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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.GA

Interstellar extinction of classical Cepheids from neighboring stars I. Methodology and application to 16 Galactic Cepheids

Wilma Kiviaho, Pierre Kervella, Mika Juvela, Alexandre Gallenne, Nicolas Nardetto, Carine Babusiaux, Rosine Lallement, Vincent Hocdé et al.

Galactic Cepheid variable stars are fundamental calibrators of the cosmic distance scale through their Period-Luminosity (PL) relation. The high-precision parallaxes expected from Gaia Data Release 4 (DR4) will enable a calibration of the Milky Way PL relation with unprecedented precision. This will place stringent requirements on interstellar extinction corrections, which remain a dominant source of uncertainty. We strive to derive highly accurate extinction values for Galactic Cepheids. We pre…

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astro-ph.COastro-ph.GA

The Lumina Project: Morphology of Ionized Bubbles and Neutral Islands

Meredith Neyer, Aaron Smith, Ali Sadain, Oliver Zier, Mark Vogelsberger, Teodora-Elena Bulichi, Xuejian Shen, Sonja M. Koehler et al.

The Epoch of Reionization is characterized by the nucleation, expansion, and percolation of ionized bubbles in the intergalactic medium. Interpreting emerging multi-wavelength observations from facilities such as JWST and next-generation 21 cm interferometers requires a detailed theoretical understanding of the 3D morphology of these HII regions and of the residual neutral structures that survive near the end of reionization. We analyze the geometry and physical properties of ionized bubbles and…

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astro-ph.GA

Investigating the ionization mechanisms powering the extreme emission lines in metal-poor galaxies

C. Daoutis, V. Lebouteiller, D. Schaerer, I. Morel, O. Bait, S. Satyapal, S. Doan, B. Trahin et al.

Extreme emission metal-poor galaxies (EEMPGs) are excellent local laboratories for understanding the extreme physical conditions and ionizing radiation fields in the early Universe. However, the exact source of high-ionization emission lines in them, whether from intermediate-mass black holes (IMBHs), ultra-luminous X-ray sources (ULXs), or radiative shocks, remains debated. We characterize the fundamental properties and ionizing radiation field on metal-poor EEMPGs, aiming to identify the domin…

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astro-ph.HE

A Tentative Line-like GeV Excess in Fermi Blazar 4FGL J1754.2+3212: Implications for Jet Physics and Beyond

Shi-Ju Kang, Yue Yin, Yong-Gang Zheng, Qingwen Wu

We report the detection of a tentative, narrow spectral feature in the GeV gamma-ray spectrum of the blazar 4FGL J1754.2$+$3212, using approximately 16.5 years of observations from the Fermi Large Area Telescope. A detailed likelihood analysis of the time-averaged spectrum reveals a localized, line-like excess at an energy of $\sim$31 GeV, with a local statistical significance of $\sim$3$σ$ (3 degrees of freedom), without corrections for multiple trials and the look-elsewhere effect. This featur…

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astro-ph.HE

Study of blazar variability through their flux distribution for CTAO long-term monitoring

A. Mikhno, J. Biteau, J. -P. Lenain on behalf of the CTAO collaboration

The CTAO Key Science Project on Active Galactic Nuclei (AGN) includes a long-term monitoring (LTM) program of blazars. The probability distribution function (PDF) of the flux extracted from unbiased blazar lightcurves can provide important insight into the physical processes taking place in relativistic jets and their connection to observed variability. The aim of this work is to define an optimal observational strategy for the CTAO LTM program using the flux distributions as a quantitative metr…

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astro-ph.COastro-ph.GA

JWST evidence for a sharp "Cosmic Daybreak" at z = 15

Jiashuo Zhang, Tom Broadhurst, Tzihong Chiueh, Keiichi Umetsu, Hsi-Yu Schive, Chian-Chou Chen, Jeremy Lim, Jose M. Diego et al.

