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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.HEastro-ph.SR

Optical observations on the young Type Ia SN 2021fxy with detached high velocity features

Liping Li, Jujia Zhang, Zhenyu Wang, Xiaofeng Wang, Qian Zhai, Shengyu Yan, Bo Wang, Jinming Bai et al.

We present optical observations on the young type Ia supernova (SN Ia) SN 2021fxy obtained within a few days after the explosion, with a focus on its prominent high-velocity features (HVFs). It reached a $B$-band maximum of $M_{\rm max}(B) = -19.36\pm0.31$ mag, corresponding to a bolometric luminosity of $\sim 1.3\times10^{43}~\rm{erg~s^{-1}}$ with a synthesized $^{56}$Ni mass of $0.58\pm0.14$ M$_{\odot}$. The early spectra exhibit strong HVFs of intermediate-mass elements that are significantly…

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astro-ph.SRastro-ph.HEastro-ph.IM

Surrogate models for type II supernovae: Probing low-energy explosions and interaction-free regimes

Zhengyang Zhang, Shuai Zha, Nikhil Sarin, Takashi J. Moriya, Chengyuan Wu, Bo Wang

To address the computational bottleneck of analyzing type II supernova samples from surveys such as the Legacy Survey of Space and Time, we present two STELLA-based neural-network surrogates: an interaction model for low-energy explosions with possible circumstellar-material (CSM) interaction and a photospheric model for standard interaction-free SNe IIP. Each uses an autoencoder to compress spectral energy distributions and an emulator to map physical parameters to the latent space. Latent-mixu…

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astro-ph.SRphysics.plasm-phphysics.space-ph

Parker Solar Probe Observations of Preferential Heating of Protons over Alpha Particles near Turbulent Coherent Structures

Jiayang Xi, Tieyan Wang, Daniel Verscharen, Yan Yang, Luca Sorriso-Valvo, Xinyi Wang, Wenhao Chen, Zuzheng Chen et al.

Solar wind alpha particles exhibit preferential heating and acceleration relative to protons; however, their behavior in the vicinity of turbulent coherent structures remains less understood. We report the first evidence of localized alpha particle and proton heating within coherent structures identified using the Partial Variance of Increments (PVI) method, based on Parker Solar Probe (PSP) observations. Our results show that high-PVI events are associated with significant, species-dependent te…

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astro-ph.HEastro-ph.GA

Optically Thick Outflow Driven by Supercritical Accretion May Explain Little Red Dots

Jun-Rong Liu, Hua Feng, Luis C. Ho

Recent JWST observations have revealed a population of compact, optically red sources known as Little Red Dots (LRDs). A popular interpretation is that LRDs host massive black holes embedded in dense gaseous envelopes, yet the physical origin of such envelopes remains unclear. We propose that the optically thick outflow driven by supercritical accretion onto black holes may explain the envelope. Based on an analytic radiative hydrodynamic outflow model, we relate the outflow properties to the bl…

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gr-qcastro-ph.HEastro-ph.IM

The impact of physically motivated calibration errors on search pipeline detection parameters for broadband burst Signals

Milan Wils, Brad Ratto, Jeffrey S. Kissel, Tjonnie G. F. Li, Marek J. Szczepańczyk, Gabriele Vedovato, Michele Zanolin

Imperfections in the calibration of gravitational wave observatories introduce frequency dependent amplitude and phase errors on the measured GW signal. Previous unmodelled burst searches have approximated these effects using prescriptions such as a uniform amplitude rescaling or a constant time shift, which do not capture the frequency-dependent structure of calibration errors. This limitation is problematic for core-collapse supernovae, whose predicted GW signals occupy a wide frequency band a…

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astro-ph.GA

A Rest-frame K-band View of Bulge Growth in Massive Dusty Star-forming Galaxies at z~2

Ken-ichi Tadaki

We study bulge formation in 16 massive dusty star-forming galaxies at z~2 by combining JWST MIRI F770W imaging, NIRCam imaging in eight bands, and ALMA 870 um data. At the median redshift of z=2.18, the F770W band probes the rest-frame 2.4 um light, close to the rest-frame K band, and traces the stellar mass distribution with little effect from dust attenuation. The effective radii measured in F770W agree with those of the 870 um dust emission, with a median ratio of 0.95, and are typically 23%…

