 10^{-4}$ for KMT-2025-BLG-1160. For KMT-202…

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gr-qcastro-ph.HEastro-ph.IM

GSpyNetTree-O4: an event validation tool used in the fourth LIGO-Virgo-KAGRA observing run

Sofia Alvarez-Lopez, Man Leong Chan, Franz S. Herbst, Dhatri Raghunathan, Airene Ahuja, Annudesh Liyanage, Julian Ding, Alejandro Garcia-Varela et al.

The frequent presence of non-Gaussian transient noise, or glitches, in gravitational-wave detector data can affect gravitational-wave searches, parameter estimation, and downstream analyses. To identify and mitigate transient noise near gravitational-wave candidates in a timely manner, the LIGO-Virgo-KAGRA Collaboration employs the Data Quality Report. In the fourth observing run, GSpyNetTree-O4 was deployed within this framework as a tool for glitch classification and event validation. We descr…

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physics.plasm-phphysics.space-ph

Statistical structure of canonical kinetic equilibrium with sheared flow

Daniel W Crews

In isothermal kinetic equilibrium of a plasma with sheared flow, the electrostatic potential is the cumulant generating function of the velocity distribution, encoding all non-Maxwellian statistics. Consequently, of the polynomial-form flux-function equilibrium flows, only the linear one is admissible, and every other equilibrium sheared flow has non-zero cumulants to all orders. The identity is shown for a sheared-flow screw pinch and specialized to the Z pinch, theta pinch, and Harris sheet. A…

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physics.plasm-phastro-ph.SR

Emergence and Detection of Electron-Scale Current Sheets in Turbulence with MMS Observations and fully kinetic 3D simulations

Zachary Davis, Alexandros Chasepis, Colby Haggerty, Luca Comisso, Derek Sikorski

The solar wind is characterized by turbulence, where a cascade produces intermittent current structures called current sheets (CS) that efficiently dissipate energy into the plasma. These have been studied with in situ spacecraft observations, but single-spacecraft techniques such as the partial variance of increments (PVI) are inherently limited since they lack spatial context. A combined analysis of in situ observations and numerical simulations can provide significant insight into the propert…

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astro-ph.SRastro-ph.HEgr-qc

Magnetic pressure anisotropy in ultra-dense white dwarfs: Landau quantization and neutronization effects

Edson Otoniel, Juan M. Z. Pretel, Victor B. T. Alves, César O. V. Flores, Clésio E. Mota

Strong magnetic fields modify the thermodynamics of white dwarf (WD) matter by quantizing the transverse motion of degenerate electrons into Landau levels and splitting the pressure into components parallel and perpendicular to the magnetic field. We investigate how this microscopic pressure anisotropy affects ultra-dense WD sequences when Coulomb lattice contributions, electron capture thresholds, neutron drip limits, and nuclear composition are treated consistently in the equation of state (Eo…

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astro-ph.GAastro-ph.SR

Radiation-Driven Evolution and Gas Kinematics of the Bright-Rimmed Cloud SFO 25

Puja Porel, Archana Soam, William D. Vacca, Janik Karoly

Bright-rimmed clouds (BRCs) are valuable laboratories for investigating how ionizing radiation from massive stars reshapes molecular clouds and influences star formation. We present a kinematic and dynamical study of the BRC SFO 25 using archival JCMT-HARP observations of the $^{12}$CO, $^{13}$CO, and C$^{18}$O ($J = 3-2$) transitions at an angular resolution of about 14-15 arcsec (0.051-0.054 pc). Gaia parallaxes of young stellar objects associated with the cloud yield a revised distance placin…

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astro-ph.SRnucl-th

Localized magnetic pressure anisotropy in strange dwarfs with crystalline crusts

Mila Leite Garcia Reis, Daniela Eller Uliana, Jaziel G. Coelho, Edson Otoniel

We study equilibrium sequences of magnetized strange dwarfs composed of a self bound MIT bag strange matter core, with \(B_{\rm bag}^{1/4}=145\,{\rm MeV}\), and an ordinary crystalline crust. The aim is to determine how nuclear composition changes and magnetic pressure anisotropy in the crust modify the mass radius relation. The strange core is kept isotropic, while the crust is described either by pure nuclei stopped at the first inverse beta threshold or by electron capture sequences extended…

