UchUchU

研究動向

宇宙工学・惑星科学・宇宙物理の最新プレプリント。

astro-ph.GA

Identification of Cosmic Chronometers in the GAMA Survey

Laura J. Hunt, Kevin A. Pimbblet, David M. Benoit

We present a pure sample of 231 massive, passively evolving elliptical galaxies as cosmic chronometer candidates selected from the Galaxy and Mass Assembly (GAMA) survey between $0.03<z<0.4$. The goal of this work is to increase the pool of high-purity cosmic chronometer candidates available in the literature and assess the effect of purity on statistical uncertainty to make $H(z)$ and $H_0$ calculations more robust in future studies. We use traditional selection criteria to identify cosmic chro…

詳細を見る →
astro-ph.SR

Plasmoid-Trapped Condensation Associated with a Transient Thermal-Instability-Like Process in Chromospheric Magnetic Reconnection

Abdullah Zafar, Lei Ni, Samrat Sen, Yuhao Chen, Mohamed Sedik, Mehdi Yousefzadeh, Jun Lin

We perform high-resolution 2.5D single-fluid magnetohydrodynamic (MHD) simulations to explore the development of cool-dense structures within plasmoids during chromospheric magnetic reconnection. The model incorporates temperature-dependent ionization degrees of hydrogen and helium, resulting in improved diffusivities and viscosity, as well as adequate radiative cooling. The numerical results show that plasma is significantly hot with temperatures reaching several tens of thousands of Kelvin in…

詳細を見る →
astro-ph.SR

Large-Scale Latitude-time Relationships Between the Green-Line Corona and Sunspot Activity During Solar Cycles 18-24

Jouni J. Takalo

We investigate the latitude-time relationship between the solar green-line corona and sunspot activity during Solar Cycles 18-24 using homogeneous coronal observations and a Gaussian representation of sunspot activity fields. The activity-field model is constructed from individual sunspot areas and latitudes in order to describe the large-scale spatial organization of solar magnetic activity more realistically than traditional sunspot number or sunspot area indices. The analysis reveals a stable…

詳細を見る →
astro-ph.GAastro-ph.HEgr-qc

Heavy Seed Black Hole Growth in Metal-Enriched Halos through Disk-Induced Stellar Disruptions: A Semi-Analytical Modelling

Zijian Wang, Zhili Wang, Yiqiu Ma, Boyuan Liu, Zheng Cai, Mengye Wang, Qingwen Wu

Recent simulations suggest that heavy seed black holes may form in weakly metal-enriched atomic cooling halos, where the supermassive-star progenitor and small-scale stellar fragments emerge nearly coevally. In this picture, the newly born heavy seed is naturally embedded in a metal-enriched Pop~I/II nuclear star cluster rather than in an isolated pristine environment. We investigate whether disk-induced tidal disruption events (TDEs) from these Pop~I/II stars can provide an efficient and sustai…

詳細を見る →
astro-ph.HE

Optical Follow-Up of Two Spider Pulsar Candidates: An Irradiated Redback and a Possible Double Giant Impostor

Bettina Due, Jundile Bridziute, Manuel Linares, Marco Turchetta, Maksat Satybaldiev

Compact binary millisecond pulsars (nicknamed "spiders") are a growing class of neutron stars: more than 100 systems are known in the Galactic field, including more than 30 candidates where pulsations have not been detected. Here we report the results of an optical follow-up of two spider pulsar candidates: 2FGL J0846.0+2820 (J0846, a huntsman candidate in an 8.1 d orbit) and 4FGL J0935.3+0901 (J0935, with a 2.4 h orbital period and proposed as a spider of either the transitional, black widow or…

詳細を見る →
astro-ph.GA

E-INSPIRE - II. Finding relics from wide-sky multi-band surveys: A proof-of-concept machine learning regression algorithm

Charles Rosen, Chiara Spiniello, John Mills, Alexey Sergeyev, Vladyslav Khramtsov, Anna Ferré-Mateu, Johanna Hartke, Michalina Maksymowicz-Maciata et al.

