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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.IM

Focal-Plane Diagnostics of Atmospheric and Dome-Induced Turbulence: Exploring techniques and applications

Begoña García-Lorenzo, Seifeldin Abouelella, Kabir Baig, Zenaida García Rodríguez, Kshitij Ghimire, Moisés Pulido Torres, Alejandro Trujillo Ramos, Jose A. Acosta-Pulido et al.

Atmospheric turbulence remains the dominant source of image degradation in ground-based astronomy. Its impact depends not only on the integrated turbulence strength but also on the wavefront spatial-coherence outer scale (\LO) and on turbulence generated within the telescope enclosure (dome seeing). While seeing, coherence time, and related parameters are routinely monitored at major observatories, measurements of \LO\ and dome-induced turbulence remain sparse, limiting our ability to predict im…

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astro-ph.SR

Back Reaction of the Untwisting Solar Corona Scars Sunspots

Chen Xing, Xin Cheng, Guillaume Aulanier, Mingde Ding

The evolution of magnetic fields in the tenuous solar corona is predominantly governed by the motions of the underlying dense photosphere. Despite, coronal magnetic restructuring driven by magnetic reconnection between interacting coronal fields can sometimes react backwards to change photospheric magnetic fields. However, the mechanism of reactions remains undetermined. Here, we report the discovery of a back-reaction phenomenon: the untwisting of coronal loops that become twisted during reconn…

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astro-ph.EP

Statistical Constraints on Albedo Structure in Asteroid Families from NEOWISE Measurements

Murat Kaplan

Interpreting asteroid family albedo distributions as compositional signatures requires distinguishing intrinsic structure from measurement artifacts, rarely quantified. We analyze 102 families using NEOWISE data with AKARI cross-validation and SDSS-based photometric checks, establishing detection limits for bimodality and quantifying selection bias in size-albedo correlations. We work primarily in logarithmic albedo space (log10 pV), which more accurately resolves the asymmetric dark/bright mixt…

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astro-ph.SR

Cataclysmic variables from SRG/eROSITA: new systems from eRASS1

A. D. Schwope, J. Brink, D. A. H. Buckley, V. A. Cúneo, S. Friedrich, S. Hernández-Díaz, K. Knauff, J. Kurpas et al.

(abridged) Aims. We aim to generate large samples of CVs selected from the SRG/eROSITA surveys to address fundamental questions about binary evolution, the role of magnetic fields in CV evolution and their contribution to the Galactic Ridge X-ray Emission (GRXE). Methods. We have trained a Random Forest (RF) classifier based on combined X-ray and optical properties to select CV candidates from the first eROSITA X-ray all-sky survey (eRASS1). Follow-up spectroscopy to securly identify the objects…

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astro-ph.GA

Angular Momentum Evolution from Core to Disk Scales in the Early Phase of Star Formation: Constraints from HH 212, HH 211, and B335

Chin-Fei Lee

I investigate the angular momentum evolution from core to disk scales in the early phase of star formation using three protostellar systems: HH 212, HH 211, and B335. Observations show that the specific angular momentum follows a power-law dependence at core scales and transitions to an approximately constant value at smaller radii, indicating dynamical collapse in the inner envelope. I model this behavior using the inside-out collapse solution of Shu (1977) and its rotating extension, the Tereb…

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astro-ph.SRastro-ph.GAastro-ph.HE

The physical origin of the maximum stellar size

Gautham N. Sabhahit, Jorick S. Vink

One might expect the most massive stars to also be the largest by size, yet they are not, and this has puzzled astronomers for decades. The Eddington limit sets an upper bound to stellar mass through the balance between radiation pressure and gravity, but a second empirical boundary on stellar radius has equally far-reaching consequences for modern Astrophysics: it affects the black-hole masses and merger rates inferred by LIGO and Virgo, determines whether a star remains a hot, compact ionising…

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astro-ph.SRastro-ph.GAastro-ph.HE

Hydrodynamical mass-loss rates for very massive stars II. New theoretical mass-loss predictions at solar metallicity (Z = 0.02)

Gautham N. Sabhahit, Jorick S. Vink, Andreas A. C. Sander

The evolutionary pathways and ultimate fates of very massive stars are governed primarily by mass loss through radiatively-driven winds. We present a new theoretical mass-loss prescription for (very) massive stars, capturing the complex dependence on the Eddington parameter $Γ_e$, luminosity, temperature, and hydrogen abundance. We calculated an extensive grid of 178 hydrodynamically consistent wind-atmosphere models in non-local thermodynamic equilibrium using the PoWR-HD code, predicting wind…