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astro-ph.IMastro-ph.HE

Imaging X-ray Polarimetry Explorer

Brian Ramsey, Paolo Soffitta, Martin C. Weisskopf

In 1971 a group from Columbia University detected polarized X rays from the Crab Nebula at about 3 sigma level during a short sounding rocket flight (Novick et al. (1972)). This measurement, later confirmed to high precision (greater than 20 sigma) by the OSO-8 satellite in 1976/77 (Weisskopf et al. (1978)) marks the real beginning of astrophysical X-ray polarimetry. Since then and before the launch of IXPE, surprisingly few additional measurements had been made. X-ray polarimetry is a demanding…

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astro-ph.IMphysics.optics

Tolerancing the PIAA-ZWFS: a practical and robust wavefront sensor that approaches the fundamental sensitivity limit

Adam K. Taras, Sebastiaan Y. Haffert, Louis Desdoigts

High-contrast imaging demands extremely sensitive wavefront sensing to correct atmospheric effects and surface errors. While the limits of the sensitivity of a wavefront sensor are well known, a practical, robust design that saturates these limits remains elusive. This work further investigates the PIAA-ZWFS (Phase-Induced Amplitude Apodization-Zernike Wavefront Sensor). In previous work, we developed a framework to optimise its design, maximising Fisher information per frame in the presence of…

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astro-ph.SR

A universal scaling between damping time and period of quasi-periodic pulsations from solar EUV brightenings to X-ray stellar flares

Daye Lim, Tom Van Doorsselaere, Valery M. Nakariakov, S. Krishna Prasad, David Berghmans, Laura A. Hayes, Kyung-Suk Cho, Sujin Kim et al.

Recent high spatial and temporal resolution extreme-ultraviolet (EUV) imaging observations have revealed that quasi-periodic pulsations (QPPs), a ubiquitous signature of impulsive energy release in solar and stellar flares, are also present in much smaller-scale coronal events known as EUV brightenings. Whether QPPs observed across such disparate spatial and energetic scales share a common physical origin remains an open question. Here we analyse 2,146 EUV brightenings observed with Solar Orbite…

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astro-ph.SRastro-ph.IM

SpecFANN: Spectral Fitting via Artificial Neural Networks I. A deep learning based fastwind emulator and fitting suite

M. Abdul-Masih, C. Hawcroft, T. Lechien, S. Simon-Diaz, H. Sana, K. Deshmukh, J. Vrancken, J. I. Villaseñor et al.

The importance of massive stars cannot be overstated: they are powerful probes of the early universe, play a vital role in the chemical and mechanical evolution of their host environments and their end products allow us to study the most extreme physics in the universe. Obtaining accurate stellar and surface parameters for large samples of massive stars is vital to our understanding of how they evolve, and how their births, lives and deaths affect their surroundings. With the large volume of dat…

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astro-ph.COastro-ph.HE

Constraints on Primordial Black Hole Dressed by Dark Matter Halo from Microlensing Effect of Fast Radio Bursts

Hong-Rui Tao, Huan Zhou, Cheng-Gang Shao, Xiao-Long Gong, Zheng-Xiang Li

Primordial black holes (PBHs) are not only considered as a candidate for dark matter, but also as potential sources of gravitational waves from binary black hole mergers by the LIGO-Virgo-KAGRA and as seeds for the supermassive black holes observed by the James-Webb Space Telescope, thereby remaining intense interest in cosmology and astrophysics. Fast radio bursts (FRBs) are bright millisecond-duration radio transients whose physical origin remains elusive, which have rapidly developed into one…

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astro-ph.IMastro-ph.HE

Calibration database design for the wide-field X-ray telescope on board the Einstein Probe

Huaqing Cheng, Hai-Wu Pan, Yuan Liu, Donghua Zhao, Wenxin Wang, He-Yang Liu, Chen Zhang, Zhixing Ling et al.

