UchUchU

Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.SRastro-ph.GA

Symbiotic binaries in the Gaia data. I. Known symbiotics in DR3 and FPR

Jaroslav Merc

Symbiotic stars are long-period interacting binaries composed of an evolved giant and a hot compact companion. Their complex spectra and variability make them both astrophysically valuable and observationally challenging. We investigate how known symbiotic stars are represented in Gaia DR3 and the Focused Product Release (FPR), assess the reliability of these data, and evaluate their usefulness for candidate analysis and searches for new systems. We crossmatched Gaia DR3 and the FPR with confirm…

Read →
nucl-thastro-ph.HEhep-ph

Thermal conductivity of dense $npΛ$ matter in neutron star cores

Tanay Choudhary, Athira S., Monika Sinha

The possible presence of hyperons in the cores of massive neutron stars has important implications for their microscopic transport properties and thermal evolution. Despite recent progress in modelling core transport, a dedicated analysis regarding the thermal conductivity of a specific \(npΛ\) mixture remains absent from the existing literature. In this work, we investigate the thermal conductivity of dense, \(β\)-equilibrated \(npΛ\) matter within the framework of the variational linearized Bo…

Read →
astro-ph.GAgr-qc

Discovery of a star sensitive to the spin of Sgr A*

K. Abd El Dayem, R. Abuter, N. Aimar, P. Amaro-Seoane, A. Berdeu, J. -P. Berger, G. Bourdarot, W. Brandner et al.

Residing in the center of the Milky Way, Sgr A* is the closest massive black hole (MBH). Its vicinity has allowed measuring individual stellar orbits around it. The stars act as test particles and probe the gravitational potential around the $4.3 \times 10^6 M_\odot$ MBH. These observations have determined the central mass to sub-percent precision, and the mildly relativistic motions of stars have given access to the dominant relativistic corrections, the gravitational redshift, the transverse D…

Read →
astro-ph.EPastro-ph.IM

Direct Retrieval of Protoplanetary Disk Dust Properties using Auto-differentiable Gaussian Processes and Its Application to the HD 169142 Disk

Tomohiro C. Yoshida, Enrique Macías, Giovanni Rosotti, Stefano Facchini, Elena Viscardi, Kiyoaki Doi

Retrieving dust properties in protoplanetary disks, including the surface density distribution, temperature, and grain size distribution, is a fundamental task in observational studies of planet formation. While multi-wavelength analysis of the spectral energy distribution (SED) using interferometers such as the Atacama Large Millimeter/submillimeter Array (ALMA) is a powerful diagnostic tool, traditional methods are often hindered by strong biases arising from a limited imaging beamsize. In thi…

Read →
astro-ph.IMastro-ph.HE

PSRDISP: A novel approach to modeling dispersive processes in single-pulsar noise analysis using epoch-wise dispersion measures

Churchil Dwivedi, Abhimanyu Susobhanan

We present PSRDISP, a novel approach to modeling deterministic and stochastic dispersive processes in pulsar timing datasets using high-precision epoch-wise dispersion measure (DM) estimates, with a Gaussian Process based approach. Unlike the conventional single-pulsar noise analysis methodology, which is applied to frequency-resolved times of arrival (ToAs) of pulses, this technique is applied to epoch-wise DMs which are derived from these ToAs. It can also be applied to wideband DMs measured s…

Read →
astro-ph.SR

Mean-field interpretation of star-in-a-box simulations of red giants

Carolina A. Ortiz-Rodríguez, Axel Brandenburg, Petri J. Käpylä

Context: The origin of magnetic fields and the dynamo mechanism in red giants are still not fully understood. Aims: We aim to interpret the dynamo behaviour of global 3D simulations of red giants using mean-field dynamo models. Methods: We use mean-field models constrained by the differential rotation profile extracted from 3D simulations. We perform $α^2$, $αΩ$, and $α^2Ω$ mean-field dynamo simulations, varying the strength of the $α$ effect and the differential rotation. Results: The mean-fiel…

Read →
astro-ph.GAastro-ph.CO

The Three Hundred project: Low Gas Fraction Galaxy Clusters properties and their environment

Francesco Guidi, Marco De Petris, Sara Santoni, Raphael Wicker, Antonio Ferragamo, Hippolyte Froget, Stefano Andreon, Weiguang Cui et al.

