Sazuna/UAT_keywords huggingface dataset:
The Atmospheric Response to Large Electron Beam Fluxes in Solar Flares. III. Comprehensive Modeling of the Brightest Observed Near-ultraviolet Continuum Source in an X9 Solar Flare. I report on the high-resolution spectra of the remarkable X9 solar flare of 2024 October 3 (SOL2024-10-03T12:08) and evaluate the extent to which nonthermal electron beams that generate dense chromospheric condensations can power very bright kernels in solar flares. One-dimensional radiative-hydrodynamic models predict extreme Hα near-wing broadening, bright continuum intensities, and a rapid Fe II red wing asymmetry evolution at the brightest near-UV (NUV) continuum source in the flare. Detailed comparisons to the spectral observations reveal that the Hα line is too broad, the Fe II red wing is too bright, and the NUV continuum decays too slowly in a fiducial high-flux beam model. However, chromospheric condensations with maximum electron densities of ne ≍ 5 × 1014 cm−3 and optical depths τ ≍ 1 in the near wing of Hα are consistent with the observed intensity of a broad spectrum in the southern ribbon. Model similarities demonstrate that Fe I emission lines and the far-UV (FUV) continuum intensity can form at chromospheric heights during flares, but I find that the ratios of the NUV to FUV continuum intensities are generally too large in the models. This suggests that radiative-hydrodynamic models of chromospheric condensations cool through T ≍ 30,000 K too rapidly. The larger-than-expected FUV continuum intensities are not nearly bright enough to explain recent stellar megaflare spectra from the Hubble Space Telescope.

Keywords: Hydrodynamical simulations, Solar flares, Solar flare spectra, Ultraviolet spectroscopy, Solar physics
Earliest Galaxy Evolution in the CANUCS+Technicolor Fields: Galaxy Properties at z ∼ 10─16 Seen with the Full NIRCam Medium- and Broadband Filters. We present a sample of zphot ∼ 10─16 galaxies by exploiting some of the richest JWST NIRCam imaging data, taken in the CANUCS survey in Cycle 1 and the Technicolor (TEC) survey in Cycle 2. The combination of the CANUCS+TEC provides multiepoch, deep NIRCam images in all medium bands (MBs) and broad bands (BBs) onboard NIRCam (22 filters in total), over  ∼23arcmin2  in three independent lines of sight. We select high-z galaxy candidates based on photometric redshifts, and obtain eight candidates at z ∼ 10─16, including a very robust candidate at z ∼ 15.4. The ultraviolet (UV) luminosity function (LF) from our sample is consistent with previous JWST studies showing a scatter of ∼0.6 dex across the literature, marking the significance of the field-to-field variance in interpreting galaxy abundance measurements at z &gt; 10. We find that the UV LF moderately evolves at z &gt; 10, and the LF normalization and the luminosity density decline by a factor of ∼7 from z ∼ 11 to z ∼ 15, indicating less steep evolution than z &lt; 11. We highlight the importance of MB filters, not only to minimize the contamination by low-z interlopers but also to maximize the completeness. In particular, faint and less blue galaxies could be missed when the sample is built solely on BB data. The contamination and incompleteness of BB-only selected samples can bias our views of earliest galaxy evolution at z &gt; 10, including the UV LF by ∼0.6 dex, the size─magnitude relation by ∼0.6 dex, and the UV slope-magnitude relation by ∆βUV ∼ −0.3.

Keywords: Luminosity function, Galaxy formation, Galaxy evolution, High-redshift galaxies, Galaxies
A Next-generation Exoplanet Atmospheric Retrieval Framework NEXOTRANS for Emission Spectroscopy: New Constraints and Atmospheric Characterization of WASP-69 b Using JWST NIRCam and MIRI Observations. Thermal emission spectra provide key insights into the atmospheric composition and especially the temperature structure of an exoplanet. With broader wavelength coverage, sensitivity, and higher resolution, JWST has enabled robust constraints on these properties, including detections of photochemical products. This advances the need for retrieval frameworks capable of navigating complex parameter spaces for accurate data interpretation. In this work, we introduce the emission retrieval module of NEXOTRANS, which employs both one- and two-stream radiative transfer approximations and leverages Bayesian and machine learning techniques for retrievals. It also incorporates approximate disequilibrium chemistry models to infer photochemical species like SO2. We applied NEXOTRANS to the JWST NIRCam and MIRI emission observations of WASP-69 b, covering the 2─12 μm range. The retrievals place robust constraints on the volume mixing ratios (VMR) of H2O, CO2, CO, CH4, and potential SO2. The best-fit model, i.e., free chemistry combined with nonuniform aerosol coverage, yields a log(VMR) =  −3.78−0.17+0.15  for H2O and  −5.77−0.10+0.09  for CO2, which has a sharp absorption at 4.3 μm. The second best-fit model, the hybrid equilibrium chemistry (utilizing equilibrium chemistry-grids) combined with nonuniform aerosol, yields a C/O of  0.42−0.13+0.17  and a metallicity of log[M/H] =  1.24−0.14+0.17 , corresponding to approximately 17.38 times the solar value. This hybrid chemistry retrieval also constrains SO2 with a log(VMR) =  −4.85−0.29+0.28 , indicating possible absorption features in the 7─8 μm range. These results highlight NEXOTRANS's capability to significantly advance JWST emission spectra interpretation, offering broader insights into exoplanetary atmospheres.

