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Research Trends

Latest preprints in space engineering and astrophysics.

gr-qcastro-ph.HEhep-ph

Probing ultralight bosons with LISA observations of spinning black hole mergers and follow-up searches of merger remnants

Ifigeneia Giannakoudi, Maxence Corman, William E. East

Ultralight bosons can trigger superradiant instabilities around rotating black holes, extracting angular momentum and leading in some cases to observable gravitational signatures. When the associated spin-down timescale is shorter than the black hole lifetimes and the spin-up timescales due to, e.g. accretion, this process imposes an upper limit on black hole spins. In addition, the formation and subsequent dissipation of boson clouds generates quasi-continuous gravitational wave emission. In th…

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astro-ph.IM

SGNAX: a unified matched-filter and excess-power pipeline for gravitational-wave detector characterization

Zach Yarbrough, Olivia Godwin, Derek Davis, Gabriela González

We present SGNAX, an open-source pipeline for gravitational-wave detector characterization that delivers matched-filter and excess-power transient triggers from a single streaming dataflow graph. Built on the Stream Graph Navigator (sgn) framework, SGNAX unifies the multi-rate sine-Gaussian matched-filter search of snax and the multi-resolution Q-transform search of omicron in one Python-native package. Auxiliary channels from an interferometer are analyzed as parallel branches sharing data-read…

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astro-ph.IM

Quasi-automatic software support for Gaia ground based optical tracking

S. Bouquillon, C. Barache, T. Carlucci, F. Taris, M. Altmann, A. H. Andrei, R. Smart, I. A. Steele et al.

The ESA Gaia satellite mission will create a catalog of 1 billion stars with unprecedented astrometric precision. To achieve its aim in terms of astrometric precision, a ground based optical tracking campaign (GBOT) of the satellite itself is necessary during the five years of the mission. We present an overview of the GBOT project as a whole in another contribution (Altmann et al. in SPIE category "observatory operations"). The present paper will focus more specifically on the software solution…

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astro-ph.IMastro-ph.HE

Pulsar Timing Array Sensitivity to Anisotropy: Empirical Sensitivity Curves, Scaling Relations, and the Multi-Resolution Pixel Basis

Taha T. Moursy, Nihan S. Pol, Gabriella Agazie, Nikita Agarwal, Akash Anumarlapudi, Anne M. Archibald, Zaven Arzoumanian, Anjana Ashok et al.

We quantify pulsar timing array (PTA) sensitivity to anisotropy in the gravitational wave background using the cross-correlation based Fisher information matrix in the pixel and spherical harmonic bases. We use a set of simulations to empirically determine scaling relations of a PTA's sensitivity to anisotropy with the number of pulsars $N_\mathrm{psr}$ in the array, the error $δt$ on the times of arrival, the frequency $f_\mathrm{GW}$ of the gravitational waves, and the angular scale $ΔΩ$ of th…

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astro-ph.HE

Exploring the multi-wavelength properties of the high energetic event ZTF20abbiixp/GRB 200524A: from prompt emission to afterglow

A. Ghosh, Dimple, K. Misra, P. Yu. Minaev, Y. Yao, D. A. Kann, M. Blazek, A. S. Pozanenko et al.

We conducted a comprehensive multi-wavelength analysis of a high energetic long-duration ZTF20abbiixp / GRB~200524A detected by \textit{Fermi} Gamma Ray Burst Monitor (GBM). Our study combines extended high-energy observations from multiple space-based observatories including \textit{Fermi} with broadband afterglow data spanning X-ray to radio wavelengths, complemented by extensive photometric and spectroscopic follow-up from several ground-based optical facilities worldwide like 3.6-m Devasthal…

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astro-ph.COastro-ph.HEgr-qc

Cross-frequency SGWB anisotropy from compact topology: CMB B-mode covariance as a transfer probe

Li-E Qiang, Peng Xu

Compact spatial topology restricts the eigenmodes of primordial tensor perturbations, and the resulting discreteness can render the primordial stochastic gravitational-wave background (SGWB) anisotropic. Here we treat the CMB tensor $B$-mode covariance as a transfer-filtered measurement of that ultra-low-frequency anisotropy. Writing the normalized angular tensor-power measure as $F(k,\hat k)=1+Q(k,\hat k)$ and its nonmonopole moments as $q_{LM}(k)$, we obtain an explicit kernel that maps $q_{LM…

