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宇宙工学・惑星科学・宇宙物理の最新プレプリント。

astro-ph.EPastro-ph.IM

Prospects for Mercury Observations with the BepiColombo Laser Altimeter (BELA): Implications for Estimating Surface Roughness from Laser Altimetry

Gaku Nishiyama, Alexander Stark, Christian Hüttig, Kai Wickhusen, Christian Althaus, Thomas Behnke, Ernst Hauber, Klaus Gwinner et al.

Surface reflectance and roughness are key to understanding Mercury's geologic evolution. The BepiColombo Laser Altimeter (BELA) will measure these properties alongside topography, but predicting its performance requires realistic modeling of laser return pulse shapes, unlike a simplified Gaussian approximation in earlier models. We develop a comprehensive return-pulse simulation framework for BELA that includes non-Gaussian transmitted pulses, analog filtering in the receiver chain, and pulse-sh…

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astro-ph.EPastro-ph.IM

Exoplanet detection through photometric orbital phase modulations

J. Lillo-Box, O. Balsalobre-Ruza

Since the detection of the first extrasolar planets thirty-five years ago, the dawn in detected signals has been driven primarily by radial velocity and transit techniques. However, other methodologies have gained significant interest due to their ability to explore specific niches that are challenging to access with traditional approaches. In this article, we focus on the photometric orbital phase modulations induced by planets, describe the methodologies and equations and highlight their devel…

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astro-ph.HEastro-ph.SR

Evolution and mergers of eccentric white dwarf binaries encountering intermediate-mass black holes

Adarsh Pandey, Aryabrat Mahapatra, Tapobrata Sarkar

We study how a close passage past an intermediate-mass black hole (IMBH) changes the evolution of an eccentric white dwarf (WD) binary that has nominal Roche lobe overflow at internal pericenter. Using three-dimensional smoothed particle hydrodynamics, we follow binaries with eccentricity $e_{\rm in}=0.6$ and mass ratios $q=0.2$ -- $0.7$ on parabolic, retrograde orbits around a Schwarzschild IMBH at two encounter strengths, $β^b=0.5$ and $1.5$. We compare them with the same binaries evolved in i…

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astro-ph.EPphysics.geo-ph

Thermal Evolution of Lava Planets Across System Ages: Predictions for Hell of a Survey

Mariana Sastre, Tim Lichtenberg, Lisa Dang, Anjali Piette, Haiyang S. Wang, Mercedes López-Morales, Thomas Wilson, Charles-Édouard Boukaré et al.

Ultra-short-period (USP) rocky exoplanets can have dayside temperatures high enough to maintain permanent magma oceans, sitting at the intersection of interior geophysics and atmospheric chemistry. Coupled feedbacks between the molten surface and outgassed atmosphere can sustain or enhance a volatile envelope, while stellar interactions can erode it. Understanding which outcome prevails, and its observable imprint, requires a multi-target approach across planets at different stages of thermal ev…

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astro-ph.SR

Investigating the inferred spatiotemporal evolution of magnetic fields during an X1-class flare

Dimitri Arramy, Jaime de la Cruz Rodríguez, Adur Pastor Yabar, Jorrit Leenaarts

Several observational studies have reported sudden temporal changes in chromospheric magnetic fields inferred during solar flares using the weak-field approximation (WFA) and nonlocal thermodynamic equilibrium (NLTE) inversions. We investigate whether these variations reflect the rapid evolution of the solar atmosphere or can be influenced by opacity changes caused by flare heating. We perform spatially coupled and regularized NLTE inversions of high-resolution observations and use the inferred…

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astro-ph.GA

Electron irradiation and temperature-programmed desorption of layered ethanolamine-water-methanol ices

Tara L. Stoib, Alejandro Guerrero-Caicedo, Duncan V. Mifsud, Péter Herczku, Gergő Lakatos, Zuzana Kaňuchová, Zoltán Juhász, Béla Sulik et al.

