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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.EPastro-ph.IM

Hybrid Spin-Orbit Tomography for Earth-like Planets: Simultaneous Mapping of Static Surfaces and Dynamic Clouds from Multicolor Light Curves

Atsuki Kuwata, Hajime Kawahara

Photometric variability of directly imaged exoplanets encodes information on both persistent surface features and time-variable phenomena such as clouds. We present Hybrid Spin-Orbit Tomography, a method that simultaneously retrieves multiple static components and a single dynamic component, together with their reflection spectra, from multiband photometric variability. The method integrates spectral unmixing and dynamic spin-orbit tomography by introducing a time-dependent component into the fo…

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astro-ph.SR

The changing optical and X-ray emission of the dormant $γ$ Cas star HD 45314

G. Rauw, Y. Nazé, E. Bryssinck, W. Vollmann, J. Guarro Fló, X. Dupont, M. A. Smith, C. Motch et al.

$γ$ Cas stars are Oe/Be stars that exhibit bright and hard X-ray emission. HD45314 belonged to this category, but lost its $γ$ Cas characteristics as its circumstellar disc started to fade away. The star was monitored in optical spectroscopy, optical photometry, and X-ray spectroscopy to follow its variability on timescales of hours to years. Time series of magnitudes, colours, line equivalent widths and violet over red peak intensity ratios were analysed with Fourier methods to uncover possible…

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astro-ph.SRphysics.plasm-ph

Connecting Dynamo Theory with DNS Data: A Computational Analysis of α and \b{eta} Effects

Kiwan Park

We investigate the influence of current helicity on the turbulent magnetic diffusivity $β$ using three complementary derivations of the $α$ and $β$ coefficients, based on the large-scale magnetic field $\overline{\mathbf{B}}$, the turbulent velocity $\mathbf{u}$, and the turbulent magnetic field $\mathbf{b}$. Applying these coefficients to raw DNS data, we reconstruct $\overline{\mathbf{B}}$ and compare the results with the original simulations. In the kinematic regime all models agree well with…

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astro-ph.SRphysics.plasm-ph

Connecting Dynamo Theory with DNS Data: A Computational Analysis of $α$ and $β$ Effects

Kiwan Park

We investigate the influence of current helicity on the turbulent magnetic diffusivity $β$ using three complementary derivations of the $α$ and $β$ coefficients, based on the large-scale magnetic field $\overline{\mathbf{B}}$, the turbulent velocity $\mathbf{u}$, and the turbulent magnetic field $\mathbf{b}$. Applying these coefficients to raw DNS data, we reconstruct $\overline{\mathbf{B}}$ and compare the results with the original simulations. In the kinematic regime all models agree well with…

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astro-ph.GAastro-ph.SR

Tracing M22's origins: Spatial and chemical constraints on its formation history

Emanuele Dondoglio, Antonino P. Milone, Randa Asa'd, Anna F. Marino, Alessandra Mastrobuono-Battisti, Fabrizio Muratore, Tuila Ziliotto, Emanuele Bortolan et al.

Globular clusters (GCs) are well known to host stellar populations characterized by light-element variations. A subset of Galactic GCs, beyond such 'canonical' populations, contains an additional group enriched in iron, s-process elements, and total C+N+O abundance (i.e., the anomalous stars). We combine multi-facility photometry with APOGEE spectroscopy to investigate the spatial distribution, chemical properties, and formation history of the stellar populations in M22, with particular focus on…

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astro-ph.HEastro-ph.SR

1LHAASO J1852+0050u: GeV-100TeV Gamma-ray emission Powered by Star-forming Region?

