Sazuna/UAT_keywords huggingface dataset:
AthenaK: A Performance-portable Version of the Athena++ Adaptive Mesh Refinement Framework. We describe AthenaK: a new implementation of the Athena++ block-based adaptive mesh refinement framework using the Kokkos programming model. Finite volume methods for Newtonian, special relativistic, and general relativistic (GR) hydrodynamics and magnetohydrodynamics (MHD), and GR-radiation hydrodynamics and MHD, as well as a module for evolving Lagrangian tracer or charged test particles (e.g., cosmic rays) are implemented using the framework. In two companion papers, we describe (1) a new solver for the Einstein equations based on the Z4c formalism, and (2) a GRMHD solver in dynamical spacetimes also implemented using the framework, enabling new applications in numerical relativity. By adopting Kokkos, the code can be run on virtually any hardware, including CPUs, GPUs from multiple vendors, and emerging Advanced RISC Machine processors. AthenaK shows excellent performance and weak scaling, achieving over 1 billion cell updates per second for hydrodynamics in three dimensions on a single NVIDIA Grace Hopper processor. It does this with a typical parallel efficiency of 80% on 65,536 AMD GPUs on the OLCF Frontier system. Such performance portability enables AthenaK to leverage modern exascale computing systems for challenging applications in astrophysical fluid dynamics, numerical relativity, and multimessenger astrophysics.

Keywords: Astrophysical fluid dynamics, Relativistic fluid dynamics, Astronomy software
RM-Tools: Software for Analyzing Polarized Radio Spectra. Polarization observations using modern radio telescopes cover large numbers of frequency channels over broad bandwidths, and require advanced techniques to extract reliable scientific results. We present RM-Tools, analysis software for deriving polarization properties, such as Faraday rotation measures, from spectropolarimetric observations of linearly polarized radio sources. The software makes use of techniques such as rotation measure synthesis and QU-model fitting, along with many features to simplify and enhance the analysis of radio polarization data. RM-Tools is currently the main software that large-area polarization sky surveys such as POSSUM and VLASS deploy for science-ready data processing. The software code is freely available and can be used with data from a wide range of telescopes.

Keywords: Spectropolarimetry, Astronomy software, Milky Way magnetic fields, Astronomy data analysis, Interstellar magnetic fields, Radio galaxies, Radio continuum emission, Radio astronomy, Extragalactic magnetic fields
Automated Detection of Coronal Mass Ejections with Few-shot Learning. Coronal mass ejections (CMEs) are a primary driver of severe space weather impacts, yet accurate delineation of CME structure in coronagraph images remains challenging. We present Segment Anything Model (SAM)─low-rank adaptation (LoRA), an efficient CME segmentation framework that employs the SAM to solar data via LoRA. The approach employs a multichannel preprocessing scheme that combines base- and running-difference coronagraph images to enhance CME morphology and localization. We compile a new, manually annotated Large Angle and Spectrometric Coronagraph dataset with CME-only and mixed CME/non-CME configurations. On CME-only data, SAM-LoRA delivers segmentation quality comparable to state-of-the-art methods while requiring substantially fewer labeled examples. On mixed data, image-level labels derived from the predicted masks (empty versus nonempty) enable high-quality CME presence detection. The parameter-efficient design reduces computational and annotation costs while retaining SAM's strong priors. These results indicate that adapting foundation models is a promising path toward reliable CME detection and segmentation and provides a basis for extensible, multitask pipelines for tracking, parameter extraction, and forecasting in heliophysics.

Keywords: Solar coronal mass ejections
Large Language Model─driven Analysis of General Coordinates Network (GCN) Circulars. The General Coordinates Network (GCN) is NASA's time-domain and multimessenger alert system. GCN distributes two data products: automated "Notices" and human-generated "Circulars" that report the observations of high-energy and multimessenger astronomical transients. The flexible and nonstructured format of GCN Circulars, comprising more than 40,500 Circulars accumulated over three decades, makes it challenging to manually extract observational information, such as redshift or observed wave bands. In this work, we employ large language models (LLMs) to facilitate the automated parsing of transient reports. We develop a neural topic modeling pipeline with open-source tools for the automatic clustering and summarization of astrophysical topics in the Circulars archive. Using neural topic modeling and contrastive fine-tuning, we classify Circulars based on their observation wave bands and messengers. Additionally, we separate gravitational-wave event clusters and their electromagnetic counterparts from the Circulars archive. Finally, using the open-source Mistral model, we implement a system to automatically extract gamma-ray burst (GRB) redshift information from the Circulars archive, without the need for any training. Evaluation against the manually curated Neil Gehrels Swift Observatory GRB table shows that our simple system, with the help of prompt-tuning, output parsing, and retrieval augmented generation (RAG), can achieve an accuracy of 97.2% for redshift-containing Circulars. Our neural search-enhanced RAG pipeline accurately retrieved 96.8% of redshift Circulars from the manually curated archive. Our study demonstrates the potential of LLMs to automate and enhance astronomical text mining and provides a foundational work for future advances in transient alert analysis.