Ethanolamine (EtA) is a recently detected interstellar complex organic molecule and a potential precursor to more functionalised N-bearing species. We investigate the electron-driven chemistry of layered EtA--H$_2$O--CH$_3$OH ices deposited at 20~K, combining 2~keV electron irradiation with subsequent temperature-programmed desorption (TPD) while monitoring the solid phase by mid-infrared spectroscopy. These controlled irradiation conditions represent a simplified laboratory analogue of the stru…

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astro-ph.IM

The SHARPEx space-to-space VLBI experiment

Freek Roelofs, Christiaan Brinkerink, Albert Catalan Artigas, Heino Falcke, Jaime Fernández, Christian M. Fromm, Felix Glaser, Marc Klein Wolt et al.

Space is the next frontier for ultra-high resolution imaging of astrophysical sources with very long baseline interferometry (VLBI). The limited size of the Earth and atmospheric absorption and turbulence at high frequencies prevent order-of-magnitude resolution improvements from current black hole imaging with the ground-based Event Horizon Telescope. A two or three-element submm space-based array like SHARP would image the thin black hole photon ring and measure the black hole spin and spaceti…

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astro-ph.GA

Physical properties of star-forming clumps in nearby galaxies from CLAUDS and HSC-SSP

Jürgen J. Popp, Hugh Dickinson, Stephen Serjeant, Lucy F. Fortson, Vihang Mehta

Giant Star-forming Clumps (GSFCs) are kpc-scale regions of enhanced star-formation with stellar masses of $10^6$ to $10^{10}\,M_\odot$ that are commonly observed in high-redshift ($z \gtrsim 1$) galaxies but their formation and role in galaxy evolution remain unclear. We applied a Faster R-CNN object detection framework (FRCNN) to identify star-forming clumps in astrophysical imaging data from a mass-complete sample of $\sim$210,000 low-redshift galaxies ($z\lesssim0.32$), located in the HSC-SSP…

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astro-ph.HEastro-ph.SR

The 2025.6 X-ray Minimum of Eta Carinae

Amit Kashi, Noam Soker

We present observations of the recent 2025.6 X-ray minimum and recovery of $η$~Carinae, obtained with NICER/XTI, Swift/XRT, XRISM/Xtend, and Chandra/HRC-I. We construct light curves in the soft (0.5--2 keV) and hard (2--10 keV) bands and derive hardness ratios. The X-ray emission reached its minimum about 10 days earlier than in the previous five cycles. As in previous events, the spectrum softened during the decline, while the X-ray luminosity varied on short timescales. These findings strength…

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astro-ph.GA

Rapid Dark Growth of Seed Black Holes in Self-Interacting Dark Matter

Yu Rong, Shuang-Nan Zhang, Jian-Min Wang, Junxian Wang

The rapid emergence of massive black holes in the early Universe, possibly related to Little Red Dots, challenges conventional growth from light seeds. Dark-matter accretion offers a distinct route, and self-interacting dark matter (SIDM) makes it possible by behaving as a collisional fluid. We show that gas inflow can drive strong local contraction of an SIDM halo, assembling a dense reservoir around a pre-existing black-hole seed. The seed then enters a rapid dark-growth phase and can gain sev…

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astro-ph.GA

Little Red Dots as a Transient Phase of Self-Interacting Dark Matter Assisted Black Hole Growth

Yu Rong, Shuang-Nan Zhang, Jian-Min Wang, Junxian Wang, Zhicheng He

The discovery of Little Red Dots (LRDs) with JWST has revealed a population of compact, red galaxies hosting rapidly growing black holes at early cosmic times. Their compact morphologies, broad emission lines, weak X-ray emission, and distinctive V-shaped spectral energy distributions indicate a short-lived phase of black-hole growth within a dense nuclear environment. Here we propose that LRDs arise from a transient episode of self-interacting dark matter (SIDM)-assisted black-hole growth durin…

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astro-ph.GA

Ten years since the NGC 6334I-MM1 accretion outburst: the impact on its environment

G. C. MacLeod, A. Caratti o Garatti, W. A. Baan, D. P. Smits, T. R. Hunter, C. L. Brogan, J. O. Chibueze, R. A. Burns et al.