Keywords: Exoplanet atmospheric composition , Hot Jupiters, Exoplanets, Extrasolar gaseous giant planets, Exoplanet atmospheres, Exoplanet atmospheric structure
Compact Size, High ΣSFR: Defining Morphological Features of Lyα Emitters. The mechanisms of Lyα photon escape are key to understanding galaxy evolution and cosmic reionization, yet remain poorly understood. We investigate the UV-continuum sizes of 23 Lyα emitters (LAEs) at Cosmic Noon (1.7 &lt; z &lt; 3.3), extending previous size analyses to include fainter galaxies (MUV ≃ −14) using gravitational lensing. Our results show that these LAEs are unusually small for their luminosity, with a mean effective radius (reff) of 170 ± 140 pc. They follow a distinct size─luminosity relation, with an intercept at MUV = −21 approximately three times smaller than typical star-forming galaxies (SFGs) at similar redshifts. This relation, however, is consistent with that of low-redshift Green Pea galaxies, suggesting that LAEs maintain compact sizes across redshifts. We also find that Lyα equivalent width increases with decreasing reff, confirming previous findings. The small sizes of LAEs lead to high star formation surface densities (ΣSFR =1─600 M⊙ yr−1 kpc−2), clearly separating them from typical SFGs in the ΣSFR versus reff space. Given that high ΣSFR is linked to strong galactic outflows, our findings imply that compact morphology plays a key role in Lyα escape, likely facilitated by outflows that clear underdense channels in the intersetellar medium (ISM). Thus, these results demonstrate that compact size and high ΣSFR can help identify LAEs.

Keywords: Starburst galaxies, Strong gravitational lensing, Galaxy structure, Emission line galaxies, Lyman-alpha galaxies, Reionization
Exploring Hard X-Ray Properties of Gamma-Ray Emitting Narrow-line Seyfert I Galaxies through NuSTAR Observations. We studied the six gamma-ray-detected Narrow Line Seyfert 1 (NLSy1) galaxies using the hard X-ray observations from Nuclear Spectroscopic Telescope Array and optical g &amp; r band from Zwicky Transient Facility. The X-ray spectra corresponding to all objects are well-fitted with a power-law spectral model, and a strong "redder-when-brighter" (RWB) trend is seen, which is mostly seen in Blazars. The X-ray light curves were produced for all the available observations, and the Fvar is estimated. In 1H 0323+342, we found that Fvar lies between 9% and 22%, suggesting significant variability in the source. Similarly, for PKS 2004-447, we found Fvar lies between 10% and 21%. We see a strong X-ray and gamma-ray spectral index correlation among these objects, suggesting that these are produced through a similar process. Comparing the X-ray spectral index with other class objects, we see that NLSy1 galaxies are similar to LBL and IBL types. We see a negative trend of X-ray flux with the gamma-ray luminosity in these objects, suggesting an anticorrelation between them. A similar trend is seen between the X-ray flux, total jet power, and disk luminosity. The X-ray spectral index also shows a negative trend with total jet power and disk luminosity. The optical variability amplitude (in magnitude) lies between 0.90 and 2.32, and the fractional variability varies from 13% to 40%. The color─magnitude plot shows mostly the RWB trend, suggesting γ-NLSy1 are much closer to flat-spectrum radio quasars than BL Lacs. Our results, overall, summarize how the various parameters in gamma-ray-detected NLSy1 are connected.

