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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.EPastro-ph.SR

Early Planet Formation in Embedded Disks (eDisk). XXV. Inclination-Induced Minor-Axis Brightness Asymmetries Reveal Limited Dust Settling in Embedded Protostellar Disks

Sidhant Kumar Suar, Zhe-Yu Daniel Lin, Zhi-Yun Li, Nagayoshi Ohashi, Shigehisa Takakuwa, John Tobin, Leslie Looney, Mayank Narang et al.

How and when dust settles in young protostellar disks is a key open question for the dust concentration needed to form planetesimals and, ultimately, planets. However, directly measuring the vertical dust distribution in embedded (Class 0/I) systems remains challenging. We show that brightness asymmetry along the minor axis of highly inclined disks provides a simple, powerful geometric diagnostic of vertical dust structure. Using radiative transfer modeling with RADMC-3D, we generate synthetic c…

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astro-ph.IM

The AI crisis for teaching: "Train your own neural network!"

Douglas Scott

Everyone seems to be thinking about so-called artificial intelligence (AI) these days. As scientists, we understand that we're not about to have a conscious computer intelligence taking over the world, but we're nevertheless concerned about how "large language models" (LLMs) and AI "agents" are impacting the way that we do science. This concern has generated several recent essays about the effects of AI on research, including in my own field of astronomy and astrophysics. These opinion pieces te…

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astro-ph.HE

Correlating Surface Magnetic Field Decay with Internal Field Depth of Isolated Neutron Stars

Kathleen Sellick, Subharthi Ray

The long-term evolution of neutron star crustal magnetic fields through Ohmic decay is governed by the transport properties of the crust. In this work, we demonstrate that the depth at which the magnetic flux is anchored plays a significant role in the dissipation timescale. We study the evolution of the magnetic field at the surface of the neutron star due to the crustal field evolution, under the assumption of Ohmic diffusion in a curved spacetime. We employ a cumulative distribution function…

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astro-ph.GAastro-ph.CO

The impact of primordial magnetic fields on the formation of galaxies

Yao-Yu Li, Shihong Liao, Yue-Lin Sming Tsai, Yi-Zhong Fan

Primordial magnetic fields (PMFs), potentially generated during cosmic inflation or early-universe phase transitions, can modify cosmic structure formation by enhancing the post-recombination matter power spectrum. In this work, we investigate the impact of PMFs on galaxy formation using a suite of high-resolution cosmological hydrodynamical simulations evolved to $z=0$. Our simulations are initialized with PMF-induced enhancements to the matter power spectrum and include more comprehensive bary…

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astro-ph.IM

The Astronomical Hub: A Unified Ecosystem for Modern Astronomical Research

Yerlan Aimuratov, Vitaliy Kim, Aleksander Serebryanskiy, Denis Yurin, Maxim Krugov, Chingiz Akniyazov, Saule Shomshekova, Maxim Makukov et al.

We present the conceptual framework of the Astronomical Hub (AstroHub), a unified platform combining various optical instruments at a single observatory. Its major approach lies in arranging conditions for research groups to install telescopes and equipment and participate in joint projects. AstroHub is planned to integrate Virtual Observatory (VO) tools, FAIR data principles, and a telescope network to create a powerful and attractive ecosystem for both robust near-Earth object (NEO) monitoring…

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astro-ph.IMastro-ph.EPcs.LG

A Missing Latent, Not a Missing Simulator: Radius-Augmented Inference for Real JWST Retrieval

Angshuman Chakravertty, P V V Raj

Amortized simulation-based inference (SBI), which is trained on radiative-transfer simulators, recovers exoplanet atmospheres accurately on synthetic James Webb Space Telescope (JWST) spectra but collapses when it comes to real reduced spectra. The flow posterior collapsed on real WASP-39b (importance-sampling effective sample size (ESS) = 1, best-fit \c{hi}2/N = 301), and such a failure is usually blamed on missing the forward-model physics, but ruling these levers out with nested sampling firs…