Keywords: Solar coronal radio emission, Transient sources, Time domain astronomy, High energy astrophysics
Identification of Strongly Lensed Gravitational-wave Events Using Squeeze-and-excitation Multilayer Perceptron Data-efficient Image Transformer. With the advancement of third-generation gravitational-wave (GW) detectors, the identification of strongly lensed GW events is expected to play an increasingly vital role in cosmology and fundamental physics. However, traditional Bayesian inference methods suffer from combinatorial computational overhead as the number of events grows, making real-time analysis infeasible. To address this, we propose a deep learning prescreening classifier, Squeeze-and-Excitation Multilayer Perceptron Data-efficient Image Transformer (SEMD), based on Vision Transformers, which classifies strongly lensed GW events by modeling morphological similarity between time─frequency spectrogram pairs. By integrating Squeeze-and-Excitation attention mechanisms and multilayer perceptrons, SEMD achieves strong feature extraction and discrimination. Trained and evaluated on astrophysically motivated simulated datasets incorporating Advanced LIGO and Einstein Telescope noise, SEMD demonstrates robust discrimination and generalization across detector sensitivities and source parameters. By reformulating lens identification as a morphology-based similarity test on paired time─frequency representations of GW signals, SEMD functions as a fast prescreen that prioritizes candidate pairs for subsequent Bayesian follow-up rather than replacing full joint parameter estimation; this substantially reduces the set of events requiring costly posterior reconstruction and thereby enables timely, resource-efficient Bayesian and subsequent multimessenger analyses.

Keywords: Strong gravitational lensing, Gravitational waves
Evolution of Stellar Activity and Habitable Zone. II. Ca II H and K Emissions of Late-type Dwarfs. Stellar chromospheric activity serves as a valuable proxy for estimating stellar ages, though its applicable range and accurate functional form are still debated. Utilizing LAMOST spectra, we have compiled a catalog of open cluster members and field stars to investigate  RHK' ─age relations across various spectral types. We find that a linear model, specifically a Skumanich-type relation, can best describe the overall decline of chromospheric activity with age, with the slope varying across different spectral types. However, we also identify variations in the decay rate along the main sequence, which call for more accurate follow-up investigation. Finally, we find that lower-metallicity stars exhibit enhanced activity for F-, G-, and K-type stars, whereas no clear metallicity dependence is observed for M dwarfs.

Keywords: Stellar rotation, Late-type stars, Stellar ages, Stellar activity
The Cyclic Variation of Magnetic Fields on the Quiet Sun Observed by SDO/HMI. Unraveling the origins of the quiet Sun's magnetic fields remains a key challenge. Using observations from Heliospheric Magnetic Imager on board Solar Dynamics Observatory, we identified over 86 million quiet region (QR) structures in daily full-disk magnetograms spanning 2010─2025, a period covering nearly the entire Solar Cycle 24 and half of Cycle 25. By analyzing the cyclic variations, our key findings are as follows. (1) The area coverage and total magnetic flux of QRs closely follow sunspot cycles, indicating that Cycle 25 is stronger than Cycle 24. Throughout Cycle 24, the QR flux surpasses active region (AR) flux for almost the entire cycle. In the first 5.5 yr of Cycle 25, the QR flux remains greater than AR flux except for nine isolated months. (2) From the detection limit to the large-scale end, both the flux and number of QR structures exhibit a sequential pattern of anticorrelation and positive correlation with sunspots. Notably, anticorrelated structures constitute more than 95% of QR structures at any given time, and dominate the QR flux during solar minimum. (3) We develop an empirical model for QR magnetic sources based on long-term flux variations, revealing that the flux contribution of ARs remnants to QRs varies in the solar cycle. During solar maximum, most of the QR flux and positive-correlated QR flux originate from ARs, while roughly 30% of the anticorrelated flux is suppressed by ARs. These findings suggest that the solar cycle should be characterized by the magnetic fields in both ARs and their associated QRs.