Keywords: Accretion, Jets, Active galaxies, Seyfert galaxies, X-ray active galactic nuclei
The SOFIA Massive (SOMA) Radio Survey. II. Radio Emission from High-luminosity Protostars. We present centimeter continuum observations of seven high-luminosity massive protostars and their surrounding sources in regions with multiple targets, as part of the SOFIA Massive (SOMA) Star Formation Survey. With data from the Very Large Array and the Australia Telescope Compact Array, we analyze the spectral index, morphology, and multiplicity of the detected radio sources. The high-sensitivity, high-resolution observations allow us to resolve many sources; 65% of the reported sources are resolved at least within the synthesized beam. We report 15 new detections, 13 of which are entirely new, and 2 have counterparts at other wavelengths but are detected here for the first time at radio frequencies. We use the observations to build radio spectral energy distributions to calculate spectral indices. With radio morphologies and the spectral indices, we give assessments on the nature of the sources, highlighting six sources that display a radio jetlike morphology and a spectral index consistent with ionized jets. Combining with the SOMA Radio I sample, we present the radio─bolometric luminosity relation, especially probing the regime from Lbol ∼ 104 to 106L⊙. Here, we find a steep rise in radio luminosity, which is expected by models that transition from shock ionization to photoionization.

Keywords: Radio jets, Stellar jets, Star formation, Interstellar medium, Radio interferometry
Micro─Tidal Disruption Events at Galactic Centers. This work explores a scenario for micro─tidal disruption events (TDEs) triggered by close encounters between high-speed white dwarfs (WDs) and stellar-mass black holes (sBHs) in galactic centers. In this model, a WD orbiting the central massive black hole (MBH) is scattered by an sBH during the sBH's early extreme mass-ratio inspiral phase. We conservatively estimate these events occur a few times per year within z ≤ 3. Significant disruption of the WD occurs when the impact parameter is comparable to the WD's radius. We derive a mathematical criterion and confirm numerically by hydrodynamical simulations. With the increase of the impact parameter and the collision speed, the WD material captured by the sBH decreases while the material that remains self-gravitating increases. A part of the WD material becomes unbound from the sBH-WD system, and its mass ranges from nearly zero to ≥50%, reaching the peak value when the impact parameter is comparable to the WD's radius. We expect the subsequent capture of WD material by the sBH to produce a prompt X-ray burst (a micro-TDE), and the accretion of unbound debris onto the MBH can power a fainter, delayed optical flare. The properties of certain transient X-ray bursts observed by Einstein Probe are consistent with this micro-TDE picture.

Keywords: Black holes, White dwarf stars, Tidal disruption, Compact objects, X-ray bursts
Formation of Substructure in Luminous Submillimeter Galaxies (FOSSILS): Evidence of Multiple Pathways to Trigger Starbursts in Luminous Submillimeter Galaxies. We present an analysis of rest-frame optical and far-infrared continuum emission in three luminous submillimeter galaxies (SMGs) at 3.0 ≲ z ≲ 4.5. The SMGs are spatially resolved down to 400─500 pc ( ∼0.″05 ) resolution by James Webb Space Telescope and Atacama Large Millimeter/submillimeter Array observations. Despite similarities in their observed far-infrared properties (flux density, infrared luminosity, and effective radius), the three SMGs exhibit heterogeneous morphologies both across wavelengths and among the sources themselves. While two of them (AzTEC-4 and AzTEC-8) show a disk-like structure in the optical continuum, AzTEC-1 is dominated by a highly concentrated component with a Sérsic index of n = 5.4, where its far-infrared continuum emission is clumpy and less concentrated. AzTEC-4, which is confirmed to be at z = 4.198, shows a two-arm spiral of dust, but not in the stellar distribution. These three SMGs exemplify that multiple physical mechanisms exist in triggering starbursts in luminous SMGs at high redshift: secular instability in gas disks (AzTEC-4) in addition to possible minor mergers (AzTEC-8), and a combination of the efficient gas supply to the central core induced by a gas-rich major merger and the re-formation of a cold gas disk (AzTEC-1).

Keywords: Starburst galaxies, High-redshift galaxies, Galaxy evolution
No Evidence for Accretion around the Intermediate-mass Black Hole in Omega Centauri. For over a decade, both theoretical predictions and observational studies have suggested that ω Centauri (ω Cen), the most massive Milky Way globular cluster, might harbor an intermediate-mass black hole (IMBH). Recently, identification of fast-moving stars in the core of ω Cen provided the strongest evidence to date for the presence of such an IMBH. One of the key questions in the study of IMBHs is their accretion efficiency, which determines their radio and X-ray signatures. We investigate the accretion signature of the IMBH in ω Cen with ultradeep radio continuum observations of the central region of the cluster. Using approximately 170 hr of Australia Telescope Compact Array observations, we achieve a root-mean-square noise of 1.1 μJy at 7.25 GHz, making this the most sensitive radio image of the cluster to date. We detect no radio emission at any of the proposed centers of the cluster, imposing stringent constraints on the presence of an accreting IMBH in ω Cen. Considering the fundamental plane of black hole activity, our findings indicate that the accretion efficiency around the black hole is exceptionally low (with a conservative 3σ upper limit of ϵ ≲ 4 × 10−3).