In this second paper of the E-INSPIRE series, we train a machine-learning-based regression on $\sim430$ nearby ($z 0.6$) values sparsely populated, leading to mild regression shrinkage toward intermediate values. However, this behaviour enables a conservative selection strategy: galaxies with predicted DoR$\ge0.6$ are strongly biased toward genuine extreme relics, making them prime targets for follow-up observations. This proof-of-concept confirms that the spectroscopically inferred DoR is robus…

詳細を見る →
astro-ph.HEnucl-th

Spin-polarization of the neutron ocean in magnetar crusts

Juliette Servais, Nicolas Chamel

Magnetars, neutron stars harboring the strongest magnetic fields known in the Universe, are associated with a broad range of observational phenomena, from giant flares to fast radio bursts, and have also been proposed as potential sites of heavy-element nucleosynthesis. These phenomena are thought to be closely linked to the structure and composition of magnetar crusts. The outer crust consists of fully ionized nuclei embedded in a degenerate electron gas, while the inner crust additionally cont…

詳細を見る →
astro-ph.EPastro-ph.SR

Terminal instability of the Solar System triggered by stochastic solar mass loss

Konstantin Batygin, Jim Fuller, Fred C. Adams

From its birth, celestial mechanics has been deeply intertwined with the question of the Solar System's dynamical stability. For the inner planets, this question is now statistically settled: Mercury's orbit carries a $\sim$1% chance of destabilization before the Sun leaves the main sequence. The outer Solar System has seemed more secure, with its intrinsic dynamical lifetime estimated at $\sim10^{18}$ years. Even accounting for the Sun's mass loss and stellar flybys, the orbital architecture of…

詳細を見る →
gr-qcastro-ph.IM

A semicoherent resampling method for long-transient gravitational wave searches with applications to subsolar-mass primordial black-hole binaries

Neil Lu, Cristiano Palomba, Ornella J. Piccinni, Ling Sun

Resampling removes the modeled phase evolution of a frequency-evolving signal, transforming it into a monochromatic one. We introduce a novel implementation for long-transient gravitational-wave searches that evaluates the Fourier spectrum of the resampled data using a type-I non-uniform fast Fourier transform (NUFFT). This implementation can be up to two orders of magnitude faster than some previous implementations, depending on coherent length, sampling rate, and desired accuracy. To demonstra…

詳細を見る →
astro-ph.SRastro-ph.GA

Magnetic Fields and Asymmetric Accretion in the Class 0 Protostellar System L1527 IRS

Hanju Nam, Woojin Kwon, Youngwoo Choi, Ian W. Stephens, Leslie W. Looney

Magnetic fields play a crucial role in regulating the collapse of dense molecular clouds, shaping the early stages of protostellar evolution. We present polarization observations in submillimeter wavelengths with the SCUBA-2/POL-2 instrument on James Clerk Maxwell Telescope toward the Class 0 protostellar system L1527 IRS (IRAS 04368+2557). The magnetic field morphology varies across the core of L1527 IRS. Magnetic fields in the eastern region are perpendicular to the outflow axis, while those i…

詳細を見る →
astro-ph.GA

The constrainability of galaxy positions in the $M_*$ -- SFR plane from SED fitting

Sabine Bellstedt, Aaron S. G. Robotham, Luke J. M. Davies, Luca Cortese, Simon P. Driver

Using a sample of 6,029 $z<0.06$ galaxies from the GAMA survey, we characterise the spread of galaxy property inferences on the M$_*$ -- SFR plane via Spectral Energy Distribution (SED) fitting. We analyse 24 different model configurations using the stellar population library code \textsc{ProGeny}, and the SED-fitting code \textsc{ProSpect}, and quantify how modelling assumptions affect inferred stellar masses, star formation rates, and the resulting classification of galaxies. We find that the…

詳細を見る →
astro-ph.SR

Superoutbursts and Superhumps of Cataclysmic Variables observed with TESS

Qi-Bin Sun, Sheng-Bang Qian, Li-Ying Zhu, Qin-Mei Li, Wen-Ping Liao, Fu-Xing Li, Wen-Xu Lin, Min-Yu Li et al.

Superoutbursts and superhumps are characteristic signatures of SU UMa-type cataclysmic variables, yet the full diversity of superhump evolutionary behaviour remains poorly constrained owing to the limitations of ground-based photometric monitoring. Here we report a systematic analysis of 30 SU UMa-type dwarf novae observed with the Transiting Exoplanet Survey Satellite, covering 37 superoutburst events. We detect coherent superhump signals in 29 systems-including five first-time detections-and d…

詳細を見る →
astro-ph.EPastro-ph.GA

KMT-2026-BLG-0083L: A Two-Jovian-Planet System Orbiting an M Dwarf Discovered by Microlensing

Cheongho Han, Chung-Uk Lee, Zhixing Li, Weicheng Zang, Andrzej Udalski, Ian A. Bond, Yoon-Hyun Ryu, Steve Heathcote et al.

