Sazuna/UAT_keywords huggingface dataset:
Different Origins of Nucleated and Nonnucleated Dwarf Elliptical Galaxies: Identified by Deep Learning. Dwarf elliptical galaxies (dEs) are the dominant population in galaxy clusters and serve as ideal probes for studying the environmental impact on galactic evolution. A substantial fraction of dEs are known to harbor central nuclei, which are among the densest stellar systems in the Universe. The large-scale distribution and the underlying origin of nucleated and nonnucleated dEs remain unresolved. Using a state-of-the-art machine learning framework, we systematically scan the Virgo cluster region (15° × 20° centered at R. A. = 187 .° 2 and decl. = 9 .° 6) and construct the largest homogeneous sample of dEs (a total of 2123) with robust nucleus classifications. We find that nucleated dEs are more spatially clustered and exhibit a stronger association with massive galaxies than their nonnucleated counterparts. This suggests that most nucleated dEs likely formed alongside massive galaxies within the cluster (i.e., the in situ formation). In contrast, nonnucleated dEs are more widely distributed across the cluster and align more closely with Virgo's global potential well, as traced by the cluster's hot gas. This indicates that most nonnucleated dEs originated outside the cluster (i.e., the ex situ formation) and were later accreted and redistributed within it. Our findings shed new light on how dEs and their central nuclei form and evolve.

Keywords: Galaxy environments, Dwarf galaxies, Galaxy nuclei
1D Vlasov Simulations of QED Cascades over Pulsar Polar Caps. Recent developments in the study of pulsar radio emission revealed that the microphysics of quantum electrodynamic pair cascades at pulsar polar caps may be responsible for generating the observed coherent radio waves. However, modeling the pair cascades in the polar cap region poses significant challenges, particularly under conditions of high plasma multiplicity. Traditional particle-in-cell (PIC) methods often face rapidly increasing computational costs as the multiplicity grows exponentially. To address this issue, we present a new simulation code using the Vlasov method, which efficiently simulates the evolution of charged particle distribution functions in phase space without a proportional increase in computational expense at high multiplicities. We apply this code to study e± pair cascades in 1D, incorporating key physical processes such as curvature radiation, radiation reaction, and magnetic pair production. We study both the Ruderman─Sutherland and the space-charge-limited flow regimes, and find quasiperiodic gap formation and pair production bursts in both cases. These features produce strong electric field oscillations, potentially enabling coherent radio emission. We construct a unified analytic model that describes the key features of the polar cap cascade, which can be used to estimate the return current heating rate that can be used to inform X-ray hotspot models. Spectral analysis shows that a significant amount of energy is carried in superluminal modes—collective excitations that could connect to observed radio features. Our results align with previous PIC studies while offering enhanced fidelity in both dense and rarefied regions.

Keywords: Neutron stars, Radio pulsars, High energy astrophysics, Plasma physics
Dynamical Masses and Radiative Transfer Modeling of HD 698: A Be Binary in Evolutionary Transition. We present a detailed analysis of the early post-mass-transfer binary system HD 698 (V742 Cas), combining high-resolution optical spectroscopy, long-baseline interferometry, and radiative transfer modeling. Counter-phased RV curves reveal a circular orbit with a period of 55.927 ± 0.001 d and component masses of MBe = 7.48 ± 0.07 M⊙ and Mcomp = 1.23 ± 0.02 M⊙. The Be primary is traced via broad Hα wings, while narrow metallic absorption lines originate from a slowly rotating companion. The angular separation measured via interferometry implies a dynamical distance of 888 ± 5 pc. The spectral energy distribution is best reproduced with a color excess E(B − V) = 0.321 ± 0.016 due to interstellar reddening and a moderately dense viscous decretion disk with base density ρ0 ≃ 5 × 10−12 g cm−3 at r = Req, declining radially as ρ(r) ∝ r−n with n = 3.0. The companion is found to be a luminous and inflated star with  Teff,comp=10.0−0.1+0.2  kK,  Rcomp=13.1−0.2+0.2R⊙ , and  logL/L⊙=3.19 , contributing significantly to the flux (Lcomp/LBe ∼ 0.3). Spectral line mismatches provide further circumstantial evidence that the companion is hydrogen poor, consistent with a stripped-envelope star enriched by CNO processing. HD 698 thus belongs to the emerging class of Be + bloated O/B binaries, representing a short-lived, high-luminosity post-mass-transfer phase, when the stripped donor is still spectroscopically detectable before reaching the subdwarf phase.