Keywords: Globular star clusters, Intermediate-mass black holes, Black holes
Direct Numerical Simulations of Oxygen-flame-driven Deflagration-to-detonation Transition in Type Ia Supernovae. We present direct numerical simulations demonstrating deflagration-to-detonation transition (DDT) driven by oxygen flames in Type Ia supernova progenitors. Using the Castro hydrodynamics code coupled with the "aprox13" 13-isotope nuclear network, we simulate combustion in isolated fuel regions where oxygen flames trail carbon flames. In a fiducial 1D run at ρ0 = 3.5 × 107 g cm−3 we observe spontaneous DDT of the oxygen flame via the Zel'dovich gradient mechanism when the carbon─oxygen separation reaches ∼10 km. The oxygen detonation then captures the carbon flame and triggers a stable carbon detonation. Systematic 1D parameter scans show that successful carbon DDT requires upstream densities in the range (3.1─3.6) × 107g cm−3 and a minimum carbon-flame thickness of ≳20 m. 2D simulations confirm DDT and demonstrate that the multidimensional cellular structure of the oxygen detonation can promote carbon detonation at somewhat lower densities than in one dimension. These results provide direct numerical evidence that oxygen-flame-driven DDT is physically plausible in turbulent white-dwarf environments and underscore the importance of multidimensional effects for Type Ia supernova explosion modeling.

Keywords: Hydrodynamical simulations, Hydrodynamics, Nuclear astrophysics, Type Ia supernovae, Astrophysical explosive burning, Astrophysical fluid dynamics
Long-term Mid-infrared Color Variations of Narrow-line Seyfert 1 Galaxies. We present a systematic investigation of long-term mid-infrared (MIR) color variability in 1718 narrow-line Seyfert 1 galaxies (NLSy1s) using 14 yr of Wide-field Infrared Survey Explorer/NEOWISE monitoring data. Through Pearson correlation analysis between photometric magnitude and color, we identify (1) a radio-quiet NLSy1 (RQ-NLSy1) population comprising 230 bluer-when-brighter (BWB) sources, 131 redder-when-brighter (RWB) sources, and 1323 objects showing weak or statistically insignificant color variations; and (2) a radio-loud NLSy1 (RL-NLSy1) population containing 5 BWBs, 2 RWBs, and 27 sources with weak/no color variations. Our analysis reveals that the BWB tendency strengthens significantly in galaxies with redder mean MIR colors  W1 -W2  and lower starlight contamination. Furthermore, this color-change pattern demonstrates that the most bolometric luminous sources exhibit the most pronounced BWB behavior. While similar trends exist for black hole mass and Eddington ratio, bolometric luminosity appears to be the primary physical driver. Potential origins of these variations (e.g., host galaxy contribution, accretion disk variability, and dust reprocessing) are discussed. We conclude that temperature-dependent dust reprocessing dominates the observed BWB, RWB, and no/weak variation patterns. This interpretation may also apply to similar MIR color variations (MCVs) observed in other extragalactic MIR transients, such as tidal disruption events, ambiguous nuclear transients, and changing-look AGNs. In addition, we find no significant difference in long-term MCVs between RL-NLSy1s and RQ-NLSy1s; however, RL-NLSy1s show significantly greater dispersion in intrinsic variability amplitude compared to RQ-NLSy1s due to jet-induced complexity, where nonthermal synchrotron emission from relativistic jets obscures thermal dust signatures.