We present the analysis of the microlensing event KMT-2026-BLG-0083, which was independently detected by the KMTNet, OGLE, and PRIME surveys and also monitored by the DREAMS survey. The combined data provide dense coverage of two distinct short-duration anomalies in the light curve that cannot be reproduced by a standard binary-lens model. Independent analyses of the two anomalies indicate that each is produced by a planetary companion to the lens, motivating a triple-lens interpretation. The mo…

詳細を見る →
astro-ph.GA

A systematic study of the long-term mid-infrared color variations of Seyfert 1 galaxies

Jiahua Wu, Liming Dou, Zhining Chen, Fupeng Zhang, Luis C. Ho, Yanli Ai, Tinggui Wang, Xinwen Shu et al.

We present a comparative analysis of long-term mid-infrared (MIR) color variations (MCVs) for 1,977 narrow-line Seyfert 1 (NLSy1) and 4,113 broad-line Seyfert 1 (BLSy1) galaxies at $z < 0.3$. Using 14 years of WISE and NEOWISE data, we quantify the correlation between $W1-W2$ color and $W1$ magnitude. We categorize sources into bluer-when-brighter (BWB), redder-when-brighter (RWB), and weak/no MCV populations. Our results show that the MCV properties of BLSy1s are consistent with those of NLSy1s…

詳細を見る →
astro-ph.HE

Evolution of first-interaction second-harmonic anisotropy in cosmic-ray air showers

Hao Sun, Cunfeng Feng

The longitudinal evolution of second-harmonic anisotropy inherited from the first interaction in extensive air showers is investigated with CORSIKA simulations. Events with large initial anisotropy are selected. Second-harmonic observables are evaluated separately using the coordinate and momentum azimuths at several atmospheric depths and compared with their corresponding initial harmonic orientations. More than 84% of the initial second-harmonic signal is attenuated within the first 20 g cm$^{…

詳細を見る →
astro-ph.HEastro-ph.GA

A Localized Current-Sheet Magnetic-Diffusion and Heating Prescription for Ideal-GRMHD Simulations of M87*-like Accretion Flows

Songyan Dai, Renyue Cen

Ideal-GRMHD calculations provide the bulk accretion flows used in black-hole emission models. A localized dissipation prescription can add a resolved map of current-sheet activity while retaining that dynamical reference. We implement such a prescription in Athena++, using a smooth threshold on the dimensionless current proxy $α_J$ to select the magnetic-diffusion coefficient. The constrained-transport update is coupled to a conservative energy-flux correction. Gas heating follows from primitive…

詳細を見る →
astro-ph.EPastro-ph.GA

High water D/H ratio of the interstellar object 3I/ATLAS is consistent with a low-metallicity origin

Kenji Furuya, Martin Cordiner, Dominique Bockelée-Morvan, Dennis Bodewits, Colin Orion Chandler, Maria N. Drozdovskaya, Nathan X. Roth, Geronimo Villanueva et al.

Recent JWST observations have revealed unusually high $^{12}$C/$^{13}$C ratios in carbon-bearing molecules of the interstellar object 3I/ATLAS, consistent with formation in a lower-metallicity environment than the present-day local interstellar medium (ISM). 3I/ATLAS also exhibits an exceptionally high water D/H ratio, exceeding those in Solar System comets and nearby low-mass star-forming regions. Here we investigate whether this high water D/H ratio can be reproduced in a low-metallicity forma…

詳細を見る →
astro-ph.GA

Stellar bar occurrence in TNG50 and TNG100: disentangling environmental effects and assembly history at z = 0