Keywords: Solar cycle, Quiet sun, Solar photosphere, Solar dynamo
The Second CHIME/FRB Catalog of Fast Radio Bursts. We present a catalog of 4539 fast radio bursts (FRBs) observed with the Canadian Hydrogen Intensity Mapping Experiment telescope between 2018 July 25 and 2023 September 15. These bursts originate from 3641 unique sources, including 981 bursts from 83 known repeating sources. For each FRB, the catalog provides an  O(10')  estimate of sky location along with corresponding measurements of cumulative exposure time and survey sensitivity over the observing period. It includes a total-intensity dynamic spectrum between 400 and 800 MHz at 0.983 ms resolution. From this spectrum, we constrain a model of the burst morphology and measure key parameters such as arrival time, intrinsic temporal width, dispersion measure, scattering time, and flux density. This second catalog includes all FRBs from the first catalog, with every event reprocessed using a uniform and improved analysis framework. We show that previously published inferences remain valid under the updated measurements. We assess consistency of the detection rate across observational parameters, present initial distributions of burst properties, and outline ongoing and future studies that will use this catalog to investigate the nature of FRBs and their utility as astrophysical and cosmological probes.

Keywords: Catalogs, Compact objects, Radio transient sources
Through Thick and Thin: The Cosmic Evolution of Disk Scale Height. To investigate the formation and evolution of vertical structures in disk galaxies, we measure global sech2 scale heights, averaging thin and thick components when present, for 2631 edge-on disk galaxies with M* &gt; 1010M⊙ at 0 &lt; z &lt; 3.5 from the JWST COSMOS-Web survey. We show that dust extinction systematically overestimates scale heights at shorter rest-frame wavelengths and therefore adopt a fixed rest-frame wavelength of 1 μm. After further correcting for projection-induced bias using a new accurate method, we find that the median disk scale height increases from 0.56 ± 0.03 kpc at z = 3.25 to 0.84 ± 0.04 kpc at z = 1.25, and subsequently decreases to 0.67 ± 0.06 kpc at z = 0.25. The bias-corrected disk scale length-to-height ratio remains constant at 2.7 ± 0.2 for z &gt; 1.5 but rises to 4.0 ± 0.4 at z = 0.25. These results imply that the high-redshift progenitors of present-day thick disks were of intermediate thickness, neither thin nor thick, yet dynamically hot and dense. The observed radial variation of scale height is consistent with the artificial flaring expected from observational effects, disfavoring minor mergers as the primary mechanism of disk thickening. Instead, we suggest that the high-redshift intermediate-thickness disks were single-component systems that increased their vertical scale height through decreasing surface mass density and/or violent gravitational instabilities, eventually producing thick disks. Thin-disk growth begins at z ≍ 2 and dominates at z ≲ 1, yielding a vertically more compact system with decreasing scale heights from z ≍ 1 to 0. The inferred thin-disk mass fraction increases from 0.1 ± 0.03 at z = 1 to 0.6 ± 0.1 at z = 0. Together, these findings reveal a continuous evolutionary link between high-redshift single-component disks and present-day disks comprising thick and thin components.