Keywords: Infrared astronomy, Seyfert galaxies, Black holes
Detecting Population III Gamma-Ray Bursts with Einstein Probe and Space-based Multiband Astronomical Variable Objects Monitor. High-redshift gamma-ray bursts (GRBs), putative counterparts of massive, low-metallicity population III (Pop III) stars, are a promising probe of the first stars. We assess the detectability of these Pop III GRBs using a metallicity-based progenitor criterion and cosmological N-body/hydrodynamical simulations with three distinct Pop III initial mass functions (IMFs), focusing on the capabilities of the Wide-field X-ray Telescope (WXT) aboard the Einstein Probe (EP) and the coded-mask gamma-ray imager (ECLAIRs) aboard the Space-based multiband astronomical Variable Objects Monitor (SVOM). Our population synthesis model, calibrated to Swift data, predicts the following population II/I (Pop II/I) GRB detection rates at z &gt; 6: ∼2.4 events yr−1 for EP/WXT and ∼0.9 events yr−1 for SVOM/ECLAIRs. For the IMF with very massive first stars (100 − 500 M⊙), we derive upper limits on the Pop III GRB rate at z &gt; 6 of &lt;0.06 events yr−1 (EP/WXT) and &lt;0.13 events yr−1 (SVOM/ECLAIRs), based on the absence of confirmed Pop III progenitors in Swift bursts at z &gt; 5.5. Our results indicate that while Pop III GRBs are subdominant to Pop II/I GRBs at z &lt; 10, their fractional contribution rises significantly with redshift, reaching ∼8% (∼34%) at z &gt; 10 and ∼28% (∼68%) at z &gt; 16 for EP/WXT (SVOM/ECLAIRs). This trend is systematically enhanced in the other two IMF models, which adopt a lower stellar mass range of [0.1, 100] M⊙. We conclude that detecting Pop III GRBs at high redshifts is a realistic prospect, and any GRB detected at z &gt; 16 is most likely of Pop III origin.

Keywords: Star formation, Gamma-ray bursts, Population III stars
Impact of Spectral Coverage on Parameter Recovery in Blazar Modeling. Understanding the impact of spectral coverage on parameter recovery is critical for accurate interpretation of blazar spectra. In this study, we examine how the data coverage influences the reliability of parameter estimation within the one-zone synchrotron self-Compton (SSC) framework. Using OJ 287, TXS 0506+056, and Mrk 421 as representative of the low, intermediate, and high synchrotron peak (LSP, ISP, and HSP) subclasses, respectively, we generate synthetic spectral energy distributions based on their best-fit models and perform 1000 fits for each of the 21 observational configurations per source type. Our analysis quantifies the coverage probability for all model parameters, such as the magnetic field strength and the electron luminosity, and reveals that different blazar subclasses exhibit distinct sensitivities to spectral gaps. For LSPs, a minimal dataset comprising optical/UV, X-ray, and GeV γ-ray bands is sufficient for robust parameter inference. In contrast, ISPs and HSPs require broader spectral coverage to constrain the physical parameters. For ISP, we find that reliable parameter recovery can be achieved with two different minimal band combinations: (i) X-ray, high-energy (HE) γ-ray, and very HE γ-ray data, or (ii) optical/UV, X-ray, and HE γ-ray data. For HSPs, the minimal configuration enabling reliable parameter recovery includes the optical/UV, X-ray, and very high energy γ-ray bands. We discuss the role of very high energy γ-ray observations, showing that they significantly enhance parameter recovery for HSPs. Our results provide practical guidelines for designing optimized multiwavelength observation campaigns and for assessing the robustness of SSC model inferences under incomplete spectral coverage.

Keywords: Blazars, Astronomy data modeling, BL Lacertae objects, High energy astrophysics
Radio Burst Phenomenology of AD Leonis and Associated Signatures of Propagation Effects. We present the high-resolution radio dynamic spectra of AD Leonis (AD Leo) between 1.0 and 1.5 GHz taken by the Five-hundred-meter Aperture Spherical radio Telescope on 2023 December 1. Over a 15 minute period, we identify complex, superimposed spectrotemporal structures, including (1) broadband, second-long modulation lanes with downward frequency drifts, (2) narrowband (≍50 MHz), short-duration S-burst envelopes with upward drifts, and (3) even narrower (≍10 MHz), millisecond-scale S-burst striae within these envelopes. Using the discrete Fourier transform and autocorrelation function, we identify two dominant periodic emission patterns, corresponding to the periodicities of the S-bursts (≍0.1 s) and the striae (≍0.01 s). The complex superposition of diverse time-frequency structures poses a challenge to interpreting all the emission variability as intrinsic to the source. We propose that the modulation lanes could be a propagation effect as the radio waves traverse an inhomogeneous, regularly structured plasma region in the AD Leo's magnetosphere. By modelling a plasma screen with sinusoidal phase variation in one dimension, we show that we could qualitatively reconstruct the observed modulation lanes. The origin of the finest structures, the striae, remains unclear. Our work highlights that propagation effects in the stellar magnetosphere can potentially probe kilometer-scale structures in the emission regions and provide novel constraints on density inhomogeneities caused by magnetohydrodynamic waves that are difficult to access by other means.

Keywords: M dwarf stars, Radio bursts, Interstellar scintillation