Sazuna/UAT_keywords huggingface dataset:
Broad-line Regions behind Haze: The Intrinsic Shape of the Brγ Line and Its Origin in a Type 1 Seyfert Galaxy. The broad-line region (BLR) of active galactic nuclei is an essential component, yet its small size keeps its origin, structure, and kinematics uncertain. Infrared interferometry with VLTI/GRAVITY is now resolving the BLR-scale emission, with data for NGC 3783 consistent with a rotating, geometrically thick configuration. However, the processes shaping the spectra remain poorly constrained, and the cloud models are tuned phenomenologically rather than derived from first-principle predictions. We address this by coupling three-dimensional radiation-hydrodynamic (RHD) simulations of gas around a supermassive black hole with radiative-transfer calculations using CLOUDY, comparing the results to the SINFONI Brγ profile of NGC 3783. We find that Brγ arises from ionized gas in the surface of the rotating thin disk, with electron temperatures of approximately Te ≍ 104 K and number densities of ne ≍ 108─1011 cm−3. However, the intrinsic line profile produced by the RHD kinematics is narrower than observed and displays a substructure. An approximate treatment of the electron scattering suggests that scattering in the surrounding diffuse ionized gas significantly broadens and smooths the intrinsic Brγ profile, making it consistent with the observed profile. This scattering medium has an electron temperature of 104─105 K and a number density of n ≲ 108 cm−3. Although a best-fit viewing angle of ≍15° is suggested, the scattered line is notably less sensitive to inclination than the intrinsic line. The observed BLR profiles may be understood as the intrinsic emission viewed through an electron-scattering haze, such that some spectral detail is plausibly redistributed rather than seen directly.

Keywords: Active galaxies
Particle Acceleration and Depolarization in the Protostellar Jet Knots HH 80 and HH 81. Linearly polarized emission is a powerful tracer of magnetic field geometry and particle acceleration in protostellar jets. We present a polarimetric study of the Herbig─Haro (HH) objects HH 80 and HH 81, where nonthermal emission has been confirmed through spectral index measurements at low frequencies. We carried out observations of HH 80 and HH 81 with the Karl G. Jansky Very Large Array at 4─6 GHz. Unlike the inner jet knots, no linear polarization is detected towards the knots HH 80 and HH 81. We place a 3σ upper limit of 30 μJy on the polarization intensity, corresponding to fractional polarization limits of  Πmax≍0.02  and 0.01 for HH 80 and HH 81, respectively. To interpret this nondetection, we assess the conditions for synchrotron polarization and the impact of depolarization mechanisms. The shock cooling parameter χs is lower in these outermost HH objects than in the inner knots, indicating that the reverse shocks in HH 80─81 are less efficient at accelerating relativistic electrons compared with the inner knots. Moreover, Faraday depolarization appears severe: the dispersion in the estimated rotation measure (RM) σRM ∼ 400 rad m−2 is comparable to or larger than observed RM values themselves. This is consistent with strong fluctuations and turbulence. Together with beam depolarization, these effects can suppress the observable fractional polarization flux densities below the detectable thresholds. We conclude that reduced acceleration efficiency (when compared to inner knots) and strong depolarization account for the absence of polarized emission towards HH 80 and HH 81.

Keywords: Polarimetry, Interstellar magnetic fields, Star formation, Interstellar synchrotron emission, Protostars, Radio astronomy
Hierarchical Test of Lorentz Invariance with Gamma-Ray Burst Spectral-lag Measurements. Gamma-ray bursts (GRBs) are among the most potent probes of Lorentz invariance violation (LIV), offering direct constraints on the quantum gravity energy scale (EQG) based on observations of energy-dependent time lags. Individual GRBs with well-defined positive-to-negative lag transitions have been used to set lower limits on EQG, but they suffer from uncertainties of spectral-lag measurements and systematics due to theoretical modeling of each burst. Here, we combine observations of 32 GRBs with positive-to-negative lag transitions to derive a statistically robust constraint on EQG through hierarchical Bayesian inference. We find that the dominant systematic uncertainty in LIV constraints arises from the intrinsic lag modeling. Accounting for this uncertainty with cubic spline interpolation, we derive robust limits of EQG,1 ≥ 4.37 × 1016 GeV for linear LIV and EQG,2 ≥ 3.02 × 108 GeV for quadratic LIV. We find that the probability for LIV, i.e., EQG,1 being below the Planck scale, is estimated to be around 90%, which we conclude as no significant evidence for LIV signatures in current GRB spectral lag observations. Our hierarchical approach provides a rigorous statistical framework for future LIV searches and can be extended to incorporate multimessenger observations.

