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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.GAastro-ph.HE

Radio-detected Lya emitters at 1.88 < z < 3.52: AGN fraction and Lya emission

Sai Zhai, Huub Röttgering, Anniek J. Gloudemans, Erin Mentuch Cooper, Maya H. Debski, Gregory Zeimann, Matt J. Jarvis, Leah K. Morabito et al.

Lya emitters (LAEs) are galaxies with strong Lya emission, tracing early star formation and ionizing radiation. Their connection to active galactic nuclei (AGNs) is key to understanding the mechanisms behind (extended) Lya emission. In this work, we measure the fraction of LAEs identified as radio-emitting AGN (fAGN,radio) and the fraction of radio sources that exhibit Lya emission (fLya) to investigate the connection between radio AGN activity and Lya emission at 1.88 < z < 3.52. We identify 92…

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astro-ph.HEastro-ph.SRhep-ph

Non-thermal emission from the vicinity of the magnetar CXOU J171405.7-381031

Manoel F. Sousa, Rita. C. Anjos

Magnetars are neutron stars with ultra-strong magnetic fields ($B \sim 10^{14}$-$10^{15}$ G) and are promising candidates for high-energy particle acceleration. We present a multiwavelength analysis of the region surrounding CXOU J171405.7-381031, a magnetar associated with the supernova remnant (SNR) CTB 37B. The broadband spectral energy distribution spanning radio to TeV energies is modeled using leptonic and lepto-hadronic scenarios, with particle populations constrained using Markov Chain M…

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astro-ph.EP

Spectral features in the visible spectra of the Enceladus particle plume and E ring: Potential evidence of organic materials and/or missing sub-micron particles

M. M. Hedman, S. M. MacKenzie

Visible spectra of the Enceladus particle plume and E ring contain evidence for a change in spectral slope around 0.5 micron. This feature can be seen in data obtained by both the Visual and Infrared Mapping Spectrometer (VIMS) and Imaging Science Subsystem (ISS) onboard the Cassini Spacecraft, and is consistent with the slope change seen in the surface spectra of Saturn's rings and moons that has been attributed to either organics or iron compounds. The observed spectral features in the plume a…

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astro-ph.EPastro-ph.GAastro-ph.SR

Extending dynamical mass measurements: probing GI as a possible origin of mm-dust spirals

V. Pezzotta, S. Facchini, A. F. Izquierdo, G. Lodato, C. Longarini, J. Bae, M. Galloway-Sprietsma, C. Pinte et al.

Constraining the total mass of protoplanetary disks is crucial to determine the availability of material for planet formation. Yet, providing accurate and precise measurements of the disk mass is challenging. Investigating the gas dynamics is a powerful, tracer-independent method to precisely characterize disk masses. By fitting the velocity rotation curves of different molecular tracers with an accurate model including the disk thermal stratification and self-gravity, we constrain the stellar m…

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physics.plasm-phastro-ph.HE

Relativistic Scaling and Magnetization-Current Feedback in Stern Gerlach-Modified Pair-Plasma Reconnection: SpinPIC2D Validation and Nonlinear Regimes

K. Nykyri

We investigate the relativistic scaling and electromagnetic feedback of Stern--Gerlach (SG) force driven spin transport in pair-plasma reconnection with SpinPIC2D. The model advances relativistic proper momentum and magnetic BMT spin precession, applies the SG force, deposits spin magnetization, and includes $\mathbf J_M=\nabla\times\mathbf M$ in Ampere's law. In a weak-seed scan at fixed $γ_{\rm tr}=2$, the normalized global magnetic flux-growth remains near the classical control-run for $Ξ\le0…

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astro-ph.GA

The S-PLUS Fifth Data-Release: Over 4500 square degrees of the Southern Sky and a multicolor view of the Hydra and Antlia galaxy clusters

Erik Vinicius Rodrigues de Lima, Gustavo Bernhard Oliveira Schwarz, Fábio Rafael Herpich, Felipe Almeida-Fernandes, Lilianne Nakazono, Eduardo Alberto Duarte Lacerda, André Santos, André Luiz Figueiredo et al.

