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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.SR

The origin of dispersion in the wind mass-loss rate--luminosity relation of massive O stars

Jiri Krticka, Iva Krtickova

Stellar winds of hot stars are accelerated by the radiative force that mainly comes from the line transitions of heavy elements. As a result, the wind mass-loss rate is expected to scale mostly with the stellar luminosity. This scaling clearly emerges from the observational analysis of O stars and their winds, but with substantial scatter. The origin of this scatter is unclear. Part of the scatter of the observational relation between the hot star wind mass-loss rate and luminosity may originate…

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astro-ph.HEphysics.plasm-ph

Guide field effects on particle acceleration in three-dimensional relativistic magnetic reconnection

Despina Karavola, Lorenzo Sironi, Maria Petropoulou

Relativistic magnetic reconnection is a key mechanism for particle acceleration in astrophysical plasmas. Recent 3D particle-in-cell simulations have shown that, for weak guide fields, particles can be accelerated at nearly the maximal rate by escaping the reconnected plasma and gaining energy from the large-scale upstream electric field. Here, we investigate whether this fast acceleration channel persists as the guide field becomes comparable to the reconnecting field. We perform 3D simulations…

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astro-ph.GA

A multi-scale view of molecular gas and magnetic fields in the Antennae galaxies

Akhil Lasrado, Enrique Lopez-Rodriguez, Claudia Cicone, Axel Weiss, Andreas Lundgren, Boy Lankhaar, Robert Wissing, Sijing Shen et al.

Major mergers are transformative events in galaxy evolution, dynamically reshaping the stellar and gas makeup of the hosts, as well as the galaxy-scale magnetic fields (B-fields) that permeate their interstellar medium (ISM), altering both B-field strength and configuration. In this work, we study in detail the link between the co-evolving gas and B-fields in the cold ISM phase of the nearby Antennae galaxy merger (NGC 4038/4039), using CO(3-2) data from the LAsMA receiver at the APEX telescope…

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astro-ph.GA

Discovery of thermal radio recombination line emission toward the high-mass protostar IRAS18162$-$2048

R. Fedriani, J. F. Gomez, Y. Cheng, M. Osorio, G. Anglada, C-Y. Law, J. M. Masque, A. F. Placinta-Mitrea et al.

The physical conditions within the innermost few tens of au of high-mass protostars ($M_*>8~M_\odot$) remain largely unexplored. At these scales, ionised emission may trace photoionised gas, the innermost regions of accretion disks, or the base of protostellar jets. We search for ionised emission in the form of radio recombination lines (RRLs) in high-mass star-forming regions. We use archival data from the Atacama Millimeter/submillimeter Array (ALMA) interferometer in band 6 ($\sim$1.3 mm) wit…

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astro-ph.GA

Merger remnant in TXS 1033+026 - I: $\rm Hα$ and HI 21-cm observations suggest counter-rotating gas

J. N. H. S. Aditya, Hyein Yoon, L. G. Dahmer-Hahn, Renzhi Su, Rajeshwari Dutta, Xiaolong Yang, Elaine Sadler, Matthew T. Whiting et al.

We have conducted eMERLIN and GEMINI IFU observations towards TXS 1033+026, a post-merger ultraluminous infrared galaxy, to study the radio continuum, $\rm Hα$ and HI 21-cm lines at sub-kpc scales. We find a symmetric, two-sided core-jet structure in both L ($\approx 1.4$ GHz)- and C ($\approx 4.8$ GHz)-band continuum images. The AGN likely has a double-double radio morphology, indicating possible multiple episodes of activity. The GEMINI IFU observations provided sub-arcsecond resolution. Resul…

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nucl-exastro-ph.SR

First strength measurements of low-energy resonances in the $^{45}$Sc($p,γ$)$^{46}$Ti reaction and its astrophysical implications

R. S. Sidhu, R. J. deBoer, J. Görres, M. Wiescher, W. N. Catford, C. Dembski, C. R. Jones, Ó. E. López-López et al.

The $^{45}$Sc($p,γ$)$^{46}$Ti reaction plays an important role in both hydrostatic and explosive nucleosynthesis. During hydrostatic oxygen and silicon burning in massive stars, including dynamic processes such as convective carbon-oxygen (C-O) shell mergers, it acts as a bottleneck that regulates the reaction flow in the Sc-Ti mass region. In oxygen-neon (ONe) novae, the ejecta indicate the production of elements up to the Fe group, as observed in V1974 Cygni, and the $^{45}$Sc($p,γ$)$^{46}$Ti…