Keywords: Circumstellar matter, Be stars, Binary stars, Emission line stars
Magnetic Fields in the Bones of the Milky Way. Stars primarily form in galactic spiral arms within dense, filamentary molecular clouds. The largest and most elongated of these molecular clouds are referred to as "bones," which are massive, velocity-coherent filaments (lengths ∼20 to &gt;100 pc, widths ∼1─2 pc) that run approximately parallel and in close proximity to the Galactic plane. While these bones have been generally well characterized, the importance and structure of their magnetic fields (B-fields) remain largely unconstrained. Through the Stratospheric Observatory for Infrared Astronomy Legacy program FIlaments Extremely Long and Dark: a Magnetic Polarization Survey (FIELDMAPS), we mapped the B-fields of 10 bones in the Milky Way. We found that their B-fields are varied, with no single preferred alignment along the entire spine of the bones. At higher column densities, the spines of the bones are more likely to align perpendicularly to the B-fields, although this is not ubiquitous, and the alignment shows no strong correlation with the locations of identified young stellar objects. We estimated the B-field strengths across the bones and found them to be ∼30─150 μG at parsec scales. Despite the generally low virial parameters, the B-fields are strong compared to the local gravity, suggesting that B-fields play a significant role in resisting global collapse. Moreover, the B-fields may slow and guide gas flow during dissipation. Recent star formation within the bones may be due to high-density pockets at smaller scales, which could have formed before or simultaneously with the bones.

Keywords: Interstellar dust, Galaxy magnetic fields, Interstellar filaments, Dense interstellar clouds, Interstellar magnetic fields, Young stellar objects, Star formation, Dust continuum emission, Protostars, Polarimetry
Dual Origins of Rapid Flare Ribbon Downflows in an X9-class Solar Flare. We detect rapid downflows of 150─217 km s−1 in Interface Region Imaging Spectrograph (or IRIS) Si IV 1402.77 nm measurements of an X9-class solar flare on 2024 October 3. The fast redshift values persist for over 15 minutes from flare onset, and can be split into two distinct stages of behavior, suggesting that multiple mechanisms are responsible for the downwards acceleration of flare ribbon plasma. The first stage of rapid downflows is synchronized with peaks in emission from the Advanced Space-based Solar Observatory Hard X-ray Imager (or ASO-S HXI) and Large Yield Radiometer (or LYRA) Lyα measurements, indicating that the chromospheric downflows (with a maximum redshift of 176 km s−1) result from chromospheric condensations associated with impulsive energy release in the solar flare. Later in the event, strong Si IV flare ribbon downflows persist (to a maximum value of 217 km s−1), despite the magnetic flux rate falling to zero and high-energy hard X-ray (HXR) and Lyα measurements returning to background levels. This is reflective of downflows in the flare ribbon footpoints of flare-induced coronal rain. HXR spectral analysis supports this scenario, revealing strong nonthermal emission during the initial downflow stage, falling near background levels by the second stage. Despite these distinct and contrasting stages of ribbon behavior, Si IV Doppler velocities exhibit quasiperiodic pulsations with a constant ∼50 s period across the 15 minutes of flare evolution (independent of loop length). We deduce that these pulsations are likely caused by MHD oscillations in the magnetic arcade. Finally, we utilize machine learning K-means clustering methods to quantify line profile variations during the stages of rapid downflows.

