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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.SRastro-ph.GA

The DESI Data Release 1 white dwarf catalogue

Andrew Swan, Boris T. Gänsicke, Paula Izquierdo, Detlev Koester, Christopher J. Manser, Laura K. Rogers, Siyi Xu, J. Aguilar et al.

The Dark Energy Spectroscopic Instrument is conducting a redshift survey, mapping the universe in three dimensions to measure the history of cosmic expansion. As well as extragalactic objects, it is targeting millions of Milky Way stars, including white dwarfs. Using Data Release 1 we assemble the largest catalogue of spectroscopically-confirmed white dwarfs to date, whose straightforward selection function enables statistically-robust population studies. We visually inspect and fit models to sp…

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astro-ph.HE

A Swift X-ray view of the SMS4 sample - III: Deeper insight into previously undetected sources

Alessandro Maselli, William R. Forman, Christine Jones, Ralph P. Kraft, Matteo Perri

We update the X-ray information given in Maselli et al. (2024) for five bright radio sources in the SMS4 catalog, thanks to additional observations with the X-Ray Telescope (XRT) on board the Neil Gehrels Swift Observatory (hereafter Swift) carried out through February 2026. X-ray emission from MRC B1754-597, previously based only on data from the eROSITA-DE DR1 catalogs, is now detected also by Swift, which yields a more precise positional uncertainty. Thanks to ~7 ks of additional exposure wit…

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

Nebular Spectra of the Extremely Metal-Poor SN II 2023ufx Over a Year After Explosion: A Massive Progenitor and Unique Circumstellar Environment

Evan Jennerjahn, Michael A. Tucker, Christopher S. Kochanek, Luc Dessart, Willem B. Hoogendam, Benjamin J. Shappee

We present new observations of the metal-poor ($< 0.1$ $\rm Z_\odot$) Type II supernova 2023ufx and its host galaxy. The deep nebular spectrum, obtained roughly a year after explosion, has a triple-peaked [O I] emission profile suggesting an asymmetric explosion. Comparison to nebular spectra models suggests a zero-age main sequence mass of $ M_{\rm ZAMS} \sim 25-35$ $\rm M_\odot$, which is supported by the low [Ca II]/[O I] emission-line ratio of $\approx0.4$. The diminishing, broad, boxy H$α$…

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astro-ph.COastro-ph.HEhep-ph

Supernova microlensing as a probe of ultracompact minihalos and primordial cosmology

Djuna Croon, Sergio Sevillano Muñoz, Miguel Zumalacarregui

We propose using supernova microlensing to search for ultracompact minihalos and other extended dark structures seeded by enhanced primordial small-scale power. Unlike conventional microlensing searches, which are often optimized for primordial black holes, cosmological supernovae are sensitive to lenses with physical sizes comparable to their Einstein radii (up to $\sim {\rm pc}\left(M/10^4M_\odot\right)^{1/2}$ scale), opening a qualitatively different region of dark object parameter space. We…

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astro-ph.IMquant-ph

Development of quantum technologies for optical/infrared interferometry

John D. Monnier

Quantum technologies may revolutionize optical interferometry through new means to distribute and preserve electric-field amplitude and phase correlations between widely separated telescopes. After reviewing existing techniques, I survey proposed quantum-sensing and quantum-networking applications and highlight recent laboratory demonstrations of key building blocks. By easing field-transport demands for baselines beyond $\sim$1 km, quantum-enhanced interferometry could enable sub-milliarcsecond…

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astro-ph.IMastro-ph.EPcs.LG

TNFlow: Amortized Posterior Inference for Trans-Neptunian Object Surface Composition

Agastya Gaur, Cristina M. Dalle Ore, Alessandra Ricca

We present TNFlow, a transformer and normalizing flow architecture for inferring the surface composition of Trans-Neptunian Objects (TNOs) from their reflectance spectra. TNFlow is trained on synthetic spectra generated by the Shkuratov radiative transfer model to act as its inverse. TNFlow takes ${\sim}$0.7s to invert one spectrum on a single CPU core, returning a multimodal posterior over simplex-valid compositions and grain sizes. On synthetic spectra, the highest-weight mode achieves a mean…