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astro-ph.EP

TOI-7475 spectroscopic follow up - detection of a massive hot Jupiter on an eccentric orbit

Joanna Pietrucha, Jakub Jerzy Tokarek, Mateusz Witczak, Wojciech Dimitrov

We present the first spectroscopic follow-up for TOI-7475, and report the detection of a planetary-mass companion. Transits with a period of 3.25 days were observed by TESS. The dips in brightness are 0.006 mag and last approximately 4.5 hours. The host star is a spectral type F5 with a mass of approximately 1.48 M$_{\odot}$. We collected 24 high resolution echelle spectra using the PST1 telescope. Analysis of the TESS photometric data and our radial velocities was performed using the Wilson-Dev…

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nucl-thastro-ph.SRnucl-ex

A Gaussian Process framework for constraining the nuclear equation of state from microscopic calculations with correlated uncertainties

Y. G. Lee, J. Kim, T. Zhao, C. Drischler

We present constraints on the nuclear equation of state (EOS) from microscopic asymmetric matter calculations at zero temperature based on chiral nucleon-nucleon and three-nucleon interactions. The constraints include the saturation point, the isospin dependence of the incompressibility, and the symmetry energy, as well as the crust-core transition density of neutron-star matter. To quantify and propagate correlated uncertainties from noisy many-body calculations to derived observables, we intro…

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astro-ph.HEastro-ph.GA

Recoiling Black Holes I. Burst of Observables

Erwan Hochart, Simon Portegies Zwart

We aim to investigate the tidal disruption and gravitational wave events shortly after a massive black hole binary merges in the galactic centre and whose remnant black hole is ejected from the galaxy. Using computational methods, black holes of mass $M_{\bullet}=10^{5}$ M$_\odot$ and $4\times10^{5}$ M$_\odot$ embedded in a nuclear star cluster are kicked at velocities of $v_k=300$ and $600$ km s$^{-1}$. Systems are integrated for $0.1$ Myr using a $4$th-order Hermite scheme. The kick instantane…

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astro-ph.IM

Wigner interferometry

Vladimir Lenok

Aims. This work aims to introduce a new method of interferometric measurements based on correlation of Wigner functions constructed for the fields from a distant source. Methods. This work presents theoretical studies of correlation of the Wigner functions. Numerical simulations support the findings. Results. It is shown that in comparison to the correlation of the fields, a correlation of their Wigner functions samples twice higher spatial frequencies of the source intensity distribution and ha…

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astro-ph.SRastro-ph.IM

Reconstruction of ASO-S/HXI Solar Flare Hard X-ray Source Images with Physics-Constrained Deep Networks

Zou SiZhong, Liu Hui, Su Yang, Hong JunChao, Chen Wei

The Hard X-ray Imager (HXI) on board the Advanced Space-based Solar Observatory (ASO-S/Kuafu-1) reconstructs solar flare hard X-ray images from the modulated counts of 91 bi-grid sub-collimators---an underdetermined problem of recovering a high-dimensional spatial distribution from low-dimensional measurements. The conventional CLEAN algorithm relies on a point-source assumption and fragments extended flare morphologies, while existing deep-learning methods learn a data-driven mapping from count…

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astro-ph.SRastro-ph.IM

Reconstruction of ASO-S/HXI Solar Flare Hard X-ray Source Images with Physics-Constrained Deep Networks

Zou SiZhong, Liu Hui, Su Yang, Hong JunChao, Chen Wei

Solar flare hard X-ray (HXR) imaging by the ASO-S/HXI instrument reconstructs source images from modulated counts of 91 bi-grid sub-collimators---an underdetermined inverse problem of recovering a high-dimensional spatial distribution from low-dimensional measurements. The conventional CLEAN algorithm relies on a point-source prior, fragments extended morphologies, and requires manual parameter tuning, while existing deep-learning methods learn a data-driven counts-to-image mapping without guara…