Ten years on, flaring continues in masers associated with NGC 6334I-MM1. Methanol and hydroxyl masers are nearing quiescent values, but water features remain elevated. Several more 1.665 GHz hydroxyl masers, notably, that flared during the accretion event in NGC 6334I-MM1, are identified and presented. Some hydroxyl masers appear to have been active prior to the 2015 event. Possible explanations are discussed. The radial infrared expansion speed during the accretion event is estimated to be ~1.8…

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astro-ph.GA

Topological Signatures of AGN Feedback in the Simba Simulations

Ryusei R. Kano, Romeel Davé, Tsutomu T. Takeuchi, Hayato Shimabukuro

Active galactic nuclei (AGN) feedback can alter the abundance and spatial distribution of galaxies within large-scale structure. We apply topological data analysis (TDA) to Simba hydrodynamical simulations with varying AGN feedback at $z=0$ to determine which galaxy populations, environments, and spatial scales are most affected. The galaxy two-point correlation function is most sensitive to feedback at $r<1 h^{-1} Mpc$. We then use Betti curves, persistence diagrams, and the 2-Wasserstein dista…

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astro-ph.HE

A 32-day Quasi-periodic Modulation in the Post-peak Light Curve of the Superluminous Supernova SN 2018bsz

Aiswarya Sankar. K, Ting-Wan Chen, Seán J. Brennan, Morgan Fraser, Keiichi Maeda, Thomas Moore, Sheng Yang, Amar Aryan et al.

Recurrent structure in supernova (SN) light curves may reveal physical clocks associated with central-engine dynamics, binary orbital motion, or interaction with structured circumstellar material (CSM). We present a multiband photometric reanalysis of the nearby hydrogen-poor superluminous SN (SLSN-I) 2018bsz (z=0.0267), using Swift/UVOT and GROND observations spanning approximately 110 rest-frame days after maximum light. After independently modelling and subtracting the smooth decline in each…

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astro-ph.GA

Polarization Observations of a sample of Excited OH masers

Derck P. Smits, Paul Fallon

Spectra of 4.7 and 6.0 GHz excited OH masers from 21 pointings towards known star-forming regions are reported. The C-band observations, using the Green Bank Telescope in full Stokes mode, have measured how polarization properties vary across the maser profiles in each spectrum and vary between different epochs of observation. Seven sources had no detections of masers at any of the OH transitions. Nine sources were observed to have 4.766 GHz masers, which include two new detections in G188.946+0…

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astro-ph.IM

Semi-automated single-mode fiber coupling for AO-fed spectrographs

Aaron J. Crepp, Brian L. Sands, Justin R. Crepp

Conventional astronomical spectrographs are seeing-limited and commonly use multimode fibers to inject starlight into downstream optics. Forthcoming Doppler radial-velocity (RV) instruments are expected to make increasing use of adaptive optics and smaller single-mode fibers (SMF), enabling higher spectral resolution and improved stabilization of the spectrograph point-spread function. However, coupling starlight into SMFs with characteristic diameters of only 5-10 microns at near-infrared wavel…

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astro-ph.SR

Meerkat measurement of the radio emission from massive stars in the Galactic plane I. Wolf-Rayet stars

Mathilde Tasseroul, Michaël De Becker, Paula Benaglia, Anandmayee Tej

Massive stars, including Wolf-Rayet stars, are predominantly found in binary systems. These systems are known to emit both thermal emission from stellar winds and, occasionally, non-thermal emission produced by relativistic electrons accelerated in the wind-wind interaction region. We intend to provide the most complete census of radio emission from WR stars in the Galactic plane, using the SARAO MeerKAT Galactic Plane Survey (SMGPS) complemented by the MeerKAT Galactic Center Survey. Our main m…

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astro-ph.EPastro-ph.IM

Reliability of Zodiacal Background Models at Small Solar Elongations

Csaba Kiss, Thomas G. Müller, Javier Licandro, Luca Conversi, Marco Delbo, Karri Muinonen, Marcel Popescu, Paolo Tanga et al.