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astro-ph.HE

Low-angular-momentum accretion shocks can power weak-to-moderate X-ray flares from SgrA*

Samik Mitra, Bożena Czerny, Michal Zajaček, Zach Sumners

X-ray flares from Sgr~A* span broad ranges in duration, fluence, and luminosity, but their origin remains unsettled. We test whether standing shocks in low-angular-momentum magnetized accretion flows can provide a viable energy reservoir to account for these events. Using semi-analytic trans-magnetosonic shock solutions, we estimate the kinetic energy available in the downstream post-shock flow and compare it with the 25-year \textit{Chandra} X-ray flare catalog. For each theoretical solution, w…

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astro-ph.GAastro-ph.HE

Fundamental differences in the X-ray accretion properties of low and high-excitation radio galaxies

R. Kondapally, T. Holc, P. N. Best, J. Aird, K. J. Duncan, L. K. Morabito, D. M. Alexander, D. J. B. Smith et al.

We characterise the accretion rate properties of radio-detected AGN by combining deep radio and X-ray observations of the Boötes field. We used deep international LOFAR telescope observations to identify 2840 radio-AGN across $0.3 < z \leq 2$, divided into samples that are complete in radio luminosity. We further split this sample into four different classes: radio-quiet AGN (RQ-AGN), high-excitation radio galaxies (HERGs), and low-excitation radio galaxies (LERGs) hosted by star-forming (SF-LER…

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astro-ph.HEastro-ph.GA

A targeted search for fast radio bursts from magnetars in elliptical galaxies

S. Paine, D. R. Lorimer, S. Sirota, G. M. Doskoch, S. Tabassum, M. Flanagan, J. Lituchy, A. Stone et al.

Motivated by predictions that globular clusters associated with nearby giant elliptical galaxies are prime environments for detecting fast radio bursts (FRBs) from magnetars, we report on a targeted high-sensitivity search across five local massive elliptical galaxies. We utilized the GREENBURST single-pulse search pipeline and the VEGAS backend on the Green Bank Telescope (GBT) to conduct an L-band (1.4 GHz) survey for FRBs in each target environment. We discovered FRB 20240817A in the directio…

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astro-ph.GAastro-ph.IM

Absolute Motion of the Infrared Counterpart to Sagittarius A* in the Gaia Celestial Reference Frame 3 and Limits on an Intermediate-mass Black Hole Companion

Rebecca A. Lewis-Merrill, Tuan Do, Matthew W. Hosek, Gregory David Martinez, Shoko Sakai, Kelly Kosmo O'Neil, Grant Weldon, Abhimat Gautam et al.

We report the first proper motion and acceleration measurements of the infrared (IR) counterpart to Sagittarius A* (Sgr A*-IR), the supermassive black hole (SMBH) at the center of our Galaxy, in the Gaia-Celestial Reference Frame (Gaia-CRF3). This reference frame realizes the International Celestial Reference System (ICRS), which is an absolute reference coordinate system defined by quasars. A combination of Gaia and Hubble Space Telescope data was used to transform Keck adaptive optics (AO) obs…

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astro-ph.HEastro-ph.GAgr-qc

Sgr A* as a Galactic PeVatron: Multimessenger Signatures of the Magnetic Penrose Process

Marina Cermeño, Pedro De la Torre Luque, Cristina Fernández-Suárez, Viviana Gammaldi, Enrique Mier-Alonso, María J. Rodríguez, Miguel Á. Sánchez-Conde, Jaume Zuriaga-Puig et al.