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astro-ph.GA

A two-stage settling of the Milky Way disk revealed by precise ChronoGal ages

David Mirabal, Carme Gallart, Tomás Ruiz-Lara, Emma Fernández-Alvar, Anna B. A. Queiroz, Guillem Aznar-Menargues, Chris B. A. Brook, Santi Cassisi et al.

The spatial distribution of Galactic disk stars of different ages and metallicities encodes its dynamical evolution history and formation pathways. The lack of precise ages for large, representative samples of stars has traditionally been a drawback for securely differentiating among formation scenarios proposed to explain the vertical properties of the Milky Way disk (e.g. upside-down formation versus secular dynamical heating). In this Letter, we use CMD-fitting of Gaia data to derive very pre…

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astro-ph.HEnucl-th

Twins in the Shadow: Phase Transitions in Proto-Neutron Stars

Jannik Milthaler, Jan-Erik Christian, Pia Jakobus, Stephan Rosswog

We study the impact of a first-order phase transition from hadronic to deconfined quark matter on the evolution of proto-neutron stars. To maximize the applicability of our results, we construct an equation of state that is highly parameterizable, where we use a relativistic mean field approach to model hadronic matter and a constant speed of sound approach to model quark matter. We approximate the cooling behavior of proto-neutron stars as a sequence of decreasing entropy at constant baryonic m…

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astro-ph.HE

The 2015-2017 Large EVPA Rotation in OJ 287: Dominant Propagating Component in a Helical Magnetic Field with Time-Dependent Viewing Geometry

Wanchaloem Khwammai, Minchul Kam, Motoki Kino, Sascha Trippe, Hiroshi Nagai, Seiji Kameno, Ilje Cho, Ioannis Myserlis et al.

We present high-cadence, multi-frequency monitoring of the blazar OJ 287 using KVN (22--129 GHz), ALMA (91.5--343.5 GHz), and Metsähovi (37 GHz), covering 2012--2023, together with published optical polarimetry. Within this decade-long dataset, an exceptionally large and smooth EVPA rotation is observed only during 2015--2017. The millimeter-band EVPA rotates by more than $\sim$300 deg over $\sim$1.5 yr, with a comparably large and more rapidly evolving rotation observed at optical wavelengths,…

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astro-ph.GAastro-ph.SR

No Convincing Evidence for Tidal Binary Clusters in the Galaxy

Juan Casado, Zahra Al

Context. The existence of tidal binary clusters (TBCs) in the Milky Way has been repeatedly suggested using Gaia DR3 astrometry and recent catalogs of binary clusters and groups. However, the dynamical feasibility of forming truly bound binary clusters through tidal capture remains uncertain. Aims. We perform a systematic reassessment of twenty star clusters, currently claimed as members of TBCs from the catalog of binary and grouped clusters of Liu et al. (2025) to ascertain their classificatio…

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astro-ph.HE

Comparing the size evolution of GRB 221009A with afterglow models

S. Giarratana, O. S. Salafia, B. Marcote, Z. Paragi, M. Giroletti, G. Ghirlanda, L. Nava, A. van der Horst et al.

We present very long baseline interferometry (VLBI) observations of GRB221009A obtained with the global-VLBI network at 5 GHz between 231 and 750 days after the burst. The quality of our observations allowed us to measure the sub-milliarcsecond full-width at half maximum of the source surface brightness distribution with a one-sigma equivalent error of 13% and 30% at 231 and 391 days post-burst, respectively. By fitting the temporal evolution of these new size measurements alongside those previo…

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astro-ph.HE

XMM-Newton Resolves Parsec-scale X-ray Jets in the PeVatron Microquasar V4641 Sgr

Naomi Tsuji, Caterina Tresoldi, Kaya Mori, Hiromasa Suzuki, Matthew Lundy, Dmitry Khangulyan, Samar Safi-Harb, Laura Olivera-Nieto et al.