The wide-field X-ray telescope (WXT) is the primary payload of the Einstein Probe (EP) mission. Utilizing innovative lobster-eye micro-pore optics (MPO), it achieves an unprecedented combination of a large instantaneous field-of-view (FoV) and high detection sensitivity. Precise scientific data analysis relies fundamentally on a standardized and robust calibration database (CALDB). In this paper, we present the design and implementation of the WXT CALDB. The database is designed to manage calibr…

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astro-ph.IMastro-ph.HE

Onboard catalog of known X-ray sources for EP-WXT

He-Yang Liu, Haiwu Pan, Yuan Liu, Hong-Bo Cai, Yuyin Tan, Haitao Xu, Changbin Xue, Xiaojin Sun et al.

The Einstein Probe (EP) is dedicated to explore the dynamic X-ray universe and capture transient events in real time with its Wide-field X-ray Telescope (WXT). However, WXT's unprecedentedly large instantaneous field of view, exceeding 3,600 square degrees, simultaneously encompasses numerous known X-ray emitters. Distinguishing genuine novel transients from these persistent sources is a critical observational challenge. To resolve this, EP-WXT incorporates a dedicated reference catalog of known…

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astro-ph.GAastro-ph.SR

The initial conditions and initial mass functions of Alpha Persei, Pleiades and Praesepe

L. Hobart, H. Baumgardt, S. Sweet

We have determined the initial mass function (IMF) and structural properties of the open clusters Alpha Persei, Pleiades and Praesepe using Gaia DR3 astrometry and photometry. Cluster members were identified using primarily Gaia astrometry, supplemented with near-infrared UKIDSS and optical HIPPARCOS survey data with stellar masses down to $0.10-0.17$ MSun. We measure and correct for unresolved binaries in each cluster using photometry and Monte Carlo simulations in a Bayesian framework, finding…

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astro-ph.GA

Ongoing Morphological Transformation from Elliptical to Spiral Galaxies Induced by Gas Accretion from Neighboring Galaxies

Gene Yun, Sang Hyeok Im, Ho Seong Hwang, Changbom Park, Hyeonguk Bahk

We present results from spectroscopic observations of three interacting galaxy systems, each associated with a primary galaxy - VCC 1748, SDSS J1106, and 2MASX J0834 - which have been proposed as potential examples of reverse morphological transformation from elliptical to spiral types driven by external gas accretion. Using Gemini/GMOS longslit spectroscopy, we obtain spectra along longslits connecting the regions of interest between the two galaxies in each pair. We model the spatially binned…

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astro-ph.GAastro-ph.SR

Super-Jeans Fragmentation and Supply-Limited Accretion: Environment-Dependent Co-Evolution of Low- and High-Mass Cores

Dan Miao, Guang-Xing Li, Patricio Sanhueza

Protostellar core formation and growth in high-mass star-forming regions remain key to understanding massive star birth. We analyze the masses of 839 cores (resolved at scales of a few thousand au) from the ASHES project targeting 39 massive infrared dark cloud clumps. The masses of the three most massive cores scale linearly with the total core mass. They maintain a constant mass fraction of ~25%, 16%, and 10% along the mass growth sequence. These fractions reveal that the progenitor seeds dest…

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gr-qcastro-ph.HE

Probing Nonlinear Logarithmic Kalb-Ramond Black Holes: Particle Dynamics, Epicyclic Oscillations and Thermodynamic Signatures

Aftab Ansari, Rajesh Kumar, Praveen Kumar Dhankar

In contrast to conventional linear coupling frameworks, the proposed work investigated the nonlinear effects that become more significant in the strong field regime of a black hole. We have investigated a new class of Kalb Ramond black holes generated by a nonlinear logarithmic coupling of the field, referred to as a Logarithmic Kalb Ramond black hole. The logarithmic coupling introduces strong-field modifications to the spacetime geometry, leading to significant departures from the Schwarzschil…

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astro-ph.SRastro-ph.GA

Magnetic fields in Massive Star-Forming Regions (MagMaR). VIII. Magnetic field overrun by gravity in GGD 27's accretion streamers

M. Fernández-López, J. A. López-Vázquez, J. M. Girart, P. Sanhueza, L. A. Zapata, P. C. Cortés, H. Beuther, G. Busquet et al.