We present the 5th data release (DR5) of the Southern Photometric Local Universe Survey (S-PLUS), covering 4592 square degrees across 2491 fields. Observations were conducted with the T80-South, a Brazilian robotic telescope equipped with the Javalambre 12-filter system, containing five broad- and seven narrowband filters. Data products feature FITS images and extensive catalogs containing fluxes, magnitudes, and shape parameters for over 113 million detections. In addition, several value-added…

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astro-ph.IMastro-ph.GA

Compressing radio interferometric visibility data into a probabilistic model using sparse Gaussian processes

Takafumi Tsukui

Next-generation radio interferometers will produce massive data volumes, making it impractical to store original visibility measurements and later combine observations in $uv$ spatial frequency space. Visibility measurements at similar $uv$ locations measure the same signal but different noise realizations. In principle, these measurements can therefore be compressed by storing only the inferred mean visibility and its uncertainty. We propose modeling the visibility with a sparse Gaussian proces…

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astro-ph.SR

Solar Cycle Variation of the Distribution of Photospheric Magnetic Flux Features

Callan N. Noble, Clare E. Parnell, Thomas Neukirch

We use statistical tools to analyse data from the Solar Dynamics Observatory Helioseismic and Magnetic Imager to determine the distribution of the magnetic flux of photospheric magnetic features and its variation over a full solar cycle. In particular, we use statistical figures of merit to test how well different types of probability density function represent the magnetic flux distribution inferred from the data and how their shape changes over the solar cycle. Our analysis shows that a double…

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astro-ph.GA

Chemical Evolution of Galaxies: Past, Present and Future

Francesca Matteucci

In this paper I will describe the basic principles of chemical evolution of galaxies, its main ingredients and uncertainties. By means of chemical evolution we can perform the so-called galactic archaeology, which consists in reconstructing the history of star formation of galaxies and in particular of the Milky Way, starting from the observed stellar and gas abundances. Galactic archaeology is a powerful tool to predict also the behaviour of galaxies at high redshift. In particular, we adopt th…

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astro-ph.HE

A cosmic-ray loaded nascent outflow driven by a massive star cluster

Marianne Lemoine-Goumard, Lucia Härer, Lars Mohrmann, Romain Bernet, Jim Hinton, Giada Peron, Brian Reville, Luigi Tibaldo et al.

Cosmic rays are widely held to drive outflows from star-forming galaxies and profoundly influence galaxy evolution. Direct evidence for cosmic-ray carrying outflows is however lacking. At the same time there is increasing awareness of the importance of massive star clusters in the acceleration of cosmic rays in galaxies. Here we report on the discovery of a nascent outflow driven by the massive star cluster Westerlund 1. Giga-electronvolt gamma-ray emission coincident with a cavity visible in at…

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astro-ph.IMastro-ph.SR

Radial velocity and atmospheric parameter calculations for the GaiaNIR spectrograph

Szabolcs Mészáros, David Hobbs, Anna Liptrott, David Katz, Ricardo Schiavon, Viktória Pap, Anthony G. A. Brown, George Seabroke et al.

Context. The upcoming GaiaNIR mission is currently planning to add a near-infrared spectrograph to its payload in order to enhance its scientific return, particularly for mapping the dust-obscured regions of the Milky Way. Aims. This study aims to identify the optimal wavelength region between 800 and 2300 nm for the proposed GaiaNIR spectrograph to maximize the precision of radial velocities and atmospheric parameters. Methods. To find its spectral range, we generated 10000 synthetic spectra fr…

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astro-ph.EPastro-ph.IM

Accuracy Analysis of VLBI Universal Time Measurement Based on a GNSS Single-Station Regional Ionospheric Model

Xu-chong Duan, Dang Yao, Yuan-wei Wu, Zhe Zhang, Jia Liu, Xu-hai Yang

Universal Time (UT1) is a key parameter characterizing Earth's rotation, and very long baseline interferometry (VLBI) is the mainstream technique for measuring UT1. To address the limitations in the timeliness and accuracy of existing global ionospheric models for single-frequency VLBI UT1 measurements, we construct a single-station regional ionospheric model using GNSS data from the VLBI stations on the Jilin-Kashi baseline. We apply this model to VLBI observations and compare its correction pe…

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astro-ph.SR

Three-dimensional evolution of a solar filament with multipoint observations

Qingmin Zhang, Jun Dai, Beili Ying, Ye Qiu, Li Feng, Chuan Li, Hongqiang Song, Yue Zhou et al.

