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Research Trends

Latest preprints in space engineering and astrophysics.

nucl-thastro-ph.HEastro-ph.SRnucl-exphysics.comp-ph

Nuclear Drip Line and the Composition of Supernova Matter

S. Maity, S. Mallik

The nuclear drip line plays a crucial role in determining the composition of matter under extreme astrophysical conditions. In core-collapse supernovae and neutron-star crusts, matter is driven far from saturation density and nuclear stability; nuclei coexist with a sea of free neutrons, an effect that is present even at zero temperature in neutron-star crusts and becomes more pronounced in the hotter, neutron-rich supernova environment. This makes a careful treatment of drip-line physics essent…

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astro-ph.GA

A posteriori correction of Gaia CRF proper motions using conditional probability and zero-parallax prior

Valeri V. Makarov

Precision of proper motions and positions given in the Gaia Celestial Reference Frame (CRF) catalog can be statistically improved introducing conditional probability based on the prior knowledge of zero parallax for these extremely distant sources. The method developed in this study produces statistically conditioned proper-motion estimates under the assumed per-source Gaussian covariance model. It is demonstrated that thus corrected proper motion vectors of 1.2 million CRF objects in Gaia DR3 s…

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astro-ph.GA

High Velocity Neutral Gas in the Fermi Bubbles: New Kinematic Limits and Spatial Structure

Felix J. Lockman, Enrico M. Di Teodoro, Savannah Cary, Andrew J. Fox

We have detected hundreds of neutral clouds entrained in the Milky Way's nuclear wind using HI data from new surveys made with the Green Bank Telescope that cover about 500 sq-degrees around the Galactic center (GC). Galactic winds are common throughout the Universe, and these data at 9.1' angular resolution (22 pc at the GC) provide the most detailed analysis of the vertical profile of a neutral nuclear wind in any galaxy. A set of 228 of these Fermi Bubble clouds with the largest values of |VL…

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astro-ph.IM

Anti-windup PI controller for millimeter-wave adaptive optics: a Nobeyama 45 m radio telescope simulation

Ichiro Jikuya, Yoichi Tamura, Akio Taniguchi, Masaki Sakakibara, Akinobu Miyake, Masato Hagimoto, Kianhong Lee, Chihiro Imamura et al.

This work addresses the control problem for Millimeter-wave Adaptive Optics (MAO), which we define as compensating for the distance variation between the primary reflector (M1) and the receiver. We utilize a measurement system developed by Tamura et al. to track these variations. The challenge is formalized as an asymptotic constant disturbance suppression problem. We demonstrate that an anti-windup proportional-integral (AWPI) controller effectively solves this problem while respecting the phys…

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physics.space-phastro-ph.IMphysics.ins-detphysics.plasm-ph

In-situ measurements of space plasma: recent progress and future challenges

Daniel Verscharen

Space plasmas like the solar wind or the Earth's space environment offer unique opportunities to observe fundamental plasma processes and their impact in situ. With modern space instrumentation, we measure the velocity distribution function of the plasma particles as well as the electromagnetic fields at high resolution and with minimal perturbation of the observed plasma systems. Plasma measurements like this are often not possible in laboratory settings on Earth. This review article focuses on…

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astro-ph.GA

Two domains of extended Lyman-alpha emission around galaxies: from local radiation to environmental regulation

Daria Kozlova, Lutz Wisotzki, John Pharo, Tanya Urrutia, Ramona Augustin, Yucheng Guo, Haruka Kusakabe, Joop Schaye et al.

We examine the relation between extended Ly$α$ halos around high-redshift galaxies and the main factors responsible for driving the emission in such halos, in particular at distances around and beyond one virial radius $r_\mathrm{vir}$. To reach the required surface brightness sensitivity we take advantage of the MUSE eXtremely Deep Field (MXDF) survey, allowing us to probe levels as faint as $\sim 10^{-20}$ erg cm$^{-2}$ s$^{-1}$ arcsec$^{-2}$ in individual Ly$α$ halos. Our sample consists of t…

