UchUchU

Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.IMphysics.flu-dynphysics.space-ph

Feasibility of Capillary-Driven Orbital Liquid Mirror Telescopes

Janoad Dietrich, Álvaro Romero-Calvo

Space-based liquid mirror telescopes (LMTs) have been recently proposed to overcome the scaling limits of traditional rigid mirrors. In these new space architectures, capillary forces would shape a reflective liquid into a spherical optical surface in microgravity. However, the equilibrium, stability, and dynamic behavior of such liquid interfaces under orbital perturbations remain largely uncharacterized. This study investigates the feasibility of space LMTs by combining axisymmetric capillary…

Read →
gr-qcastro-ph.HE

Bekenstein--Hod Bound: A $3.3σ$ Confirmation from GW250114

Hai-Tian Wang, Shao-Peng Tang, Yi-Zhong Fan

Black holes link gravity, thermodynamics and information via limits on the relaxation rate of a perturbed system. The Bekenstein-Hod bound imposes a minimum relaxation time at fixed temperature, but its observational test demands both black hole thermodynamic characterization and decay time measurement. Here we test this bound with GW250114, the loudest gravitational-wave signal yet observed from a binary black-hole merger. We infer the remnant temperature from pre-merger data truncated at least…

Read →
astro-ph.IMastro-ph.HE

The Auger Radio Infill SKALA Extension (ARISE): Science Case and Instrumentation (ARENA 2026)

Frank G. Schröder for the Pierre Auger Collaboration

The Auger Radio Infill SKALA Extension (ARISE) at the Pierre Auger Observatory in Argentina was deployed in 2025 and measures cosmic-ray air showers in the energy region of the Galactic-to-extragalactic transition. ARISE is comprised of 18 SKALA-2 antennas featuring two polarization channels each, deployed within $100\,$m of a surface detector station in the enhancement area of the Pierre Auger Observatory. This area of the surface array features a denser spacing of $433\,$m between surface stat…

Read →
astro-ph.GA

ALMA CO(2-1) Gas Dynamics in NGC 315: A Multi-Method Benchmark for Supermassive Black Hole Mass Measurement

Dieu D. Nguyen, Benjamin D. Boizelle, Hai N. Ngo, Elena Gallo, Tuan N. Le, Sabine Thater, Tien H. T. Ho, Tinh Q. T. Le et al.

We present ALMA Cycle~7 \cotwo\ observations of the circumnuclear disk in NGC~315 at an angular resolution of $0\farcs230\times0\farcs175$, improving on past measurements and resolving the sphere of influence (SOI) of the supermassive black hole (SMBH), whose mass has previously been estimated of $M_{\rm BH}= \left(2.08^{+0.33}_{-0.15}\right) \times 10^9$~M$_\odot$ The high spatial resolution and sensitivity enable robust full-cube forward modeling of the molecular gas kinematics and a direct co…

Read →
gr-qcastro-ph.HE

Constraining equation of state of neutron star using neutron star-black hole mergers

Vasudev Dubey, Rahul Kashyap, Yugesh Bhoge

In this work, we study tidal effects that can be observed in gravitational wave transient from neutron star-black hole (NSBH) mergers. It has been well known that neutron star's tidal deformation has imprint of equation of state and hence composition of neutron star matter. Compared to binary neutron star mergers, where we observe a combined effect of two neutron stars by measuring the parameter known as lambda tilde. In neutron star black hole mergers, we measure the tidal deformability of the…

Read →
astro-ph.HEastro-ph.IM

The First Array-Wide Diffuse Flux Search for UHE Neutrinos with the Askaryan Radio Array

Alan Salcedo-Gomez, Marco Stein Muzio, for the ARA Collaboration

The Askaryan Radio Array (ARA) is an ultrahigh energy (UHE) neutrino detector at the South Pole that searches for impulsive broadband radio signals from neutrino-induced particle showers in glacial ice. ARA consists of five autonomous stations with receiving antennas deployed up to 200 m deep and has accumulated the largest livetime of any in-ice radio array. We present the first array-wide diffuse UHE neutrino search using data collected from January 2013 to December 2023, incorporating improve…

Read →
astro-ph.IM

METIS high-contrast imaging simulations: From instrument modelling to science readiness

Gilles Orban de Xivry, Olivier Absil, Iain Hammond, Thomas Bertram, Roy van Boekel, André Boné, Gaël Chauvin, Valentin Christiaens et al.