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astro-ph.HEastro-ph.CO

Electromagnetic Counterparts of Stellar-mass Binary Black Hole Mergers in AGN Accretion Disks: Theoretical Models and Observational Status

Lei He, Liang-Gui Zhu, Ken Chen, Zi-Gao Dai, Ye-Fei Yuan, Jian-Min Wang, Wen Zhao

The discovery of the binary neutron star merger GW170817 and its electromagnetic counterparts marked the beginning of the era of multimessenger gravitational-wave astronomy. In contrast, binary black hole (BBH) mergers, which constitute the majority of gravitational-wave sources detected to date, are generally expected to be electromagnetically dark. However, if BBH mergers occur within the dense gaseous environments of active galactic nucleus (AGN) accretion disks, interactions between the merg…

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astro-ph.GA

AGC 322753: a Dark Galaxy Candidate detected by ALFALFA and FASHI

Marco Monaci, Duncan A. Forbes, Warrick J. Couch, Jean P. Brodie

We report the possible detection of a Dark Galaxy Candidate (DGC; AGC 322753), via the cross-matching of the Arecibo Legacy Fast ALFA (ALFALFA) and the FAST All Sky HI (FASHI) HI blind surveys. It is detected by both surveys at the same recessional velocity, with a comparable HI mass of $2\times10^{9}$ M$_\odot$, and with similar HI spectral features. The ALFALFA and FASHI spectra show a double-peaked profile, compatible with a disc-like ordered rotation, and an HI linewidth at 50 per cent of th…

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astro-ph.IMastro-ph.CO

The Simons Observatory: Design and Initial Performance of the Detector Readout System for the Large-Aperture Telescope

Thomas P. Satterthwaite, Tristan Pinsonneault-Marotte, Shawn W. Henderson, Zeeshan Ahmed, Kam Arnold, Declan Baker, Andrew Bazarko, Josh Borrow et al.

We present the design, implementation, and initial performance of a highly multiplexed cryogenic superconducting detector readout system in the context of its deployment to the Simons Observatory large-aperture telescope (LAT). The Simons Observatory is a cosmic microwave background experiment located at 5,200 m in Chile's Atacama Desert. In addition to its 6 m LAT, whose broad range of science goals spans probing large-scale structure to searching for new Solar System objects, the observatory a…

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astro-ph.HEgr-qc

Improved Population and EOS Joint Inference for Binary Neutron Star Systems

Marc Ebiri, Richard O'Shaughnessy

The extreme environment within neutron stars presents the opportunity to probe the nuclear equation of state at high densities while studying the properties of these stellar remnants. Historically, the equation of state and neutron star mass distribution have been inferred separately, with the latter often simply assumed to be fixed in studies of the former, but the dependence of the equation of state on neutron star mass indicates they should be inferred together. In this work, we extend the ge…

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astro-ph.GAastro-ph.CO

Stacked strong and weak lensing united: Improved measurement of the stellar and dark matter distributions in massive early-type galaxies at $z\sim 0.5$

Momoka Fujikawa, Masamune Oguri

We present a new measurement of the stellar and dark matter distributions in massive early-type galaxies at redshift $0.4<z<0.6$ by combining stacked strong and weak lensing measurements. The stacked weak lensing measurements down to the small radius of $0.013\,\mathrm{Mpc}/h$ enabled by the Subaru Telescope Hyper Suprime-Cam data are combined with stacked enclosed projected mass measurements from 13 strong lens systems. We find that adding strong lensing constraints improves constraints on the…

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astro-ph.GA

The "Fork" Geometry in the DESI Main Survey DR1: Implications of Target Selection for Galaxy Evolution Studies

A. Nigoche-Netro, P. Lagos, R. J. Diaz, E. García-Manzanárez, J. A. Quezada-Pérez, R. Ibarra-Nuño

The Dark Energy Spectroscopic Instrument (DESI) Main Survey Data Release 1 (DR1) provides an unprecedented spectroscopic view of galaxies and quasars across a large fraction of the observable Universe. However, the survey's tracer-dependent targeting strategy introduces complex observational selection effects that strongly influence the apparent distribution of galaxies in the redshift-luminosity plane. In this work, we investigate the origin of the characteristic "fork" geometry observed in DES…