Keywords: Galaxy stellar disks, Galaxy structure, Galaxy photometry, Galaxy kinematics, Galaxy evolution, Milky Way evolution, High-redshift galaxies
Spectral Reflectance Properties (0.3─2.5 μm) of LL Ordinary Chondrites. Spectral characterization of asteroids relies on meteorite spectral calibration to constrain their surface mineralogy. We have conducted a comprehensive spectroscopic study of LL chondrites to shed light on the factors that control their reflectance spectra in the 0.3─2.5 μm region. Our results show that the ratio of the area of an absorption feature in the 2 μm region to that of Band I (termed the band area ratio (BAR)) decreases with increasing petrologic grade. Grain-size variations can cause systematic changes in the spectral slope, albedo, absorption depths, and BAR of LL chondrites. The chip spectra of LL chondrites have a blue spectral slope and shallow absorption depths when compared to their corresponding powder spectra. Phase-angle variation has a systematic effect on the spectral slope and albedo of LL chondrite spectra. The shock effect can cause systematic changes in the albedo and absorption depths of LL chondrites. Whether or not the metal/magnetic particles are removed has little effect on the spectra of LL chondrites. Terrestrial weathering significantly reduces the 0.5/0.6 μm reflectance ratio of LL chondrites, but this ratio has no clear trend with weathering grade. We also applied these results to four well-known asteroid mission targets. Our results suggest that the spectral difference between smooth terrain and rough terrain of 25143 Itokawa may be due to the presence of fine-grained regolith in the smooth terrain. The contents of olivine and pyroxene in 4179 Toutatis, 99942 Apophis, and 469219 Kamo'oalewa are comparable to those in L chondrites, LL chondrites, and LL chondrites, respectively.

Keywords: Chondrites, Asteroids, Spectroscopy
Cosmic-ray Magnetohydrodynamics: A New Two-moment Framework with Numerical Implementation. Cosmic rays (CRs) play a pivotal role in various astrophysical systems, delivering feedback over a broad range of scales. However, modeling CR transport remains challenging due to its inherently multiscale nature and complex microphysics. Recent advances in two-moment CR hydrodynamics have alleviated some of these challenges, improving our understanding of CR feedback. Yet, current two-moment methods may not be able to directly incorporate all relevant CR transport processes, while the outcome of CR feedback sensitively depends on these underlying microphysics. Furthermore, numerical challenges persist, including instabilities from streaming terms and ambiguities in the solver design for coupled CR─MHD systems. In this work, we develop a two-moment description for CR hydrodynamics from first principles. Beyond canonical CR streaming, our formulation accounts for CR pressure anisotropy and Alfvén waves propagating in both directions along the magnetic field, providing a general framework to incorporate more CR transport physics. We implement this framework as a new CR fluid module in the Athena++ code, and validate it through a suite of benchmark tests. In particular, we derive the full dispersion relation of the two-moment CR─MHD system, identifying the CR-acoustic instability as well as other wave branches. These CR─MHD waves serve as rigorous benchmarks and also enable the use of realistic signal speeds in our Riemann solver. We propose a time step guideline to mitigate numerical instabilities arising from streaming source terms.

Keywords: Magnetohydrodynamics, Cosmic ray astronomy, Plasma astrophysics, Computational methods, Interstellar medium, Circumgalactic medium, Perturbation methods, Cosmic rays
Unveiling Quasars in Gaia DR3: Multimodal Classification and Redshift Estimation of BP/RP Sources with Deep Learning. We present a multimodal deep learning framework that classifies stars, galaxies, and quasars and accurately estimates quasar redshifts using Gaia DR3's low-resolution BP/RP (XP) spectra, alongside astrometric, photometric, and CatWISE mid-infrared data. Our hierarchical classification model achieves an overall accuracy of 99.90%. Evaluating class-specific performance under a one-versus-rest framework, a precision of 99.61% and a recall of 99.83% are achieved for quasars. Furthermore, our spectral redshift regression model, SpecNet-Z, attains an rms error of 0.0682, a normalized median absolute deviation (σNMAD) of 0.0048, and a catastrophic outlier rate of only 0.42%, demonstrating superior performance in the template-fitting approach in Gaia DR3. Applying this framework to the 219 million sources with public XP spectra, we produce the XP-Quasars catalog, containing 123,342 high-purity quasar candidates. This catalog includes 3763 new candidates not listed in the official GDR3 QSO catalog. Our work provides a robust and scalable method that serves as a valuable resource for current active galactic nuclei and cosmological studies and as a vital precursor for the analysis of the complete XP spectra dataset anticipated in Gaia DR4. The XP-Quasar catalog and associated source code are publicly available via Zenodo (https://doi.org/10.5281/zenodo.17960118) and GitHub (https://github.com/Shijinghang/xp-quasars).