Keywords: Gamma-ray bursts, Quantum gravity
Plasma Characteristics of Active Region Footpoints before Eruptive and Confined Flares. Solar flares are powerful, explosive events that occur in solar active regions (ARs). They are typically classified as either eruptive or confined, depending on whether they are associated with coronal mass ejections. While many studies have focused on magnetic field evolution during flares or over the full AR lifecycle, less attention has been given to plasma conditions shortly before flare onset. In this study, we investigate plasma characteristics in AR footpoints during the 1 to 2 hr preceding flare onset, using high-cadence data from the Solar Dynamics Observatory Atmospheric Imaging Assembly and Hinode EUV Imaging Spectrometer. Through differential emission measure and spectral analyses, we examine temporal variations in Doppler velocity, nonthermal velocity, and plasma density across four footpoint regions for two representative events: an M2.6 eruptive flare and an M1.4 confined flare. The results reveal distinct preflare signatures: prior to the eruptive flare, we observe increasing upflow speeds and decreasing plasma density, while the confined flare exhibits decreasing upflow speeds and stable or increasing densities, depending on location. Although nonthermal velocities differ in magnitude between the two flares, they show no consistent temporal trend. These findings confirm and extend earlier observations, particularly by identifying new features in density evolution. We propose that loop expansion plays a critical role in shaping the distinct preflare behaviors of eruptive and confined events.

Keywords: Solar flares, Solar extreme ultraviolet emission, Solar flare spectra, Solar coronal mass ejections, Spectroscopy, Solar activity
Forging Neon-distilling White Dwarfs in the Stellar Engulfments of Helium White Dwarfs. Once carbon─oxygen white dwarfs cool sufficiently, they crystallize from the inside out. If the white dwarf is rich enough in 22Ne, these crystallized solids are buoyant and rapidly rise, efficiently liberating potential energy, which may halt the cooling of the white dwarf or power magnetic phenomena. Although this 22Ne distillation process may explain the cooling anomaly in Q-branch white dwarfs and anomalous emission lines in DAHe white dwarfs, its operation demands unusually high 22Ne abundances not generically predicted by isolated stellar evolution. We show that the engulfments of helium white dwarfs by both main-sequence and red giant stars can result in carbon─oxygen white dwarfs with 22Ne abundances high enough to distill 22Ne. This enhancement occurs because carbon dredged up following an especially energetic and off-center helium flash can be processed into 22Ne by subsequent hydrogen shell burning and helium shell burning. 22Ne-distilling white dwarfs from these merger channels are predicted to be somewhat more massive than typical white dwarfs (up to ≃0.7M⊙) and may have anomalous rotation rates, consistent with DAHe white dwarfs. These binary formation channels for 22Ne-rich white dwarfs reveal new connections between binary interactions and white dwarf cooling phenomena.

Keywords: White dwarf stars, Red giant stars, Stellar mergers
The Growth of the Central Black Holes in Quasi-stars. Observations by JWST have confirmed the presence of supermassive black holes (BHs) at redshifts z ≳ 10, lending support to scenarios in which BHs experience rapid growth through intense gas accretion. Here we investigate the growth of a BH embedded at the center of a quasi-star, a theoretically predicted object formed via direct collapse. In a quasi-star, the central BH accretes at a highly super-Eddington rate, while the excess energy is transported outward by convection and radiated at approximately the Eddington luminosity of the entire star. We employ the open-source stellar evolution code MESA to construct quasi-star models and follow the time-dependent growth of the central BH under different prescriptions for the accretion rate at the inner boundary Ri, and further considering the effect of winds. For the case Ri = NRB, where N is a constant and RB is the Bondi radius corresponding to the mass of the BH and the gas infalling onto it, our models terminate when the BH mass reaches a critical value  Mcrit(N)=cs,i3/(12N3G3πρi)  (where cs,i and ρi are the sound speed and density at Ri, respectively), a limit we also derive analytically. Models that feature an inner convective region matched to an outer adiabatic envelope exhibit BH growth up to approximately MBH/M⋆ ≃ 0.33, largely independent of the stellar mass M⋆ itself. This ratio is approximately preserved even in the presence of mass loss, as several properties of the model are independent of the quasi-star's total mass.