Galaxy cluster samples based on X-ray and Sunyaev-Zel'dovich (SZ) observations are affected by selection biases. These catalogs preferentially include systems with high gas content and surface brightness. Excluding objects with depleted gas content, low-gas-fraction clusters (LGFCs), could lead to an incomplete sampling. We aim to investigate the abundance and the properties of the LGFCs population using The Three Hundred hydrodynamical simulations, focusing on the Gadget-X code. In particular,…

Read →
physics.space-ph

Unraveling the Generation Mechanism of a Mid-Latitude Plasma Blob and the Evidence of Its Rare Interaction with a MSTID Phase Front

D. Patgiri, R. Rathi, V. Yadav, D. Chakrabarty, M. V. Sunil Krishna, S. Kannaujiya, S. Sunda, Y. Otsuka et al.

We report observations of two distinct nighttime F-region irregularities, plasma blob (localized density enhancement) and medium-scale traveling ionospheric disturbance (MSTID), in O(1D) 630.0 nm all-sky airglow images from Hanle (32.7°N, 78.9°E; Mlat~24.1°N), Ladakh, India, during the geomagnetically quiet (Ap=6) night of 06 July 2021. Global vertical total electron content (VTEC) maps revealed that the plasma blob developed beyond the southern edge of imager's field-of-view before appearing in…

Read →
astro-ph.HEhep-ph

Machine Learning Detection of Non-Axisymmetric Fast Flavor Instabilities in Compact Objects

Madhurima Chakraborty, Sajad Abbar, Meng-Ru Wu, Francois Foucart, Zewei Xiong

Neutrinos in dense astrophysical environments such as core-collapse supernovae (CCSNe) and neutron star mergers (NSMs) can undergo FFCs, which could develop on extremely small scales. A necessary condition for the occurrence of FFCs is the presence of a zero crossing in the electron lepton number (ELN) angular distribution of neutrinos. In this work, we explore machine learning (ML) approaches to detect non-axisymmetric ELN crossings in these environments, based on input features of the $ν_e$ an…

Read →
astro-ph.HEastro-ph.SR

Photometric and Spectroscopic Studies of Type Ic Supernovae SN 2020akf and SN 2021mxx

Mulchand Kurre, K. R. Sahu, Shrutika Tiwari, Yogita Patel, N. K. Chakradhari, D. K. Sahu, Rishabh Singh Teja, G. C. Anupama et al.

We present a comprehensive analysis of optical photometry and medium-resolution spectroscopy for Type Ic supernovae (SNe) SN 2020akf and SN 2021mxx. Our study covers the evolution of SN 2020akf from -5 to 109 days and SN 2021mxx from -3 to 115 days relative to their B-band maximum. Their peak quasi-bolometric luminosities are estimated at logL_bol = 42.37 +- 0.02 and 42.21 +- 0.02 erg/s, respectively. The velocities of the ejecta, derived from the Fe II 5169 A line at maximum light, are approxim…

Read →
astro-ph.IM

Estimation of the laser guide star uplink tip-tilt using aperture size diversity

Pierre Jouve, Thierry Fusco, Carlos M. Correia, Cédric Taissir Heritier, Jean-François Sauvage, Benoit Neichel

Laser guide star (LGS) adaptive optics cannot directly measure tip-tilt (TT), forcing reliance on natural guide stars and limiting sky coverage. We propose estimating the uplink TT from telemetry acquired at the laser launch telescope alone, operated in a monostatic configuration as both emitter and receiver. Extracting TT over concentric disks of different diameters within the receiving pupil yields signals mixing uplink and downlink contributions in different proportions; this aperture size di…

Read →
astro-ph.EPphysics.geo-ph

Discrimination of Tectonic, Swarm and Impact-related Marsquakes using Spectral Characteristics

Simon C. Stähler, Savas Ceylan, Nikolaj Dahmen, John Clinton, Domenico Giardini

The NASA InSight mission observed over 2000 marsquakes in the course of its three year mission. These quakes varied in magnitude between 1.5 and 4.5, as well as in spectral content. We present a simple framework to describe the spectral characteristics of all observed marsquakes, based on source process; propagation through the mantle or crust; and local, receiver-side amplification. We assign to each quake an objective measure of its amplitude, as well as the spectral decay created by the durat…