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astro-ph.GA

Linking dynamics and chemistry in barred galaxies through action-space mapping

Tetsuro Asano, Victor P. Debattista, Michiko S. Fujii

We aim to extend the action-based framework, proposed by a previous study, for assigning chemical information to collisionless $N$-body simulations of barred galaxies, enabling more realistic comparisons with observations. We developed a new method to map chemistry of star-forming $N$-body+hydrodynamical simulations (donor models) onto pure $N$-body simulations (target models) using a matching algorithm. We applied the method to two barred $N$-body galaxies, one Milky Way (MW)-like with a classi…

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astro-ph.GA

A Deep Look at the Ultra-Faint Milky Way Satellite Virgo III with Rubin Observatory Data Preview 2

Aashay Pai, Alex Drlica-Wagner, Peter S. Ferguson, William Cerny, Chin Yi Tan, Jeffrey L. Carlin, Yumi Choi, Željko Ivezić et al.

We analyze the ultra-faint Milky Way satellite Virgo III using data from the Vera C. Rubin Observatory Data Preview 2 (DP2). Virgo III was observed in the Rubin "Cosmic Treasure Chest" (M49) First Look field, which contains 924 visits in the u,g,r,i bands comprising ~10.5hrs of exposure time with LSSTCam. These data are considerably deeper than the majority of DP2, with a $5σ$ limiting magnitude that approaches the expected 10-year depth of LSST (~25.2-26.5mag, depending on band). We report the…

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astro-ph.GAastro-ph.HE

How massive and clumpy must a quasar wind be to create emission line blueshifts?

James H. Matthews

Blue asymmetries (``Blueshifts'') in the C IV 1550A emission line are common in luminous quasars. If they are formed in winds, how much energy, momentum and mass do those winds transport? We address this question by considering how much mass must be supplied through the line-forming region to maintain a given density and ionization state. Using a combination of 1D analytic and 2D numerical models, we find that for blueshifted C IV lines to form in a wind, the wind must have mass outflow rates of…

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astro-ph.GA

The $σ_s^2-\mathcal{M}$ relation in the multi-phase ISM: Exploring the density PDF with the Cloud Factory simulations

Mairi Nonhebel, Rowan J. Smith, Ralf S. Klessen

The density probability distribution (PDF) of molecular clouds is a crucial component of analytical theories of star formation. In idealised simulations of isothermal turbulence, the width of the density PDF, $σ_s^2$, is dependent on the sonic Mach number of the medium, $\mathcal{M}$. The $σ_s^2-\mathcal{M}$ relation is widely used to connect cloud-scale turbulence to the density PDF, and further to star formation activity, yet its validity within individual phases of the multi-phase interstella…

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astro-ph.HEastro-ph.SR

A radio view on Gamma-Loud Protostars: Derivation of jet mechanical luminosity

Javier Méndez-Gallego, Carlos Carrasco-González, Rubén López-Coto, Iván Agudo, Stefano Menchiari, Rubén Fedriani, Emma de Oña Wilhelmi, Guillem Anglada et al.

Context. Gamma-Loud Protostars (GLPs) have been recently reported as Galactic hadronic accelerators whose acceleration site is situated in their protostellar jets. Theoretical and observational analysis situate radio cm luminosity as a thermal tracer of jet activity, presenting an unique opportunity to study jet properties as accelerators. Aims. We aim to develop a way to estimate the kinetic power of protostellar jets and compare their energetics with those extracted from the non-thermal gamma-…