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astro-ph.HEphysics.plasm-ph

Collisionless Shock Driven by a Supersonic Velocity Shear

Kazuki Kamiido, Yutaka Ohira

The long-term evolution of a relativistic collisionless velocity shear in an unmagnetized electron-positron plasma is investigated using a first-principle particle-in-cell simulation. The Alves instability converts the shear kinetic energy into thermal and magnetic field energy. The resulting pressures push the plasma, leading to the formation of collisionless shocks. The generated collisionless shocks would accelerate high energy particles, which is a possible solution to the injection problem…

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astro-ph.IM

Galaxy Morphology Classification: Uncertainty Modeling and Out of Distribution Detection

Prem Prakash, Shantanu Desai, P. K. Srijith

We present a comprehensive framework for galaxy morphology classification that combines enhanced ``out-of-distribution (OOD)'' detection with improved uncertainty quantification. Using ``Galaxy Zoo DECaLS'', we trained a ResNet-34 architecture under three configurations: standard cross-entropy loss as a baseline, IsoMaxPlus loss function for OOD detection, and hybrid IsoMaxPlus+MonteCarlo Dropout for enhanced uncertainty quantification. IsoMaxPlus replaces the conventional SoftMax logits with di…

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astro-ph.HE

Broadband Properties of the Harmonic of Type-C Quasi-periodic Oscillation in MAXI J1348-630

Xin-Lei Wang, Zhen Yan, Jun-Feng Wang, Fu-Guo Xie, Zhan-Yi Liu, Ren-Yi Ma

Harmonics are common features of quasi-periodic oscillations (QPOs) in black hole X-ray binaries; however, their physical origins remain poorly understood. Using broadband Insight-HXMT data, we investigated the Type-C QPO harmonic in MAXI J1348-630. The harmonic is significantly detected exclusively during the hard intermediate state and displays prominent energy-dependent properties: while it is strong in the soft X-ray band ( 10 keV), where its rms amplitude is generally several times lower th…

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astro-ph.HEgr-qc

Population-Level Verification of the Black-Hole Area Law with First- and Second-Generation Black Holes

Shao-Peng Tang, Yin-Jie Li, Yi-Zhong Fan

Hawking's area theorem states that the total event-horizon area of classical black holes (BHs) can never decrease. Existing gravitational-wave tests analyze single loud events (GW150914, GW230814, GW250114) and therefore certify the law only for the specific mergers observed. Here we perform the {\it first} population-level test, exploiting the recent decomposition of the GWTC-5 BBHs into a low-spin subpopulation of stellar-collapse origin and a high-spin subpopulation formed through hierarchica…

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astro-ph.EP

From Earth Meteors to Mars: Predicting Where to See the First Martian Meteors

Maximilian Vovk, Peter G. Brown, Denis Vida

Predictions of optical meteors at Mars have largely relied on classical single-body ablation models, despite high-resolution terrestrial observations showing that mm-sized meteoroids frequently fragment. This study quantifies how fragmentation alters the predicted brightness and peak-luminosity altitudes of sporadic mm-sized meteoroids in the Martian atmosphere and evaluates the single-body approximation as a reference baseline. Physical properties were inferred for 144 sporadic meteoroids obser…

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astro-ph.IM

Millimeter-wave adaptive optics: Demonstrating closed-loop correction for lowest Zernike modes

Yoichi Tamura, Akio Taniguchi, Kotaro Iwakami, Ichiro Jikuya, Shion Takeno, Sachiko K. Okumura, Masaki Sakakibara, Akinobu Miyake et al.

We report on a five-element prototype wavefront sensor for millimeter-wave adaptive optics (MAO), enabling closed-loop correction of tip-tilt and defocus via secondary mirror (M2) displacement. MAO is essential for large ground-based millimeter/submillimeter telescopes to maintain surface accuracy under wind and thermal distortions. Our sensor, based on radio interferometry, measures excess path lengths from the primary mirror to a focal-plane receiver. A previous two-element prototype achieved…

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astro-ph.HE

Cosmogenic neutrinos from FRII galaxies as potential origin of the ultra-high-energy KM3-230213A event