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physics.plasm-phastro-ph.SRphysics.space-ph

The Second Quadratic Invariant of Astrophysical Gyrokinetics

Benjamin D. G. Chandran, Alfred Mallet, Romain Meyrand

We show that gyrokinetics in a spatially uniform equilibrium (or `astrophysical gyrokinetics') possesses a previously unknown quadratic invariant, which we call the gyrokinetic helicity. We derive the limiting forms of the gyrokinetic helicity in five subsidiary expansions of astrophysical gyrokinetics: the isothermal electron fluid (ITEF) approximation, kinetic reduced magnetohydrodynamics (KRMHD), electron reduced magnetohydrodynamics (ERMHD), finite-Larmor-radius magnetohydrodynamics (FLR-MHD…

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astro-ph.HEhep-ph

Comparative Periodogram Analysis of 22 Years of Super-Kamiokande Solar $^{8}\mathrm{B}$ Neutrino Data: Classical, Phase-Based, and Information Theoretic Methods

Liangliang Ren, Ze-Lin Zhang, Bing Xu, Tian-Cheng Huang, Ran Wang, Jia-Xin Dong, Yan-Ping Wang

Solar $^8\mathrm{B}$ neutrinos offer a unique probe of solar interior dynamics and neutrino electromagnetic properties. We present a systematic, multi-method periodogram analysis of the 22-year Super-Kamiokande solar neutrino dataset (1996--2018), comparing nine algorithms. Through hierarchical temporal segmentation, we disentangle astrophysical signals from detector systematics. The Generalized Lomb-Scargle (GLS) method provides the most statistically robust detections by correctly handling het…

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astro-ph.HEhep-ph

Comparative Periodogram Analysis of 22 Years of Super-Kamiokande Solar $^{8}\mathrm{B}$ Neutrino Data: Classical, Phase-Based, and Information Theoretic Methods

Liangliang Ren, Ze-Lin Zhang, Bing Xu, Tian-Cheng Huang, Ran Wang, Jia-Xin Dong, Yan-Ping Wang

Solar $^8\mathrm{B}$ neutrinos offer a unique probe of solar interior dynamics and neutrino electromagnetic properties. We present a systematic, multi-method periodogram analysis of the 22-year Super-Kamiokande solar neutrino dataset (1996--2018), comparing nine algorithms. Through hierarchical temporal segmentation, we disentangle astrophysical signals from detector systematics. The Generalized Lomb-Scargle (GLS) method provides the most statistically robust detections by correctly handling het…

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astro-ph.GA

A search for HI absorption in distant star-forming galaxies with ASKAP-FLASH - II. Direct observations and stacking of 21 cm line

Sophie L. Eden, Elaine M. Sadler, Kevin A. Pimbblet, Stephen J. Curran, Julia Healy, Filippo M. Maccagni, Elizabeth K. Mahony, Hyein Yoon et al.

We present results of a search for associated and intervening HI 21 cm absorption in star-forming galaxies and a control sample of radio galaxies at 0.4 < $z$ < 1.0, using ASKAP's FLASH HI 21 cm absorption survey. We report the detection of a new HI 21 cm absorption line in radio galaxy NVSS J214954-004657 at $z_{\mathrm{HI}}$ = 0.863. Additionally, we present results of HI 21 cm stacking for associated and intervening star-forming and radio galaxy catalogues. For the first time at these redshif…

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astro-ph.GA

Invariant manifolds in barred galaxy simulations. III. Self-regulated weakening of strong spiral arms

T. Soler-Terricabras, S. Roca-Fàbrega, M. Romero-Gómez

We investigated the origin of the weakening of strong spiral arms in barred galaxies, seeking the physical mechanism responsible for the decline in the fraction of manifold-trapped particles over time. We reconstructed the gravitational potential of a fully self-consistent N-body simulation of a barred galaxy using AGAMA, computed the Lagrangian points, and quantified how their spiral-induced angular displacement affects the geometry of the invariant manifolds and the associated orbital flows. W…

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astro-ph.HEastro-ph.SR

High-mass binary black hole mergers from detailed binary evolution models

Max M. Briel, Olcay Bıyıklı, Tassos Fragos, Anarya Ray, Zepei Xing, Monica Gallegos-Garcia, Abhishek Chattaraj, Jeff J. Andrews et al.