Keywords: Accretion, Early universe, Black hole physics, Quasars
The Most Probable Behavior of the Dark Energy Equation of State Indicates a Thawing Quintessence Field: Tomographic Alcock─Paczyński Test with Redshift-space Correlation Function II. We apply an extended Alcock─Paczyński (AP) test to the Sloan Digital Sky Survey data to constrain the dark energy models with the Chevallier─Polarski─Linder (CPL) parametrization of the dark energy equation of state. The extended AP test method uses the full shape of redshift-space two-point correlation function (CF) as the standard shape in order to measure the expansion history of the universe. We calibrate the standard shape by using the cosmology-dependent nonlinear evolution of the CF shape in the multiverse simulations. Further validation of the method and calibration of possible systematics are performed based on mock samples from the Horizon Run 4 simulation. Using the AP test alone, we constrain the flat CDM plus CPL-type dark energy model (flat wCPLCDM) to have  Ωm=0.290−0.031+0.029 ,  w0=−0.800−0.100+0.208 , and  wa=−0.238−0.972+0.650 . When combined with other results from the low-redshift universe, such as the Pantheon+ supernova compilation and DESI baryon acoustic oscillation data, the constraints on dark energy become  w0=−0.857−0.042+0.051 , and  wa=−0.153−0.356+0.347 . The best-fit wCPL(z) suggests no phantom-divide crossing at z &lt; 0.7, and the dark energy behavior is consistent with a thawing quintessence field. It is only when the CMB data are combined with late-time cosmological probes that a phantom-divide crossing at low redshift is favored.

Keywords: Cosmology, Large-scale structure of the universe, Dark energy
Probabilistic Interpolation of Sagittarius A*'s Multiwavelength Light Curves Using Diffusion Models. Understanding the variability of Sagittarius A* (Sgr A*) requires coordinated, multiwavelength observations that span the electromagnetic spectrum. In this work, we focus on data from four key observatories: Chandra in the X-ray (2─8 keV), GRAVITY on the Very Large Telescope in the near-infrared (2.2 μm), Spitzer in the infrared (4.5 μm), and the Atacama Large Millimeter/submillimeter Array in the submillimeter (340 GHz). These multiband observations are essential for probing the physics of accretion and emission near the black hole's event horizon, yet they suffer from irregular sampling, band-dependent noise, and substantial data gaps. These limitations complicate efforts to robustly identify flares and measure cross-band time lags, key diagnostics of the physical processes driving variability. To address this challenge, we introduce a diffusion-based generative model, for interpolating sparse, multivariate astrophysical time series. This represents the first application of score-based diffusion models to astronomical time series. We also present the first transformer-based model for light-curve reconstruction that includes calibrated uncertainty estimates. The models are trained on simulated light curves constructed to match the statistical and observational characteristics of real Sgr A* data. These simulations capture correlated multiband variability, realistic observation cadences, and wavelength-specific noise. We compare our models against a multi-output Gaussian process. The diffusion model achieves superior accuracy and competitive calibration across both simulated and real datasets, demonstrating the promise of diffusion models for high-fidelity, uncertainty-aware reconstruction of multiwavelength variability in Sgr A*.

Keywords: Black hole physics, Black holes, Gaussian Processes regression, Interdisciplinary astronomy, Galaxies
CORINOS. IV. Quantifying Baseline-fitting Uncertainties in SO<SUB>2</SUB> Ice Measurements with JWST/MIRI. Sulfur dioxide (SO2) ice has been tentatively detected in protostellar envelopes, but its reliability as a solid-state sulfur reservoir remains unclear. We present new measurements of SO2 ice from 6.8─8.5 μm toward four Class 0 protostars observed with JWST's Mid-Infrared (MIRI) Medium Resolution Spectrometer, as part of the COMs ORigin Investigated by the Next-generation Observatory in Space (CORINOS) program. The sample spans a luminosity range from 1 L⊙ (B335, IRAS 15398─3359) to 10 L⊙ (L483, Ser-emb 7). To assess continuum placement uncertainty in absorption spectra, we apply randomized polynomial fits over the restricted region. We fit laboratory spectra from the Leiden Ice Database for Astrochemistry using the open-source Python library Omnifit. We detect the 7.7 μm CH4 band in all sources and find its column density robust to baseline choice, providing a reference for evaluating the weaker SO2 feature on its blue shoulder and quantifying baseline-related uncertainty. Three SO2 laboratory ices were tested: pure SO2 ice yields 0.3%─1.2% of volatile sulfur may be locked in SO2 ice (lower and upper limits); CH3OH:SO2 ice gives 0.02%─0.18%, but with lower quality fitting. The best-fitting H2O:SO2 ice yields 0.2%─0.9%, which we consider the most realistic. These ranges define plausible bounds on SO2 ice abundances in our sample. We find evidence for SO2 in Ser-emb 7, L483, and IRAS 15398─3359, but emphasize the noisy spectrum of B335 prevents a definitive detection. Comparing SO2 ice abundances across the different environments, we assess how conditions influence the role of SO2 as a potential sulfur reservoir and implications for the longstanding "missing sulfur" problem.

