Sazuna/UAT_keywords huggingface dataset:
A Nitrogen-rich AGN Powering a Large Ionizing Bubble at z = 8.63. We report the detection of Lyα in CANUCS-LRD-z8.6, a recently discovered active galactic nucleus (AGN) at z = 8.63 by R. Tripodi et al. (2025), in new NIRSpec/MSA G140H/F070LP observations. We detect broad Lyα emission (FWHM = 1540 ± 260 km s−1) near the systemic velocity, which suggests a large ionizing bubble, considering that the Universe is almost fully neutral at the redshift. Through Lyα line-shape modeling assuming a Strömgren sphere, we find a large bubble radius, Rb =  1.5−0.2+0.3  pMpc, and a moderately high Lyα escape fraction, fesc = 11% ± 3%. The intrinsic line width is inferred to be broad (2200 ± 280 km s−1), likely originating in the broad-line region. Existing data indicate that CANUCS-LRD-z8.6 is within a mild overdensity, δ =  1.8−0.6+3.0 , suggesting that other galaxies in its proximity might have contributed to the formation of the bubble. The high N IV]λ1488/C IVλ1548 and N IV]λ1488/O III]λ1661 line ratios measured in existing NIRSpec/PRISM data indicate nitrogen enrichment in this metal-poor, low-luminosity AGN. The spectroscopic features are overall similar to those of other nitrogen-rich galaxies discovered in the literature, such as GN-z11 and GHZ2/GLASSz12. This suggests that CANUCS-LRD-z8.6 may represent one of the evolutionary phases of those nitrogen-rich galaxies.

Keywords: Lyman-alpha galaxies, Reionization, Chemical abundances, AGN host galaxies
Magnetic Topology and Loop Statistics in Observed Coronal Holes Using Potential Field Modeling. Potential field source surface (PFSS) models are widely used to study the solar corona and form the basis for solar wind forecasting, yet they often fail to reproduce observed properties of coronal holes. We analyze 702 observed coronal holes between 2010 and 2019 and compute corresponding PFSS magnetic field extrapolations to examine their magnetic topology and loop statistics, comparing them with quiet-Sun regions. Our goal is to determine how observed coronal holes are represented in a PFSS model and to identify sources of known discrepancies. We find that low-lying loops covering the weak, balanced background field in coronal holes are statistically smaller and narrower than in quiet-Sun regions, with a median height strongly correlated to the coronal holes mean magnetic flux density (ccPearson = 0.81). This suggests that at low altitudes, the coronal hole magnetic topology is primarily governed by its flux density, unlike in quiet-Sun regions. Coronal holes also contain loops extending much higher into the corona than typical quiet-Sun loops, although it is unclear if these are truly closed or reflect source surface height limitations. Overall, differences in modeled magnetic structures of coronal holes and quiet-Sun regions are evident, even when the PFSS model does not indicate any open fields. These results suggest that observed coronal holes correspond to distinct photospheric magnetic structures and that discrepancies with PFSS models reflect modeling limitations rather than the absence of coronal holes.

Keywords: Solar coronal holes, Solar coronal loops, Quiet solar corona, Solar magnetic fields
oMEGACat. VIII. A Subpopulation Census of ω Centauri. An understanding of the assembly history of the complex star cluster Omega Centauri has long been sought after, with many studies separating the stars on the color─magnitude diagram into multiple groupings across small magnitude ranges. Utilizing the oMEGACat combined astro-photometric and spectroscopic data set, we parse 14 subpopulations from the upper red giant branch to below the main-sequence turnoff. We combine our results with previous works to estimate the age and age spread of each population. We find that the chemically enhanced (P2) populations are all ∼1 Gyr younger (∼11.6 Gyr old) and have significantly higher intrinsic age spreads (0.6 Gyr) than the primordial (P1) populations (∼12.6 Gyr old, 0.3 Gyr spread), with the intermediate (Im) populations falling in between the two. Additionally, we connect for the first time the chromosome diagram to the two-stream age─metallicity relation, allowing us to link the P1 and P2 stars to the distinct star formation tracks, proposed to be in situ and ex situ contributions to the cluster's assembly. Our results are consistent with some suggested formation models and rule out others, but no current model can explain all observed features of the subpopulations.