In this paper, we first devise a geometrical model, featuring a torus-like flux rope based on the shape of 3DCORE model. The global shape of the torus is an ellipse, while the cross sections are circular along the torus. The thinnest point is located between the Sun center and photosphere. Deflections and inclination are considered as well. Using multiwavelength observations from perspectives of Earth, Ahead-STEREO (STA), and Solar Orbiter, we apply the model to three-dimensional (3D) reconstruc…

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astro-ph.GA

Testing various assumptions for radiolysis, non-diffusive chemistry, and chemical desorption in cold cores

V. Wakelam, T. Tu

To study interstellar gas and grain chemistry, gas-phase astrochemical models have been developed since the early 1980s and gas-grain models since the 1990s. Each published model includes various assumptions mainly for surface processes. In this paper, we compare recently added mechanisms for grain surface chemistry, namely, non-diffusive chemistry, radiolysis, and chemical desorption. Several formalisms for these processes have been added to our astrochemical model Nautilus, and we tested them,…

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astro-ph.HE

Stable X-ray reverberation lags in the black hole X-ray binary Swift J1727.8-1613

Wei Yu, Sinan Allak, Zi-Xu Yang, Xiao Fan, Andrea Santangelo, Tian-hao Xie

Aims. We investigate the evolution of X-ray reverberation lags in the black hole X-ray binary Swift J1727.8-1613 during its 2023 outburst, with the aim of probing the inner accretion flow geometry across spectral states. Methods. We analyzed NICER observations covering the low-hard state (LHS) and hard-intermediate state (HIMS). The time lags were computed using Fourier-based techniques, and we constructed lag-frequency and lag-energy spectra. To obtain a robust estimate of the soft lag amplitud…

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astro-ph.SR

Explainable AI for Solar Flare Prediction: Quantitative Magnetic Field Analysis of Model-Focused Regions

Z. Zheng, Q. Hao, C. Li, P. F. Chen, J. R. Hu, M. D. Ding, C. Fang

Solar flares are intense energy release events in the solar atmosphere that may pose significant space weather hazards, which makes developing reliable prediction models essential. Although deep learning methods, particularly convolutional neural networks (CNNs), demonstrate strong predictive performance when using solar magnetograms, their scientific credibility is undermined by a lack of physical interpretability. Explainable artificial intelligence (XAI) offers a potential solution. However,…

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astro-ph.EP

Debris Evolution from Spacecraft Fragmentation in Earth-Moon Distant Retrograde Orbits

Yuyan Wu, Peng Shu, Yuqiang Li

With the rapid surge in lunar exploration and the planned expansion of cislunar infrastructure, cislunar space has become a strategic focal point for global aerospace activities. This proliferation of spacecraft heightens the risk of fragmentation events, such as unintended explosions or orbital collisions which serve as the primary source of hazardous orbital debris. Given the potential threat these fragments pose to mission safety and long-term orbital sustainability, it is imperative to inves…

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astro-ph.IM

Torsional-X Seismometer for Lunar Decihertz Gravitational-Wave Detection

Yulin Xia, Denis Martynov, Huan Yang, Haixing Miao

The lunar gravitational-wave antenna concept uses the Moon as a resonant detector instrumented with precision seismometers, targeting the decihertz band between ground- and space-based observatories. We propose a compact monolithic fused-silica torsional-X seismometer that re-engineers garden-gate acceleration-to-rotation transduction for this regime through a high-tension dual-fiber suspension. Its designed millihertz-scale resonance and ultra-low mechanical dissipation enable a nearly order-of…

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astro-ph.EP

Distant TNO Inclinations as a Constraint on Primordial Cluster Perturbations in the Presence of Planet Nine

