Sazuna/UAT_keywords huggingface dataset:
A JWST Transmission Spectrum of the Temperate Sub-Neptune TOI-732 c. In recent years, JWST has facilitated detections of carbon-bearing molecules in the atmospheres of temperate sub-Neptunes orbiting M dwarfs, ushering in a new era in the characterization of this intriguing planetary regime. We report the transmission spectrum of the temperate sub-Neptune TOI-732 c, observed with JWST NIRISS, NIRSpec G395H, and MIRI Low Resolution Spectrometer between 0.9 and 12 μm. The observations provide evidence for methane (CH4) in a H2-rich atmosphere, at a volume mixing ratio of ∼1%, and nondetection of NH3 and HCN, along with nominal constraints on other prominent molecules H2O, CO, and CO2, which are typically expected in H2-rich atmospheres. We conduct a comprehensive survey of 250 chemical species and find moderate to strong evidence (up to  lnB∼5.9 , 3.9σ) for additional absorption due to one or more complex molecules including higher-order hydrocarbons and/or sulfur-bearing molecules. The spectral features are strongly degenerate among these molecules and with methane, which we find at  lnB=3.2−8.8  (up to 3.0σ─4.6σ) significance. Two complex molecules are preferred with at least moderate evidence ( lnB≳2.5 ) in both the near- and mid-infrared, while several others show such evidence in at least one of the two wavelength ranges. The preferred molecules are found in trace quantities on Earth, with no significant sources identified in other planetary atmospheres, requiring future work to assess their physical plausibility in this planet. Future observations are required to resolve the degeneracies and place more robust constraints on these species. We highlight the need for further theoretical and experimental work to robustly characterize the atmospheric and internal composition of TOI-732 c and similar sub-Neptunes.

Keywords: Infrared spectroscopy, Exoplanets, James Webb Space Telescope, Atmospheric composition, Habitable planets, Exoplanet atmospheres
Enhanced Nonthermal Line Broadening inside Coronal Cavities above Solar Prominences Revealed by Spectral Imaging CoronaGraph. Coronal cavities, often associated with prominences, are crucial structures in understanding coronal heating and the eruption mechanism of coronal mass ejections. Previous studies have identified their lower density, higher temperature, and flux-rope structures. However, spectroscopic observations are still relatively scarce. In this study, we utilize the newly developed Spectral Imaging Coronagraph (SICG), Chinese Hα Solar Explorer, and Atmospheric Imaging Assembly (AIA) Solar Dynamics Observatory to analyze the morphology, temperature, Doppler shift, and nonthermal velocity of two coronal cavities observed on 2024 November 13. We find that coronal cavities are distinctly visible in SICG Fe XIV 5303 Å and AIA 193 Å, whereas they are nearly absent in SICG Fe X 6374 Å and AIA 171 Å. The spectroscopic measurements show that the two coronal cavities display asymmetric, ringlike structures in the Fe XIV 5303 Å Doppler shift maps. The nonthermal velocities inside coronal cavities are significantly higher than those of the surrounding streamer areas. In addition, the core regions of coronal cavities, located directly above the prominences, exhibit the highest nonthermal velocities and Doppler velocities. Our results suggest the presence of waves and turbulence in coronal cavities, which are likely more intense than those in the adjacent streamer regions. We suggest that the interaction and exchange between the cold, dense prominence materials and the hot, low-density coronal materials are the main drivers of the waves and turbulence inside coronal cavities.