Read →
astro-ph.IM

Scaling laws for multi-object spectrographs: empirical relationships and the photonic advantage of CAWSMOS

Kalaga V. Madhav, Martin M. Roth

Conventional multi-object spectrographs (MOS) incur masses and costs that scale unfavourably with channel count~$N_\mathrm{ch}$ and resolving power~$\mathcal{R}$. A dataset of eight fibre-fed MOS-VIS instruments (1995--2024) is compiled and analysed. Ordinary least-squares fitting yields a mass function $M \propto N_\mathrm{ch}^{0.78\pm0.28}$; the resolving-power exponent is empirically consistent with zero ($γ= 0.20\pm0.37$) but is predicted analytically to lie in $\mathcal{R}^{0.8\text{--}2.0}…

Read →
astro-ph.EPastro-ph.GAastro-ph.IM

A Fast Concentric-disk Contour Integration Method For Microlensing Limb-darkening Effect

Suwei Wang

Incorporating limb darkening is a computationally demanding step in contour-integration-based microlensing modeling. Conventional concentric-ring integration is incompatible with high-order quadrature schemes, limiting efficiency. We develop a new concentric-disk method, which reformulates the limb-darkening integral and enables the application of high-order adaptive quadrature, significantly accelerating the computation. While mainly demonstrated using a linear limb-darkening profile, the metho…

Read →
astro-ph.GAastro-ph.HE

Accretion-disk formation around orbiting stellar black holes in gaseous star clusters

Zacharias Roupas

We consider low-mass black holes (BHs) moving in regular orbits in the cores of non-rotating gaseous star clusters, representative of proto-stellar clusters or the centers of protogalaxies. We argue that as the BH's sphere of influence -- the Bondi sphere -- is advected along the BH trajectory, the transverse velocity shear between the inner and outer hemispheres injects angular momentum, driving the formation of an accretion disk. Coriolis forces oppose angular momentum injection, delaying disk…

Read →
astro-ph.GA

Bridging the mass gap: Diffuse radio emission in GAMA galaxy groups using EMU and DINGO survey data

Sai Wagh, Tessa Vernstrom, Luke J. M. Davies, Lister Staveley-Smith, Stefan Duchesne, Christopher J. Riseley, Timothy J. Galvin, Franco Vazza et al.

Diffuse radio emission provides a powerful probe of non-thermal processes in the large-scale structure, yet its properties in galaxy groups remain poorly constrained. Using deep 943 MHz radio continuum data from the Evolutionary Map of the Universe (EMU) and 1.37 GHz data from the Deep Investigations of Neutral Gas Origins (DINGO) survey, we investigate diffuse radio emission in 400 galaxy groups selected from the GAMA survey at $z < 0.1$. We employ a multi-resolution filtering technique to supp…

Read →
astro-ph.HEastro-ph.GA

Astrophysical Population Coordinates for Supermassive Black Hole Binaries in Pulsar Timing Array Inference

Yikun Li, Muhammad Ahmad, Shaoguang Guo, Lang Cui

Pulsar timing arrays can probe the population physics of supermassive black-hole binaries through the nanohertz gravitational-wave background. We construct a phenomenological forward model that follows source abundance, binary residence time, the high-mass population, finite-source strain moments, and the pulsar timing response. The simulated observables constrain three standardized population coordinates: $β$, which controls the residence-time and spectral response; $φ_{eff}$, which describes s…

Read →
astro-ph.IM

The Lightspeed project: high-speed, ultra-low read noise imaging and polarimetry for the Magellan telescopes

Christopher Layden, Kevin Burdge, John J. Piotrowski, Gabor Furesz, Juliana Garcia-Mejia, Jack Dinsmore, Roger W. Romani, David Osip et al.