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astro-ph.IMcs.CV

Unsupervised Domain Adaptation for Multitask Image Analysis in Realistic Context with Extreme Label Shift; Application to the CTAO first Large Sized Telescope

Michaël Dell'aiera, Thomas Vuillaume, Alexandre Benoit

Unsupervised domain adaptation is a widespread set of methods that leverages the knowledge of a labeled source domain to train a model to perform well on a related unlabeled target domain. They generally introduce an auxiliary adaptation-related task that can be integrated into the multitask paradigm, which aims to merge multiple single-task models into a unified architecture. In this paper, we propose to associate domain adaptation and multitask balancing in the realistic context of an extreme…

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

A Chemical Inventory of the Disk around the Class 0 Protostar L1527 IRS with ALMA

Merel L. R. van 't Hoff, Łukasz Tychoniec, John J. Tobin, Daniel Harsono

Planet formation starts in disks that are still embedded within their natal envelopes. Here, we compile an extensive inventory of the chemical composition of the disk and envelope ($<$ 3500 au) around the Class 0 protostar L1527 IRS. Using all publicly available ALMA (Atacama Large Millimeter/submillimeter Array) data, we report the detection of 39 molecules, including isotopologues. Of these, 22 are different molecular species and 28 are reported here for the first time toward L1527 in ALMA obs…

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astro-ph.GA

Ubiquitous Interstellar Neutral Helium Detected with JWST

Jane R. Rigby, D. Koutroumpa, M. Galeazzi, T. Hutchison, K. D. Kuntz, Rosalia O'Brien, Marshall Perrin, F. S. Porter et al.

We report the discovery of ubiquitous neutral helium emission in sky spectra taken with JWST's NIRSpec instrument. The emission, with a wavelength of 1.0833 micron, resembles one of the "sky lines" that are seen by ground-based observatories. We examine this emission in all suitable NIRSpec spectra in the public archive, totaling 22 days of exposure time. We find that this He I emission is almost always present: it is well-detected in 80 percent of the observations, and in 53 percent of the indi…

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astro-ph.SRastro-ph.GA

Sector-based morphological analysis of four planetary nebulae (J 320, NGC 2610, A 6672 and PRTM 1) observed with UVIT/ASTROSAT

Anisha Hazra, Ranjan Kumar, Sonika Piridi, Ananta C. Pradhan

Four planetary nebulae (PNe), Jonckheere 320, NGC 2610, A 6672, and PRTM 1, have been imaged in the far-ultraviolet (FUV) filter F148W ($λ_{\mathrm {eff}} = 1481\, \mathring{A} $) using the Ultraviolet Imaging Telescope (UVIT) onboard ASTROSAT. The FUV images reveal faint extended emission structures surrounding the bright central star. A novel sector-based structural analysis technique was employed to examine the detailed FUV morphologies of PNe. In this method, sector strengths were calculated…

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astro-ph.GA

Searching for low-surface-brightness galaxies with compact neural networks A parameter-efficient approach to first-pass selection of diffuse galaxy in HSC-SSP imaging

Günther K. Heemann, Henri Cecatka, Dominik J. Bomans

Low-surface-brightness galaxies (LSBGs) trace a diffuse and observationally challenging regime of galaxy formation that remains highly susceptible to selection effects in optical surveys. We present a hybrid LSBG detection pipeline that integrates compact convolutional neural networks (cCNs) as a morphological validation stage within a multi-step detection framework applied to HSC-SSP imaging. Permissive low-threshold source detection with SEP is followed by cCN-based morphological filtering, ph…

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astro-ph.GAastro-ph.SR

Dust production in the harsh environment of Sgr A* - MIRI/JWST observation of the O-rich asymptotic giant branch star IRS~3

F. Peißker, M. García Marín, A. Eckart, G. Wright, O. C. Jones, D. Dicken, A. Alonso Herrero, D. Rouan et al.

Studies of the interstellar medium (ISM) have frequently revealed signatures of the dust produced in the envelopes of asymptotic giant branch (AGB) stars, demonstrating a connection between the dust composition of the ISM and that of AGB stellar envelopes. Investigating this relationship in the extreme, radiation-dominated environment surrounding Sgr A*, the center of our own galaxy, reveals how such conditions might influence dust composition and the recycling of material in galactic centers. I…