The LHAASO Collaboration

Star-forming regions (SFRs), including HII regions, have recently attracted significant attention as potential sites of particle acceleration capable of producing PeV cosmic rays, i.e. as potential Galactic PeVatrons. Yet, SFRs known as candidate PeVatrons are still very rare. Here we report a highly likely physical association between the UHE gamma-ray source 1LHAASO J1852+0050u and coincident star-forming regions. Using $\sim$4 years of LHAASO data, the extended source 1LHAASO J1852+0050u (cal…

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astro-ph.SRastro-ph.EPastro-ph.IM

Automated Detection of Double-Lined Spectroscopic Binaries in High-Resolution Spectra and a Probabilistic Analysis of Stellar Multiplicity

William B. Salazar, Steven Giacalone, Andrew W. Howard

The characterization of Sun-like stars, including determining whether those stars are single or have stellar companions, has become increasingly important for missions seeking planets beyond the Solar System. With upcoming missions like the Habitable Worlds Observatory (HWO) on the horizon, vetting stars for binarity and confirming potential targets as viable is essential precursor science. In this paper, we present an automated algorithm that searches for double-lined spectroscopic binaries (SB…

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astro-ph.GAastro-ph.CO

CROCODILE-SIDM: Tidal Formation of Dark Matter-Deficient Galaxies as a Test Case

Kenji Kihara, Kentaro Nagamine, Lissandre Bourrat, Leonard Romano, Yuri Oku, Daisuke Toyouchi

We introduce CROCODILE-SIDM, a framework for treating self-interacting dark matter (SIDM) with the $N$-body part of GADGET4-Osaka code, as part of CROCODILE simulation family. As a test case, we investigate the impact of SIDM on the tidal formation of dark matter-deficient galaxies (DMDGs) with velocity-dependent cross-section models. We demonstrate that our implementation reproduces the analytic scattering rate in isolated halos. Including dynamical friction self-consistently, we evolve a dwarf…

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astro-ph.HEastro-ph.GA

Aarmed with Data: Bumps, Outflows, and Disk-like Emission in TDE 2025aarm

Aysha Aamer, Kate D. Alexander, Charlotte R. Angus, Panos Charalampopoulos, Iair Arcavi, Giorgos Leloudas, Matt Nicholl, Jennifer Andrews et al.

The origin of the optical emission in tidal disruption events (TDEs) remains one of the major outstanding questions in the field, in part due to the limited number of nearby events with high-cadence monitoring to track their evolving photometric and spectroscopic properties. We present multi-wavelength observations of the nearby ($z=0.01368$) TDE\,2025aarm, including near-daily spectroscopic coverage prior to the optical peak. Its proximity makes it one of the brightest TDEs discovered, reaching…

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astro-ph.SR

The FU Ori outburst of PR Ori B

Carlos Contreras Pena, Zsofia Nagy, Gregory Herczeg, Jeong-Eun Lee, Agnes Kospal, Peter Abraham, Doug Johnstone, Bo Reipurth et al.

We report the discovery of a nearby FU Ori-type outburst (FUor), PR Ori B, in the L1641 cluster of the Orion star-forming region. The high-amplitude variability was first identified in the NEOWISE (3-5 $μ$m) photometry of the unresolved PR Ori binary system. Long-term, resolved optical photometric monitoring demonstrates that PR Ori B is the driver of a $ΔG=5~$mag outburst, while PR Ori A has remained constant over the last 20 years. The near-IR spectrum of PR Ori B changes from a late K-type sp…

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astro-ph.HE

The Evolution of Thermal and Non-thermal Emission Components in GRB 250920C

Jia-Ming Chen, Ke-Rui Zhu, Shan Chang, Dan Zhu, Yu-Lu Gong, Zhao-Yang Peng, Yong-Gang Zheng, Li Zhang et al.

We present a temporal and time-resolved spectral analysis of GRB 250920C using \textit{Fermi}/GBM and \textit{Swift}/BAT data. The prompt emission consists of two distinct episodes, EI and EII, separated by a significant quiescent interval. We perform Bayesian spectral fitting with empirical, thermal, composite, and physical synchrotron models. In EI, the spectra show clear evidence for an additional thermal component. The BB+PL model is preferred in most bright time bins, and joint \textit{Ferm…

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astro-ph.HE

Searching for Type Ia Supernovae in the Dark Energy Spectroscopic Instrument

Xiaoyu Zhuang, Song Ran, Dezheng Meng, Weiyu Ding, Ranfang Zheng, Yao Yao, Zheyu Lin, Bingxue Fu et al.