Keywords: Protostars, James Webb Space Telescope, Ice spectroscopy, Astrochemistry
DESI Strong Lens Foundry. I. HST Observations and Modeling with GIGA-Lens. We present the Dark Energy Spectroscopic Instrument (DESI) Strong Lens Foundry. We discovered ∼3500 new strong gravitational lens candidates in the DESI Legacy Imaging Surveys using residual neural networks (ResNet). We observed a subset (51) of our candidates using the Hubble Space Telescope (HST). Except for one ambiguous case, we have confirmed 50 of the 51 candidates to be strong lenses. We also briefly describe spectroscopic follow-up observations by DESI and Keck NIRES programs. From this very rich data set, a number of studies will be carried out, including evaluating the quality of the ResNet search candidates and lens modeling. In this paper, we present our initial effort in these directions. In particular, as a demonstration, we present the lens model for DESI-165.4754−06.0423, with imaging data from HST, and lens and source redshifts from DESI and Keck NIRES, respectively. In this effort, we have applied a fully forward-modeling Bayesian approach (GIGA-Lens), using multiple GPUs, to a strong lens with HST data, and achieved statistical convergence.

Keywords: Bayesian statistics, Infrared spectroscopy, Strong gravitational lensing, Gravitational lensing, GPU computing, Galaxy spectroscopy
Mass─Radius Constraints for 2S 0918─549 from an RXTE Superexpansion Burst: A Direct Cooling-tail Analysis. Thermonuclear (Type I) X-ray bursts from accreting neutron stars (NSs) offer a means to determine NS mass (M) and radius (R) and thereby probe the properties of matter at supranuclear density. A subset of these events, photospheric radius-expansion bursts, provide a particularly powerful tool to constrain the NS M and R. Here, we apply the direct cooling-tail method to 2S 0918−549, using a rare superexpansion burst observed by Rossi X-ray Timing Explorer. We fit only the posttouchdown data within F/Ftd ∈ [0.6, 0.95], employing modern atmosphere models (pure-He and metal-enriched). The pure-He atmosphere yields a good description of the cooling tail (χ2/ν = 18.12/14), whereas metal-rich models fail; information-criterion tests (Akaike information criterion/Bayesian information criterion) disfavor adding a free absorption edge in every time bin, indicating that heavy-element ashes are unnecessary. The joint fit gives a distance d = 4.1─5.3 kpc and mass─radius constraints M = 1─2 M⊙ and R = 9.7─11.9 km (99% confidence). These results suggest that representative families of both gravity-bound and self-bound equations of state remain viable at the 1σ confidence level.

Keywords: Low-mass x-ray binary stars, Neutron stars, X-ray bursts
JWST Observations of Cosmic-Ray-excited H<SUB>2</SUB> in Barnard 68: Spatial Variations and Constraints on Cosmic-Ray Attenuation. We present James Webb Space Telescope (JWST) NIRSpec observations of the starless dark cloud Barnard 68 (B68) that reveal the spatially resolved signature of cosmic-ray-excited molecular hydrogen (CRXH2) emissions for the first time. Following up on our initial detection of CRXH2 emissions from B68, we now exploit JWST's sensitivity and spatial multiplexing to map CRXH2 rovibrational lines across 16 sight lines through the cloud. By disentangling the CRXH2 and UV-pumped H2 components, we isolate the para-H2-dominated spectrum attributable to cosmic-ray (CR) excitation. We find that there are significant spatial variations in the ratio of the CRXH2 line intensity to the line-of-sight H2 column density; these cannot be accounted for by dust extinction alone and demonstrate a clear attenuation of the CR flux with increasing shielding column. Modeling B68 as a Bonnor─Ebert sphere, we constrain both the unshielded CR ionization rate,  ζH2 , and how it decreases with shielding column. At a reference depth of N(H2) = 3 × 1021 cm−2, we infer  ζH2≍1.4×10−16  s−1, a factor of ≍3 higher than the average value derived from H 3+  absorption studies. These results provide the most direct probe to date of CR penetration into cold, dense gas, offering new constraints on both the microphysics of CR─H2 interactions and the attenuation of low-energy CRs in molecular clouds. Our findings establish CRXH2 emission as a powerful new diagnostic of the CR environment in interstellar space.