Avni Bansal, Ian Brunton, Konstantin Batygin, Gabriele Pichierri, David Nesvorný

The Sun was almost certainly born in a stellar cluster, implying some degree of external forcing from neighboring stars during the Solar System's infancy. Published estimates of the strongest relevant stellar encounter, however, span a broad range, from relatively gentle perturbations to violently disruptive flybys. The modest inclination dispersion of the distant trans-Neptunian population has previously been used to argue that strong primordial encounters were unlikely and that the outer Solar…

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astro-ph.GA

Identifying and Distinguishing Quenching Galaxies with Spatially Resolved Star Formation in Mock CASTOR and NGRST Observations

Cameron Lawlor-Forsyth, Michael L. Balogh, Sean L. McGee, Gregory H. Rudnick

We present synthetic images of galaxies that are in the stages of star formation quenching for the Cosmological Advanced Survey Telescope for Optical and UV Research (CASTOR) and Nancy Grace Roman Space Telescope (NGRST), based on simulations coming from the IllustrisTNG suite, as processed using the stellar population synthesis library \textsc{galaxev}. We account for the effects of dust and various sources of noise to produce mock observations that should mirror real observations. Using these…

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astro-ph.SR

Oscillation Period Properties of Sunspots in the 8-10 $μ$m Infrared Band: A Multi-Dataset Analysis

Suo Liu

Sunspot oscillations probe magnetic-plasma interactions in the solar atmosphere. We investigate oscillation periods in six sunspot active regions observed in the 8-10 um band with the Accurate Infra-red Magnetic-field Solar Telescope (AIMS) at Lenghu Observatory. Light curves were extracted from umbra, penumbra, and quiet Sun regions. Wavelet analysis was applied using four methods: pixel-wise with mean/median aggregation, and spatial mean/median prior to analysis. The weighted mean period is mo…

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astro-ph.GA

The FAST HI 21-cm Absorption Blind Survey. III. OH Absorption Search in the 21-cm Absorber Sample and Continued HI Absorption Search

Wenkai Hu, Yougang Wang, Jeremy Darling, Zheng Zheng, James R. Allison, Elaine M. Sadler, Wenxiu Yang, Yichao Li et al.

We present the first blind search for OH 18-cm absorption with the Five-hundred-meter Aperture Spherical Telescope (FAST), conducted alongside the HI 21-cm absorption search. Our previous FAST blind HI absorption search identified 34 systems. In this work, we extend the search using 2024 and part of the 2025 CRAFTS and FASHI data (394.4 hr and 1622.1 deg$^{2}$) together with FATHOMER observations, yielding three known and four new HI absorbers, for a total of 41 HI absorption systems. We search…

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astro-ph.HE

High-Density Sound Speed and Post-Merger Dynamics

John Stroud, David Radice, Sanjay Reddy

The density dependence of the speed of sound in cold neutron star matter remains poorly constrained and is central to determining the high-density equation of state (EOS). While binary neutron star (BNS) merger simulations increasingly incorporate detailed microphysics, the direct impact of the sound-speed in the neutron star core on observable signatures has not been systematically explored. We address this by introducing a simplified parametrization that suppresses microphysics while allowing…

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astro-ph.COastro-ph.GA

Morphological Bias: How Ellipticals and Spirals Trace the Cosmic Web Differently

Paula S. Ferreira, Carlos A. P. Bengaly, Renyue Cen

We present a data-driven measurement of galaxy bias and scale-dependent relative bias for elliptical and spiral galaxies using angular auto- and cross-power spectra from DES and DESI Legacy Imaging Surveys DR8. We introduce the cross-tracer clustering ratio (CTCR), which uses the ratio of auto- to cross-power spectra to isolate the relative clustering of morphological tracers as a function of angular multipole $\ell$. Across both surveys, ellipticals are more strongly clustered than spirals; the…

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astro-ph.GAastro-ph.HE

22 Newly Identified Repeating Changing-look AGNs and Evidence for Extreme Broad-line Region Breathing

Litao Zhu, Zhongxiang Wang, Alok C. Gupta, Yiyang Zeng, P. U. Devanand, Karan Dogra, Riya Bhowmick, Ju-Jia Zhang et al.