The magnetic Penrose process (MPP) is one of the most efficient mechanisms for extracting rotational energy from a magnetized Kerr black hole (BH), enabling charged particles to reach very-high energies. We investigate this process in Sagittarius A* (Sgr A*), the supermassive BH at the Galactic center (GC), focusing on its ultra-high-efficiency regime, in which neutrons undergo beta decay inside the BH ergosphere. As a key novelty, we compute the neutron production spectrum in the accretion flow…

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astro-ph.SRastro-ph.GA

Ionized Nebulae Around Two New Symbiotic Stars: GR Cygni and [D75] 141

Howard E. Bond, Calvin Carter, Sven E. Eklund, Peter Goodhew, Ulisse Munari, Jonathan Talbot, Gregory R. Zeimann

In the course of selecting targets for a spectroscopic survey of faint planetary-nebula nuclei, we encountered two anomalous cases of late-type variable stars surrounded by nebulosities discovered by amateur astronomers. We obtained follow-up deep narrow-band images of the two nebulae: StDr Objet 14 (diameter 1.5 arcmin) and StDr 4 (diameter 2.5 arcmin). StDr Objet 14 is found to be a low-excitation nebula, bright only in Ha+[N II], and showing a unique double-ring "bull's-eye" morphology. StDr…

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astro-ph.GA

Two sets of potential-density basis pairs for the study of radial perturbations in collisionless spherical stellar systems

E. V. Polyachenko, I. G. Shukhman

The Kalnajs matrix method is a widely used framework for studying the global linear stability and possible Landau damping of collisionless stellar systems. However, for radial perturbations ($l=0$) in three-dimensional spherical models with infinite boundaries, standard biorthogonal sets such as the Clutton-Brock basis often converge slowly. This stems from a physical constraint: mass-conserving radial modes force the perturbed potential to decay faster than a point mass at infinity, whereas ind…

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gr-qcastro-ph.HE

Eight Local Couplings of Gravitational Waves from Unified Field Equations

Hong-Bo Jin, Yue-Liang Wu

A gravitational-wave (GW) detector records a linear mixture of local couplings under the assumption that extra polarizations enter geodesic deviation. Vacuum general relativity (GR) admits two transverse-traceless (TT) amplitudes. It remains to determine the largest set of couplings that can sit in that mixture, and whether a tensor-only arm-length result selects GR uniquely. The little group \(E(2)\) of a null four-momentum classifies the strain amplitudes \(\mathbf{p}=(p_{+},p_{\times},p_{x},p…

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astro-ph.EPastro-ph.IMastro-ph.SRphysics.ao-phphysics.space-ph

Detection of hydrocarbons in Titan using high-resolution cross-correlation spectroscopy

Maria Coelho, Rafael Rianço-Silva, Diogo Gonçalves, Pedro Machado, Zita Martins

High-resolution cross-correlation spectroscopy (HRCCS) is a powerful technique for detecting molecules whose individual spectral lines are too weak to be identified directly, but its sensitivity is limited by the availability and quality of high-resolution opacity data. Many molecules of atmospheric and astrobiological interest lack complete line lists, restricting traditional template-based searches. In this work, we use Titan as a controlled testbed to develop and validate a new cross-section-…

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astro-ph.HEhep-phnucl-th

Ultra-compact twin stars with hybrid equations of state from bosonic dark matter

Ishfaq Ahmad Rather, Sarah Louisa Pitz, Jürgen Schaffner-Bielich

The properties of compact stars with a strong first-order phase transition to quark matter and with an additional fluid of self-interacting bosonic dark matter (DM) are studied. We find that the inclusion of DM changes considerably the stability of mass-radius configurations relative to the naive one-fluid criterion. For compact star configurations with similar masses and different radii, so-called twin stars, the presence of DM removes the unstable segment between the hadronic and the hybrid br…

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astro-ph.SR

Interferometric Survey of Stellar Parameters: Mass of the metallic A-type binary $β$ Aur

J. Jonák, D. Mourard, J. D. Monnier, S. Hoin, M. Brož, A. Oplištilová, K. A. Kubiak, N. Ebrahimkutty et al.

With the capabilities of the new visible CHARA/SPICA instrument and the multiple spectral band operation of CHARA, our goal is to resolve orbits of short-period binaries and develop a robust framework for combining interferometric, spectroscopic, and photometric observations into a single consistent model. For our target sample, we selected suitable binaries based on brightness, angular separation, and orbital properties based on the expected performance of the CHARA/SPICA instrument. As a case…

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astro-ph.EP

Properties of Seasonal Ice at Sisyphi Cavi and Implications for Current Modification of Martian Gullies

Apolline Leclef, Mathieu Vincendon, Cateline Lantz, François Andrieu, Marie Ausseresse, John Carter, Susan J. Conway, Marion Massé et al.