Keywords: Solar coronal heating, Solar prominences, Solar corona
Fast X-Ray Variability from the Coronae of Supermassive Black Holes. We present the first systematic study of short-timescale X-ray variability in radio-quiet active galactic nuclei (AGN), utilizing archival Chandra observations of approximately 3000 broad-line AGN selected from the Sloan Digital Sky Survey and Dark Energy Spectroscopic Instrument spectroscopic surveys. We identify 14 AGN exhibiting rapid (on timescales of tens of kiloseconds) X-ray flux variations by factors of 2 or more that are statistically significant (p ≤ 6 × 10−4), indicative of fast coronal variability. By converting minimum variability timescales to light-crossing times, we place upper limits on the sizes of the variable coronal regions, finding typical scales of ≲10−4 pc. The coronal variable region size upper limits of an AGN in our sample are found to be much smaller than the typical coronal sizes inferred from microlensing, suggesting that its corona is composed of localized, transient structures rather than smooth, homogeneous plasmas. Such efficient magnetic energy dissipation in compact volumes is consistent with expectations for magnetically dominated coronae and is supported by recent general relativistic magnetohydrodynamic simulations. Future high-throughput X-ray observatories will enable the detection of even faster coronal variability, providing direct constraints on the physical mechanisms driving plasma energization and flux fluctuation near supermassive black holes. Our results suggest that luminous AGN hosting massive black holes are prime targets for probing the small-scale structure and dynamics of AGN coronae.

Keywords: X-ray active galactic nuclei, Active galactic nuclei
Reconnection-driven Flares in M87*: Proton─Synchrotron-powered GeV Emission. Magnetic reconnection in current layers that form intermittently in radiatively inefficient accretion flows onto black holes is a promising mechanism for particle acceleration and high-energy emission. It has been recently proposed that such layers, arising during flux eruption events, can power the rapid TeV flares observed from the core of M87. In this scenario, inverse-Compton scattering of soft radiation from the accretion flow by energetic electron─positron pairs produced near the reconnection layer was suggested as the primary emission mechanism. However, detailed calculations show that radiation from pairs alone cannot account for the GeV emission detected by the Fermi observatory. In this work, we combine analytic estimates with 3D radiative particle-in-cell simulations of pair─proton plasmas to show that the GeV emission can be naturally explained by synchrotron radiation from protons accelerated in the current sheet. Although the exact proton content of the layer is uncertain, our model remains robust across a broad range of proton-to-pair number density ratios. While protons are subdominant in number compared to pairs, our simulations demonstrate that they can be accelerated more efficiently, leading to a self-regulated steady state in which protons dominate the energy budget. Ultimately, proton synchrotron emission accounts for approximately 5%─20% of the total dissipation power. The majority is radiated as MeV photons via pair synchrotron emission, with a smaller fraction emitted as TeV photons through inverse-Compton scattering.

Keywords: Black hole physics, Special relativity, Plasma astrophysics, Active galactic nuclei, Gamma-rays
Star Formation under a Cosmic Microscope: Highly Magnified z = 11 Galaxy behind the Bullet Cluster. We present measurements of stellar population properties of a newly discovered, spectroscopically confirmed,  z=11.10−0.26+0.11 , gravitationally lensed galaxy, using JWST NIRSpec PRISM spectroscopy and NIRCam imaging. The arc is highly magnified by the Bullet Cluster (magnification factor  μ=14.0−0.3+6.2 ). It contains three star-forming components of which one is barely resolved and two are unresolved, giving intrinsic sizes of ≲10 pc. The clumps also contain ∼50% of the total stellar mass. The galaxy formed the majority of its stars ∼150 Myr ago (by z ∼ 14). The spectrum shows a pronounced damping wing, typical for galaxies deep in the reionization era and indicating a neutral intergalactic medium at this line of sight. The intrinsic luminosity of the galaxy is  0.086−0.030+0.008L*  (with L* being the characteristic luminosity for this redshift), making it the lowest-luminosity spectroscopically confirmed galaxy at z &gt; 10 discovered to date.

Keywords: Strong gravitational lensing
A Bridge between Young Stars Formed by Gravitational Interaction. The majority of stars are born in clustered environments. In these environments, close encounters between young stars with planet-forming disks are expected to occur frequently. However, direct evidence of such interactions remains rare. Here, we report clear signatures of a recent dynamical interaction between the young stellar systems L1448 IRS3A and L1448 IRS3B. Millimeter wavelength observations reveal a distinct, tidally stripped bridge between the two systems. Together with previously reported spiral arm structures at the outer edge of the IRS3A disk and at the inner and outer regions of the IRS3B disk, these features imply that the systems are undergoing a dynamical flyby. Hydrodynamical simulations reproduce these features and suggest that the closest approach occurred about 15,000 yr ago. These findings offer rare insight into how stellar interactions can reshape disk structures and influence the formation of young multiple stellar systems.