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astro-ph.GA

Observational Tests of Sgr A*'s State of the Accretion Flow

F. Yusef-Zadeh, R. G. Arendt, H. Bushouse, C. J. Chandler, D. Kunneriath, S. M. Ressler, M. Wardle

General relativistic magneto-hydrodynamic (GRMHD) simulations of the possibly magnetically arrested disk (MAD) of the accretion flow of Sgr A* predict short and long time variability, lumpiness in the flow, strong magnetic fields, reconnection driving flux eruptions and a jet aligned with its spin angular momentum. We carried out simultaneous multi-wavelength observations with the objective of placing some constraints on these predictions. Our analysis supports most of the predictions of the MAD…

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gr-qcastro-ph.HEastro-ph.IMcs.LG

Fast, accurate, and differentiable: a neural-network surrogate for NRSur7dq4 precessing binary black hole waveforms

Michael Pürrer, Ashwin Girish, Lucy M. Thomas, Scott E. Field, Vijay Varma

We present a neural network surrogate model that emulates the NRSur7dq4 gravitational waveform model for precessing binary black hole mergers. The surrogate decomposes the waveform into constituent quantities and trains an independent multilayer perceptron (MLP) for each. We validate the surrogate against NRSur7dq4 on 10,000 waveforms spanning its full parameter space ($1 \leq q \leq 4$, $|χ_{A,B}| \leq 0.8$). For representative total masses between 60 and 300 $M_\odot$, median sky-averaged freq…

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astro-ph.SR

Empirical H- and K-band Limb Darkening for 31 CHARA Stars: A Near-Infrared Benchmark for Stellar-Atmosphere Models

Narsireddy Anugu, John D. Monnier, Antoine Mérand, Becky Flores, Alexandre Gallenne, Douglas R. Gies, Mayra Gutierrez, Robert Klement et al.

Limb darkening, the decrease in stellar intensity from the disk center to the limb, encodes the temperature structure and opacity of stellar atmospheres. Direct spatially resolved measurements of this center-to-limb variation remain scarce, especially in the near-infrared. We present interferometric limb-darkening measurements for 31 stars observed simultaneously in the $H$ and $K$ bands with the CHARA Array. The sample spans spectral types F--M and luminosity classes IV--I. The targets are well…

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astro-ph.HE

Simulation of combined radio and radar signals at the Radar Echo Telescope for Cosmic Rays

K. Nivedita, I. Loudon, J. Loonen, P. Allison, J. J. Beatty, D. Z. Besson, A. Connolly, A. Cummings et al.

To explore neutrino astronomy at high energies (> 10 PeV), the Radar Echo Telescope for Cosmic Rays (RET-CR) was developed to assess the feasibility of a radar technique for detecting particle cascades in ice, serving as a precursor to the Radar Echo Telescope for Neutrinos (RET-N). The main concept of RET-CR is that, as a high-energy cosmic-ray air-shower core propagates into the high-altitude ice sheet, a dense secondary-particle cascade is created, which is very similar to that of an in-ice h…

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astro-ph.GAastro-ph.CO

Reaching the Metallicity Floor at $z\sim 10$: Lensed Star Clusters at Cosmic Dawn and Cosmic Noon

Raul Jimenez, Elena Tomasetti, Carmela Lardo, Licia Verde

Origins of globular clusters (GCs) are linked to the assembly of their host galaxies. We analyze star-cluster populations in two strongly lensed systems that bracket Cosmic Dawn and Cosmic Noon: the Cosmic Gems arc (GEMS) at z=9.625, among the first galaxies, and the Sparkler at z=1.378. New STARRED deconvolution photometry of GEMS provides SEDs for ten unique, doubly imaged cluster candidates, while a homogeneous Bayesian analysis places both populations on a common cosmological timeline. The G…

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astro-ph.HEastro-ph.SRgr-qc

Gravitational Wave Modeling of White-Dwarf--Compact-Object Binaries and Observational Outlook