With the development of large-scale photometric surveys, an increasing number of supernova candidates are being discovered, leading to a rapidly growing demand for supernova spectra. In addition to equipping photometric surveys with follow-up spectroscopic facilities, archival spectra from large multi-object spectroscopic surveys can be mined to provide spectroscopic classifications for candidates and to find supernovae missed by previous surveys. In this work, we combine Principal Component Ana…

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astro-ph.HE

Pulse Signal Simulation of Pulsars

Jalormi Brahmachari, Mayuresh Surnis

The present thesis is a work in progress on improving the simulation of integrated pulse profiles of pulsars. Pulsars, highly magnetized rotating neutron stars, serve as precise cosmic clocks useful for studying gravity and the interstellar medium. Although periodic pulses from many pulsars are observed and modeled at differ- ent radio frequencies, a robust realistic simulation of their profiles utilizing their parameters remain underdeveloped. The present study focuses on developing a physicall…

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astro-ph.GAastro-ph.SR

High Resolution Spectroscopic Follow-up Observation Results for 13 EMP Candidates Selected by Narrow-band Photometry

Huiling Chen, Yang Huang, Huawei Zhang, Zhen Guo

Extremely metal-poor (EMP; [Fe/H] < -3.0) stars preserve key information about the earliest stages of Galactic chemical evolution. Based on a training set of spectroscopic metallicities, we constructed catalogs of more than 120,000 EMP candidates from large-scale narrow-band photometric surveys. To validate this approach, we obtained high-resolution CFHT/ESPaDOnS spectra for 13 candidates selected from the SkyMapper-based catalog. The follow-up observation confirms that the narrow-band photometr…

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astro-ph.IMastro-ph.EPastro-ph.SR

A pilot study on the CSST astrometric capability: Detecting astrometric binaries with Gaia synergy via simulated data

Shangyu Wen, Shilong Liao, Zhaoxiang Qi, Zhensen Fu, Xiyan Peng, Ye Ding, Qiqi Wu, Qi Xu et al.

Context. The China Space-station Survey Telescope (CSST) will provide deep, wide-field epoch astrometry during its 10-year mission. Astrometric binary orbits constrain the masses of stellar and compact-object components. Orbital recovery depends on astrometric precision and temporal coverage. Combining CSST and Gaia data extends the baseline and improves binary detection. Aims. We evaluate CSST, Gaia, and joint astrometry for binary-candidate selection and 12-parameter (12p) orbit fitting at fai…

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astro-ph.SRastro-ph.GA

Planetary Nebula Central Stars as Tracers of Planetary Nebula-Star Cluster Associations in the Galaxy

Vasiliki Fragkou, Luis Lomelí-Núñez, Dante Minniti, Arianna Cortesi, Denise R. Gonçalves

Planetary nebulae (PNe) that are physically associated with star clusters are rare but crucial for stellar evolution studies because they allow their initial and final stellar properties to be determined independently, contributing to constraints on the initial-to-final-mass relation (IFMR), which traces stellar mass loss. Although the identification of such pairs is essential, most reported cases have been identified incidentally rather than through systematic searches. Here, we attempt to unco…

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astro-ph.GAastro-ph.HE

Time-Domain Dust Astrophysics. II. TransRAT: Time-Dependent Grain Alignment and Disruption by Cosmic Transients and Their Observational Signatures

Thiem Hoang

We introduce {\it TransRAT}, a self-consistent time-domain framework that follows the coupled dynamical response of dust to transient irradiation and predicts its observable signatures. We apply {\it TransRAT} to a Type~IIP supernova illuminating a one-zone molecular cloud. Radiative heating raises the grain temperature, modifying the magnetic susceptibility and Larmor precession, while the enhanced radiation field accelerates radiative precession and can switch the alignment axis from the magne…

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astro-ph.GA

Phase-Spirals Across Galactic Disks II: Using large-scale "macro-spirals" in phase-spiral amplitude to derive perturbation times

Kiyan Tavangar, Kathryn V. Johnston, Jason A. S. Hunt, Axel Widmark, Vandana G. Kaushik, Adrian M. Price-Whelan

Phase-space spirals in the Milky Way disk are a key observable remnant of recent perturbations to the Galaxy. They provide insight into the disk's potential, dynamical evolution, past interactions, and even substructure. However, the complex dynamics of phase-spiral formation and evolution have made clear interpretations challenging. For example, recent work has shown that the "winding time" -- measured from how tightly wound a phase-spiral is -- is a biased estimate of the true time since the i…

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astro-ph.HEastro-ph.GA

First Detection of Radio Polarization During Jet Formation in the Changing-Look AGN 1ES 1927+654

Onic I. Shuvo, Eileen T. Meyer, Sibasish Laha, Agniva Roychowdhury, Dev R. Sadaula, Tracy E. Clarke, Wendy M. Peters, Mitchell C. Begelman et al.