The microquasar V4641 Sagittarii (V4641 Sgr) has recently been established as one of the most powerful Galactic PeV cosmic-ray accelerators (PeVatrons) through the detection of degree-scale gamma-ray emission to 0.8 PeV. Using XMM-Newton, we performed an X-ray survey of its gamma-ray-emitting regions during the quiescent phase. We discovered extended X-ray emission to the north and south of V4641 Sgr, aligned with the radio-jet axis, revealing X-ray jet structures extending over several tens of…

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astro-ph.HE

Candidate X-ray Counterparts of Ultra-High-Energy Emission of the Galactic Microquasar V4641 Sgr Revealed by Einstein Probe

Yi-Heng Chi, Shao-Qiang Xi, Ping Zhou, Hua Feng, Ruo-Yu Liu, Songzhan Chen, Naomi Tsuji, Caterina Tresoldi et al.

Microquasars have emerged as promising PeVatron candidates capable of accelerating particles to PeV energies, with recent observations revealing ultra-high-energy (UHE) $γ$-ray emission from extended structures associated with these systems. Multi-wavelength studies of such extended structures are crucial for understanding the acceleration, transport, and radiation processes of UHE cosmic rays (CRs), yet observational evidence remains limited. Here, we report the discovery of diffuse X-ray struc…

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

Plato benchmark stars I. The initial benchmark sample

T. Merle, P. F. L. Maxted, O. L. Creevey, U. Heiter, D. B. Palakkatharappi, K. G. Hełminiak, C. C. Aguilera Gómez, M. Bazot et al.

The ESA PLATO mission aims to detect and characterise Earth-size exoplanets orbiting bright, late-type stars using high-precision photometry and asteroseismology. Precise stellar parameters of host stars are essential for exoplanet characterisation and model benchmarking. This work defines the PLATO benchmark stars (PBS) catalogue, a comprehensive sample of well-characterised stars designed to support all mission phases. We compiled data from eclipsing and spectroscopic binaries, interferometry,…

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astro-ph.HE

Study of the Ultra-Long GRB 220627A: Exploring a Possible Blue Supergiant Collapsar Origin

Ayush Garg, Amit Shukla, Dorottya Szécsi, G. C. Anupama

Ultra-long gamma-ray bursts (ul-GRBs) challenge standard collapsar models because their extreme durations require central engines active for $\sim10^{3}-10^{4}$ s. While the prompt spectral evolution of typical GRBs is difficult to resolve due to their short durations, ul-GRBs provide a unique opportunity to study spectral evolution on extended timescales. We present a time-resolved spectroscopic study of GRB 220627A, one of the most luminous ul-GRBs known ($E_{\rm iso}\sim10^{54}$ erg, $T_{90}>…

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hep-phastro-ph.HE

Kinetic Equilibrium between SIMP Dark Matter and Radiation via Internal Bremsstrahlung

Xiaoyong Chu, Ajay Kaladharan, Yassine El Mohtadi

As an alternative to standard dark matter freeze-out via two-body annihilation, strongly interacting massive particles are proposed to regulate their relic abundance through three/four-body self-annihilation. During such freeze-out, dark matter must undergo both number reduction and energy dissipation. The former requires number-reducing processes, and the latter requires an efficient energy-dissipation mechanism. In this work, we propose a novel mechanism where internal Bremsstrahlung processes…

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astro-ph.EP

Joint RV-Astrometric Analysis of two-planet system HD 65216: Prospects for Gaia DR4

Alexander L. Wallace, Robert A. Wittenmyer, Jonathan Horner

We provide updated mass and orbital constraints on the planetary system around HD 65216, consisting of at least two giant planets on eccentric orbits. We first analyse new RV data to constrain the periods and eccentricities of both planets, before applying the Hipparcos-Gaia proper motion anomaly to constrain the inclination of HD 65216 c. From this joint analysis, we find that HD 65216 c is most likely in an eccentric orbit ($e$ = 0.42$\pm$0.05) with a longer period (7007$^{+192}_{-161}$ days)…

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astro-ph.SR

Formation and Eruption of a Vortex-driven Magnetic Flux Rope in the Simulated Quiet Sun