Denis Allard, Bruny Baret, Noémie Globus, Etienne Parizot

Aim : We investigate whether the ultra-high-energy neutrino KM3-230213A can be interpreted as a cosmogenic neutrino produced by ultra-high-energy cosmic rays (UHECRs) accelerated in the lobes of FRII radio galaxies. Method : We model the UHECR, cosmogenic neutrino and photon fluxes expected at Earth using a recent luminosity-dependent density evolution of radio galaxies, empirical relations between radio luminosity and jet kinetic power, and standard assumptions for the UHECR output of FRII lobe…

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astro-ph.IM

Tradeoff between segment density and IWA for high-contrast imaging of exoplanets with a large segmented space mission

Lucie Leboulleux, Raphaël Pourcelot, Laurent Pueyo, Bryony Nickson

Imaging Earth-like exoplanets with coronagraphs on future large segmented space telescopes such as the Habitable Worlds Observatory requires contrasts down to $10^{-10}$ at separations below 100 mas, imposing segment phasing control down to a few picometers. We evaluate how this constraint can be relaxed by optimizing telescope and instrument design, quantifying the impact on performance stability under segment phasing aberrations. We propose a system-level approach, adjusting the primary mirror…

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astro-ph.SRastro-ph.GA

CO rotational line emission in very red carbon stars in the Magellanic Clouds

M. A. T. Groenewegen, A. Nanni, M. L. Boyer, L. Decin, S. R. Goldman, K. Justtanont, F. Kerschbaum, I. McDonald et al.

Stars of low and intermediate initial mass lose most of their stellar mass at the end of their lives during the asymptotic giant branch (AGB) phase. Determining their gas and dust mass-loss rates (MLRs) is crucial for quantifying the contribution of evolved stars to the life cycle of dust and gas in the Universe. The Atacama Large Millimeter/submillimeter Array was used to observe 38 carbon stars (C stars) in the large Magellanic cloud (LMC) and three C stars in the small Magellanic cloud (SMC)…

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astro-ph.SRastro-ph.GA

CO rotational line emission in very red carbon stars in the Magellanic Clouds

M. A. T. Groenewegen, A. Nanni, M. L. Boyer, L. Decin, S. R. Goldman, K. Justtanont, F. Kerschbaum, I. McDonald et al.

Stars of low and intermediate initial mass lose most of their stellar mass at the end of their lives during the asymptotic giant branch (AGB) phase. Determining their gas and dust mass-loss rates (MLRs) is crucial for quantifying the contribution of evolved stars to the life cycle of dust and gas in the Universe. The Atacama Large Millimeter/submillimeter Array was used to observe 38 carbon stars (C stars) in the large Magellanic cloud (LMC) and three C stars in the small Magellanic cloud (SMC)…

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astro-ph.SR

Detection and Characterization of Microlensing Events due to Isolated Black Holes towards the Magellanic Clouds in the Rubin Observations

Sedighe Sajadian, Martin Makler

Gravitational microlensing surveys potentially discover isolated black holes (IBHs) at large distances through their gravitational effects on apparent brightness and motion of collinear stars. Here, we study detecting and characterizing IBHs within the mass range $[3,~5000]M_{\odot}$ with either stellar or dark matter origins in the upcoming observations by Vera~C.~Rubin Observatory towards the Large and Small Magellanic Clouds (LMC and SMC). We consider four lens mass functions (MFs:~$dN/dM\pro…

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astro-ph.SRphysics.optics

Machine Learning in Application to Automatic Noise Processing of Solar Spectrograms

I. I. Yakovkin, A. O. Bartenev, N. V. Petrova

In this paper, a machine learning approach for processing solar spectral data were developed. Its performance was demonstrated using the example of the limb solar flare on July 17th, 1981. The results indicated that machine learning can be effectively utilized to transform between differently digitized spectra, fill gaps in unique experimental data, and undertake spectrum cleaning. Specifically, convolutional neural networks were devised to transform between reflective and transmissive scans of…

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gr-qcastro-ph.HEnucl-th

Limiting cases of second-order moments of relativistic stars and their universality