The Mid-infrared Extremely Large Telescope (ELT) Imager and Spectrograph (METIS) instrument, expected to see first light in early 2030, aims to detect and characterise exoplanets and circumstellar disks through high- contrast imaging (HCI) and spectroscopy. The High-contrast End-to-End Performance Simulator (HEEPS), initially developed to support the design of the METIS HCI modes, has evolved into a crucial tool for the METIS science team to prepare and optimize observations. HEEPS is an open-so…

Read →
astro-ph.EP

Öpik-type collision frequency for Kozai-driven projectiles: Target bodies on eccentric and inclined orbits

Youpeng Liang, Xiaodong Liu

For high-inclination projectiles undergoing Lidov--Kozai secular evolution, coupled variations in eccentricity and inclination complicate estimates of long-term collision frequencies with a target body. Previous collision-frequency studies for Kozai-driven projectiles have considered target-body orbits that are either circular or confined to the reference plane. The present study considers the general case in which the target body's orbit has both non-zero eccentricity and non-zero inclination.…

Read →
astro-ph.SRastro-ph.GA

From spectroscopic abundances to evolutionary [$α$/Fe] in stellar models

Pedro Diaz Reeve, Aldo Serenelli

Large-scale, high-resolution spectroscopic surveys map detailed chemical abundance patterns for millions of stars. However, libraries of stellar evolution models and isochrones still rely on a simplified description of chemical abundances, generally assuming either solar-scaled compositions or a constant enrichment for all $α$-elements. Moreover, the definition of $α$-enrichment is survey-dependent and is not necessarily the most relevant quantity for stellar structure and evolution. In the era…

Read →
astro-ph.HEastro-ph.COastro-ph.IM

The DSA/Chronoscope fast radio burst survey: forecasts and science overview

Liam Connor, Kaitlyn Shin, Vikram Ravi, Stella Koch Ocker, Casey J. Law, Kritti Sharma, Samuel McCarty, Gregg Hallinan et al.

Fast radio bursts (FRBs) are bright extragalactic transients with several mysteries surrounding their origins. Large FRB samples enable accurate measurements of the cosmic matter distribution, in particular on scales $\lesssim 10$ Mpc. These measurements will impact cosmological inference and our understanding of astrophysical feedback, from the circumgalactic medium to cluster scales. Here we forecast the expected yields, redshifts, and host galaxies of FRBs as observed by the Deep Synoptic Arr…

Read →
astro-ph.IM

Beyond $X_\mathrm{max}$ : Reconstructing Air Shower Profiles with Information Field Theory with SKA-Low

Keito Watanabe, Tim Huege, Torsten Enßlin, Vincent Eberle, Sjoerd Bouma, Justin Bray, Stijn Buitink, Arthur Corstanje et al.

While radio measurements of extensive air showers have shown to achieve a high precision of $X_\mathrm{max}$ sensitivity, it has been shown that parameters beyond $X_\mathrm{max}$ can also be reconstructed. These shape parameters contain additional sensitivity to the hadronic physics in the shower as well as its mass composition. In this work, we showcase a reconstruction framework to recover the full longitudinal profile from realistic radio measurements. The framework is based on Information F…

Read →
astro-ph.SRastro-ph.IMstat.AP

Extremes of solar spectral irradiance in the SORCE/XPS record

Enzo Brasil, Cira E. G. Otiniano, Carolyne Brito, Beatriz Albernaz, Fidel Morales

Extreme and rare changes in space mission solar irradiance records are scientifically relevant but difficult to quantify because these records are finite, instrument dependent, and affected by observational gaps and time varying measurement quality. We evaluated extreme daily logarithmic changes in the band integrated 0.1-7.0 nm irradiance measured by photodiode 7 of the Solar Radiation and Climate Experiment/X-Ray Photometer System (SORCE/XPS) from 2005 to 2019. After constructing a regular dai…