Gravitational-wave observations reveal a population of binary black hole (BBH) mergers with primary masses above ${\sim}40\,\mathrm{M}_\odot$, extending into and potentially beyond the pair-instability mass gap, with a possibly flat mass-ratio and broader χ_\mathrm{eff} distribution. We investigate whether super-Eddington accretion during stable mass transfer in isolated binary evolution can produce BBH mergers consistent with these properties across primary BH mass, mass-ratio, and χ_\mathrm{ef…

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astro-ph.SR

SRG/eROSITA X-ray selected cataclysmic variable candidates observed in SDSS-V DR20

J. Brink, A. D. Schwope, K. G. Pradeep, T. Dwelly, S. F. Anderson, C. Andonie, S. Aviram, C. Aydar et al.

We report on the spectroscopic observations obtained during SDSS-V DR20 of accreting compact binaries (ACB), specifically the cataclysmic variables (CVs), that were identified as likely compact binary candidates from the SRG (Spectrum Roentgen Gamma) eROSITA eRASS1 and eRASS:3 observations. Our primary aim is to obtain a complete inventory of all CVs that were detected in eRASS1 and eRASS:3, with the goal to help better understand close-binary evolution, the population density, and demographics…

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astro-ph.SR

The Study of Quasi-Periodic Pulsations in Solar and Stellar Flares with SKA

Valery M. Nakariakov, Atul Mohan, Vishal Upendran, Teresa Monsue, Hamish A. S. Reid, Dmitrii Y. Kolotkov, Sergey A. Belov, Kyung-Suk Cho et al.

An intensively studied phenomenon which is not described by the standard flare model are quasi-periodic pulsations (QPP) of the flaring emission. As analysis of the QPP phenomenon intrinsically requires a combination of high time and spatial resolutions, especially in the radio band, the unprecedented capabilities of SKA offer us a unique opportunity to reach a breakthrough progress in the observational study of QPP. The SKA-Mid-frequency band falls in a unique window where both coherent emissio…

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astro-ph.IM

DM/WFS mis-registration tracking: Implementation and on-sky validation of SPRINT at LBT

Ben Buky, Cédric Taïssir Héritier, Fabio Rossi, Juan Carlos Guerra, Charlotte Z. Bond, Noah Schwartz, Guido Agapito, Enrico Pinna et al.

The advent of telescopes with an integrated deformable mirror (DM) presents new challenges for adaptive optics (AO) systems. The alignment between the DM and wavefront sensor (WFS) is expected to regularly evolve during operations due to their large separation. Without tracking and correction, these mis-registrations between the DM and WFS lead to loop instability, preventing diffraction limited performance from being realised. SPRINT\cite{heritier2021} provides an approach to track these mis-re…

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astro-ph.GA

The eROSITA X-ray luminosity function of active galactic nuclei

W. Roster, J. Buchner, M. Salvato, R. Shirley, A. Merloni, T. Dwelly, J. Aird, A. Georgakakis et al.

The X-ray luminosity function (XLF) of active galactic nuclei (AGN) provides an observational probe of the growth of supermassive black holes (SMBHs) across cosmic time. With its large survey grasp, Spectrum Roentgen Gamma (SRG)/eROSITA samples the luminosity--redshift plane with a depth--area balance complementary to pencil-beam surveys, providing the volume needed to detect rare luminous AGN, previously limited by small-number statistics. We measure the soft XLF, leveraging an eROSITA sample s…

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hep-thastro-ph.HEgr-qchep-ph

Non-conformal obstructions to bubble expansion

David Mateos, Mikel Sanchez-Garitaonandia, Pedro Tarancón-Álvarez

We investigate the hydrodynamics of expanding bubbles in first-order phase transitions with non-conformal thermodynamics. We analyze a broad class of equations of state interpolating between bag-model descriptions, commonly used for electroweak transitions, and QCD-like theories. As a concrete benchmark, we determine the bubble solutions for pure SU(3) Yang-Mills theory. We uncover a new set of hydrodynamic obstructions to bubble expansion. These obstructions arise both at the bubble wall and al…

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astro-ph.HEgr-qchep-phhep-th