Zhizhen Ye, Feng Chen

Magnetic flux ropes (MFRs) are key structures for understanding flares and coronal mass ejections in active regions, but their characteristics in the quiet Sun remain poorly understood. With a radiative MHD simulation spanning from the upper convection zone to the corona, we analyze the formation and eruption of a supergranular-scale flux rope. We use a clustering method to group the closed field lines by their connectivity. The clusters are gathered further into 8 persistent cluster assemblies…

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astro-ph.IMastro-ph.HE

Robust Bayesian non-linear pulsar timing and noise analysis using a sequential data-tempered ensemble sampler

Abhimanyu Susobhanan

We develop a sequential ensemble MCMC scheme for Bayesian pulsar timing and noise analysis that uses data size as the tempering parameter. The method enables gradual and reliable convergence from potentially uninformed initial points by iteratively increasing the data size, thereby increasing sensitivity and progressively narrowing the target distribution until the posterior of the full dataset is reached. The initial iterations use sub-datasets that can be orders of magnitude smaller than the f…

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astro-ph.SR

A New Analysis Tool for Radial Pulsations

Hiroyasu Ando

Wave-energy relation is introduced as a new analysis tool for linear radial pulsations. Wave energy consists of kinetic energy, acoustic-potential energy, dynamical-potential energy, and entropy-potential energy. The relation describes changes in the wave energy caused by non-adiabatic processes and by leakage of wave energy. It is applied to modal analysis of adiabatic pulsations for the massive Zero Age Main Sequence models (10, 20, and 30 solar masses). The ordinary modes are well trapped in…

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astro-ph.HE

The Structure in the Structure Function of Black Hole Light Curves

Daniel C. M. Palumbo, Alejandro Cárdenas-Avendaño, Lena Murchikova

Of the two black holes, M87$^\ast$ and Sgr A$^\ast$, for which event-horizon-scale imaging is currently achievable, only Sgr A$^\ast$ at our Galactic Center exhibits sub-hour variability, making light curve observations of the inner accretion flow especially valuable for time-domain studies of the spacetime and the surrounding plasma. Observed light curves are often sampled with variable cadence, so a structure function is often used to quantify their variability properties. In this work, we ass…

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astro-ph.SRastro-ph.HEphysics.data-anphysics.flu-dynphysics.plasm-ph

Mesoscale Turbulence in Type Ia Supernova Deflagrations II. Evidence for Fuel Preheat Due to Flame Thermal Expansion from Lagrangian Analysis

Ryan Learn, Andrey Zhiglo, Tomasz Plewa

Thermonuclear flame fronts in Type Ia supernovae develop hydrodynamic instabilities that generate turbulent mesoscale flow and substantial local thermodynamic variability. Recent work by \citet{Brooker+25} demonstrated systematic shortening of fuel ignition times near Rayleigh--Taylor unstable deflagration fronts, but the physical origin remained unclear. We investigate the thermodynamic evolution of fuel near the flame front using multidimensional simulations and Lagrangian tracer-particle anal…

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astro-ph.COastro-ph.HEhep-phhep-th

Distinguishing the origin of cosmic birefringence: dark energy, dark matter, and neutrino asymmetry

Lu Yin, Eiichiro Komatsu

Cosmic birefringence, the isotropic rotation of the plane of linear polarization of photons from sources at cosmological distances, can be generated by different parity-violating mechanisms. While the net rotation angle of a single polarized source carries little information about its physical origin, sources at various redshifts $z$ can be used to distinguish between different origins. Parity-sensitive correlations of the $E$- and $B$-mode polarization fields of the cosmic microwave background…

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astro-ph.HE

A Refined Analytic Oblate--Schwarzschild Model for Thermal X-Ray Pulse Profiles of Rotating Neutron Stars

Xi Yang, Tong Zhao, Renxin Xu

Thermal X-ray pulse profiles constrain neutron-star masses and radii through the effects of gravitational light bending and rotation on surface emission. The precision anticipated from the enhanced X-ray Timing and Polarimetry (eXTP) mission motivates more accurate analytic light-bending formulae that retain the efficiency needed for repeated model evaluations. We derive a refined analytic flux expression within the oblate--Schwarzschild (OS) approximation that combines bending, propagation-dela…

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astro-ph.EPastro-ph.IM

Performance of AutoRegressive Planet Search methodology on simulated PLATO lightcurves