Read →
astro-ph.IMgr-qc

Detectability-Aware Screening of Post-Merger Gravitational-Wave Damping Anomalies in Real Detector Noise: A Graph-Spectral Approach with Empirical Null Calibration

Ruslan Alaskarov

A two-stage methodological proof of concept for screening simplified post-merger gravitational-wave damping anomalies in real LIGO Livingston noise is presented. The injected signal is a controlled damped-sinusoid proxy rather than a physically complete binary-neutron-star post-merger waveform; it is used to test statistical detectability and damping-time scoring under real-noise calibration. Stage 1 constructs a local time-frequency graph from Constant-Q representations of whitened candidate wi…

Read →
astro-ph.SR

Study of Butterfly-Shaped Coronal Hole Evolution Across the Solar Disk

Bhairab Ale, Khagendra Katuwal, Shiv Narayan Yadav

We studied the evolution of a butterfly-shaped coronal hole (CH) observed from 2025 September 8 to 14 using SDO/AIA 193~Å images and SDO/HMI line-of-sight magnetograms. The CH boundary was identified using a fixed 100~DN intensity threshold, and its area, mean EUV intensity, and total unsigned magnetic flux were tracked across the solar disk. As the CH approached the central meridian, its area increased from approximately $7.70\times10^{16}$ to $1.63\times10^{17}$~m$^{2}$ and its unsigned magnet…

Read →
astro-ph.GA

Stellar streams around dwarf galaxies are observationally rare in the local Universe

Joanna D. Sakowska, David Martíınez-Delgado, Sarah Pearson, Francisco J. Riquel-Castilla, Tjitske K. Starkenburg, Giuseppe Donatiello, Alis Deason, Denis Erkal et al.

The frequency and properties of stellar streams around dwarf galaxies remain observationally under-explored. Building a statistically significant sample is challenging because dwarf galaxies are smaller, fainter, and far more numerous than massive galaxies. We present the first results from a systematic survey for stellar streams around dwarf galaxies. We first introduce a classification metric for satellite accretion features (streams, shells, and asymmetric stellar haloes) using DECam imaging…

Read →
astro-ph.IMastro-ph.HE

Radio measurements of air showers with the IceCube-Gen2 surface prototype station at the Pierre Auger Observatory

Stef Verpoest, or the IceCube-Gen2 Collaboration, for the Pierre Auger Collaboration

The design of the IceCube-Gen2 observatory, proposed as a next-generation extension of IceCube, includes a surface array consisting of scintillators and radio antennas. In addition to several such detectors already deployed at IceCube's surface array at the South Pole, a complete prototype station including three SKALA antennas has been operating at the Pierre Auger Observatory for several years. This setup has been used to successfully observe radio signals from air showers, demonstrated throug…

Read →
astro-ph.IMastro-ph.HE

Radio measurements of air showers with the IceCube-Gen2 surface prototype station at the Pierre Auger Observatory

Stef Verpoest, for the IceCube-Gen2 Collaboration, for the Pierre Auger Collaboration

The design of the IceCube-Gen2 observatory, proposed as a next-generation extension of IceCube, includes a surface array consisting of scintillators and radio antennas. In addition to several such detectors already deployed at IceCube's surface array at the South Pole, a complete prototype station including three SKALA antennas has been operating at the Pierre Auger Observatory for several years. This setup has been used to successfully observe radio signals from air showers, demonstrated throug…

Read →
astro-ph.GAastro-ph.SRphysics.plasm-ph

Magnetohydrodynamics of charged interstellar dust. Multifluid models and study of the linear modes

Gabriel Verrier, Patrick Hennebelle, Ugo Lebreuilly, Valentin Vallucci-Goy

Interstellar grains play key roles in star and planet formation, including the coupling of the gas to the magnetic field during the protostellar collapse. These roles depend on the local grain size distribution, which requires a multifluid treatment of charged dust. We aim to understand the fundamental physics of the dynamics of a dust distribution in interaction with the gas and the magnetic field. In particular, the purpose is to characterize the (de)coupling conditions of these different comp…

Read →
astro-ph.SR

The umbrella effect: Magnetic canopy topology modulates spatially averaged chromospheric three-minute power

Shahin Jafarzadeh, David B. Jess, Marco Stangalini, Bernhard Fleck, Richard J. Morton, Samuel D. T. Grant, Peter H. Keys, Luc Rouppe van der Voort et al.