Thermal Breaking of the I-Love Universality for Hot White Dwarfs

Jinyi Lv, Jing-Yi Wu, Hongji Chen, Kexin Jia, Weihan Sun, Kilar Zhang

The universal I-Love-Q relations for compact stars have significant applications in gravitational-wave astronomy, but thermal effects can break these relations in low-mass white dwarfs. In this work, we employ the stellar evolution code MESA to construct realistic models of $0.15 \, M_{\odot}$ helium-core and $0.6 \, M_{\odot}$ carbon-oxygen core white dwarfs at various temperatures. By utilizing the Clairaut-Radau equation, we quantitatively extract the radial variation of the eccentricity of i…

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physics.space-phastro-ph.EP

Ranking the drivers of the Venusian bow shock and ion composition boundary locations

Philippe Garnier, Moa Persson, Sofia Bergman, Yoshifumi Futaana

The Venusian interaction with the solar wind leads to the formation of an induced magnetosphere structured by plasma boundaries. Their dynamics is complex, due to the combined influence of external (solar photons, solar wind plasma and interplanetary magnetic field (IMF)) and internal (ionized atmosphere) drivers. Studying these drivers helps understanding the transfer of energy and momentum throughout the Venusian system, and has thus implications for the erosion of the atmosphere through its c…

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astro-ph.GA

Revealing the Physical Driver of the Baldwin Effect: Gas Density in the Broad-Line Region

Wen-Qiang Liang, Zhi-Fu Chen, Rui-Jing Lu, Cheng-Feng Peng, Shao-Hua Zhang, Zhe-Geng Chen, Zhi-Qing Chen, Yi-Qi Chen et al.

The Baldwin effect --- the inverse correlation between the equivalent width of emission lines and the continuum luminosity in active galactic nuclei (AGNs) --- has been known for nearly five decades, yet its physical origin remains poorly understood. Using a sample of 41,159 radio quasars constructed from the Sloan Digital Sky Survey and the Low-Frequency Array Two-metre Sky Survey, we investigate the origin and underlying physics of the Baldwin effect of MgII broad emission lines in both radio-…

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astro-ph.SR

Unveiling the period-bounce population of cataclysmic variables: Spectroscopic and time-domain follow-up of eROSITA-selected candidates

S. Hernández-Díaz, B. Stelzer, A. Schwope, D. Muñoz-Giraldo, M. R. Schreiber, J. Brink, K. G. Pradeep, B. T. Gänsicke et al.

During their secular evolution, cataclysmic variable stars (CVs) evolve toward shorter orbital periods ($P_{\rm orb}$) until reaching a minimum near $P_{\rm orb}\sim80$ min, after which they evolve back toward longer periods. CVs that have evolved past this evolutionary turning point are known as period-bouncers (PBs). Despite predictions that 40-80% of all CVs should be PBs, only 3-25% of the observed CV population is composed of PBs, a discrepancy likely due to their intrinsic low luminosities…

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astro-ph.SR

The X-ray catalogue of FGK stars within 10 pc: The coronal temperature-brightness relation explained with the RTV scaling law

M. M. Bennedik, B. Stelzer, M. Caramazza, S. Orlando, A. Binks, J. Robrade

A comprehensive measurement of stellar X-ray emission has important implications for our understanding of stellar dynamos, exoplanet atmosphere loss, and evaporation of protoplanetary disks. We present a catalogue of X-ray detections of the FGK-type main-sequence stars within 10 pc, which accounts for stellar multiplicity and optical loading of the detectors. To build the X-ray catalogue, we analysed all observations from SRG (Spectrum Roentgen Gamma)/eROSITA and XMM-Newton for stars in the FGK…

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astro-ph.SRastro-ph.GA

The Volans-Carina association An X-ray Bridge Between Younger and Older Stellar Populations

Daniela Muñoz-Giraldo, Beate Stelzer, Alex Binks, Enza Magaudda, Stefanie Raetz, Christian Schneider

Nearby young moving groups (NYMGs) provide benchmarks for studying the evolution of magnetic activity and planetary environments at early ages. The Volans-Carina association (VCA), as a pre-main sequence association at a distance of ~90 pc, occupies a sparsely sampled region of parameter space between younger nearby associations and older distant open clusters. We have re-evaluated the membership probabilities of the VCA catalog presented in Gagne et al. (2018a) with BANYAN as well as updated ki…