We present a multiwavelength radio study of the changing-look AGN 1ES 1927+654 following its renewed X-ray brightening since mid-2022, combining VLBA imaging with multi-band and time-resolved VLA observations. Our main results are: (i) VLBA observations continue to reveal the bipolar jet structure first reported in Meyer et al. (2025), with new X-band detections confirming the morphology at larger separation and K-band imaging revealing a bridge of emission consistent with a continuous outflow;…

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gr-qcastro-ph.HEhep-th

From driven oscillations to free ringdown: a particle plunging into Kerr

Colin Weller, Andrew Laeuger, Fulin Li, Neil Lu, Rowina S. Nathan, Sizheng Ma, Yanbei Chen, Ling Sun et al.

We show that a ringdown waveform can admit a constant-coefficient quasinormal-mode (QNM) representation while its individual QNM-pole contributions remain driven. To establish this result, we construct a first-principles rational approximation to the Kerr Green's function from its QNM poles, physical residues, and horizon-frequency zeros. For particles plunging from the innermost stable circular orbit into Kerr black holes with spins 0.5-0.9, each QNM-pole contribution initially follows the sour…

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nucl-thastro-ph.HEhep-ph

MUSES workflows for pQCD constraints on dense matter with finite quark masses

Isabella Danhoni, Mateus Reinke Pelicer, Débora Mroczek, Yumu Yang, Mauricio Hippert, Jacquelyn Noronha-Hostler

We present a modular implementation of next-to-leading order (NLO) perturbative QCD (pQCD) thermodynamics with finite strange quark mass in the MUSES Calculation Engine, enabling reproducible connections between high-density QCD calculations and neutron star observables. Using this implementation, we investigate the interplay between flavor symmetry and physically motivated renormalization-scale prescriptions in cold, $β$-equilibrated quark matter. We compare prescriptions associated with the co…

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astro-ph.HEastro-ph.SR

Multi-Wavelength Identification of a Luminous Mid-Infrared Supernova Powered by Circumstellar Interaction with Binary-Driven Pre-supernova Mass Loss

Kohki Uno, Kishalay De, Geoffrey Mo, Viraj Karambelkar, Kaitlyn Shin, Christoffer Fremling, Jesper Sollerman, Daichi Hiramatsu et al.

Terminal mass-loss in massive stars is commonly reconstructed from observations of circumstellar interaction in core-collapse supernovae (CCSNe); however, such signatures can be easily missed depending on the phase when they appear. In this paper, we present a multi-wavelength study of SN\,2022yyz, a nearby CCSN selected by its luminous late-time mid-infrared (MIR) excess in NEOWISE at $> 500$ days after the discovery. Classified as a Type II SN at discovery, it reached a peak bolometric luminos…

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astro-ph.SRastro-ph.HEphysics.space-ph

On modelling the 2017 galactic cosmic ray depression

O. P. M. Aslam, D. MacTaggart, M. S. Potgieter, M. D. Ngobeni, I. I. Ramokgaba

In the second half of 2017, as Solar Cycle 24 approached its minimum, a pronounced and rigidity-dependent depression in the galactic cosmic ray (GCR) proton flux was observed using AMS-02. This event was driven by a sequence of strong coronal mass ejections (CMEs). In this work, we model the modulation of GCR protons during this period using a steady-state Parker transport framework with parameters constrained by AMS-02 observations. Treating the event as a purely long-term modulation interval y…