Tristan S. Weaver, David Radice, Donghui Jeong, Victor Liu

We investigate the end stages of circular white-dwarf--compact-object binaries by developing a novel integrator implementing mass transfer and 2.5-order Post-Newtonian kinematics. White-dwarf--compact-object binaries are subject to two phases: a slow inspiral during which binary evolution is dominated by weak-gravity radiation reaction and a quicker ``outspiral" dominated by mass transfer. These systems have unique gravitational waveforms with several characteristic features including an accumul…

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astro-ph.SR

A Test of FeH Line Parameters using DR19 APOGEE spectra of Benchmark M Dwarfs

Anderson Silva-Andrade, Diogo Souto, Katia Cunha, Verne V. Smith, Carlos Allende Prieto, Ricardo P. Schiavon, Verónica Loaiza-Tacuri, Aida Behmard et al.

Recent studies have suggested a mismatch of up to 0.20 dex between iron abundances derived from Fe I and FeH lines in the H-band spectra of M dwarfs, and in this work we investigate the nature of this possible offset. We analyze near-infrared H-band APOGEE spectra of stars in 18 binaries composed of a G-dwarf primary and an M-dwarf secondary, together with four M-dwarf stars having measured angular diameters from the literature, and six M-dwarf members of the Hyades and Coma Berenices open clust…

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cs.LGastro-ph.GAcs.AIstat.ML

Multiclass Classification without Labels via Posterior Simplex Geometry

Raphaël Bonnet-Guerrini, Johann Ioannou-Nikolaides, Troels Petersen, Vincenzo Piuri

In many classification problems, reliable instance-level labels are unavailable. However, it is often possible to construct weakly enriched unlabeled samples: datasets selected by different cuts, sources, populations, or experimental conditions that change latent class proportions without revealing them. Classification without Labels (CWoLa) shows that, in the binary case ($K=2$), a classifier trained to distinguish two impure mixtures with different class proportions can recover an optimal clas…

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astro-ph.SRastro-ph.GA

Investigating the Observational Progenitor Mass Gap in the White Dwarf Initial-Final Mass Relation. I. Cluster Census and Characterization of the First White Dwarfs in the Gap

David R. Miller, Jeremy Heyl, Pier-Emmanuel Tremblay

In recent years, Gaia has been the primary driver of the expansion of the white dwarf (WD) initial-final mass relation (IFMR) in open clusters. The increased sample size has highlighted a pronounced observational gap at progenitor masses of $\simeq2$--$2.7\,M_\odot$, with no spectroscopically confirmed cluster-member WDs in this range. Analysis of the Milky Way open cluster census shows that this absence is primarily driven by the scarcity of appropriately aged, nearby clusters capable of hostin…

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gr-qcastro-ph.HE

Tidal deformation of an accreting compact object

Avijit Chowdhury, Chiranjeeb Singha, Kazuharu Bamba, Sumanta Chakraborty

Tidal deformation of a compact object serves as a sensitive probe of the strong-gravity regime and nature of the compact object. It captures how a compact object responds to the external perturbing field of a companion. In realistic astrophysical settings, compact objects are typically immersed in matter-rich environments, which can significantly alter the response. In this work, we investigate the static deformability of Schwarzschild-like exotic compact objects (ECOs) embedded in a quasi-stati…

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astro-ph.GA

Using Scattered Near-Infrared Light to Map Water Ice in Prestellar Cores with SPHEREx

Tamojeet Roychowdhury, Jennifer B. Bergner, Jens Kauffmann, Thushara G. S. Pillai, Silvia Spezzano

We present the first coreshine-derived, spatially-resolved maps of the 3 $μ$m H$_2$O ice absorption feature in four prestellar cores, using SPHEREx spectra. Ices are a key component of dense cores in molecular clouds, playing a central role in the chemistry of planet formation around young stars. However, spatially resolved abundance studies remain limited, typically relying on unevenly distributed background star sightlines. Here, we take advantage of the all-sky spectrophotometric capabilities…