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

Global simulations of accretion flows onto perturbers embedded in magnetized disks -I. MRI and jet formation in ideal MHD

Raúl O. Chametla, F. J. Sánchez-Salcedo, Martin E. Pessah, Mauricio Reyes-Ruiz

We present the highest resolution global MHD simulations to date of gas flow around a low mass a perturber with mass ratio $q\in[10^{-4},10^{-3}]$, embedded in an accretion disk around a massive central object. We find that gas flow onto the secondary self-consistently forms a turbulent, magnetized mini-accretion disk. The mini-accretion disk sustains a large-scale magnetic field generated by the dynamo effect of the MRI and the accretion flow into the perturber. Simultaneously, a bipolar, colli…

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astro-ph.GA

The Environmental Dependence of Star Cluster Demographics

Jianling Tang, Kathryn Grasha, Mark R. Krumholz, Tomasz Różański

Both the star cluster mass function and the lifetimes of clusters may vary with galactic environment, but measuring this variation is challenging because in observational surveys real features of cluster demographics are invariably entangled with catalogue incompleteness. Here we analyse $\approx$ 8300 star clusters in 12 galaxies drawn from the LEGUS survey using the slug Bayesian forward modelling framework coupled to our new c-4 neural network-based completeness estimator, which allows us to…

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astro-ph.GA

A Partial Lyman Limit Absorber in the Halo of a Galaxy Pair: A Possible Signature of Gas Inflow

Sumukha R. Bharadwaj, Anand Narayanan, Sowgat Muzahid, Jane C. Charlton, Sebastiano Cantalupo

We present an analysis of a partial Lyman limit system at z = 0.87641 detected in the HST/COS spectrum of the background quasar LBQS 0107-0235. The absorber exhibits a simple kinematic structure, with the metal-lines and the H I Lyman-series absorption well described by a single component. Photoionization modeling yields a gas metallicity of one-tenth solar and a hydrogen number density of n_H \approx 8.5 \times 10^{-4} cm^{-3} (log_{10}(n_H/cm^{-3}) \approx -3.1). At the absorber redshift, the…

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astro-ph.HE

Hyperaccreting Magnetised Neutron Stars inside Rotating Massive Envelopes: Low-Power Jets and Precursor Flares

Patrick Chi-Kit Cheong, Christopher L. Fryer, David Radice

The engulfment of a neutron star (NS) by a massive companion initiates a highly dynamic common-envelope (CE) evolution phase. As the NS spirals into the dense stellar core, it is subjected to hypercritical accretion rates that threaten to rapidly collapse the NS into a black hole (BH). However, if the infalling envelope possesses sufficient angular momentum and magnetic fields, the NS might survive longer and launch feedback-driving jets. To investigate this, we perform fully coupled, axisymmetr…

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astro-ph.EPcs.LG

A Machine Learning Based Search for Lunar Anomalies

Cameron Kelahan, Daniel Angerhausen, Adam Lesnikowski, Valentin T. Bickel

The Lunar Reconnaissance Orbiter (LRO) has been collecting high-resolution images (at around 0.5-2 meters per pixel linearly with its Narrow Angle Camera) of the Moon since 2009, amassing a large dataset of images and offering researchers the opportunity to study the surface of the Moon at unprecedented scale. Here, we aim to test the abilities of the Beta-Variational Autoencoder (VAE) created by Lesnikowski et al. (2024), an unsupervised learning model which identifies anomalous features across…

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astro-ph.HEastro-ph.SR

Rapid Orbital Decay in the Ultracompact Double-degenerate Binary eRASSU J060839.5$-$704014

Rahul Sharma, Chandreyee Maitra, Frank Haberl, Joheen Chakraborty, Susanne Friedrich, Yong-Feng Huang, Chichuan Jin, Zhaosheng Li et al.