Keywords: Neural networks, Classification, Galaxies, Quasars
MARVEL Analysis of the Measured High-resolution Spectra of CO Isotopologues. Carbon monoxide is thought to be the second most abundant molecule in the Universe. This makes observation of both its parent isotopologue (12C16O) and its stable isotopologues, 13C16O, 12C18O, 12C17O, 13C18O, and 13C17O, important in variety of objects. Here the Measured Active Rotational-Vibrational Energy Levels algorithm is used to determine precise rotational─vibrational energy levels for the five minor isotopologues of carbon monoxide in their electronic ground state. A review of 27 literature sources yields 3716, 1454, 89, 728, and 57 validated transitions for 13C16O, 12C18O, 12C17O, 13C18O, and 13C17O, respectively, giving 863, 499, 33, 345, and 45 empirically determined, rotation─vibration energy levels, respectively.

Keywords: Molecular physics, Molecular spectroscopy, Laboratory astrophysics
COCONUT: A Coronal Model with an Energy Decomposition Strategy. In this paper, we propose an energy decomposition method combined with a Harten─Lax─van Leer Riemann solver that includes an additional dissipation term in the energy equation to improve the numerical stability of the fully implicit, time-evolving coronal model COolfluid COroNal UnsTructured (COCONUT) and extend its applicability to solar-maximum phases. In MHD simulations that evolve conservative variables in time, the thermal pressure is typically computed by subtracting the magnetic and kinetic energies from the total energy. In low-β (the ratio of thermal to magnetic pressure; &lt;10−3) regions, discretization errors of magnetic energy can be comparable to the thermal pressure, potentially leading to negative thermal pressure and causing the simulation to crash. Therefore, we update the decomposed energy, excluding the magnetic energy, at each time step. It avoids subtracting a large magnetic energy from the total energy to obtain a very small thermal pressure in low-β regions, thereby improving the numerical stability of MHD models. We validate the algorithm using a time-evolving solar-maximum Carrington rotation simulation in 2025, which the previous code failed to run to completion. We also perform quasi-steady-state coronal simulations and 2D benchmark tests to further assess the algorithm's performance. The simulation results show that the algorithm produces results nearly identical to those obtained using the traditional full energy equation during solar minimum, while significantly improving COCONUT's ability to simulate coronal evolution under strong magnetic fields, even including fields exceeding 100 G with β &lt; 10−3. This method provides a promising approach for performing quasi-realistic coronal simulations during solar maxima.

Keywords: The Sun, Solar corona, Magnetohydrodynamics, Magnetohydrodynamical simulations
MESA Isochrones and Stellar Tracks (MIST). III. The White Dwarf Cooling Sequence. We present a substantial update to the MESA Isochrones and Stellar Tracks (MIST) library, extending the MIST model grids and isochrones down the white dwarf (WD) cooling sequence with realistic physics for WD cooling timescales. This work provides a large grid of MESA models for carbon─oxygen core WDs with hydrogen atmospheres (spectral type DA/DC), descended from full prior stellar evolution calculations. The model tracks, isochrones, and WD cooling timescale contours are available on the MIST project website and at doi:10.5281/zenodo.15242047. Our WD models provide a very large, publicly available grid with detailed physics for WD cooling timescales: realistic interior and envelope compositions, with element diffusion and heavy-element sedimentation, nuclear burning at the base of the WD hydrogen envelope, core crystallization, and C/O phase separation. As a large grid of open-source stellar evolution models, these WD models provide both out-of-the-box model tracks for comparison with observations and a framework for building further WD models to investigate variations in WD physics.

Keywords: White dwarf stars, Stellar physics
An Introduction to Single-antenna Radio Astronomical Polarimetry. This tutorial reviews the mathematical foundations of single-antenna radio polarimetry with the aim of fostering a conceptual understanding of the relationships between a physical description of signal propagation (gain, delay, reflection, down-conversion, etc.), the corresponding transformations of the electric field vector, and the equivalent operations on the Stokes parameters. The adopted framework is based on the work of Britton and Hamaker and applied to analyze the signal path described by Hamaker et al. with additional corrections for phase convention and reflection. Some objective criteria for selecting a model of the instrumental response are introduced and discussed, along with some practical guidelines that facilitate polarimetric calibration. Further relevant background material and lengthier mathematical proofs are included in the appendix, which introduces the vector, matrix, and tensor notation and concepts of linear algebra used in this work. The appendix also reviews some of the basics of analog and digital signal processing that are relevant to radio astronomy, and discusses some numerical instabilities that arise when modeling observations.

Keywords: Radio astronomy, Polarimetry