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astro-ph.HE

Tidal Disruption Events with the SKA

T. An, A. J. Goodwin, J. C. A. Miller-Jones, M. Pérez-Torres, L. Rhodes, X. Shu

Tidal disruption events (TDEs) and related nuclear transients probe jet launching, disk formation and circularization, particle acceleration, and the circumnuclear medium (CNM). However, the small fraction of events launching relativistic jets, the weak or delayed radio emission of many thermal TDEs, and the black-hole demographics of galactic nuclei remain poorly understood. SKA, with microJy sensitivity, wide bandwidth, long baselines, rapid response, and commensal surveys across 50-350 MHz (S…

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astro-ph.HEastro-ph.CO

Thermal or Non-thermal? Diffuse emission in the infall region of stacked galaxy groups

E. Bulbul, X. Zhang, Z. Ding, T. Mistele, M. Kluge, E. Artis, Y. E. Bahar, K. Dennerl et al.

The faint infall regions surrounding the virial radius of galaxy groups remain largely unexplored due to their low X-ray surface brightness. Using the large statistical power of SRG/eROSITA survey observations, we present the first spectroscopic measurement of the intragroup medium (IGrM) in the infall regions of a large sample of low-mass galaxy groups ($M_{\rm tot}<1\times10^{14}\,M_{sun}$), extending to $\sim2\,R_{200m}$ (2.2 Mpc). Through spectral stacking of 827 nearby groups from the first…

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astro-ph.HE

The SRG/eROSITA All-Sky Survey DR2: Cumulative X-ray catalogues from the first three surveys and multi-wavelength counterparts in the western Galactic hemisphere

M. E. Ramos-Ceja, G. Lamer, M. Salvato, A. Merloni, J. S. Sanders, A. Georgakakis, T. Liu, E. Bulbul et al.

The eROSITA telescope array on board the Spektrum-Roentgen-Gamma (SRG) mission began its all-sky survey program in December 2019, scanning the sky at an approximately six-month cadence. Here, we present new catalogues of point-like and extended X-ray sources derived from the first three completed eROSITA all-sky surveys (eRASS:3), covering the western Galactic hemisphere, which Germany's eROSITA consortium holds proprietary rights for. We describe the observational strategy, data processing, and…

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astro-ph.EPastro-ph.SR

Accretion Burst Crystallizes Silicates in a Planet-Forming Disk

Jeong-Eun Lee, Chul-Hwan Kim, Jaeyeong Kim, Seokho Lee, Young-Jun Kim, Seonjae Lee, Giseon Baek, Joel D. Green et al.

Crystalline silicates form at high temperatures (> 900 K; Fabian et al. 2000; Hallenbeck et al. 1998). Their presence in comets (Hanner et al. 1994; Hayward et al. 2000; Wooden et al. 2002; Shinnaka et al. 2018) suggests that high-temperature dust processing occurred in the early Solar System and was subsequently transported outward to comet-forming regions. However, direct evidence for this crystallization and redistribution in Sun-like protostars has remained elusive. By comparing James Webb S…

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astro-ph.EPastro-ph.IM

The International Lunar Reference System

Agnès Fienga

As the exploration of the Moon accelerates in the coming years, there is already an urgent need to standardise the Position, Navigation and Timing of spacecraft, and consequently for the definition of the lunar reference system and frame. This document gathers the most recent recommendations of the the International Association of Geodesy (IAG) / International Astronomical Union (IAU) Joint Working Group (WG) 1.1.3 "Lunar Reference frames" on the topic. Despite the challenges for producing a Lun…

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astro-ph.SR

Long-term high-resolution spectroscopic monitoring of the evolved metal-poor binary PS Gem

V. G. Klochkova, V. E. Panchuk, J. K. Zhao, Y. Q. Wu, N. S. Tavolzhanskaya, G. Zhao

We present results of long-term high-resolution spectroscopic monitoring of the extremely low-metallicity star PS Gem (=HD 52961), associated with IRAS 07008+1050. The spectra were obtained with the 6-meter BTA telescope at a resolving power of R=60000 during 1997--2025, providing a homogeneous dataset spanning nearly three decades. Quantitative measurements of the H$α$ two-peaked profile reveal repeatable phase-dependent variations of the peak-intensity ratio $I_{\rm V}/I_{\rm R}$ and the absor…

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