Keywords: Observational astronomy, Young stellar objects, Star formation, Protostars, Radio astronomy
Very Massive, Rapidly Spinning Binary Black Hole Progenitors through Chemically Homogeneous Evolution—The Case of GW231123. Among the over 200 gravitational wave detections reported so far, GW231123 is a remarkable event that not only holds the record for the most massive black hole merger but also exhibits extreme spins. Its origin is actively debated. Proposed scenarios include dynamical formation through hierarchical mergers, Population III stars, accretion in active galactic nucleus disks and also more exotic explanations including primordial black holes and cosmic strings, each facing different challenges. Recent work showed that the incoming black holes of GW231123 could form from massive, rapidly rotating collapsing helium stars. Here, we address the question how such stars can be formed in very close binary systems and explore chemically homogeneous evolution (CHE) involving progenitors with masses above the pair-instability mass gap. We compute a grid of detailed massive binary models with the stellar evolution code MESA to follow the early evolution of binary progenitors and show that (i) very massive (Mi &gt; 140 M⊙) CHE binaries at low metallicity (Z = 10−5) naturally produce rapidly rotating progenitors with high masses and high spins matching the properties of the black holes in GW231123 and (ii) the maximum spin of the progenitors is bound by their critical rotation rate, producing a tight correlation between the dimensionless spin and mass, a ∝ M−0.9, in models without any hydrogen left. We conclude that the CHE channel appears to be a viable and natural scenario to produce progenitors. We compare and discuss the differences with earlier studies and comment on the large uncertainties in the final fate and collapse.

Keywords: Binary stars, Black holes, High energy astrophysics, Close binary stars, Massive stars, Gravitational wave sources, Gravitational wave astronomy, Rotating black holes, Gravitational waves
Multiband Optical Variability of the Blazar 3C 454.3 on Diverse Timescales. Due to its peculiar and highly variable nature, the blazar 3C 454.3 has been extensively monitored by the WEBT team. Here, we present for the first time these long-term optical flux and color variability results using data acquired in B, V, R, and I bands over a time span of about two decades. We include data from WEBT collaborators and public archives such as SMARTS, Steward Observatory, and Zwicky Transient Facility. The data are binned and segmented to study the source over this long term when more regular sampling was available. During our study, the long-term spectral variability reveals a redder-when-brighter trend, which, however, stabilizes at a particular brightness cutoff of ∼14.5 mag in the I band, after which it saturates and evolves into a complex state. This trend indicates increasing dominance of jet emission over accretion disk (AD) emission until jet emission completely dominates. Plots of the variation in spectral index (following F  ν  ∝ ν ‑α ) reveal a bimodal distribution using a one-day binning. These correlate with two extreme phases of 3C 454.3, an outburst or high-flux state and a quiescent or low-flux state, which are respectively jet- and AD-dominated. We have also conducted intraday variability studies of nine light curves and found that six of them are variable. Discrete correlation function analysis between different pairs of optical wave bands peaks at zero lags, indicating cospatial emission in different optical bands.

Keywords: Supermassive black holes, Blazars, Flat-spectrum radio quasars, Relativistic jets, Active galactic nuclei, Markov chain Monte Carlo
The Resolved Behavior of Dust Mass, Polycyclic Aromatic Hydrocarbon Fraction, and Radiation Field in ∼800 Nearby Galaxies. We present resolved 3.6–250 μm dust spectral energy distribution (SED) fitting for ∼800 nearby galaxies. We measure the distribution of radiation field intensities heating the dust, the dust mass surface density (Σd), and the fraction of dust in the form of polycyclic aromatic hydrocarbons (PAHs; q PAH). We find that the average interstellar radiation field ( ) is correlated both with stellar mass surface density (Σ⋆) and star formation rate surface density (ΣSFR), while more intense radiation fields are only correlated with ΣSFR. We show that q PAH is a steeply decreasing function of ΣSFR, likely reflecting PAH destruction in H II regions. Galaxy-integrated q PAH is strongly, negatively correlated with specific star formation rate (sSFR) and offset from the star-forming "main sequence" (ΔMS), suggesting that both metallicity and star formation intensity play a role in setting the global q PAH. We also find a nearly constant M d/M * ratio for galaxies on the main sequence, with a lower ratio for more quiescent galaxies, likely due to their lower gas fractions. From these results, we construct prescriptions to estimate the radiation field distribution in both integrated and resolved galaxies. We test these prescriptions by comparing our predicted   to results of SED fitting for stacked "main-sequence" galaxies at 0 &lt; z &lt; 4 from M. Béthermin et al. and find sSFR is an accurate predictor of   even at these high redshifts. Finally, we describe the public delivery of matched-resolution Wide-field Infrared Survey Explorer and Herschel maps along with the resolved dust SED-fitting results through the Infrared Science Archive.