We present timing and spectral analysis of the recently identified ultracompact double-degenerate (DD) white dwarf binary eRASSU J060839.5$-$704014 using observations from NICER and Einstein Probe (EP), together with archival XMM-Newton data. By phase-connecting the long-term XMM-Newton, NICER, and EP observations, we obtain a coherent quadratic timing solution, yielding an orbital period of 374.15013 (2) s and an orbital decay rate of $\dot{P}= -4.7\,(1) \times 10^{-11} \mathrm{~s~s^{-1}}$. Thi…

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astro-ph.IMastro-ph.GAastro-ph.SR

Kratos-linerad: GPU-accelerated Monte Carlo radiative transfer of lines with efficient imaging

Lile Wang

Spectral lines encode the velocity, the temperature, and the chemical structure of astrophysical gas; interpreting them requires radiative transfer that is accurate at high optical depth, consistent with the local excitation, and efficient enough to synthesize velocity-resolved images. We present Kratos-linerad, a GPU-accelerated Monte Carlo radiative transfer code for spectral lines. The level populations can be iterated to statistical equilibrium together with the escaping photon distribution,…

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astro-ph.HE

Astrophysical origins of TeV features in the cosmic-ray lepton spectrum

Zhen Xie, Ruizhi Yang

Precise measurements of high-energy cosmic-ray electrons and positrons have revealed spectral structures that are difficult to capture with a single smooth power-law background. The rising positron fraction measured by PAMELA and AMS-02, together with the all-electron excess reported by ATIC and the high-precision all-electron spectrum measured by DAMPE, has motivated interpretations ranging from nearby astrophysical accelerators to dark-matter annihilation or decay. In this work we revisit the…

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math.NAastro-ph.IMphysics.comp-phphysics.flu-dyn

High-order fully discrete multi-entropy-stable and bound-preserving schemes for relativistic Euler equations

Linfeng Xu, Kailiang Wu

A discrete entropy inequality is the principal nonlinear stability estimate available for systems of conservation laws, and evaluating it presupposes a physically admissible state. So far, however, the two have been secured separately. Entropy-stable schemes are almost always semi-discrete, are built around one selected entropy pair, and take for granted the positivity of density and pressure that makes the entropy well defined in the first place, whereas bound-preserving limiters keep the solut…

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astro-ph.GA

AGN activity in nearby disk galaxies: the roles of bar strength and spiral-arm morphology

Zh. R. Martirosyan, A. A. Hakobyan, V. Adibekyan, L. V. Barkhudaryan, M. H. Gevorgyan, A. G. Karapetyan

(abridged) We investigate the dependence of AGN activity on bar strength and spiral-arm morphology in nearby spiral galaxies, with particular emphasis on disentangling their individual and joint effects while controlling for galaxy stellar mass and color. We constructed a sample of 843 morphologically undisturbed Sa-Sd galaxies from the MaNGA survey in the redshift range $0.026 \leq z \leq 0.1$. Bar strengths, stellar masses, colors, and AGN classes were adopted from the literature, while spiral…

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astro-ph.HEastro-ph.GA

Impact of disk magnetic fields on the propagation of stellar-scale jets in the magnetically arrested accretion disks of active galactic nuclei

Bao-Quan Huang, Tong Liu, Jian-Fu Zhang

It is widely recognized that active galactic nucleus (AGN) disks host numerous massive stars and compact objects. Stellar-scale jets triggered by collapses of massive stars and mergers of compact objects could propagate through the disk and produce observable electromagnetic radiation. Magnetically arrested disks (MADs), supported by both numerical simulations and observations, possess strong magnetic fields (MFs). As jets travel within such environments, the MFs should regulate jet evolution an…

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astro-ph.IM

Pointing Model Meets Deep Learning: A Retrospective Study on a MeerKAT+ Telescope Applying Deep Learning Methods for Blind Pointing Corrections

Stefan Thoms, Matthias Reichert

This study aims to compare the effectiveness of deep learning methods, specifically Feedforward Neural Networks (FNNs), with traditional Pointing Models (PMs) for compensating Blind Pointing Errors in astronomical instruments. Ambitious projects like the ongoing study for the Atacama Large Aperture Submillimeter Telescope (AtLAST) inspired the investigation of possible improvements to traditional Pointing Error (PE) modeling. The study assesses the practicality of FNNs by applying them to data f…

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