Keywords: Stellar populations, Galaxy nuclei, Stellar ages, Globular star clusters
Matching JWST Ultraviolet Luminosity Functions with Refined ΛCDM Halo Models. The James Webb Space Telescope (JWST) has unveiled a population of unexpectedly massive and luminous galaxies at redshifts z ≳ 7, posing a significant challenge to the standard Lambda cold dark matter (ΛCDM) cosmological paradigm. In this work, we address the tension between early JWST observations of luminous high-redshift galaxies and predictions of the standard ΛCDM model by revisiting the physics of dark matter halo formation. Employing refined halo mass functions derived by A. Del Popolo et al. (DP1 and DP2) that incorporate angular momentum, dynamical friction, and redshift-dependent collapse barriers, we demonstrate a significant enhancement in the abundance of massive halos at z ≳ 7 compared to the conventional Sheth─Tormen (ST) formalism. Using a semiempirical framework linking halo mass to UV luminosity, we show that the DP2 model reproduces the observed UV luminosity functions (UVLFs) from z = 7 to 14 with moderate star formation efficiencies, whereas the ST model requires implausibly high efficiencies. A normalized reduced χ2 analysis quantitatively confirms that the DP2 model provides the best statistical match to the JWST UVLF data in the vast majority of redshift bins. Our results suggest that the JWST overabundance problem stems not from new physics beyond ΛCDM, but from oversimplified treatments of gravitational collapse, highlighting the critical role of small-scale dissipative dynamics in early structure formation.

Keywords: Luminosity function, James Webb Space Telescope, Cold dark matter, Galaxy evolution
A New Approach for Constraining Large-scale Temperature Fluctuations in the Intergalactic Medium. The reionization of helium is thought to occur at 2.5 ≲ z ≲ 4, marking the last phase transition and final global heating event of the intergalactic medium (IGM). Since it is driven by rare quasars, helium reionization should give rise to strong temperature fluctuations in the IGM between neutral and recently ionized regions of order  σ(lnT)∼∆T/T=20%−50% . We introduce a novel method to search for reionization-induced temperature fluctuations in the IGM, by using the effective optical depths of the Lyα forest toward a large number of background quasars. Higher IGM temperatures give rise to lower effective optical depths in the Lyα forest, implying that temperature fluctuations will broaden the observed optical depth distribution. We measure the distributions of the effective Lyα forest optical depths across 71 X-Shooter spectra from the XQ-100 survey in four redshift bins, from z = 3.76 to z = 4.19, and compare them to a large-volume cosmological hydrodynamical simulation. A good agreement is found between the observations and the simulation, which does not include temperature fluctuations; therefore, we do not detect a signature of helium reionization. We then postprocess the simulations to include an increasing amount of temperature fluctuations, until the model becomes inconsistent with the observations. We obtain tight constraints on  σ(lnT)&lt;0.29(&lt;0.40)  at 2σ (3σ) at z = 3.76 when averaging over a scale of 100 comoving Mpc, with weaker constraints for higher redshifts and smaller scales. Our constraints are the tightest to date, implying that either the IGM temperature contrast caused by helium reionization is less than ∼30% or the process has not yet significantly started at z = 3.76.

Keywords: Lyman alpha forest, Quasars, Large-scale structure of the universe, Intergalactic medium, Reionization
Convection-driven Multiscale Magnetic Fields Determine the Observed Solar Disk Gamma Rays. The solar disk is a continuous source of GeV─TeV gamma rays. The emission is thought to originate from hadronic Galactic cosmic rays (GCRs) interacting with the gas in the photosphere and uppermost convection zone after being reflected by solar magnetic fields. Despite this general understanding, existing theoretical models have yet to match observational data. At the photosphere and the uppermost convection zone, granular convection drives a multiscale magnetic field, forming a larger-scale filamentary structure while also generating turbulence-scale Alfvén wave turbulence. Here, we demonstrate that the larger-scale filamentary field shapes the overall gamma-ray emission spectrum, and the Alfvén wave turbulence is critical for further suppressing the gamma-ray emission spectrum below ∼100 GeV. For a standard Alfvén wave turbulence level, our model's predicted spectrum slope from 1 GeV to 1 TeV is in excellent agreement with observations from the Fermi Large Area Telescope and HAWC, an important achievement. The predicted absolute flux is a factor of 2─5 lower than the observed data; we outline future directions to resolve this discrepancy. The key contribution of our work is providing a new theoretical framework for using solar disk gamma-ray observations to probe hadronic GCR transport in the lower solar atmosphere.