Keywords: Interstellar dust, Polycyclic aromatic hydrocarbons, Infrared photometry
The Impact of Host-galaxy Properties on Supernova Classification with Hierarchical Labels. With the advent of the Vera C. Rubin Observatory, the discovery rate of supernovae (SNe) will surpass the rate of SNe with real time spectroscopic follow-up by 3 orders of magnitude. Accurate photometric classifiers are essential to both select interesting events for follow-up in real time and for archival population-level studies. In this work, we investigate the impact of observable host-galaxy information on the classification of SNe, both with and without additional light-curve and redshift information. We find that host-galaxy information alone can successfully isolate relatively pure (&gt;90%) samples of Type Ia SNe with or without redshift information. With redshift information, we can additionally produce somewhat pure (&gt;70%) samples of Type II SNe and superluminous SNe. Additionally with redshift information, host-galaxy properties do not significantly improve the accuracy of SN classification when paired with complete light curves. In the absence of redshift information, however, galaxy properties significantly increase the accuracy of photometric classification. As a part of this analysis, we present the first formal application of a new objective function, the weighted hierarchical cross entropy, to the problem of SN classification. This objective function more naturally accounts for the hierarchical nature of SN classes and, more broadly, transients. Finally, we present a new set of SN classifications for the Pan-STARRS Medium Deep Survey of SNe that lack spectroscopic redshift, increasing the full photometric sample to &gt;4400 events.

Keywords: Light curve classification , Supernovae, Neural networks
Astronomical Pointlike Source Detection via Deep Feature Matching. This study introduces PSDetNet, an innovative deep neural network tailored for the autonomous detection of pointlike astronomical sources by leveraging feature-matching techniques. PSDetNet comprises two primary modules: feature extraction and matching localization. The feature extraction module is built on residual blocks and adopts an encoder–decoder framework to distill features from images robustly. The matching localization module employs a patch-by-patch comparison against a preconstructed template, which is crafted through the alignment and weighted aggregation of numerous exemplar pointlike source samples, capturing the quintessential distribution characteristics of pointlike sources. The experimental results demonstrate that this network can accurately detect pointlike sources in astronomical imagery with high purity and completeness. It operates end to end and uses a fully convolutional architecture that allows for flexible processing of images of any size. This ability considerably enhances its applicability across various practical scenarios.

Keywords: Optical identification, Astronomical seeing, Astronomical object identification
Data-space Validation of High-dimensional Models by Comparing Sample Quantiles. We present a simple method for assessing the predictive performance of high-dimensional models directly in data space when only samples are available. Our approach is to compare the quantiles of observables predicted by a model to those of the observables themselves. In cases where the dimensionality of the observables is large (e.g., multiband galaxy photometry), we advocate that the comparison is made after projection onto a set of principal axes to reduce the dimensionality. We demonstrate our method on a series of two-dimensional examples. We then apply it to results from a state-of-the-art generative model for galaxy photometry (pop-cosmos) that generates predictions of colors and magnitudes by forward simulating from a 16-dimensional distribution of physical parameters represented by a score-based diffusion model. We validate the predictive performance of this model directly in a space of nine broadband colors. Although motivated by this specific example, we expect that the techniques we present will be broadly useful for evaluating the performance of flexible, nonparametric population models of this kind, and other settings where two sets of samples are to be compared.