Luminous young galaxies have been uncovered with relative ease by JWST, extending to z=14.5, so it is puzzling that deeper spectroscopy of fainter candidates now finds only interlopers. This redshift `ìmpasse" is underscored by the measured stellar ages of these high-z galaxies, which we show converge to zero by z=15, with a marked absence of earlier star-formation. Taken literally, such a late transition from the Dark Ages to luminous galaxies is unlike the gradual Cosmic Dawn of standard LCDM,…

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astro-ph.COastro-ph.GA

JWST evidence for a sharp "Cosmic Daybreak" at z = 15

Jiashuo Zhang, Tom Broadhurst, Tzihong Chiueh, Hsi-Yu Schive, Keiichi Umetsu, Jose M. Diego, Paloma Morilla, Alvaro Pozo et al.

Luminous young galaxies have been uncovered with relative ease by JWST, extending to z=14.5, so it is puzzling that deeper spectroscopy of fainter candidates now finds only interlopers. This redshift `ìmpasse" is underscored by the measured stellar ages of these high-z galaxies, which we show converge to zero by z=15, with a marked absence of earlier star-formation. Taken literally, such a late transition from the Dark Ages to luminous galaxies is unlike the gradual Cosmic Dawn of standard LCDM,…

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astro-ph.HE

4U 1624-490 as a possible intermediate-mass X-ray binary: constraints from XRISM and NuSTAR spectroscopy

R. Iaria, A. Anitra, T. Di Salvo, A. Sanna, F. Barra, L. Burderi, C. Maraventano, S. Caserta et al.

High-inclination dipping neutron-star X-ray binaries provide a direct view of accretion-flow structure because the line of sight intercepts ionised plasma above the disc. We analyse two XRISM/Resolve observations of 4U 1624$-$490 with simultaneous NuSTAR coverage, dividing the data into seven orbital-phase intervals. Phase-resolved fits include neutral partial covering, a photoionised absorber, thermal Comptonisation, and ionised disc reflection. Fe XXV and Fe XXVI absorption are detected over m…

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astro-ph.HE

Radio component of the multi-messenger emission from the anticipated T Coronae Borealis outburst

O. Petruk, T. Kuzyo, S. Orlando, L. Chomiuk, F. Bocchino, M. Miceli, V. Beshley

T Coronae Borealis is the nearest symbiotic recurrent nova and is expected to undergo a new eruption soon, offering a rare opportunity to study shock evolution and particle acceleration. We predict radio emission from the outburst and assess how radio observations can constrain the circumbinary medium (CBM) and cosmic-ray acceleration. We post-process three-dimensional (3D) hydrodynamic nova simulations with a multi-zone model for particle acceleration and radio emission, computing thermal free-…

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astro-ph.EP

The dust in Sauron's eye - Observational and experimental results on the debris disk around HR 4796

M. Bonduelle, J. Milli, O. Poch, N. Engler, M. Rigouleau, R. Tazaki, J. Ma, J. Olofsson et al.

The optical properties (scattering phase function SPF; degree of linear polarization DoLP; reflectance) of the dust particles orbiting in debris disks can be retrieved through scattered light imaging and are linked to the physicochemical properties of the dust (size, shape, composition...). Among debris disks, the bright, narrow disk surrounding HR 4796A presents several peculiarities, in particular unusually high DoLP values at small scattering angles. We aim at improving the constraints on the…

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astro-ph.HE

Gamma-ray emission toward supergiant shells in the Large Magellanic Cloud

Qixin Yu, Olaf Reimer, Anita Reimer

The Large Magellanic Cloud (LMC), a satellite galaxy of our Milky Way, is considered to be a very good target for investigations of diffuse gamma-ray emission. Observations have shown that diffuse emissions are related to the large- and small-scale structures of the LMC. Particularly, it has been suggested that some of the small-scale bright diffuse emissions coincide with supergiant shells (SGSs) previously identified based on H$α$ images. We analyzed the gamma-ray emission from the LMC using m…

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nucl-thastro-ph.HEastro-ph.SR

The compressible liquid drop model with curvature included algebraically for the pasta phases in neutron stars