Keywords: Solar flares, Solar ultraviolet emission, Solar magnetic reconnection, Solar flare spectra, Solar x-ray emission, Solar oscillations, Active solar chromosphere
Constraining the Baryon Content of Cosmic Filaments Using Localized Fast Radio Bursts and DESI Imaging Data. Cosmic filaments are thought to host a substantial fraction of the missing baryons at redshifts z &lt; 2. In this study, we constraint the baryonic content of these filaments using localized fast radio bursts (FRBs). Filaments are identified from the galaxy distribution in the Dark Energy Spectroscopic Instrument imaging surveys using the DisPerSE algorithm. We find tentative evidence (∼3σ significance) for a divergence in the relationship between the dispersion measure contributed by the intergalactic medium and redshift for FRBs whose signals intersect cosmic filaments compared to those that do not, suggesting excess baryons in the filamentary structures. Assuming an isothermal β-model gas profile with β = 2/3, this discrepancy is best explained by a central baryon overdensity of  δ0=21−12+13 , broadly consistent with previous simulation and observational results. The inferred baryon fraction residing in filaments decreases with redshift, from approximately 0.25 to 0.30 Ωb at z = 0.02 to 0.15─0.30 Ωb at z = 0.5, and 0.03 to 0.04 Ωb at z = 0.8. These estimates are likely lower bounds, particularly at z &gt; 0.5, due to the limited number of identified filaments and localized FRBs at higher redshifts. We also examine various factors that may affect the statistical significance of our results. Our method offers an independent approach to tracing baryons in cosmic filaments and underscores the importance of expanding localized FRB samples and deepening galaxy surveys—key steps toward refining these estimates and addressing the missing baryon problem.

Keywords: Cosmology, Large-scale structure of the universe, Radio bursts, Cosmic web, Intergalactic medium, Radio transient sources
The SDSS-V Black Hole Mapper Reverberation Mapping Project: Light Echoes of the Coronal-line Region in a Luminous Quasar. We present a reverberation mapping (RM) analysis of the coronal line [Ne V] λ3427-emitting region of the quasar COS168 (SDSS J095910.30+020732.2). [Ne V] λ3427 is known as one of the "coronal lines," which are a species of emission lines present in active galactic nuclei (AGN) spectra with high ionization potentials (≥ 100 eV) that can serve as tracers for AGN activity. The spatial extent of the coronal line region has been studied with only spatial resolving techniques that are not sensitive to the innermost regions of AGN. Through our RM analysis of [Ne V] λ3427, we measure a nominal "optimal emission radius" for [Ne V] λ3427 of  381.1−22+16  lt-day (observed frame). We place the coronal line region in context with other AGN regions by comparing it with the characteristic radius of Hα, the dust-sublimation radius, and the dusty torus. The coronal line region is located at a larger radius from the black hole than the characteristic radius of the dusty torus, measured using a torus─radius luminosity relationship. The virial product (v2R/G) of both Hα and [Ne V] λ3427 is consistent within the uncertainties, implying that the coronal line region, as probed by the [Ne V] λ3427 line, may be in a virialized orbit that is dominated by the gravitational potential of the black hole. This plausibly suggests that coronal lines could be an effective method for estimating black hole masses.

Keywords: Supermassive black holes, Reverberation mapping, Active galactic nuclei, Quasars
The GHOSDT Simulations. II. Missing H<SUB>2</SUB> in Simulations of a Self-regulated Interstellar Medium. Observations in the Galaxy and nearby spirals have established that the H I-to-H2 transition at solar metallicity occurs at gas weight of PDE/kB ≍ 104 K cm−3, similar to solar neighborhood conditions. Even so, state-of-the-art models of a self-regulated interstellar medium (ISM) underproduce the molecular fraction ( Rmol≡MH2/MHI ) at solar neighborhood conditions by a factor of ≍2─4. We use the GHOSDT suite of simulations at a mass resolution range of 100─0.25 M⊙(effective spatial resolution range of ∼20─0.05 pc) run for 500 Myr to show how this problem is affected by modeling choices such as the inclusion of photoionizing radiation, assumed supernova energy, numerical resolution, inclusion of magnetic fields, and including a model for subgrid clumping. We find that Rmol is not converged even at a resolution of 1 M⊙, with Rmol increasing by a factor of 2 when resolution is improved from 10 to 1 M⊙. Models excluding either photoionization or magnetic fields result in a factor 2 reduction in Rmol. The only model that agrees with the observed value of Rmol includes our subgrid clumping model, which enhances Rmol by a factor of ∼3 compared with our fiducial model. This increases the time-averaged Rmol to 0.25, in agreement with the solar circle value, and closer to the observed median value of 0.42 in regions comparable to the solar neighborhood in nearby spirals. Our findings show that small-scale clumping in the ISM plays a significant role in H2 formation even in high-resolution numerical simulations.