Keywords: Magnetohydrodynamics, Galactic cosmic rays, Solar granulation, Alfven waves, Solar magnetic fields, Gamma-rays
Stratified Evolution of Ryugu's Regolith Revealed by Spectroscopic Analyses of Two Hayabusa2 Collected Particles. We present Fourier transform infrared (FTIR) and Raman spectroscopic analyses of two particles (A0226 and C0242) returned from the C-type asteroid Ryugu by the Hayabusa2 mission. These particles, recovered from two different stratigraphic depths during the touchdown operations, provide a unique opportunity to investigate the compositional heterogeneity, alteration history, and space weathering processes of a primitive asteroid. All particles exhibit the 2.7 μm OH absorption feature, consistent with phyllosilicate hydration. However, the subsurface particle C0242 shows a significantly deeper OH band and stronger spectral signatures of carbonates and organic matter, suggesting the preservation of primitive material compared to the surface of the A0226 particle, which is distinctly affected by space weathering. To characterize compositional diversity, we applied unsupervised machine learning methods (Uniform Manifold Approximation and Projection for dimensionality reduction and Hierarchical Density-Based Spatial Clustering of Applications with Noise for cluster detection), identifying five spectral clusters linked to variations in their surface evolution and surface texture. This provides an objective framework to resolve spectral heterogeneity beyond median analyses. Raman spectroscopy of a fragment of A0226 reveals broad D and G bands typical of disordered carbonaceous matter, with spectral variations attributable to space weathering effects, consistent with FTIR analyses. These results, integrated with Hayabusa2 remote sensing data, support a model of stratified regolith evolution on Ryugu shaped by impact gardening, mass wasting, and surface irradiation. By modeling the reduction of the 2.7 μm band over time, we estimate surface exposure of 105 yr for C0242 and 106 for A0226.

Keywords: Near-Earth objects, Asteroids, Spectroscopy
CH<SUB>3</SUB>CCH as a Thermometer in Warm Molecular Gas. Kinetic temperature is a fundamental parameter in molecular clouds. Symmetric top molecules, such as NH3 and CH3CCH, are often used as thermometers. However, at high temperatures, NH3(2,2) can be collisionally excited to NH3(2,1) and rapidly decay to NH3(1,1), which can lead to an underestimation of the kinetic temperature when using rotation temperatures derived from NH3(1,1) and NH3(2,2). In contrast, CH3CCH is a symmetric top molecule with lower critical densities of its rotational levels than those of NH3, which can be thermalized close to the kinetic temperature at relatively low densities of about 104 cm−3. To compare the rotation temperatures derived from NH3(1,1) and (2,2) and CH3CCH rotational levels in warm molecular gas, we used observational data toward 55 massive star-forming regions obtained with Yebes 40 m and TMRT 65 m. Our results show that rotation temperatures derived from NH3(1,1) and (2,2) are systematically lower than those from CH3CCH 5─4. This suggests that CH3CCH rotational lines with the same J+1 → J quantum number may be a more reliable thermometer than NH3(1,1) and (2,2) in warm molecular gas located in the surroundings of massive young stellar objects or, more generally, in massive star-forming regions.

Keywords: Interstellar molecules, Massive stars, Star formation
Discovering Pulsars in Compact Binaries with a Hidden Markov Model. Discovering radio pulsars in compact binaries, whose orbital periods Pb satisfy Pb ≲ 1 day, is computationally challenging, because the time-dependent pulse frequency fp(t) is strongly Doppler modulated by the binary motion. Here we present a new, fast, semi-coherent detection scheme based on a hidden Markov model (HMM) combined with a maximum-likelihood matched filter, the Schuster periodogram. The HMM scheme complements traditional acceleration searches by dividing fp(t) into piecewise-constant blocks and tracking the block-to-block evolution efficiently using dynamic programming. Monte Carlo simulations show that the new method can detect compact binaries with flux densities S ≥ 0.50 mJy and orbital periods Pb ≥ 0.012 day under observing conditions (e.g., cadence) typical of radio pulsar surveys, with and without impulsive, narrowband radio-frequency interference. The new method is fast; it employs the classic Viterbi algorithm to solve the HMM recursively. The central processing unit runtime scales nominally as  Trun≍2.8NB(NT/102)(NQlnNQ/104ln104)s  for NB subbands, NT coherent segments, and NQ frequency bins.