Koutarou Kyutoku

Extending the work presented in a workshop ``From Quarks to Neutron Stars: Insights from kHz gravitational waves'', we discuss some limiting cases of the moment of inertia, tidal deformability, and spin-induced quadrupole moment for relativistic stars. First, conjecturing that a hierarchy of the length scale is the key to proposed universality among these second-order moments, we revisit the relation for incompressible relativistic stars (known as Schwarzschild's interior solution) as a candidat…

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astro-ph.GAastro-ph.CO

RIOJA. Environmental Effects on Stellar Populations and Ionized Gas in a Protocluster at $z=7.88$

Wataru Osone, Takuya Hashimoto, Javier Álvarez-Márquez, Luis Colina, Akio K. Inoue, Ken Mawatari, Yuma Sugahara, Carmen Blanco-Prieto et al.

Protoclusters in the epoch of reionization provide key laboratories for investigating how environment shapes early galaxy formation and evolution, and may also have contributed to cosmic reionization. We analyze 23 member galaxies of A2744-z7p9OD, a protocluster at $z=7.88$, using JWST/NIRCam and NIRSpec to investigate their stellar population properties, rest-frame UV sizes, and ionized-gas properties. We also quantify the internal structure of A2744-z7p9OD using the projected distance to the m…

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astro-ph.GA

Coronal gas excitation as a tracer of supermassive black hole mass: on the mid-IR coronal [Ne v] lines

J. S. Elford, A. Prieto, A. Rodríguez-Ardila

Coronal lines (CL) may be a reliable proxy of supermassive black hole (SMBH) masses in active galactic nuclei (AGN) because the production of these high ionisation potential (IP) lines is sensitive to the shape of the ionising continuum which, for a thin accretion disc, relies on the black hole mass. In this work we study the connection between the [Ne\,v] coronal lines and the SMBH mass. We analyse the \textit{Spitzer spectra} of a sample of 27 AGN spanning three orders of magnitude in SMBH mas…

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astro-ph.SRastro-ph.EP

Characterizing Stellar Flares in Ariel Targets: Activity Analysis and Transit Contamination

G. Galletta, S. Colombo, G. Micela

Stellar flares are sudden releases of magnetic energy that can distort exoplanet transit photometry and transmission spectroscopy, biasing planet radius estimates, transit timings, and atmospheric characterization. Understanding flare activity in Ariel targets is therefore essential to identify stars where flares may compromise observations and to characterize the radiation environment affecting atmospheric escape and photochemistry. We analyzed 290 Ariel target stars using TESS light curves. Fl…

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astro-ph.IM

A NICE (Nulling Interferometry Cryogenic Experiment) update: Beyond 1e-5 and towards cryogenic operation

Jonah T. Hansen, Thomas Birbacher, Germain Garreau, Julio Pino-Jiménez, Emilie Bouzerand, Felix A. Dannert, David Eglin, Lee Feinberg et al.

The Nulling Interferometry Cryogenic Experiment (NICE) is a mid-infrared laboratory testbed at ETH Zürich that aims to not only reproduce the deep ($<1\times10^{-5}$) broadband nulls of the nulling testbeds of the early 2000s, but also at the required sensitivity levels expected for the LIFE space mission. This sensitivity enforces the experiment to go cryogenic at temperatures around 15 K; an ambitious task for an ultra-precise interferometer. We share our results of the ambient precursor exper…

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astro-ph.IM

Cryogenic characterisation for the Nulling Interferometry Cryogenic Experiment (NICE)

Jonah T. Hansen, Emilie Bouzerand, Adrian M. Glauser, Bastien Rouzé, Noah Stocker, Walter Bachmann, Marcel Baer, Cindy Bellanger et al.