Keywords: Hydrodynamical simulations, Interstellar medium
Comparing Inside-out and Outside-in Quenching Modes in MaNGA Observation and MaNGIA Simulation. This study probes the inside-out and outside-in quenching status of galaxies to understand the internal and external quenching sources responsible and their roles in galaxy evolution. We utilize data from the MaNGA survey and MaNGIA, a mock MaNGA sample derived from the high-resolution TNG50 simulation, comparing their spatially resolved galaxy properties to address this knowledge gap. Our analysis begins with an assessment of the integrated and spatially resolved star-forming main sequence, finding good agreement between the two datasets. We also observe excellent consistency in radial profiles of stellar mass surface density. Using the surface density of the specific star formation rate (ΣsSFR) to identify quenched regions, we investigate inside-out and outside-in quenching modes across different stellar masses and environments via three classification methods. We find broad consistency between MaNGA and MaNGIA for high-mass galaxies, where inside-out quenching dominates regardless of environment. However, for lower-mass galaxies, we find discrepancies in the dominant quenching mode in middle halo mass environments. The environmental dependence of inside-out quenching in both MaNGA and MaNGIA aligns with an internal quenching scenario, such as feedback from active galactic nuclei or morphology quenching. In contrast, MaNGA reveals a weaker environmental dependence for outside-in quenching, suggesting a roughly even contribution of multiple physical processes, whereas MaNGIA indicates a stronger environmental role, with group environments likely playing a significant part.

Keywords: Galaxy environments, Galactic and extragalactic astronomy
Pulsation Mode Identification and Classification of 46 High-amplitude δ Scuti Stars from 50 Candidates with TESS Observations. Asteroseismic modeling of high-amplitude δ Scuti (HADS) variables critically depends on their accurate classification, which provides robust constraints on stellar physical parameters. As a foundational step in this direction, we present a detailed analysis of the pulsational behavior of 50 HADS star candidates using high-precision photometric data from the Transiting Exoplanet Survey Satellite. We confirm 46 as genuine HADS variables, with 40 stars having their dominant frequencies identified for the first time. Among them, 7 pulsate solely in the fundamental mode, 21 exhibit the fundamental mode alongside at least one low-amplitude nonradial mode, 5 are pure double-mode pulsators (the fundamental and first-overtone modes), and 13 show double-mode pulsations accompanied by additional low-amplitude nonradial modes. The remaining four stars are classified as other types of variables: two (TIC 69546708 and TIC 110937533) are confirmed hot subdwarfs, one (TIC 8765832) is a cataclysmic variable, and one (TIC 32302937) is a likely hot subluminous star, but it requires further spectroscopic confirmation. We investigate the period─luminosity relation, also known as the Leavitt law, for these 46 confirmed HADS stars, deriving a revised relation:  MV=(−3.31±0.39)logP+(−1.68±0.39) . This result is consistent with previous studies. Their distribution in the Hertzsprung─Russell diagram indicates that HADS stars are not strictly confined to be within a narrow instability strip that was previously found but can extend beyond it, with a distribution toward lower temperatures. The refined classifications presented here establish a high-quality sample for precise asteroseismic modeling and enhance the potential for future machine-learning-assisted searches and classifications of HADS stars in large-scale photometric surveys.