Keywords: Binary pulsars, Rotation powered pulsars, Radio pulsars
Discovery of a New Spectral Transition in Swift J0243.6+6124 in the Sub-Eddington Regime. We have conducted a detailed spectral analysis of Swift J0243.6+6124 in its sub-Eddington regime, as observed by Insight-HXMT and NICER during a series of outbursts including the giant one in 2018, and discovered a new transition at Lt ∼ 4.5 × 1037 erg s−1 accompanied by the evolution of the spectral parameters, in particular a significant turnover of the blackbody normalization. Lt in the sub-Eddington regime represents the fifth transition luminosity identified so far, further increasing the complexity of Swift J0243.6+6124, and it may be explained by introducing a multipolar magnetic field configuration, where weak (∼2.8 × 1012 G) and strong (∼1.6 × 1013 G) magnetic poles govern the emission at different accretion rates. Such a magnetic field configuration is equivalent to a relatively weak pure dipole magnetic field of ∼6.6 × 1012 G on the scale of the magnetospheric radius, and allows the local magnetic field of the neutron star to exceed 1013 G.

Keywords: High mass x-ray binary stars, Binary pulsars
On the Relationship between Nanoflare Energy and Delay in the Closed Solar Corona. Determining the relationship between nanoflare energies and their delays is the key for understanding the physical mechanism of the events and the plasma response. Nanoflares analyzed in this study were generated self-consistently via prescribed photospheric motions in a 3D multistrand simulation of a subset of active region magnetic flux. Energies and durations were quantified using three distinct methods. In this study, we investigated the correlation between nanoflare energies (E) and delays (τD) using two nonparametric, rank-based statistical tests. Across all methods, results consistently show little to no correlation. This is further supported by the distribution of the exponent α in the assumed relation  E∝τDα , which peaks near zero, and by broad delay distributions within fixed energy bins. These findings are irrespective of whether delays are correlated with the energy of the preceding or subsequent event. They also hold for a subset of high-energy nanoflares. The absence of correlation suggests that nanoflare onset is not solely determined by a critical value of magnetic stress and may involve triggering by other events, perhaps related to a locally complex topology.

Keywords: Solar active region magnetic fields, Solar magnetic reconnection, Solar coronal loops, Solar coronal heating, Solar active regions, Active solar corona
Radio Studies of Supernovae 1979C, 1986J, and 2006X with LOFAR. We present LOw Frequency ARray (LOFAR) studies of supernovae SN 1979C, SN 1986J, and SN 2006X, focusing on new observations from the LOFAR Two-metre Sky Survey (LoTSS) and the International LOFAR Telescope (ILT). For Type Ia supernovae (SNe Ia) SN 2006X, we derive a 3σ upper limit of 0.7 mJy at 0.146 GHz, and using radio emission models based on the CS15DD2 explosion model, we constrain the circumstellar density to nH ≲ 10 cm−3 for the microphysical parameters ϵrel = ϵB = 0.01. SN 1979C is clearly detected in the LoTSS image with a flux density of 4.6 ± 0.36 mJy nearly 40 yr postexplosion. Modeling its radio evolution suggests a steep flux decay (Fν ∝ t−2.1) between 22 and 42 yr, a break in the spectrum near 1.5 GHz possibly due to synchrotron cooling, a progenitor mass of ∼13 M⊙, and a progressive steepening with velocity for the density slope of the supernova ejecta. Our findings for SN 1979C contradict scenarios involving central compact object emission, and we obtain X-ray temperatures close to those derived from recent observations. For SN 1986J, we present the first ILT image showing a flux density of 6.77 ± 0.2 mJy at 0.146 GHz. The spectral index of the shell emission is found to be 0.66 ± 0.03, consistent with previous estimates, although variations at low frequencies warrant further investigation. Our results highlight the power of LOFAR for studying long-term radio evolution in supernovae.