Dmitry Kobyakov

In the compressible liquid drop model (CLDM), the curvature energy term has been included in many works in the literature, and its effects on the presence of pasta phases have also been extensively investigated. However, the analytical part of the inclusion used to cease once a 4-order algebraic equation for the optimized size of the nucleus was written. In this paper, an optimization is suggested to the analytical part of the solution of the CLDM equations. Solving analytically the 4-order alge…

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gr-qcastro-ph.IMhep-exhep-ph

MAGGIE: A Magnetic Gravitational Wave Induction Experiment

Jasper Jödicke, Marios Maroudas, Toma-Stefan Cezar, Dieter Horns

Gravitational waves (GWs) can induce effective electromagnetic currents when interacting with external electric and magnetic fields, as described by linearized gravity modifications to Maxwell's equations. This coupling enables a novel detection approach for high-frequency gravitational waves (HFGWs) using axion haloscope experiments. Here we present the MAGnetic Gravitational wave Induction Experiment (MAGGIE), the first lumped-element HFGW detector proposed in Europe, designed to probe HFGWs i…

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astro-ph.HE

Variable opacity and accretion-column regimes of magnetized neutron stars

Galina Lipunova, Pavel Abolmasov

Radiation-supported accretion columns of magnetized neutron stars can operate in several distinct regimes. As the accretion rate increases, magnetospheric accretion may proceed through hot-spot emission, efficiently cooling radiative shocks, and advective sinking columns. The structure of the accretion flow is determined by the global parameters such as magnetic field strength and mass accretion rate, but is also affected by opacity variations in strong magnetic fields. A decrease of opacity for…

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astro-ph.HE

Shock-free super-Eddington accretion onto magnetized neutron star

Galina Lipunova, Pavel Abolmasov

Strong magnetic fields allow accreting neutron stars to form magnetically controlled funnel flows. At sufficiently high accretion rates, such flows become radiation-pressure-supported. In the conventional picture, the magnetospheric flow contains a nearly free-falling transonic outer region, a radiation-mediated shock, and a subsonic accretion column. We investigate the regime in which the height of the column is expected to exceed the magnetospheric radius. In this case a self-consistent transo…

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astro-ph.HE

First X-ray detection of symbiotic nova CN Cha with eROSITA/SRG

Sara Saeedi, Jaroslav Merc, Manami Sasaki, Lorenzo Ducci, Michael Freyberg

Aims. We report on the first X-ray detection of the symbiotic star CN Cha with eROSITA (extended Roentgen Survey with an Imaging Telescope Array) onboard Spektrum-Roentgen Gamma (Spektr-RG). Methods. We analyse the eROSITA observations from eRASS2 to eRASS5 individually, as well as the combined eRASS:5 data of all five surveys in order to investigate the X-ray spectral and timing properties of CN Cha throughout the eRASS. Results. Although CN Cha was not detected during the first eROSITA All-Sky…

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astro-ph.SR

Nature of small-scale Ca II H brightenings associated with weak fields in a quiet Sun region

Xiang Li, H. N. Smitha, S. K. Solanki, T. L. Riethmüller, L. P. Chitta, S. Jafarzadeh

Context. Chromospheric emission observed in the Ca II H and K resonance lines is generally positively correlated with photospheric magnetic fields. However, a fraction of strong Ca II H&K brightenings are found to occur over regions of low photospheric magnetic flux density. Aims. We aim to understand the origin of these chromospheric brightenings associated with weak fields in quiet Sun regions. Methods. We use Ca II H observations taken by the SuFI along with the photospheric magnetograms reco…

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astro-ph.GA

Detection of metal absorption lines in quasar spectra: a neural network approach using U-Net

Elena Sofia Mangola, Francesco Pistis, Michele Fumagalli, Matteo Fossati, Ting-Yun Cheng, Ryan J. Cooke, Rajeshwari Dutta, Ignasi Pérez-Ràfols et al.