Lightspeed will be an ultra-fast (> kHz), ultra-low read noise, multicolor (ugriz + IR) imager for the 6.5 meter Magellan Clay telescope. In a single-channel configuration, Lightspeed will also enable single-shot linear polarimetry, narrowband imaging, or white-light imaging. Lightspeed is designed around groundbreaking single-photon-resolving detector technologies: deep sub-electron read noise CMOS image sensors from Fairchild Imaging and a HgCdTe avalanche photodiode array from Leonardo. Here…

Read →
astro-ph.IMastro-ph.GAastro-ph.SRphysics.data-an

Demystifying image-recovery from radio interferometers: toward a multiscale predictive model

Dan Miao, Guang-Xing Li

Radio interferometers suffer from the missing short-spacing problem, losing large-scale diffuse emission. This missing flux underestimates gas mass and biases key metrics like star formation efficiency. Quantifying this scale-dependent loss currently relies on computationally intensive mock observations, lacking an analytical image-domain framework. We introduce the Constrained Diffusion Decomposition (CDD) method to decompose an input image ($I_{\mathrm{in}}$) into $n$ continuous scale-space co…

Read →
astro-ph.GA

A FLASH HI absorption search in compact sources in the pilot ASKAP interplanetary scintillation field

Paris E. Gordon-Hall, Emily F. Kerrison, Elizabeth K. Mahony, Elaine M. Sadler, Hyein Yoon, J. N. H. S. Aditya, James R. Allison, Rajan Chhetri et al.

In this pilot study, we use data from the First Large Absorption Survey in HI (FLASH) to search for redshifted HI 21cm absorption at $0.4<z<1$ towards 157 bright radio sources with Interplanetary Scintillation (IPS) measurements at 820MHz in a single field observed with the Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope. The ASKAP IPS measurements, which use only 2.5 minutes of observing time in total, allow us to estimate the compactness of these radio sources on sub-arcse…

Read →
astro-ph.GA

Environmental Imprints on the Assembly of the Cool Gas around Bright Cluster Galaxies

Runyu Zhu, Hu Zou, Taotao Fang, Enci Wang, Zeyu Chen, Zhaobin Chen, Weiyu Ding, Jinfu Gou et al.

Galaxy clusters represent extreme cosmic laboratories where environmental processes dramatically reshape their constituent galaxies, yet their effect on the gaseous halos of central galaxies remains poorly constrained. Here we present the first statistical mapping of cool gas around massive brightest cluster galaxies (BCGs) at $z\approx0.55$. Using Mg II absorption in stacked sight-line spectra from over a million background quasars observed by the Dark Energy Spectroscopic Instrument, we compar…

Read →
astro-ph.SR

Pulsation harmonics reveal the origin of the century-old Blazhko effect

Jia-Shu Niu

The Blazhko effect -- a quasi-periodic modulation of pulsation amplitude and phase observed in all subtypes of RR Lyrae stars -- has defied physical explanation for over a century. Here we show that pulsation harmonics of the Blazhko RRab star V783 Cyg, traditionally regarded as passive replicas of the fundamental mode, encode a direct observational signature of the effect's origin. Using Kepler short-cadence photometry, we identify a subset of harmonics -- here termed ``disharmonized harmonics'…

Read →
astro-ph.HE

Pulsar anti-glitches: starquakes driven by magnetism?

Hanyuan Long, Ruipeng Lu, Weiyang Wang, Shunshun Cao, Hao Tong, Han Yue, Renxin Xu

In the conventional starquake model of pulsar glitches, it is usually assumed that such events arise from fault slip induced by the self-gravity of compact objects. This inevitably decreases the moment of inertia, producing a glitch with an amplitude of only $Δν/ν> 0$. However, an increasing number of anti-glitches ($Δν/ν< 0$) have been observed in extremely magnetized pulsars, the magnetars, and this cannot be explained by that framework. In the present study, we hypothesis that magnetic stress…

Read →
astro-ph.GA

Testing the recovery of the NGC 6505 Einstein ring in deep OSN 1.5-m imaging

Homer Dávila Gutiérrez, Julio Carlos Bertua Marasca, Alejandro Heredia Teva, Irene Naranjo Arroyo, Fernando Núñez Martínez, Miguel Ruiz Travesí, Eugenio Grande Sáez

The discovery of a complete Einstein ring around the nearby elliptical galaxy NGC 6505 (z = 0.042) by the Euclid mission provides a rare, precisely characterised low-redshift strong lens. Its Einstein radius of 2.500 arcsec is comparable to the angular resolution attainable from typical mid-aperture ground-based facilities, which makes the recoverability of the ring from the ground an open practical question. We test whether the ring can be recovered in deep Cousins-R imaging of NGC 6505 obtaine…