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astro-ph.GA

The impact of the turbulent Mach number on star formation and the initial mass function

Sajay Sunny Mathew, Christoph Federrath, Amit Seta

Turbulence regulates star formation by influencing the density structure and fragmentation of molecular clouds, and therefore it is expected to play a key role in setting the initial mass function (IMF). We study how the strength of the turbulent shocks affects star formation and the IMF by comparing a series of magnetohydrodynamical (MHD) simulations of star cluster formation in clouds with three different rms Mach number values, $M=2.5, 5$, and $10$, but otherwise the same Alfvén Mach number (…

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astro-ph.EP

Planetesimal Formation under Realistic Gas Dynamics: Dust Concentration in Turbulent and Windy Protoplanetary Disks

Pinghui Huang, Xue-Ning Bai

Planetesimals are a key intermediate stage of planet formation and originate from dust concentration in protoplanetary disks, which is strongly regulated by gas dynamics. In this study, we use the multifluid dust module of Athena++ to investigate dust concentration in 2D axisymmetric global non-ideal MHD (ambipolar diffusion, AD) simulations of outer disks. Our simulations simultaneously launch large-scale MHD disk winds and resolve both streaming instability (SI) and vertical shear instability…

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astro-ph.IM

MATCH: Performance Characterization and Scientific Observations of the Wuhan University 1-m Optical Telescope

Sai-En Xu, Bei You, Han He, Shuai-Kang Yang, Xiao Fan, Yi-Fei Qu, Rui-Xiang Hu, Hui-Bo Fei et al.

The Multi-mode Autonomous Terminal for Compatible Hybrid-optics (MATCH), operated by Wuhan University and located at Lenghu, is a 1-m Ritchey--Chrétien telescope equipped with imaging and spectroscopic instruments. MATCH has been in trial operation since October 2025. In this work, we present the telescope and instrument configuration, characterize its performance during the first year of operation, and describe the integrated observing workflow developed for routine and time-domain observations…

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astro-ph.HE

Pulsar glitches triggered by quakes when stress reaches a threshold

Zixuan Zhou, Ruipeng Lu, Weiyang Wang, Han Yue, Renxin Xu

The starquake model of pulsar glitches is revisited in light of accumulated observational data. A statistical comparison between the time-predictable and the magnitude-predictable models, borrowed from seismology and grounded in the classical spring-slider framework, is performed against a sample of 245 glitch events from 9 pulsars. It is found that the data supports the time-predictable model, i.e., a quake resulting in a glitch could be triggered when the developed stress reaches a critical th…

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physics.space-ph

Revisiting magnetotelluric theory: layered induction and geoelectric fields

Dennies Bor

We review the magnetotelluric (MT) theory of a horizontally layered Earth under plane wave forcing and its use in calculating geoelectric fields. Starting from Maxwell's equations, we derive the diffusion approximation and the impedance recursion by matching electric and magnetic fields at layer boundaries. The equivalent transmission line connects the surface impedance to attenuation with depth, apparent resistivity, phase, and the electric response to a magnetic time series. Three evaluations…

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astro-ph.SR

Magnetic field diagnostics of a solar active region filament

Daiki Yamasaki, Yu Wei Huang, Yuki Hashimoto, Satoru UeNo, Kiyoshi Ichimoto

We performed spectropolarimetric observations of an active region filament in He I 10830 angstrom and Si I 10827 angstrom lines to investigate its magnetic field structure. We carried out full-Stokes inversions with the HAZEL code, which takes into account the Zeeman and Hanle effects. As a result, we yielded a mean field strength of 101 $\pm$ 33 G and a horizontal field nearly parallel to the filament axis, such that the distinction between the two classical normal- and reverse-polarity models…

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physics.ins-detastro-ph.IM

Kilopixel Performance of the Kinetic Inductance Detectors for the Terahertz Intensity Mapper

Justin S. Bracks, Reinier M. J. Janssen, Steve Hailey-Dunsheath, Talia Saeid, Bruce Bumble, Logan Foote, Elijah Kane, Lun-Jun Liu et al.