Context. Accretion streamers connected to protostellar disks and/or envelopes are thought to transport material across several thousand of au. Whether the motions of the gas comprising these streamers are dominated by gravity, large scale external turbulence or the action of magnetic fields is still under scrutiny. Aims. The aim of this work is to understand the role of the magnetic fields in the star-formation processes, in particular the role that magnetic forces have in potentially leading fl…

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astro-ph.GA

Disentangling the Morphology of Palomar~5: Effects of the Bar, Spiral Arms, LMC, and Halo Flattening

Zhenghao He, Long Wang, Zi-yi Zhou, Yang Huang, Eugene Vasiliev

The Palomar~5 (Pal~5) globular cluster and its tidal tails provide a sensitive probe of globular-cluster evolution in the time-dependent Milky Way potential. We study the past 3~Gyr evolution of Pal~5 using collisional direct \(N\)-body simulations with \texttt{PeTar}, adopting Galactic potential models that include spiral arms, the Galactic bar, halo flattening, the Large Magellanic Cloud (LMC), and bar deceleration. We find that halo shape strongly influences the projected stream track, reflec…

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nucl-thastro-ph.HEastro-ph.SRhep-th

The equation of state for neutron stars

Veronica Dexheimer

This chapter is intended as an introduction to dense matter and the equation of state of neutron stars and their mergers. It begins with a brief description of neutron star interiors, followed by a historical overview of the theoretical frameworks used to describe them focusing on relativistic formalisms, including different degrees of freedom, models, symmetries, and phases. It also provides an overview of our current understanding of dense matter (including theory, experiments, and observation…

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astro-ph.SR

Constraining the radial decay timescale of solar surface magnetic field through a comparative study of data-assimilative 2D surface flux transport and 3D dynamo models

Soumyadeep Chatterjee, Gopal Hazra

The polar magnetic field is the most reliable precursor for predicting the amplitude of the solar cycle, and the 2D surface flux transport (SFT) model is widely used to reconstruct its evolution. Traditional 2D SFT models can not capture the surface-interior coupling of the surface field, causing delays in polar field reversals. This deficiency is conventionally corrected by adding a decay term $-B_r/τ$ with a poorly constrained radial decay timescale $τ$. Here, we present a self-consistent esti…

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astro-ph.IMastro-ph.SR

Continuous Ultra-Low-Frequency Solar Radio Monitoring with ALBATROS from the High Arctic

Aman Chokshi, Mohan Agrawal, Christopher Barbarie, Joëlle-Marie Bégin, Benjamin Cheung, Hsin Cynthia Chiang, Cherie K. Day, Eamon Egan et al.

In the Canadian High Arctic, nearly five months of continuous daylight enable uninterrupted low-frequency solar monitoring. We present the first solar science results from the Array of Long Baseline Antennas for Taking Radio Observations from Seventy-Ninth Parallel (ALBATROS). This broadband radio array is designed to explore the largely uncharted radio sky below 30 MHz, where polar ionospheric conditions permit access to frequencies rarely accessible from ground-based sites. Using observations…

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astro-ph.GAgr-qc

Temporal Correlations Between Fuzzy Dark Matter and Baryonic Matter in Virialized Core-Halo Structures

Ivan Alvarez-Rios, Francisco S. Guzman

Fuzzy Dark Matter (FDM) predicts the existence of virialized halos with interference-driven granular structure generated by the wave nature of ultralight bosons. Since these fluctuations produce time-dependent gravitational fields, they can be proposed as a potential source of observable dynamical effects on baryonic matter. In this work we test whether such fluctuations generate measurable temporal correlations between FDM and a coupled gas component. We evolve coupled FDM-gas configurations wi…

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astro-ph.HEgr-qc

Electromagnetic Emission from a Black Hole Evaporating in External Magnetic Field

Soumya Samrat Mandal, Maxim Lyutikov

We describe a classical (non-quantum) radiation process: additional (to Hawking) emission by a black hole evaporating in an external magnetic field in vacuum. The electromagnetic radiation process is completely electric charge-free and bears some resemblance to the Gertsenshtein-Zel'dovich effect. The time evolution of the spacetime metric perturbs a static background magnetic field, inducing a radiative field that acts as an effective electromagnetic source even in the absence of physical charg…