Three-minute ($\sim$5 mHz) oscillations are a prominent signature of wave propagation in the solar chromosphere, but their measured power can vary substantially between full-disc observations and small, high-resolution fields of view. We investigate whether chromospheric magnetic canopy topology, particularly its lateral continuity and areal filling, modulates field-of-view-averaged three-minute power. We analyse H$α$ and Ca II 8542 Å spectral imaging from the Swedish 1-m Solar Telescope, compar…

Read →
astro-ph.GA

Constraining Baryonic Feedback at $z\sim 1$ with the H$α$ Luminosity Function

Ivan Rapoport, Vincent Desjacques, Ehud Behar, Shmuel Bialy

Baryonic feedback remains one of the primary uncertainties in galaxy formation models because of its impact on the interstellar medium (ISM) and star formation. We investigate its effect on the H$α$ luminosity function (LF) using the Illustris and IllustrisTNG simulations, incorporating direction-dependent dust attenuation and a physically motivated treatment of the propagation of Lyman-series photons. We model three sources of H$α$ emission: star-forming H II regions, collisional excitation and…

Read →
astro-ph.HE

STOKES tables and KY codes

Jakub Podgorný, Michal Dovčiak

The family of KY codes is an XSPEC-compatible package of fully relativistic models for spectro-polarimetric modeling of X-ray binary systems and active galactic nuclei. Within Kerr space-time, they compute accretion disc line profiles, reflection spectra from discs illuminated by Comptonized coronal radiation, and thermal disc emission including disc-corona interaction and disc self-irradiation. Many of these models include polarimetric computations, and more advanced timing variants compute X-r…

Read →
astro-ph.IM

On-sky demonstration of a vector Zernike wavefront sensor in a cascaded adaptive optics system

M. Motte, V. Chambouleyron, R. Fétick, F. Oyarzun, M. A. Alagao, A. Striffling, E. Vinerskas, J. -F. Sauvage et al.

To directly image and characterise Earth-like exoplanets, future high-contrast instruments will require adaptive-optics systems operating at increasingly high loop frequencies to reduce temporal errors. Increasing the loop frequency reduces the signal-to-noise ratio per wavefront-sensor frame, making highly sensitive wavefront sensors, such as the Zernike wavefront sensor (ZWFS), attractive candidates. However, the limited dynamic range of the classical ZWFS makes on-sky operation challenging. W…

Read →
astro-ph.SR

Astrometric modeling of unresolved variable binary systems. II. Application to Gaia epoch astrometry of nearby pulsating and convective red giants

L. Decin, K. Sivkova, P. Kervella, A. Chiavassa, E. Beguin

(Abbreviated) The interpretation of high-precision astrometry for intrinsically variable stars remains challenging, particularly for unresolved binary systems containing asymptotic giant branch (AGB) stars. In such systems, large-amplitude pulsations and evolving convective surface structures induce time-dependent photocentre displacements that perturb the observed orbital motion. At the same time, Gaia DR4 epoch astrometry offers the prospect of deriving accurate orbital solutions and parallaxe…

Read →
astro-ph.HEastro-ph.GA

TeV Gamma Rays and Neutrinos from Winds Driven by Radiatively Inefficient Accretion Flows of Low-Luminosity Active Galactic Nuclei

Nobuyuki Sakai, John F. Beacom, Kohta Murase

Recently, the Large High Altitude Air Shower Observatory (LHAASO) reported the first TeV gamma-ray detection from a low-luminosity active galactic nucleus (LLAGN) lacking a strong jet. This source, NGC 4278, is one of the nearest LLAGNs that can be studied in detail as a template for more distant objects. Most previous studies have focused on the month-scale-variable gamma-ray activities, seeking to explain them with weak jets. We focus instead on NGC 4278's quiet-period emission, proposing a di…

Read →
astro-ph.IM

Learning Radio Astronomical Representations with LeJEPA and Very Small Models

Erica Lastufka, Mariia Drozdova, Vitaliy Kinakh, Taras Holotyak, Miroslava Dessuages-Zavadsky, Daniel Schaerer, Svyatoslav Voloshynovskiy