Current and future large spectroscopic surveys are significantly enhancing the volume and resolution of quasar spectra that are observed, which requires the creation of efficient and precise automated techniques to detect absorption features. This study focuses on the detection of metal absorption features using a novel U-Net model on WEAVE-like mock spectra in the quasar rest-frame wavelength interval $1230\,\mathring{\mathrm{A}} \leq λ_{\rm RF} \leq 3095\,\mathring{\mathrm{A}}$. We test the ne…

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astro-ph.SR

High-Resolution Modelling of Coronae and Winds in Solar-type Stars with Varying Rotation Rates II. Stellar Winds

Yue-Hong Chen, Julián D. Alvarado-Gómez, Xin Cheng, Victor See, Yu Dai, Maarit J. Korpi-Lagg, Jörn Warnecke, Chen Xing et al.

Observations suggest a connection between steady-wind mass loss and coronal X-ray activity in low-mass main-sequence stars. Interpreting this connection is challenging because the wind is controlled mainly by the large-scale open field, whereas X-ray emission traces heating in small-scale closed fields often unresolved in global wind models. Here we use Space Weather Modelling Framework-Alfvén-Wave Solar Model with global convective dynamo-generated magnetic maps and solar magnetograms. We model…

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astro-ph.HE

A Diagnostic Method for Proto-Neutron Star Magnetic Fields by Supernova Fallback Neutrinos

Akihiro Inoue, Yudai Suwa, Ryuichiro Akaho, Shinsuke Takasao, Kazumi Kashiyama, Hiroyuki R. Takahashi

Young isolated neutron stars exhibit a wide range of magnetic field strengths. To understand the origin of this diversity, it is important to observationally constrain magnetic fields during the proto-neutron star (PNS) phase. We propose a novel diagnostic of PNS magnetic fields using neutrinos associated with supernova fallback. By performing one-dimensional general-relativistic magnetohydrodynamic simulations of the supernova fallback onto a magnetized PNS, we investigate how the energy spectr…

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gr-qcastro-ph.IM

Neural Network Guided Parameter Space Constraints for Gravitational Wave Searches from Binary Black Holes

Chetan Verma, Amit Reza, Gurudatt Gaur, Dilip Krishnaswamy, Sarah Caudill

The detection of gravitational waves (GWs) from compact binary coalescences (CBCs) using matched filtering is computationally demanding because detector data must be correlated with many template waveforms spanning a high-dimensional intrinsic parameter space. In our previous work, we showed that a convolutional neural network (CNN) can classify noisy signals against pure noise and constrain the intrinsic parameter space of a true non-spinning binary black hole (BBH) signal, enabling a narrower…

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astro-ph.GA

The Neutral Hydrogen Gas Content of Star-forming and Quiescent S0 Galaxies

D. A. A. Lee, Karen L. Masters, David V. Stark, Z. Z. Abidin

Lenticular (or S0) galaxies that remain actively star-forming (SFS0s) are a unique transition population among galaxies. We investigated the HI (21cm) neutral hydrogen content of a sample of lenticular galaxies identified from within the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey and which have been classified as star-forming or quiescent (qS0s). We compared these populations to each other and to a sample of star-forming spiral galaxies in MaNGA. We found that the HI Mass…

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astro-ph.IMastro-ph.GAastro-ph.HE

AstroGenesis: A Domain-Specific Multi-Agent AI for Astrophysical Research

N. Sahakyan, M. Khachatryan, A. Mahabal, D. Pasham, A. Khachatryan, V. Markosyan, N. Unkovskii, V. Vardanyan et al.

Modern astrophysical research requires the integration of rapidly expanding scientific literature, heterogeneous observational data, and increasingly complex physical models. We introduce AstroGenesis (https://astrogenai.com), a domain-specific multi-agent AI framework that integrates literature retrieval, multiwavelength data access and analysis, theoretical modeling, and research ideation within a unified research environment.The current implementation focuses on blazar research, with speciali…

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cs.LGastro-ph.SRcs.AIphysics.space-ph

PISCES: Physics-Informed Solar-wind Convolutional autoEncoder for Space-weather Anomaly Detection and Early Warning

Kevin Lee, Alison J. March

Space weather early warning depends on detecting solar wind transients in in-situ measurements at the first Sun-Earth Lagrange point (L1), before they reach Earth. Fixed thresholds can miss combined magnetic and plasma structure, and many learning methods provide a single anomaly score. We present the Physics-Informed Solar-wind Convolutional autoEncoder for Space-weather (PISCES), a convolutional autoencoder trained without catalog labels on OMNI solar wind measurements under physics constraint…