We characterize a flight-grade array of lumped-element kinetic inductance detectors (LEKIDs) developed for the long-wavelength module of the Terahertz Intensity Mapper (TIM). From an 864-pixel science array, we select 490 well-isolated resonators spanning the focal plane and readout band and measure their thermal response, optical responsivity, and noise using a ZCU111-based multitone readout system intended for flight. The thermal and optical response of the detector population is consistent wi…

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astro-ph.HE

HLX-1 as a Repeating Partial Tidal Disruption Event around an Intermediate-Mass Black Hole

Fangyuan Yu, Andrew Mummery, Muryel Guolo

ESO 243$-$49 HLX--1 is one of the first known compelling intermediate-mass black hole (IMBH) candidates, but the origin of its recurrent X-ray outbursts remains unsettled. In this work we fit the HLX--1 outbursts simultaneously with a relativistic thin-disk time-dependent model. The black-hole and disk-geometry parameters are tied across epochs, while the injected mass and timing parameters are fitted separately for each outburst. We also include a contemporaneous \textit{HST} UV/optical/IR spec…

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astro-ph.HE

New Constraints on $r$-process Nucleosynthesis in Neutron Star Mergers from GW170817 Late-Phase Spectra

Salma Rahmouni, Masaomi Tanaka, Daiji Kato, Gediminas Gaigalas, Kenta Hotokezaka

The neutron star merger event GW170817 provided the first direct evidence of $r$-process nucleosynthesis. Observed spectra of its electromagnetic counterpart AT2017gfo exhibited several features that encode information on the nature and abundance of the synthesized $r$-process elements. In this study, we investigate the late nebular-phase spectral features of AT2017gfo, which provide important probes of the elemental abundance of the ejecta. We construct an analytic spectral model that computes…

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astro-ph.EPastro-ph.IMnlin.AOphysics.data-anstat.AP

A Probabilistic Trajectory and Dispersion Study of Martian Tumbleweed Rover Swarms in Global Dust Storm Conditions

Emma-Catherine Belhadfa, Gabriele MT D'Eleuterio

Global Dust Storms (GDSs) dominate the Martian climate, yet the mechanisms of dust lifting, transport, and deposition remain poorly constrained because in situ observations are limited: landers are stationary, and their Radioisotope Thermoelectric Generators (RTGs) contaminate local measurements. Our solution is a swarm of lightweight, wind-propelled spherical rovers -- Dust Rovers (DRs) -- that follow natural wind patterns to collect high-spatial-resolution in situ dust data during storms. Here…

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astro-ph.HE

Chandra X-ray Spectral Evidence of the Dual AGN Nature of the Gravitational lens MG B2016+112 at z=3.273 with 175 pc separation

Daniel A. Schwartz, Julia M. Sisk-Reynes, Anna Barnacka

We use a new 175 ks Chandra X-ray observation of the z=3.273 radio-loud gravitational lens system MG B2016+112 to present definitive X-ray spectral evidence that it contains a dual active galactic nucleus (AGN). With a projected separation of 175 parsecs, this is the tightest separation confirmed AGN pair at high redshift. Prior multi-epoch very long baseline interferometry (VLBI) and archival Chandra data had revealed two distinct emitters, but could not rule out a single AGN with a complex, hi…

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astro-ph.SR

Sunrise III/SUSI reveals extended and spectrally structured Ca II K emission above the solar limb

Ivan Milić, Christopher M. J. Osborne, Francisco A. Iglesias, Juan Sebastián Castellanos Durán, Damien F. Przybylski, Lakshmi Pradeep Chitta, Sanghita Chandra, Andreas Lagg et al.