Karol Chim-Ramirez, Bernardo Cervantes-Sodi, Yetli Rosas-Guevara

In this work, we investigate the dependence of bar presence on environment using TNG50 and TNG100 simulations at z=0. We select disc galaxies within $2 R_{200}$, with stellar mass M$_{\star} \geq 10^{10}$ M$_{\odot}$ (TNG100) and M$_{\star} \geq 10^{9}$ M$_{\odot}$ (TNG50). With these criteria, our final samples consist of 1719 and 859 satellite galaxies in TNG100 and TNG50, respectively. The environment is characterised by host halo mass: massive (M$_{\rm h} \geq 10^{14}$ M$_{\odot}$), intermed…

詳細を見る →
astro-ph.GA

Mapping the Quasar Main Sequence in the UV range: A Connection with the UV Fe III Emission

D. Martínez Collipal, M. L. Martínez-Aldama, A. Pandey, M. Cardenas, P. Marziani, S. Panda

The quasar main sequence (MS) provides a consistent unification scheme for type I AGNs. This framework, constructed from the relative flux between the optical emissions $\mathrm{H}β$ and $\mathrm{Fe\,II\,(\lambda4570)}$, and the $\mathrm{FWHM(Hβ)}$, organizes quasars into two populations (B, A) and the subpopulation xA, which typically consists of highly accreting sources. We explored the use of the UV 1900 blend emissions ($\mathrm{Al\,III}\,\mathrmλ1860$, $\mathrm{Si\,III]}\,\mathrmλ1892$, $\m…

詳細を見る →
astro-ph.HE

Electromagnetic Probes of the Supernova Engine

Chris L. Fryer

Explosions from stellar collapse are important in nearly all aspects of astronomy: formation of compact remnants (including the potential seeds of supermassive black holes), the production of compact binaries the produce X-ray binaries and radio pulsars, the origin of many of the heavy elements (a critical aspect of galactic chemical evolution), and as standard candles to probe the early universe (including the nature of star formation). Because these explosions occur in extreme conditions, if w…

詳細を見る →
physics.space-ph

Low-frequency Intermittency and Structures in the Solar Wind at 1 au

Jiaming Wang, Francesco Pecora, Yan Yang, William H. Matthaeus

Intermittency in the solar wind is commonly studied within the inertial and dissipative ranges, where scale-dependent magnetic field distributions become increasingly non-Gaussian toward smaller scales until dissipation becomes important. Conversely, whether Gaussianity is recovered at large scales remains unclear. To address this, we systematically examine magnetic field increment kurtosis over scales from 1 minute to 1 year using more than two decades of in situ observations from NASA's Wind a…

詳細を見る →
astro-ph.EPastro-ph.IM

OSIRIS-REx Returned a Pristine Sample of Asteroid Bennu: Takeaways from the Mission's Contamination Control and Knowledge Program

Jason P. Dworkin, Scott A. Sandford, Nicole G. Lunning, Kevin Righter, Charles C. Lorentson, Daniel P. Glavin, Kathie L. Thomas-Keprta, Loan Le et al.

NASA's OSIRIS-REx mission had the objective of delivering a pristine sample from asteroid (101955) Bennu to Earth for scientific analysis--where "pristine" signifies the absence of foreign materials that could affect sample measurements. OSIRIS-REx returned 121.6 g of regolith in September 2023; this study documents the systematic investigation of suspected contaminants encountered during the mission's sample analysis phase. Most suspected contaminants did not originate from the spacecraft or sa…

詳細を見る →
astro-ph.EP

Steepening Optical Slopes in Exoplanet Transmission Spectra with Charged Hazes

Masayuki Inai, Kazumasa Ohno, Shota Notsu

Observations of exoplanetary atmospheres have revealed the ubiquity of aerosols, yet their microphysics remain largely uncertain. Haze charging is a key microphysical process in aerosol-rich Solar System atmospheres, but it has been ignored in exoplanetary haze models. Here we develop a microphysical framework that includes haze charging for exoplanet atmospheres and investigate its effects on transmission spectra. Electrostatic repulsion suppresses coagulation, maintaining smaller particle radi…

詳細を見る →
astro-ph.SR

Plasma Heating and Energization in Hot-Onset Flare Precursor Events

H. Da, J. F. Drake, M. Swisdak

Recent observations of solar flares have revealed a distinct 'hot onset' phase preceding the impulsive phase, characterized by elevated plasma temperature (>10 MK), a steady increase in emission measure, and the absence of detectable nonthermal emission. The standard flare model attributes the formation of hot flare plasma to chromospheric evaporation driven by energy deposition from nonthermal electrons, and therefore does not naturally explain why thermal heating precedes nonthermal emission.…