Representations learned by vision foundation models pretrained on natural images have been shown to be useful for out-of-domain astronomical images. Performance on scientific downstream tasks increases with model size, which both carries higher inference costs and limits scalability, even when considering parameter-efficient adaptation. An alternative is to learn representations directly from astronomical observations rather than natural images, through self-supervised pretraining. We evaluate L…

Read →
nucl-thastro-ph.HEastro-ph.IMhep-ph

NS-UNO: Neutron Star EoS Inference from an Unconstrained Number of Observations

Valéria Carvalho, Márcio Ferreira, Michał Bejger, Constança Providência

Future multimessenger observations of neutron stars (NS) are expected to substantially increase both the number and precision of astrophysical constraints on the equation of state (EoS) of dense matter. This motivates inference frameworks capable of accommodating a variable, non fixed number of observations while preserving the posterior information associated with each measurement. In this work, we introduce NS-UNO, a Neural Posterior Estimation framework for NS EoS inference designed to accomm…

Read →
astro-ph.HEhep-ph

Cascades from ultra-high-energy neutrinos

Gaetano Di Marco, Rhorry Gauld, Rafael Alves Batista, Alfonso García-Soto, Miguel Á. Sánchez-Conde

Neutrinos produced at the highest energies can interact with cosmic neutrino and radiation backgrounds during their propagation to Earth. The many available $νν$, $ν\barν$, and $νγ$ channels can lead to their absorption or energy redistribution, whilst the leptonic and hadronic final states may feed secondary fluxes of neutrinos, protons, and electromagnetic particles through the decay or hadronisation of the heavy leptons, bosons, and quarks produced. We present a framework to characterise thes…

Read →
astro-ph.SRastro-ph.GA

Interferometric Survey of Stellar Parameters: Towards homogeneous FGK stars parameters and surface-brightness color relation in the context of PLATO space mission

Romina V. Ibañez Bustos, Denis Mourard, Nicolas Nardetto, Jeremy Jones, Nayeem Ebrahimkutty, Juraj Jonák, Hugo Nowacki, Mathieu Vrard et al.

The estimation of stellar angular diameters can be performed from the surface brightness - color relation (SBCR) and photometry. The SBCR have been considered by the PLATO space mission as an independent empirical alternative for estimating stellar radii of FGK stars. In this context, we have implemented an homogeneous approach not only for calibrating the SBCR for FGK-IV/V stars but, also for determining their fundamental parameters in order to place the stars reliably on the HR diagram and to…

Read →
astro-ph.SRastro-ph.EP

Joint Observations of PTPS Targets (JOTA). Combined spectroscopic and photometric analysis of 16 SB1 systems

Robert Jaros, Andrzje Niedzielski, Sohaib Ali, Divyansh Srivastava, Julia Sierzputowska, Monika Adamów, Jorge Lillo-Box, Dmytro Orikhovskyi et al.

Context. The Pennsylvania-Toruń Planet Search, which operates on a sample of $\sim$1000 northern-hemisphere stars, has been underway since 2004. Stars with radial velocity (RV) amplitudes exceeding 2 km s$^{-1}$ represent a backup subprogram sample dedicated to monitoring binary stars with multiple instruments. Aims. We used almost 21 years of combined RV measurements to search for Doppler signals consistent with stellar or brown dwarf companions and to produce a catalog of both known and previo…

Read →
astro-ph.SR

Equilibrium \(\mathrm{H}_2^+/\mathrm{H}^-\) Abundance Ratios in MARCS Atmosphere Models

Aiganym Sarsembayeva, Hernando Quevedo

We investigate the equilibrium abundance ratio of the molecular hydrogen ion \(\mathrm{H}_2^+\) and the negative hydrogen ion \(\mathrm{H}^-\) in stellar atmospheres using compact Saha-type equilibrium expressions and layer-by-layer partial pressures from MARCS model atmospheres. The analysis distinguishes the temperature-dependent coefficient ratio \(K_{\mathrm{H}_2^+}(T)/K_{\mathrm{H}^-}(T)\) from the full abundance ratio, which also depends on the local ionisation factor \(N_{\mathrm{H}^+}/N_…

Read →