Martian gullies are geologically recent landforms that may form either through liquid-water activity and/or through processes involving CO2 ice. We investigated the mechanisms responsible for the formation or modification of these features by focusing on the active site of Sisyphi Cavi (68°S, 1°E), located outside the typical latitude range of gully presence. Using CRISM and OMEGA infrared data, we characterized the composition and physical state of seasonal surface ices to test the relevance of…

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astro-ph.IM

nufftcf: Fast Auto- and Cross-Correlation Function Estimation for Irregularly-Sampled Time Series via the Non-Uniform FFT

Jean-Eric Campagne

Estimating the auto-correlation function (ACF) and the cross-correlation function (CCF) of sampled series is a standard task across different physics fields, such as astronomy, and environmental sciences. We aim to provide an ACF/CCF estimator primarily designed for irregularly sampled series that is numerically consistent with established, well-validated kernel-weighted definitions, while scaling as O(n log n) rather than O(n^2). nufftcf evaluates the Wiener-Khinchin theorem for irregularly sam…

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astro-ph.HEgr-qc

A catalogue of insights from the fourth LIGO-Virgo-KAGRA observing run

Christopher P L Berry, Daniel Williams

Over the last decade, gravitational-wave science has developed from an era where a single detection was a Nobel-winning achievement to an (almost) everyday occurrence. The LIGO-Virgo-KAGRA (LVK) Collaboration's flagship scientific results are now their catalogues of detections, which include a comprehensive set of analysis results characterising the astrophysical properties of sources, and their implications for fundamental physics and cosmology. We review discoveries from the fourth observing r…

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astro-ph.IMastro-ph.GA

Morphology of Radio Sources in Representation Space

Nicolas Baron Perez, Marcus Brüggen, Luisa Lucie-Smith

Understanding radio source morphologies and their classification remains challenging. We previously developed a deep clustering method based on self-supervised learning to classify a subsample of radio sources from the LOFAR Two-meter Sky Survey DR2. This yielded a labelled subset used to fine-tune an ensemble of classifiers. We aim to identify rare morphological classes in a subsample of LoTSS-DR3, which contains > 13 million sources, beyond the 12 classes previously recognised in the DR2 sampl…

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

Disk survey in the Serpens star-forming region: Environmental effects in nearby star-forming regions

Simin Tong, Nienke van der Marel, Jonathan P. Williams, Alexa R. Anderson

The external environment where protoplanetary disks are embedded regulates disk evolution. External irradiation, which heats and evaporates gas, as well as frequent stellar encounters, which truncate disks, can reduce disk sizes and masses. Disk surveys in nearby star-forming regions with various environments can help us understand how external environments impact disk evolution. The Serpens star-forming region, which is thought to be dense but not highly irradiated by massive stars, is an ideal…

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astro-ph.HE

The Physics of the Nebular Phase in Black Hole X-ray Binaries: Modelling V404 Cygni

A. Ambrifi, T. Muñoz-Darias, J. A. Fernández-Ontiveros, J. Casares, D. Mata Sánchez, J. H. Matthews

Some of the most extreme galactic black hole transients exhibit a nebular phase at the end of their outbursts. This stage was first identified in the 2015 outburst of V404 Cygni, when it dominated the optical spectrum for ~4 days. It is characterised by exceptionally strong optical emission lines, together with a significant increase in the Balmer decrement. The emission features show broad wings reaching velocities consistent with outflow speeds derived from prominent P-Cygni profiles that prec…

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astro-ph.SR

New scaling relations from MESA models for mass and radius of subgiant stars: application to Kepler targets

T. Çakır Alsaç, M. Yıldız, S. Örtel

The precise determination of the fundamental parameters of stars is crucial for understanding stellar structure and evolution. In this regard, the asteroseismic parameters of solar-like oscillating stars obtained from space telescopes are very useful for determining the mass ($M$) and radius ($R$) of single stars using classical scaling relations. These relations still need to be improved. In this study, we develop alternative scaling relations based on reference frequencies ($ν_{\rm min}$) due…