Eric D. Feigelson, Marco Montalto, Geert Jan Talens, Suzanne Aigrain, Luca Malavolta, Valerio Nascimbeni, Tiziano Zingales

AIM. This study examines the PLATO mission sensitivity to small transiting planets (radii between 0.5 and 2.0 R$_\oplus$) using Autoregressive Planet Search (ARPS) methodology based on simulated lightcurves. Methods. Several thousand simulations of PLATO-like lightcurves from magnetically active stars expected from the PLATO Long Observation Phase South 2 (LOPS2) field with injected transiting planets smaller than 2.0 R$_\oplus$ radius are examined. The lightcurves are analyzed with ARPS that us…

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

The 200-300 GHz Survey for 18 Class II Disks in the Ophiuchus Star-Forming Complex

Chia-Ying Chung, Hauyu Baobab Liu, Chuan-Yung Lin, Linjing Feng, Sean M. Andrews, Mark A. Gurwell, Melvyn Wright

We measured the 198-310 GHz flux densities of 18 Class II protoplanetary disks in the Ophiuchus star-forming complex using the Submillimeter Array (SMA). The $\sim$200-300 GHz spectral indices ($α_{200-300}$) of these disks are $2.3^{+0.2}_{-0.5}$. In this observed frequency range, emission properties of the Ophiuchus disks are very similar to the 48 spatially compact Class II disks in the Taurus-Auriga region observed in a previous SMA survey. Combining the Ophiuchus and Taurus-Auriga samples,…

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astro-ph.IM

Do Astronomical Foundation Models Know When They Will Fail?

Vaidehi Bulusu, Mehul Goyal, Md Rabius Sany Apu, Michael J. Smith, Shashwat Sourav

Astronomical foundation models are increasingly used as reusable representations across surveys, but it is unclear when the same object remains consistently represented across instruments or whether a model can warn us before transfer fails. We present a conformal framework for auditing cross-survey representations using cross-matched Legacy Survey--HSC, HSC--JWST, and SDSS--HSC objects. Astronomy-specific AstroPT embeddings show lower translation errors and tighter conformal regions than genera…

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astro-ph.GA

Star Cluster Populations in 38 Spiral Galaxies: Evidence for Near-Universal Mass and Age Distributions from PHANGS

Rupali Chandar, Matthew R. Floyd, David A. Thilker, Kiana Henny, Bradley C. Whitmore, Janice C. Lee, Sinan Deger, Daniel A. Dale et al.

We present the largest study to date of star cluster mass and age distributions in nearby galaxies. The analysis is based on a uniformly selected catalog of over 15,000 (36,000) human (machine) classified compact clusters across 38 spiral galaxies in the PHANGS-HST survey, with improved photometric SED age dating that mitigates key degeneracies with reddening and metallicity. The galaxies span a factor of ~100 in star formation rate (SFR) and in their surface density of star formation and molecu…

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astro-ph.GA

The Largest Catalog of Dwarf Galaxy Groups: Transient Structures or Building Blocks of the Universe?

Marko Mićić

Elusive dwarf galaxy groups provide a rare opportunity to study hierarchical galaxy assembly at the lowest-mass scales, but whether such associations are gravitationally bound systems or transient configurations remains uncertain. We present the largest catalog of isolated dwarf galaxy groups, identified using the DESI Survey, comprising 74 systems with three to six members per group. The groups have a median line-of-sight velocity dispersion of $\sim53$ km s$^{-1}$ and a median crossing time of…

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astro-ph.GA

DESI Interacting Dwarfs Survey: Multiple Evolutionary Channels of Dwarf Galaxies Driven by Major Dwarf Interactions

Marko Mićić, Sugata Kaviraj

Dwarf-dwarf interactions are a major driver of galaxy evolution in the early Universe, but observational constraints on their impact across mass, separation, and environment remain scarce. Using the Dark Energy Spectroscopic Instrument Early Data Release, this study constructs the largest sample of dwarf galaxy pairs, spanning stellar masses $6.5 \leq \log(M_\star/M_\odot) \leq 9.5$ and redshifts $0.015 \leq z \leq 1.5$. We analyze the evolution of star formation rates and multiwavelength colors…

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