The Nulling Interferometry Cryogenic Experiment (NICE) is an experimental testbed for the beam combiner of the Large Interferometer For Exoplanets (LIFE) space mission. Until now, progress on NICE has been confined to an ambient bench, where we have recorded progress in deep ($<10^{-5}$) nulls at wavelengths between 4 and 5 microns at 300 K. However, the ultimate goal and requirement of NICE is to repeat these measurements at the sensitivity levels expected for a planetary system, requiring deep…

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gr-qcastro-ph.HEhep-th

Exceptional points of the Schwarzschild spectrum under local potential perturbation: The Princess and the Pea

Mohamed Ould El Hadj, Sam R. Dolan

Black-hole quasinormal modes (QNMs) may coalesce at exceptional points (EPs) in the frequency spectrum. We study EPs and their phenomenology for gravitational perturbations of a Schwarzschild black hole whose Regge-Wheeler potential is perturbed by a localized delta-function of amplitude $ε$ at radius $r_0$. For real $ε$, we find infinite families of discrete EPs. Each family approaches a distinct unperturbed QNM overtone frequency as $r_0$ grows large. Under perturbation at fixed $r_0$, we find…

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astro-ph.HEgr-qchep-ph

Multipolar Neutrino Radiation in Binary Neutron Star Mergers: Angular Structure, Rotational Variability, and Implications for Electron Fraction

Kutay Arınç Çokluk, Albino Perego, Federico Maria Guercilena, Kadri Yakut

The angular structure and temporal variability of neutrino emission from binary neutron star mergers are characterized using fully general-relativistic simulations with energy-integrated M1 neutrino transport across a representative set of equations of state, total masses, and mass ratios. The angle-dependent neutrino energy flux is extracted on a spherical surface outside the remnant and decomposed into spherical harmonics to quantify its multipolar content and evolution. Following the initial…

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astro-ph.IM

Direct Imaging and Gradient-Based Analysis of the 12 August 2026 Partial Solar Eclipse from a Freely Rotating High-Altitude Balloon

Bjoern Poppe, Enno Gronewold, Matti Gehlen, Jona Schrader, Delia Gauk, Lisa Cordes, Maike I. Schmitz, Peter Schoenfeld et al.

We report a proof-of-concept observation of the partial solar eclipse of 12 August 2026 using a freely rotating high-altitude balloon launched from Oldenburg, northern Germany. The payload carried two Insta360 ONE RS cameras equipped with 4K Boost wide-angle lenses; covered by filter material taken from a BRESSER eclipse viewing glass. Interval photographs were acquired every 10 s at ISO 800 and 1/1000 s. Of approximately 1,300 images, 21 contained a directly visible image of the eclipsed Sun, s…

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astro-ph.EPastro-ph.IM

Optical-NIR Multi-band Photometric Analysis and Characterization of Giant Exoplanets with CPI-C

Yiming Zhu, Gang Zhao, Xi Zhang, Gang Wang, Bingli Niu, Zhonghua Lv, Jiangpei Dou

We present a multi-band photometric approach to characterize giant exoplanets, which represents one of the anticipated core scientific outcomes of Cool Planet Imaging Coronagraph (CPI-C). CPI-C operates with two observational channels covering visible and near-infrared wavelengths, each equipped with four broadband filters. The planet--star flux ratio integrated over each filter bandpass is calculated for photometric analysis. For cool planets observed in the visible bands, the data are primaril…

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astro-ph.EP

The dust-rich, gas-depleted protosolar disk as the birthplace of chondrules

Sota Arakawa, Hidekazu Tanaka, Toshihiko Kadono, Takayuki Ushikubo, Makiko Nagasawa, Hiroshi Kobayashi

Chondrules are the primary components of primitive meteorites known as chondrites, and understanding their formation and accumulation is essential for elucidating the history of planet formation in the Solar System. Although a variety of chondrule formation mechanisms have been proposed, it remains challenging to satisfy the key constraints on chondrule abundance, formation timing, and mineralogical and chemical characteristics within a single model. In particular, the planetesimal bow-shock mod…

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astro-ph.GA

A Radio-Bright Local Little Red Dot Analog

Luis F. Rodriguez, I. FElix Mirabel, Rosa A. Gonzalez-Lopezlira, Laurent Loinard

The James Webb Space Telescope revealed the existence in the early Universe ($z >$ 4) of large populations of little red dots (LRDs), compact red luminous sources that host rapidly growing supermassive black holes (SMBHs) surrounded by coeval nuclear starbursts. LRDs have defining properties, one of which is the absence of radio detections. LRDs could be radio-undetected because of their large distances. A way to investigate the radio properties of LRDs is to search for radio emission in their l…

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