詳細を見る →
quant-phastro-ph.IMphysics.optics

Path-Degenerate Quantum Interferometry for Decoherence Mitigation in Gravitational-Wave Detectors

Jonas Rittmeyer, Niels Boettner, Farid Khalili, Mikhail Korobko, Roman Schnabel

Optical decoherence degrades quantum correlations in squeezed states of light, severely limiting the quantum-nondemolition (QND) sensitivity of gravitational-wave detectors. Here, we propose the path-degenerate quantum interferometry scheme that obviates the need for entire optical subsystems---including additional filter cavities, auxiliary parametric amplifiers, and Faraday isolators---thereby drastically reducing spatial mode mismatches while inherently integrating variational output, a long-…

詳細を見る →
astro-ph.GA

NOEMA probes the [CII] and dust content in a 2175Å UV Bump Galaxy at $z=7.1$

Katherine Ormerod, Renske Smit, Joris Witstok, Anna de Graaff, Michael V. Maseda, Irene Shivaei, Andrew J. Bunker, Gareth C. Jones et al.

The detection of the $2175$Å UV bump at $z>6$ challenges existing models of dust formation, suggesting rapid formation of small carbonaceous dust grains within the first billion years of cosmic time. We present the results of the first direct attempt at linking far-infrared (FIR) observations to the UV bump within the Epoch of Reionisation (EoR), through NOEMA observations of GNWY-7379420231 at $z=7.108$, a galaxy exhibiting the strongest known UV bump feature at $z>4$. We detect the [CII] 158$μ…

詳細を見る →
astro-ph.IMastro-ph.HE

An X-ray Data Primer: What I Wish I Knew When Starting X-ray Astronomy

Nicholas P. Lee, Jonathan C. McDowell, Evan D. Tingle, Karla M. Guardado

This guide is intended for astronomers new to X-ray astronomy. It provides a brief overview of the data products typically encountered by the user and highlights analysis considerations usually not discussed in more formal introductions to the discipline. In X-ray and $γ$-ray astronomy the primary data set is an event list (a table of individually detected photons with position, arrival time, and an instrumental energy estimate) rather than the image or visibility array familiar from other wavel…

詳細を見る →
astro-ph.HE

Hidden structures in the UHE sky: unveiling potential sources via spectral signatures

Mateus Zeferino Rennó, Cainã de Oliveira

The search for the origin of ultrahigh-energy cosmic rays (UHECRs) typically relies on identifying directional excesses in the particle flux. While this approach is well established, it cannot detect localized spectral features, which could provide constraints on the sources of UHECRs if measured. In this work, we propose a complementary metric for directional searches, based on a functional $μ_E$ of the energy spectrum in a given arrival direction. We demonstrate that $μ_E$ mathematically decou…

詳細を見る →
astro-ph.IMastro-ph.HE

A Proliferated Space Architecture for Time-Domain Astrophysics

Daniel Kocevski, Eric Burns, Thomas Barclay, Nicholas E. White, Massimiliano Galeazzi, Brendan O'Connor, Amy Lien, Chris Fryer et al.

Time-Domain and Multi-Messenger Astrophysics (TDAMM) is entering a discovery-rich but follow-up-limited era, creating an urgent need for responsive, multiwavelength space-based capabilities. The Hydra constellation is a concept for a proliferated space architecture for time-domain astrophysics. The constellation would act as a disaggregated observatory composed of coordinated, relatively low-cost spacecraft that collectively provide capabilities traditionally concentrated within a single large m…

詳細を見る →
astro-ph.HEhep-ph

Probing Lorentz Invariance Violation in Cosmogenic Neutrino Propagation with KM3-230213A

Rodrigo Sasse, Rodrigo Guedes Lang, Rita de Cássia dos Anjos

We investigate superluminal Lorentz invariance violation (LIV) in the neutrino sector using cosmogenic neutrino fluxes generated with ultrahigh-energy cosmic-ray propagation models. Standard fluxes are calculated with \texttt{CRPropa 3.2} and subsequently modified using a prescription based on LIV-induced neutrino splitting. Superluminal LIV suppresses the flux at the highest energies while producing an enhancement at PeV - EeV energies. We use the KM3-230213A event as a benchmark to evaluate th…

詳細を見る →