Changing-look active galactic nuclei (CL AGNs) show the appearance or disappearance of broad emission lines on timescales of years. Among them, the repeating CL (RCL) AGNs may provide a clear clue for our understanding of the CL transitions because the same nucleus crosses some physical boundaries more than once. We search for RCL AGNs in known CL-AGN samples using long-term multi-band light curves, and selected 34 candidates for spectroscopic follow-up. We confirm 25 RCL AGNs, including 22 newl…

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astro-ph.SR

Investigation of projected rotational velocities of Be-type stars in LAMOST DR7

Zhicun Liu, Jiao Li, Jiaming Liu, Xiao-Long Wang, Guozhen Hu, Wenyuan Cui

Stellar rotation plays a key role in the transfer of angular momentum, and a large sample of Be-type stars with reliable projected rotational velocities is crucial for understanding their formation and evolution. In this work, we derive the projected rotational velocities ($v$\,sin\,$i$) of 479 Be-type stars using the Fourier transform method, based on their LAMOST Medium-resolution Survey (MRS) spectra. Our results suggest that the Fourier transform method can provide reliable $v$\,sin\,$i$ val…

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astro-ph.SRastro-ph.EP

Silicate Clouds, SiO, and Molecular Trends across the L-T Sequence: A JWST/MIRI LRS Spectral Library of Brown Dwarfs

Sam Barber, Stanimir Metchev, Genaro Suárez, Samantha Lambier, Paulo A. Miles-Páez, Étienne Artigau, Beth Biller, Adam J. Burgasser et al.

We present the results of a survey program with JWST's MIRI LRS that obtained 5$-$14 $μ$m R~100 spectra of twenty-three L0$-$T6 dwarfs. This spectral type range spans the formation, growth, and sedimentation of silicate condensate clouds, as well as the appearance of methane and ammonia in the atmospheres of brown dwarfs. The initial onset of silicate absorption at spectral type L0 as well as the evolution of this feature with spectral type are both examined in unprecedented detail. We detect 7.…

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astro-ph.GA

Gas-Phase Metallicity and Nitrogen Abundances in Low-Mass Galaxies Down to $M_\star\simeq10^{5.7}\,M_\odot$ at $z\simeq4.5$--$10.1$ from JWST Lensing Cluster Surveys

Hiroya Umeda, Masami Ouchi, Kimihiko Nakajima, Kuria Watanabe, Yuichi Harikane, Yuki Isobe, Moka Nishigaki, Ono Yoshiaki et al.

We analyze 405 deep JWST/NIRSpec spectra of star-forming galaxies at $z=4.5$--$10.1$ from DREAMS and other lensing-cluster surveys to study chemical enrichment in intrinsically faint, low-mass galaxies. The sample covers $M_{\rm UV}\simeq-12$ to $-22$ and reaches $M_\star\simeq10^{5.7}\,M_\odot$, with 50\% of the sources at $M_{\rm UV}>-17.5$ magnified by $μ>3$. From individual spectra and mass-binned stacks, we derive the gas-phase metallicity together with nitrogen and carbon abundances using…

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hep-phastro-ph.COastro-ph.HE

PBH formation and Gravitational Waves as Multi-messenger Signals of First-order Phase Transitions

Bhaskar Dutta, Cash Hauptmann, Peisi Huang, Adrian Thompson

The collapse of false-vacuum domains during first-order phase transitions in the early Universe may lead to primordial black hole (PBH) formation whose signatures form a multimessenger complement to gravitational wave (GW) production. We focus on PBH formation through the gravitational collapse of false-vacuum domains, described using a junction condition formalism. This formalism develops the Schwarzschild collapse criterion dynamically, avoiding the usage of critical overdensity thresholds in…

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astro-ph.IMastro-ph.GA

Star formation, stellar evolution, and planets in high-resolution X-ray imaging

Hans Moritz Günther, Scott J. Wolk, Sean J. Gunderson, Ruchi Pandey, Keivan G. Stassun, Lynne Valencic

Stars set the conditions for planet formation, planet evolution, and habitability -- all major topics in astronomy today. Stars are also important in their own right as the most visible component of galaxies. In cool stars, X-ray emission is powered by magnetic fields, and so far our Sun is the only system in which those fields are spatially resolved. High-resolution X-ray (HiReX) imaging can track the origin and evolution of those fields, see how they connect young stars to their disks and outf…

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