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astro-ph.SRastro-ph.GA

Escaped White Dwarf Candidates from Open Clusters

Huahui Yan, David R. Miller, Jingkun Zhao, Jincheng Guo, Chengyuan Li

Observations reveal a pronounced deficit of white dwarfs (WDs) in open clusters (OCs) relative to theoretical expectations, suggesting that a significant fraction of WDs may have escaped from their parent clusters after formation. In this work, we perform a systematic search for escaped WD candidates from OCs by back-tracing the motions of WDs and star clusters from Gaia DR3 catalogs. We identify 476 candidate WDs with kinematics consistent with having escaped from one of 175 OCs. A control-fiel…

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astro-ph.GAastro-ph.SR

Machine learning prediction of binary formation in three-body gravitational encounters

Ahmad Farhani Asl

Three-body encounters are frequent events in stellar systems, intrinsically chaotic, and computationally costly to model with direct N-body integration. Predicting whether such encounters lead to binary formation is therefore challenging, particularly in large-scale simulations. We aim to develop an accurate and physically interpretable machine-learning model that predicts binary formation from the initial conditions of three-body encounters, to assess its reliability, and to identify the physic…

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astro-ph.SRastro-ph.GA

Determination of [Fe/H] in Fundamental mode Classical Cepheids from Gaia DR3 light curve Fourier parameters

Roberto Molinaro, Vincenzo Ripepi, Marcella Marconi, Massimiliano Gatto, Erasmo Trentin, Mami Deka, Giulia De Somma, Ilaria Musella et al.

Estimating the iron abundance ([Fe/H]) of Classical Cepheids (CCs) is crucial both for validating the cosmic distance scale through the Period-Luminosity relation and for tracing the chemical evolution of young stellar populations. However, standard spectroscopic determinations are highly time-consuming, limiting their application to large or distant samples. This work delivers a practical, multi-band alternative by investigating whether light-curve Fourier parameters derived from Gaia mission p…

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astro-ph.GAastro-ph.SR

Predicting the unpredictable: binary--single scattering with machine learning

Ahmad Farhani Asl, David Fonseca Mota, Dennis Fremstad, Fatemeh Rahimi

Binary--single encounters occur frequently in stellar systems, constitute a non-integrable chaotic three-body problem, and are computationally expensive when treated with N-body codes. We aim to construct an accurate and physically interpretable surrogate model for binary--single scattering final states (ionization, flyby, exchange, or hierarchical), evaluate the reliability of its probabilistic predictions, and trace its predictive failures to the underlying chaotic nature of the scattering pro…

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astro-ph.HE

Fermi-LAT Detection of a Gamma-ray Excess toward the Radio-quiet Narrow-line Seyfert 1 Galaxy 1H 1934-063

Yangji Li, Jinming Bai, Xiong Jiang, Kaixing Lu

We report a $γ$-ray excess toward the radio-quiet narrow-line Seyfert 1 galaxy 1H 1934-063 using data collected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope and taking into account the LAT 16-year Source List (FL16Y). During the flare interval, the excess is detected in the 1--500 GeV band at a significance of $\sim 5.2σ$ (TS = 27.12), with a photon flux of $(4.94\pm2.33)\times10^{-10}$ ph cm$^{-2}$ s$^{-1}$ and a hard photon index of $Γ=1.50\pm0.25$. The best-f…

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astro-ph.GAastro-ph.SR

Molecule-dependent Abundance Behavior of Oxygen-bearing Complex Organics in High-Mass Star-Forming Regions: A Uniform 50-source Survey

Xuefang Xu, Mingwei He, Qian Gou, Jiao He, Junzhi Wang, Donghui Quan, Di Li, Laurent Pagani et al.

We present a uniform IRAM-30\,m survey analysis of four oxygen-bearing complex organic molecules (COMs), methanol (CH$_3$OH), acetaldehyde (CH$_3$CHO), methyl formate (CH$_3$OCHO), and dimethyl ether (CH$_3$OCH$_3$), toward 50 high-mass star-forming regions (HMSFRs) associated with 6.7\,GHz methanol masers. Column densities were derived through a homogeneous rotation-diagram approach, with CH$_3$CN used as a proxy excitation-temperature reference when needed. In CH$_3$OH-normalized abundance-rat…

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