Keywords: Interstellar line emission, Infrared spectroscopy, Molecular clouds, Dark interstellar clouds, Interstellar medium, Cosmic rays
Investigating Enols Chemistry in the Interstellar Medium: Rotational Spectroscopy and Interstellar Search of (E)-1-Propenol. Enols represent highly reactive intermediates toward the synthesis of complex organic molecules in the interstellar medium (ISM) and serve as key tracers of nonequilibrium chemistry driven by Galactic cosmic rays. However, only few enols have been identified in the ISM, thus limiting the insights that can be derived from their observations. To expand the inventory of interstellar enols and improve our understanding of their chemistry, we provide the first spectroscopic characterization of 1-propenol, one of the simplest enols potentially observable in the ISM, which is a key step toward enabling its astronomical detection. 1-Propenol was generated through the retro Diels─Alder reaction of 3-methylnorborn-5-en-2-ol using a flash vacuum pyrolysis apparatus, and its rotational spectrum was recorded between 80 and 500 GHz using a millimeter/submillimeter-wave frequency-modulation spectrometer. High-level quantum chemical calculations supported the spectral analysis and provided accurate predictions of spectroscopic parameters. Over 2200 rotational transitions of (E)-1-propenol were successfully assigned and analyzed with the XIAM code, yielding precise rotational and centrifugal distortion constants and the methyl internal rotation barrier. Despite being essentially isoenergetic with the E form, (Z)-1-propenol could not be identified in our spectrum due to the experimental conditions. A targeted astronomical search was also carried out toward the Galactic center molecular cloud G+0.693-0.027 using ultrasensitive millimeter-wave surveys, which, however, did not reveal any hints of emission from (E)-1-propenol. Only an upper limit for its column density could be derived, which is fully consistent with ratios observed for other keto-enol pairs, indicating that more sensitive observations are required.

Keywords: Laboratory astrophysics, Interstellar abundances, Millimeter-wave spectroscopy, Astrochemistry, Interstellar medium
Fragmenting Filaments and Evolving Cores—Insights from Dust Polarization Study of a Filament in Northern Orion B. We present an analysis of polarized dust emission at 850 μm for a parsec-long filament in the northern part of the Orion B molecular cloud. The region was observed by the James Clerk Maxwell Telescope SCUBA-2/POL-2 polarimeter. The filament has a line mass (∼80 M⊙ pc−1) larger than the critical (magnetic) line mass (∼37 M⊙ pc−1) and hosts one starless, three prestellar, and four protostellar cores, with masses in the range 0.13 to 9.13 M⊙. The mean (debiased) polarization fraction (PF) of the filament and core pixels was calculated to be 5.3% ± 0.3% and 3.2% ± 0.3%, respectively, likely reflecting their distinct physical conditions. The PF for the cores does not depend on the type of core, and was found to decrease with increasing column density, varying from 6% to 11% at the filament edges to 1 −0.1+0.7 % in the denser parts (NH2 ≳ 2 × 1022 cm−2). Magnetic field orientation of the protostellar cores, in contrast to prestellar cores, appears to be relatively aligned with the magnetic field orientation of the local filament in this region. Using the Davis─Chandrasekhar─Fermi formalism, the plane-of-sky magnetic field strength for the protostellar cores (∼39─110 μG) was found to be higher than that of the prestellar cores (∼22─61 μG) and weakest for the starless core (∼6 μG). The average value for the filament was found to be ∼31 μG. The magnetic field-volume density relation for the prestellar/starless cores and protostellar cores suggests a transition from a weak field case to a strong field case as the cores evolve from prestellar to protostellar phase.

Keywords: Interstellar filaments, Interstellar magnetic fields, Star formation, Submillimeter astronomy, Polarimetry