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gr-qcastro-ph.IM

Space-Based Lock-In Determination of Newton's Gravitational Constant

Ulrich D. Jentschura

Inspired by a recent ground-breaking space-based measurement of Newton's gravitational constant, we outline a proposal for a general layout of an optimized space-based approach that combines the advantages of a largely disturbance-free environment with lock-in techniques, null coordinates and the method of covariances. The method of covariances, and cross-covariances, is used for an optimized statistical analysis of data originating from two distinct experimental channels. One of two distinct me…

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astro-ph.EPastro-ph.IMastro-ph.SR

Detecting White Dwarf Exoplanets in the Roman Era

Zifan Lin, Tansu Daylan

White dwarfs (WDs) provide an unparalleled opportunity for detecting and characterizing exoplanets because of the large planet-to-star size ratio. However, only one transiting WD exoplanet is confirmed to date, and occurrence rate constraints remain loose because the rapid transits and weak phase curve modulations of WD exoplanets require high-precision, high-cadence photometry. The Galactic Bulge Time Domain Survey (GBTDS) of the Nancy Grace Roman Space Telescope will provide exactly this by ob…

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physics.ao-phastro-ph.EPphysics.flu-dyn

Scale analysis for the Madden$-$Julian oscillation

Hing Ong

This study performs a scale analysis for the dynamics of equatorial flow systems like the Madden$-$Julian oscillation (MJO). This analysis makes three assumptions about the geometry of the flow and focuses on the leading order terms of the mass continuity and momentum equation system. First, the flow is meridionally narrow. Second, the zonal structure is planetary wavenumber 1. Last, the flow is vertically shallow. When constrained by these geometric assumptions, the system shows a time scale mu…

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astro-ph.EPastro-ph.IM

Earth-Projected Clustering of Historical Optical Transients in the Palomar Observatory Sky Survey-I (POSS-I)

Stephen Bruehl, Beatriz Villarroel, Hichem Guergouri, Brian Doherty, Alina Streblyanska

Palomar Observatory Sky Survey-I (POSS-I) images obtained before the launch of Sputnik contain star-like point sources consistent with sub-second flashes that are absent from all subsequent observations. The nature and origin of these transients remain poorly understood. Based on models suggesting they are in geosynchronous orbit, we estimated the latitude/longitude over which POSS-I transients appeared. From a dataset of 107,875 POSS-I transients, we selected a subset with high probability of r…

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astro-ph.GAastro-ph.IM

JWST Spectra Conclusively Show an Excess of Neutral Gas Outflows in Quiescent Galaxies at z=2-5

Rion Oh, Gourav Khullar, Arianna S. Long, Julissa Sarmiento, Hollis B. Akins, Caitlin M. Casey, Yingjie Cheng, Andreas L. Faisst et al.

Galaxies exhibit a broad range of star formation activity, from actively star-forming to quiescent systems. Yet, the mechanisms responsible for the rapid shutdown and continued suppression of star formation remain poorly understood, particularly for the quiescent galaxies recently uncovered by JWST at $z>3$. Neutral gas outflows provide a direct tracer of gas removal and regulation in quiescent galaxies. We therefore present a NaID $λ\lambda5891,5897$ absorption--line stacking analysis of 274 ga…

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astro-ph.GA

Characterization of Orbits in Bars in Disc Galaxies Using Fourier Frequencies

A. Silva-Castro, I. Puerari, D. Valencia-Enríquez

Bars are among the most prominent dynamical structures in disc galaxies, yet their long-term evolution and the orbital families that sustain them remain only partially understood. In this work, we introduce a new methodology based on frozen potentials combined with Fourier analysis of particle trajectories to identify regular and sticky orbits in self-consistent $N$-body simulations. This approach allows us to isolate particles belonging to the $x_1$ family, directly associated with the bar, and…

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astro-ph.GA

Characterization of Orbits in Bars in Disc Galaxies Using Fourier Frequencies

A. Silva-Castro, I. Puerari, D. Valencia-Enríquez

Bars are among the most prominent dynamical structures in disc galaxies, yet their long-term evolution and the orbital families that sustain them remain only partially understood. In this work, we introduce a new methodology based on frozen potentials combined with Fourier analysis of particle trajectories to identify regular and sticky orbits in self-consistent $N$-body simulations. This approach allows us to isolate particles belonging to the $x_1$ family, directly associated with the bar, and…

Read →