Keywords: Supernovae, Galaxies
Semianalytic Orbits: A Practical Implementation of Lynden-Bell's Planar Orbits and Extension to Vertical Oscillations. We present a practical implementation of the perturbation theory derived by Lynden-Bell for describing, to arbitrary precision, the orbit of a particle in an arbitrary spherically symmetric potential. Our implementation corrects minor but important errors in the initial derivation, and extends the formalism in two ways. First, a numerical method is developed to efficiently and precisely solve the analogue to the Kepler problem, and second, a method is introduced to track the particle's vertical oscillations about an axisymmetric disk, even when the vertical oscillation frequency varies with radius. While not as flexible as numerical integration, this method guarantees conservation of energy, angular momentum, and related quantities, and it may be used to evaluate a particle's position and velocity in constant time. Our implementation is written in Python and is pip installable as the package lbparticles.

Keywords: Orbits, Galaxy dynamics
Unifying the Circumstellar Environment in Broad-lined Type Ic Radio Supernovae toward Off-axis Gamma-Ray Burst Exploration. Decades have passed since the first confirmed association between a broad-lined Type Ic supernova (Type IcBL SN) and a long gamma-ray burst (GRB), and the number of known GRB-SN associations has steadily increased. However, it is important to note that the radiation from GRB afterglows and the radio emission from SNe may both be produced by outflows evolving within the same ambient medium. In this study, we present the first comprehensive theoretical predictions of radio emission from a Type IcBL supernova associated with a GRB jet, explicitly accounting for the structure of the ambient medium. We model each component of the radio emission, with particular emphasis on exploring wide ranges of isotropic explosion energy and viewing angle in our GRB afterglow calculations. We show that, within specific regions of parameter space, the composite radio light curve exhibits a characteristic double-peaked structure. This clear double-peaked feature emerges when either (1) the isotropic explosion energy is small (low-luminosity GRB) or (2) the viewing angle is large (off-axis GRB). Our results demonstrate that follow-up radio observations carried out within a few years of the optical discovery of nearby Type IcBL SNe (100 Mpc) can provide a unique diagnostic of off-axis GRBs that would otherwise remain undetected in Type IcBL SNe. This represents a step toward revealing the nature of long GRB progenitors and clarifying their connection to Type IcBL SNe.

Keywords: Type Ic supernovae, Gamma-ray bursts, Radio astronomy
SpecCLIP: Aligning and Translating Spectroscopic Measurements for Stars. In recent years, large language models (LLMs) have transformed natural language understanding through vast data sets and large-scale parameterization. Inspired by this success, we present SpecCLIP, a foundation model framework that extends LLM-inspired methodologies to stellar spectral analysis. Stellar spectra, akin to structured language, encode rich physical and chemical information about stars. By training foundation models on large-scale spectral data sets, our goal is to learn robust and informative embeddings that support diverse downstream applications. As a proof of concept, SpecCLIP involves pretraining on two spectral types—LAMOST low-resolution and Gaia XP—followed by contrastive alignment using the Contrastive Language─Image Pretraining (CLIP) framework, adapted to associate spectra from different instruments. This alignment is complemented by auxiliary decoders that preserve spectrum-specific information and enable translation (prediction) between spectral types, the former being achieved by maximizing mutual information between embeddings and input spectra. The result is a cross-spectrum framework that enables intrinsic calibration and flexible applications across instruments. We demonstrate that fine-tuning these models on moderate-sized labeled data sets improves adaptability to tasks such as stellar-parameter estimation and chemical-abundance determination. SpecCLIP also enhances the accuracy and precision of parameter estimates benchmarked against external survey data. In addition, its similarity search and cross-spectrum prediction capabilities offer potential for anomaly detection. Our results suggest that contrastively trained foundation models enriched with spectrum-aware decoders can advance precision stellar spectroscopy. Our code SpecCLIP is publicly available on GitHub ✎.

Keywords: Fundamental parameters of stars, Astronomy data analysis, Galaxy stellar content