Read →
physics.plasm-phphysics.space-ph

Exact Solution of the Direct and Inverse Dynamo Problem in the Expanding Plasma Ball

Yurii V. Dumin

It was found that the differential equation of dynamo effect (i.e., generation of the electric fields and currents) in a uniformly-expanding plasma ball with strongly anisotropic conductivity possesses the unique mathematical property: namely, the spectrum of its eigenvalues is universal and independent of physical parameters of the medium. As a result, it becomes possible to introduce a special set of eigenfunctions - which we called the generalized spherical functions - that can be used to sol…

Read →
physics.ao-phastro-ph.EPnlin.AO

Modeling the response of the marine carbon cycle to extreme CO$_2$ injection events

Punit Gandhi, Rowan Lockwood, Corinne Myers, Parimita Roy, Ivan Sudakow, James Witts, Hao Helen Zhang

We explore how the response of a conceptual model of the marine carbon cycle depends on the way in which carbon is injected from the atmosphere. We find that, for single-injection pulses, the threshold amount required for a large response of the excitable system depends on pulse duration but not on its specific form. We do, however, see differences in the number of large transient responses in carbon and, correspondingly, the duration of the response for different pulse shapes. These differences…

Read →
astro-ph.GA

A differentiable hydrodynamical approach to the Milky Way bar pattern speed with CO longitude--velocity data

Junichi Baba, Kohei Hattori

We present a differentiable hydrodynamical framework for modeling barred gas flow in the Milky Way and constraining broad low-loss regions in bar-pattern-speed parameter space from Galactic longitude--velocity data. The method evolves a neutral-gas disk in a fixed barred potential, projects it into longitude--velocity ($\ell$--$v$) space, and compares predicted and target maps using a cosine-distance loss applied to processed and masked maps. This emphasizes large-scale morphology rather than th…

Read →
astro-ph.GA

Discovery of a gravitational arc candidate at photometric redshift 4.4 in MACS J0308.9+2645 from a catalogue-based search of JWST imaging

Homer Dávila Gutiérrez

We report a strong gravitational arc (A1) in the massive Reionization Lensing Cluster Survey (RELICS) cluster MACS J0308.9+2645 (z_l = 0.356), identified in public JWST/NIRCam imaging from programme GO-5293. A1 is an extended, curved, tangentially aligned source (axis ratio a/b = 6.5, catalogue length 3.9 arcsec) located 50.9 arcsec from the cluster X-ray centre. Its six-band (1.15-4.10 micron) photometry yields a photometric redshift of z_phot = 4.4 (+0.1/-0.3), with P(z > 3) = 0.99. Using the…

Read →
astro-ph.IM

The Interstellar Laser Beacons Hypothesis and the Cosmic Lighthouses Project

Daniel Apai, Chia-Lung Lin, Kevin Wagner

In this paper, we argue that in a realistic, resource-limited scenario senders whose intent is to maximize successful communication at the lowest cost will utilize very long-lived, pulsed beacons. Further, we argue that mass-producible laser beacons with simpler technology ($μ$s or ms pulses instead of ultrashort fs pulses) are more optimal if placed on interstellar orbits. Our extensive, existing surveys are mostly blind to the $μ$s/ms-second universe and to such beacons. We show, however, that…

Read →
astro-ph.EP

TESS Photometry and Radial Velocity Analysis of the sub-Neptune Exoplanet π Mensae c and the Wider π Mensae Planetary System

Skylar S. Larsen, Jake D. Turner, Nikole K. Lewis, Maryame El Moutamid, Diana Solano-Oropeza, Lili Alderson, V. Abby Boehm, Daniel A. Yahalomi et al.

Exoplanet characterization relies on precise measurements of planetary orbital and physical parameters. This is particularly important for planetary dynamics and atmospheric evolution, as orbital parameters help constrain system evolution, resolve ambiguities, and gauge atmospheric retention. The first exoplanet discovered by the Transiting Exoplanet Survey Satellite (TESS), $π$ Men c, is a warm sub-Neptune orbiting a bright Sun-like star in a system containing (at least) one other planet with a…

Read →