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astro-ph.HE

Semi-Analytic Solutions For Warped, Super-Eddington Accretion Disks with Outflows

Gabriel Wohlfarth, Matthew Middleton, Omer Blaes, P. Chris Fragile

The discovery of billion solar mass black holes at high redshift challenges any standard Eddington-limited growth model. Previous work has shown that an advective accretion disk can account for these early black holes with episodic accretion. It has also been shown that if the accretion disk of a black hole is misaligned from the spin axis of the black hole, the disk can become advective within a certain radius. While warped and misaligned accretion disks have been explored in numerical simulati…

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astro-ph.SRastro-ph.EP

Stellar flares with Ariel: detection prospects and impacts on exoplanet spectroscopy

K. Vida, B. Seli, B. Edwards

Stellar flares are important tracers of magnetic activity and can significantly influence the characterization of exoplanet host stars by introducing time-dependent astrophysical variability. ESA's Ariel mission, designed for atmospheric characterization of exoplanets, will include the VISPhot instrument, providing high-cadence optical photometry offering an opportunity to study stellar flares while identifying and mitigating their impact on transit spectroscopy. We discuss Ariel's potential for…

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astro-ph.SRastro-ph.EP

ALMA's sharpest view of IRAS 08544-4431: Unveiling the dust distribution asymmetries in the circumbinary disk

Maksym Mohorian, Devika Kamath, Elizabeth Cappellazzo, Kateryna Andrych, Jacques Kluska, Hans van Winckel, Daniel Price, Toon De Prins et al.

The interactions between post-asymptotic giant branch (post-AGB) binaries and their circumbinary disks play a central role in shaping the evolution of these systems. Circumbinary disks around post-AGB binaries are stable, though relatively short-lived structures ($10^4-10^5$ years) and their physical properties and evolution remain poorly understood. In this study, we target IRAS 08544-4431, one of the best-studied post-AGB binaries. This system has well-constrained stellar and orbital parameter…

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physics.plasm-phastro-ph.HE

Anisotropy and energy distribution of leptons and photons in radiative relativistic Alfvénic turbulence

Peng Liu, Xiaochun Wei, Zheng Gong

The anisotropic evolution of relativistic particles in magnetically dominated Alfvénic turbulence is a fundamental process governing nonthermal emissions in high-energy astrophysical environments. In this work, we develop a theoretical framework by deriving scaling equations that characterize the pitch-angle dynamics of leptons and photons across both weak- and strong-radiative cooling regimes. Our model reveals a universal coupling between particle energy and angular distribution, arising from…

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physics.plasm-phastro-ph.HE

Anisotropy and energy distribution of leptons and photons in radiative relativistic Alfvénic turbulence

Peng Liu, Xiaochun Wei, Zheng Gong

The anisotropic evolution of relativistic particles in magnetically dominated Alfvénic turbulence is a fundamental process governing nonthermal emissions in high-energy astrophysical environments. In this work, we develop a theoretical framework by deriving scaling equations that characterize the pitch-angle dynamics of leptons and photons across both weak- and strong-radiative cooling regimes. Our model reveals a universal coupling between particle energy and angular distribution, arising from…

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astro-ph.EP

Nordic-based observations of binary asteroid (163693) Atira reveal a hydrated CM chondrite composition

Eric M. MacLennan, Grigori Fedorets, Zuri Gray, Teemu Willamo, Tuomas Salo, Anne Virkki, Mikael Granvik, Karri Muinonen et al.

We present photometric, spectroscopic, and polarimetric observations of (163693) Atira collected on the night of 05 March 2024. A dual-band lightcurve acquired in the V and R_C filters using the Metsähovi Observatory (L08) in Kirkkonummi, Finland spans nearly 8~hours. From these measurements we estimate a V-R_C = 0.43 +/- 0.07 mag. A visible spectrum and linear polarisation measurement were obtained with the Nordic Optical Telescope in La Palma, Spain. We employ a semi-empirical model to recover…

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