Keywords: Astrostatistics techniques, Bootstrap, Principal component analysis, Galaxy photometry, Redshift surveys
FASHI: An Untargeted Survey of the 21 cm H I Absorption Galaxies with FAST. The FAST All Sky H I survey (FASHI) will cover the entire observable sky (∼22,000 square degrees) with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). With the currently released data, we perform an untargeted survey of 21 cm H I absorption galaxies at redshift z ≲ 0.09 over an area of about 10,000 square degrees. We have detected 51 H I absorbers, including 21 previously known and 30 new ones. The probability of occurrence for the H I absorbers in all H I galaxies is 1/1078. The radio flux densities of the FASHI absorbers are mainly concentrated in the range of S 1.4GHz = 10 ∼ 100 mJy, but also as low as 2.6 ± 0.4 mJy. We find that the host galaxies of the associated H I absorbers have relatively high star formation rates, and there is a negative correlation between the H I column density and the stellar mass in the host galaxy. Consequently, FAST has significantly improved the capabilities and performance for H I absorption observations and has provided a true untargeted survey of 21 cm H I absorption galaxies for such studies.

Keywords: Extragalactic radio sources, Radio telescopes, Redshift surveys, H I line emission
Prediction of Large Solar Flares Based on SHARP and High-energy-density Magnetic Field Parameters. The existing flare prediction primarily relies on photospheric magnetic field parameters from the entire active region (AR), such as Space-Weather HMI Activity Region Patches (SHARP) parameters. However, these parameters may not capture the details of the AR evolution preceding flares. The magnetic structure within the core area of an AR is essential for predicting large solar flares. This paper utilizes the area of high photospheric free energy density (high-energy-density, hereafter HED, region) as a proxy for the AR core region. We construct two data sets: SHARP and HED data sets. The ARs contained in both data sets are identical. Furthermore, the start and end times for the same AR in both data sets are identical. We develop six models for 24 hr solar flare forecasting, utilizing SHARP and HED data sets. We then compare their categorical and probabilistic forecasting performance. Additionally, we conduct an analysis of parameter importance. The main results are as follows: (1) Among the six solar flare prediction models, the models using HED parameters outperform those using SHARP parameters in both categorical and probabilistic prediction, indicating the important role of the HED region in the flare initiation process. (2) The transformer flare prediction model stands out significantly in true skill statistic and Brier skill score, surpassing the other models. (3) In parameter importance analysis, the total photospheric free magnetic energy density (E free) within the HED parameters excels in both categorical and probabilistic forecasting. Similarly, among the SHARP parameters, the R_VALUE stands out as the most effective parameter for both categorical and probabilistic forecasting.

Keywords: Solar activity, Solar active region magnetic fields, Solar flares, Astronomy data analysis
The Local Ultraviolet to Infrared Treasury. I. Survey Overview of the Broadband Imaging. The Local Ultraviolet to Infrared Treasury (LUVIT) is a Hubble Space Telescope program that combines newly acquired data in the near-ultraviolet (NUV), optical, and near-infrared (NIR) with archival optical and NIR imaging to produce multiband panchromatic resolved stellar catalogs for 23 pointings in 22 low-mass, star-forming galaxies ranging in distance from the outskirts of the Local Group to ∼3.8 Mpc. We describe the survey design, detail the LUVIT broadband filter observations and the archival data sets included in the LUVIT reductions, and summarize the simultaneous multiband data reduction steps. The spatial distributions and color–magnitude diagrams (CMDs) from the resulting stellar catalogs are presented for each target, from the NUV to the NIR. We demonstrate in which regions of the CMDs stars with NUV and optical, optical and NIR, and NUV through NIR detections reside. For each target, we use the results from artificial star tests to measure representative completeness, bias, and total photometric uncertainty as a function of magnitude in each broadband filter. We also assess which LUVIT targets have significant spatial variation in the fraction of stars recovered at a given magnitude. The panchromatic LUVIT stellar catalogs will provide a rich legacy data set for a host of resolved stellar population studies.

Keywords: Stellar populations, Dwarf irregular galaxies, Multi-color photometry