Present models of the zodiacal light (scattered sunlight from interplanetary dust in the visible) and zodiacal emission (thermal emission in the mid-infrared) are primarily constrained by surface-brightness measurements obtained at relatively large solar elongations (e >~ 60 deg). As a result, their predictive accuracy at smaller elongations remains uncertain. This is particularly relevant for solar elongations of e ~ 30-60 deg, where next-generation near-Earth-object discovery missions such as…

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astro-ph.HE

Investigating the influence of the full-kinematics treatment for charged-current processes in binary neutron star mergers

Ramon Jaeger, Henrique Gieg, Tim Dietrich

Weak interactions are fundamental in the merger of binary neutron stars (BNS). They provide cooling, change the composition of matter outflows, and can lead to significant secular outflows through neutrino-driven winds. Hence, the inclusion of neutrino transport has become standard in numerical-relativity simulations of mergers involving neutron stars. In more detail, the interactions of neutrinos with matter in a truncated two-moments scheme (M1) are described through interaction rates, calcula…

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astro-ph.HEastro-ph.GA

The rise and decline of a transient obscuration event in a moderately distant type-I quasar

A. Akylas, A. Georgakakis, E. Pouliasis, I. Georgantopoulos, C. Ricci, M. Chira, A. Ruiz, E. M. Xilouris et al.

Outflows of ionised material, often dubbed warm absorbers (WAs), are common in nearby Seyferts but sparse in distant and more energetic quasars (QSOs). We present multi-epoch X-ray and optical observations of the serendipitously identified type-I QSO 2MASS J14302580+4159572 at a redshift of $z=0.35$, revealing the rare rise and decline of a transient ionised absorber over a 22-year timescale. The discovery observations were obtained with XMM-Newton between 2002 and 2005. The first two observatio…

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astro-ph.SR

Highly bipolar planetary nebula Hen 2-57 and its possible symbiotic core

J. Merc, J. Mikołajewska, K. Iłkiewicz, A. Udalski

We present a multi-wavelength analysis of the highly bipolar object Hen 2-57 based on new optical spectroscopy from the Southern African Large Telescope (SALT), complemented by archival imaging, and long-term time-series photometry from OGLE and NEOWISE. The nebula exhibits a pronounced hourglass morphology with a symmetry axis at a position angle of $110\pm5^{\circ}$ and an average lobe opening angle of $\sim$$53^{\circ}$. We also identify pronounced north--south brightness asymmetry, with the…

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astro-ph.SRastro-ph.GA

On the Constancy of Binary Star Fractions in Local Star Clusters

Priya Hasan, Mohammed Saifuddin

We investigate the unresolved binary-star fraction in a complete sample of 376 open clusters located within 1 kpc of the Sun using Gaia DR3 and ASteCA based synthetic colour magnitude diagram modelling. The binary fraction is a global photometric quantity, sensitive primarily to unresolved binaries that produce measurable broadening above the single-star main sequence. We find that the median binary fraction of the sample is nearly constant, $0.29\pm 0.03$, with no clear dependence on cluster ag…

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astro-ph.EPphysics.space-ph

Widespread plasma jets in the Martian magnetosheath revealed by dual-spacecraft observations

Abigail Tadlock, Chuanfei Dong, Chi Zhang, Savvas Raptis, Hongyang Zhou, Xinmin Li, Jiawei Gao

Plasma jets in planetary magnetosheaths are transient, high dynamic pressure structures capable of strongly perturbing downstream magnetospheres and modulating solar wind energy transfer. Although recently identified at Mars, their formation mechanisms and global occurrence remain poorly constrained. Using dual-spacecraft observations from Mars Atmosphere and Volatile EvolutioN (MAVEN) and Tianwen-1, we show that magnetosheath jets occur throughout the Martian magnetosheath, in striking contrast…

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astro-ph.HE

Polarization of Synchrotron Emission from Rotation Powered Pulsars

Seima Saeki, Shota Kisaka, Jumpei Takata

With the launch of the Imaging X-ray Polarimeter Explorer in 2021, recent observations have provided X-ray polarization data for several rotation-powered pulsars. To fully exploit these data, it is important to better understand the relationship between polarization properties and the magnetospheric structure. In this paper, we investigate polarization properties in the outer gap model, incorporating both outward emission and inward emission toward the rotation axis, which has not been considere…