The Sunrise III/SUSI instrument performed a sit-and-stare observation of the off-limb emission in the Ca II K line core, with a combination of excellent temporal and spectral resolution. The emission reaches up to 6 Mm above the solar limb, indicating the existence of off-limb structures akin to spicules. In this letter, we describe the spatio-spectral properties of the observed emission, focusing on the spectral line shape resolved in detail by Sunrise III/SUSI, and compare the observation with…

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astro-ph.HE

Angular structure of finite-field vacuum birefringence in magnetars

Shahram Abbassi, S. R. Valluri

Vacuum birefringence in a strong magnetic field is often modelled by combining the finite-field splitting for perpendicular propagation with the familiar $\sin^2θ$ angular factor. That separation is exact only at leading response order. Continuing our previous study of the field-strength dependence of the birefringence, we examine the angular dependence of the full one-loop refractive indices in the local Heisenberg--Euler theory. We show analytically that, on the positive-birefringence branch,…

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astro-ph.EPastro-ph.IM

aRieL - Reinforcement Learning for the Ariel Space Telescope Scheduling

James Kostas Ray, Kai Hou Yip, Alexandra Thompson, Luís F. Simões, Nikolaos Nikolaou

The Ariel mission will conduct a population level survey of hundreds of exoplanet atmospheres, requiring observations to be scheduled across a large and diverse catalogue of potential targets. By framing Ariel scheduling as a long-horizon optimisation problem in which individual decisions affect both mission time and the scientific opportunities available later in the survey, Reinforcement Learning (RL) can be utilised as a framework for target selection. We introduce aRieL, a simulated observin…

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astro-ph.HE

Nonthermal hotspot orbiting the supermassive black hole Sgr A*

Alejandro Cruz-Osorio, David Barrero-González, Juan J. Zaldívar, Yosuke Mizuno

Recent millimeter wavelength observations at 230 GHz by the Event Horizon Telescope have resolved the innermost structure of the Galactic Center, Sgr A*, revealing a ring-like structure consistent with synchrotron emission from a magnetized torus surrounding a supermassive black hole. These observations reveal two key features: three prominent hotspots near the photon ring and low light-curve variability, with a modulation index of $\barσ/\barμ \lesssim 0.1$. State-of-the-art general relativisti…

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astro-ph.GAastro-ph.HEastro-ph.SR

A triple-induced merger in T Ori C, solves the proplyd lifetime problem and the curiously young shell of M42

Maite Wilhelm, Alessandro Alberto Trani, Simon Portegies Zwart

There has long been a tension between the stellar ages in the Orion Nebula Cluster and the rapid external photoevaporation of its protoplanetary discs. Recently, the shell of the Orion Nebula has similarly been found to be dynamically younger than the stars. We propose a new scenario to resolve both age problems. In our scenario the ONC's most massive star, $θ^1$~Ori~C1, formed from the merger between two binary stars induced by vZLK oscillations due to the present-day binary companion $θ^1$~Ori…

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astro-ph.EP

Modeling of the Yarkovsky effect. I. Thermal dependence

O. Golubov, O. Mikhalchenko, V. Lipatova, D. J. Scheeres

We investigate how the Yarkovsky effect created by one flat surface element on the asteroid depends on the thermal parameter. Then we integrate the Yarkovsky force over the surface of a spherical asteroid. In the next articles of the series, we will investigate the Yarkovsky force for bodies of more complicated shape and compute the change of the asteroid's orbit. Using perturbation theory, we analytically solve the one-dimensional heat conduction equation under the surface element and use the s…

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astro-ph.HEgr-qc

Relativistic Spherical Accretion in Nonrotating Black Hole Spacetimes: Astrophysical Implications

David Barrero-González, Alejandro Cruz-Osorio

We present a systematic analysis of spherically symmetric accretion flows onto thirteen non-rotating black hole spacetimes, including charged and regular black holes, scalar and dilaton fields, dark energy, cosmological constants, modified gravity, and parametrized metrics. We generalize the Michel solution to arbitrary diagonal spacetimes and investigate the density, temperature, velocity, Mach number, mass accretion rate, and bremsstrahlung luminosity equilibrium profiles. Using the Schwarzsch…

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