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astro-ph.GAastro-ph.HE

S301 and friends: Measuring the spin of Sgr A*

T. Piran, P. Amaro-Seoane, B. Aytac, G. Bourdarot, A. Burkert, D. Calderon, J. Cuadra, F. Eisenhauer et al.

The discovery of S301 (GRAVITY Collaboration et al., 2026) with pericenter distance rp= 280rg and eccentricity e=0.9825, opens the prospect of measuring the spin parameter of Sgr A* through Lense--Thirring (LT) nodal precession. A major obstacle is Newtonian confusion: any non-spherical extended mass distribution can also induce nodal precession. We aim to separate the LT spin signal of S301 from the Newtonian nodal precession. We compare the secular Newtonian torque exerted by a disk or flatten…

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astro-ph.GA

Observational Evidence for Anisotropic Metal Excess around Galaxies

Cheqiu Lyu, Enci Wang, Zeyu Chen, Chengyu Ma, Yangyao Chen, Haoran Yu, Xu Kong

The exchange of matter and energy between galaxies and their surroundings drives the cosmic baryon cycle, yet mapping metal transport remains an observational challenge. While simulations predict that galactic winds escape anisotropically along minor axes, evidence for chemical enrichment in neighboring galaxies is limited. We analyze 1,433 galaxy pairs from the Dark Energy Spectroscopic Instrument survey and detect a gas-phase metallicity excess of 14.6% $\pm$ 3.7% to 24.2% $\pm$ 2.6% in neighb…

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astro-ph.SRastro-ph.IM

Syntriod: A Robust Initial Parameter Estimator for Radial Velocity Curve Solutions Beyond Conventional Sampling Limits

Emre Barbaros, Hasan Ak, N. Filiz Ak

We present Syntriod, an orbital-phase domain radial velocity (RV) template-based algorithm designed to provide robust initial orbital parameter estimates for spectroscopic binaries across diverse observational sampling conditions. Rather than performing full orbital inference, Syntriod constrains the parameter space with physically consistent solutions to guide subsequent optimization procedures. We evaluate its performance using 10,000 synthetic Keplerian orbits spanning diverse configurations…

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astro-ph.COastro-ph.GAastro-ph.IM

Interlopers as Signal in Line Intensity Mapping

Anirban Roy

Line intensity mapping measures the combined emission of atomic and molecular lines from unresolved galaxies, offering a way to map cosmic structure across enormous volumes. A single observed frequency, however, contains emission from several spectral lines at different redshifts. These interlopers are usually removed before cosmological inference. We show that this removal is not always optimal. Once the possible emitting lines and their redshifts are included in the model, interlopers become a…

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astro-ph.GAastro-ph.HE

Vigorous turbulence driven by quasar-mode feedback in a cluster core

Satoshi Yamada, Shutaro Ueda, Hirofumi Noda, Yutaka Fujita, Misaki Mizumoto, Kentaro Nagamine, Claudio Ricci, Shoji Ogawa et al.

Quasars are among the most luminous objects. They are powered by accretion onto supermassive black holes. They are thought to impact cosmological evolution primarily through energetic winds, known as quasar-mode feedback, yet the efficiency and spatial extent of this process remain poorly constrained. Here we present X-Ray Imaging and Spectroscopy Mission (XRISM) observations of H1821+643---the nearest galaxy cluster with a central quasar (redshift z = 0.297)---which was a rare opportunity to di…

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astro-ph.IMphysics.optics

Demonstrating the integration of a photonic lantern with an all-fiber-based nulling interferometer

Jordan Diaz, Rebecca Jensen-Clem, Philip M. Hinz, Daren Dillon, Pradip Gatkine, Aditya R. Sengupta, Dan Sirbu, Sarah Tedder et al.

High-contrast imaging of Solar System scale exoplanets and protoplanets demands advancements in instrumentation to access deeper starlight suppression at smaller angular separations than today's state-of-the-art. The multi-mode to single-mode conversion capabilities of photonic lanterns (PLs) provide new avenues to implement techniques such as nulling interferometry due to the inherent spatial filtering of single-mode waveguides. In this work, we present laboratory results on an all-fiber-based…

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