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astro-ph.GA

Kinematics of the System of Young Open Clusters based on Gaia DR3 Data

A. K. Dambis, A. S. Rastorguev

We use a kinematical model including circular rotation of the Milky-Way disk incorporating effects produced by a spiral density wave with constant radial and vertical components of the velocity dispersion tensor and adopted solar Galactocentric distance R_0=8.277kpc (inferred by GRAVITY collaboration in 2022) to derive the velocity field parameters for a sample of 2384 open clusters from the Hunt and Reffert (2024) catalog having ages no greater than 100 Myr almost all of which reside at Galacto…

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astro-ph.EPastro-ph.GA

Delayed Methane Detection in 3I/ATLAS: GCR-Driven Subsurface Stratification and Interstellar Exposure Age Constraints

Akshat Rawat, Kinsuk Acharyya

Interstellar comet 3I/ATLAS shows unusual volatile activity, including strong H$_2$O, CO, and CO$_2$ production and a delayed post-perihelion detection of CH$_4$. In this work, we investigate the delayed CH$_4$ detection in an H$_2$O, CO$_2$, and CO ice matrix using a shape model coupled with a thermophysical nucleus model that incorporates interstellar processing by Galactic Cosmic Rays. We track the sublimation, trapping, depletion, and release of these volatiles as a function of heliocentric…

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astro-ph.COastro-ph.IM

Probing submillimeter number counts below the confusion limit: extreme-value statistics of the P(D) distribution and its modulation by gravitational lensing

Kaustuv Basu, Andrea Guerrero, Frank Bertoldi

The shape of the submillimeter galaxy number counts below the confusion limit is a key record of cosmic star formation but is accessible only statistically, through the one-point distribution of map surface brightness, $P(D)$. Classical $P(D)$ analysis compresses the counts into flux-integrated constraints and requires a full instrument forward model. We introduce an extreme-value-theory analysis of the confusion $P(D)$ tail: the peaks-over-threshold formalism, in which exceedances above a thres…

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astro-ph.GA

Early steps in the hierarchical assembly of a Milky Way-mass galaxy 1 Gyr after the Big Bang

Yoshihisa Asada, Marcin Sawicki, Guillaume Desprez, Jon Judez, Marusa Bradac, Kartheik Iyer, Nicholas S. Martis, Adam Muzzin et al.

We report JWST observations of a $z_{\rm spec}=5.196$ compact group of three strongly lensed low-mass galaxies ($M_\star \sim 10^{6-7} M_\odot$ each) whose small line-of-sight velocity offsets (from $-120\pm100$ to $+160\pm110$ km s$^{-1}$) and projected separations ($\sim2$ kpc) suggest that they are undergoing merging. On the basis of abundance-matching arguments, the trio appear to be destined to evolve into a Milky Way-mass galaxy by the present day. Our spectrophotometric analysis suggests…

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astro-ph.GAastro-ph.IM

On the Probability Distribution and Null-hypothesis Testing of Cross-correlation for Light Curves in Active Galactic Nuclei

Yan-Rong Li, Jian-Min Wang

Cross-correlation is crucial in studies of multiwavelength flux variability in active galactic nuclei (AGNs), especially for reverberation mapping analysis, where interpolated cross-correlation function is widely used to measure time lags between light curves. While time-lag uncertainties can be estimated via the flux randomization and random subset selection method, an appropriate framework for assessing cross-correlation significance remains lacking in the literature. Here we attempt to fill t…

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astro-ph.SRastro-ph.GA

The Contribution of Starspots to the Lithium Spread in NGC 2264

Yan Luo, Gregory J. Herczeg, Min Fang, Qinghui Sun, Xiaoting Fu

Star clusters with ages of a few Myr have a previously unexplained dispersion in the lithium equivalent widths. In this work, we show that much of the lithium spread of the young cluster NGC 2264 can be attributed to the observational presence of starspots. We demonstrate that the equivalent width of Li I 6708 Angstrom changes with observed spot coverage, using a sample of 15 Weak-Lined T Tauri Stars (WTTSs) with multi-epoch high-resolution ESPaDOnS spectra and photometry. To quantify the contri…

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