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astro-ph.SRphysics.space-ph

The Role of Preceding CMEs and SIRs in Enhancing Shock Acceleration of Electrons

Xiaomin Chen, Seve Nyberg, Rami Vainio, Immanuel Christopher Jebaraj, Chuan Li, Nina Dresing

The role of large-scale pre-existing interplanetary structures, including preceding coronal mass ejections (CMEs) and stream interaction regions (SIRs), in shaping the shock acceleration environment for energetic electrons remains not fully understood. In this study, we investigate nine interplanetary shocks observed by the Solar Terrestrial Relations Observatory (STEREO) that are associated with significant MeV electron enhancements, as such enhancements are rarely observed at interplanetary sh…

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astro-ph.GAastro-ph.HE

Rapid Growth of Intermediate-Mass Black Holes through Disk-induced Stellar DisruptionsRapid Growth of Intermediate-Mass Black Holes through Disk-induced Stellar Disruptions

Mengye Wang, Yiqiu Ma, Qingwen Wu, Boyuan Liu, Zijian Wang, Zhili Wang

Dense nuclear star clusters provide unique environments for studying the dynamical interactions between stars and massive black holes. When an accretion disk is present, dissipative star--disk interactions can capture surrounding stars, drive their inward migration, and ultimately lead to disk-induced tidal disruption events\,(dTDEs). The long-term feeding rate from this process, however, cannot be inferred from single-orbit migration estimates alone, as it depends on the coupled evolution of di…

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astro-ph.GAastro-ph.HE

Rapid Growth of Intermediate-Mass Black Holes through Disk-induced Stellar Disruptions

Mengye Wang, Yiqiu Ma, Qingwen Wu, Boyuan Liu, Zijian Wang, Zhili Wang

Dense nuclear star clusters provide unique environments for studying the dynamical interactions between stars and massive black holes. When an accretion disk is present, dissipative star--disk interactions can capture surrounding stars, drive their inward migration, and ultimately lead to disk-induced tidal disruption events\,(dTDEs). The long-term feeding rate from this process, however, cannot be inferred from single-orbit migration estimates alone, as it depends on the coupled evolution of di…

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astro-ph.COastro-ph.GA

Prospects for probing dark matter with filamentary 21cm emission

Yizhou Liu, Yingjie Jing, Haoran Shi, Huijie Hu

The cosmic web contains most of the matter in the Universe, and its filamentary structure is closely related to the properties of dark matter. Compared with the cold dark matter (CDM) model, warm dark matter (WDM) suppresses the formation of low-mass halos and produces smoother cosmic filaments. In this work, we explore whether filamentary 21cm emission can be used to distinguish between these two dark matter models at $z=4$ and $2.5$. We generate intrinsic 21cm brightness temperature maps from…

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astro-ph.HE

NuSTAR View of the 2025 Mini-Outburst of the Black Hole X-ray Binary GRS 1739-278: Spectral and Timing Evolution in the Soft State

Arshad Hussain, Umananda Dev Goswami

We present a dedicated timing and spectral analysis of three NuSTAR observations of the Galactic black hole candidate GRS 1739-278 obtained during the decay of its 2025 mini-outburst (September 18-30, 2025). The source is found in a soft, disk-dominated state throughout, with a declining $3$-$79$ keV count rate (from $112.4$ to $99.4$ cts s$^{-1}$), a low and only mildly evolving hardness ratio ($\approx0.14$-$0.16$) and a fractional variability that drops from $3.2\%$ to $1.1\%$; no periodic or…

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astro-ph.HE

KM3NeT/ARCA stacking search for high-energy neutrino point sources: the case of ultra-luminous infrared galaxies and blazars

The KM3NeT Collaboration

A stacking search for high-energy astrophysical neutrino emission is presented using three candidate source populations: ultra-luminous infrared galaxies and two categories of blazars, specifically high-synchrotron-peaked BL Lacs and extreme blazars. The analysis is based on 336 days of data from the Astroparticle Research with Cosmics in the Abyss component of the KM3NeT research infrastructure (KM3NeT/ARCA), collected with detector configurations comprising 19-21 detection units, yielding 1544…

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