Keywords: Stellar oscillations, Asteroseismology, Delta Scuti variable stars
Hard X-Ray Emission in AU Mic Flares: A Minor Contributor to Planetary Atmospheric Escape. Stellar flares are potent drivers of atmospheric evolution on orbiting exoplanets, primarily through extreme ultraviolet (EUV) and soft X-ray irradiation. However, the contribution of hard X-rays (HXR; 3─20 keV), which penetrate deeper into planetary atmospheres, to mass loss and particle acceleration has remained poorly understood. To quantify the HXR share of the total radiative budget, we conducted quasi-simultaneous observations of the active M-dwarf AU Mic using NuSTAR, Swift, and the Einstein Probe. Our analysis detected two major flares, and we performed an empirical check by deriving a quiescent-phase soft X-ray (SXR; 0.3─3 keV) to HXR relation and then applying it to the flares. By combining this with the quiescent coronal SXR─EUV relation conversion of J. Sanz-Forcada et al, we computed the total high-energy flux (EUV + SXR + HXR) and assessed the relative role of HXR in atmospheric escape. We find that HXR accounts for only a few percent of the total radiative energy budget during both quiescent and flaring states. While a high-energy spectral tail is detected in the second flare, time-resolved spectroscopy reveals a dominant chromospheric-evaporation signature, indicating that the flare energetics are primarily thermal.

Keywords: Star-planet interactions, X-ray transient sources, Stellar flares, Stellar activity
On the Orbital Evolution of Multiple Wide Super-Jupiters: How Disk Migration and Dispersal Shape the Stability of the PDS 70 System. Direct imaging has revealed exoplanet systems hosting multiple wide-orbit Super-Jupiters, where planet─planet interactions can shape their long-term dynamical evolution. These strong perturbations may lead to orbital instability, raising questions about the long-term survival of such systems. Shortly after formation, planet─disk interactions can shepherd planets into mean-motion resonances, which may promote long-term stability, as seen in HR 8799. However, early-stage processes such as photoevaporation and disk viscosity can influence these outcomes. The ∼5 Myr old PDS 70 system offers a unique laboratory to investigate these processes: its two massive (&gt;4 MJup), wide-orbit (&gt;20 au) giants are still embedded in their natal disk. We perform 2D hydrodynamic simulations of the system, allowing the disk to disperse via photoevaporation. Once the disk dissipates, we continue to track the planets' orbital evolution over gigayear timescales using N-body simulations. We find that the system is likely to remain stable for &gt;1 Gyr. To assess the importance of disk-driven evolution, we compare these results with disk-free N-body simulations using orbital parameters constrained by orbit fits that include recent relative astrometry and radial velocities from the literature. In this case, we find that only ≲4% of posterior is stable for 100 Myr, highlighting the importance of considering disk-driven evolution for long-term dynamics stability of exoplanetary systems. We also simulate two three-planet configurations including the proposed inner candidate "PDS 70 d," finding that a higher photoevaporation leads the system to become unstable in &lt;10 Myr.

Keywords: Hydrodynamical simulations, Exoplanets, Hydrodynamics, Planetary system formation, Protoplanetary disks, Planet formation, Dynamical evolution
Measurement of the Photosphere Oblateness of γ Cassiopeiae via Stellar Intensity Interferometry with the VERITAS Observatory. We use the stellar intensity interferometry system implemented with the Very Energetic Radiation Imaging Telescope Array System at Fred Lawrence Whipple Observatory as a light collector to obtain measurements of the rapid rotator star γ Cassiopeiae, at a wavelength of 416 nm. Using data from baselines sampling different position angles, we extract the size, oblateness, and projected orientation of the photosphere. Fitting the data with a uniform ellipse model yields a minor-axis angular diameter of 0.43 ± 0.02 mas, a major-to-minor-radius ratio of 1.28 ± 0.04, and a position angle of 116° ± 5° for the axis of rotation. A rapidly rotating stellar atmosphere model that includes limb and gravity darkening describes the data well with a fitted angular diameter of  0.604−0.034+0.041  mas corresponding to an equatorial radius of  10.9−0.6+0.8R⊙ , a rotational velocity with a 1σ lower limit at 97.7% of breakup velocity, and a position angle of  114.°7−5.7+6.4 . These parameters are consistent with Hα line spectroscopy and infrared-wavelength Michelson interferometric measurements of the star's decretion disk. This is the first measurement of an oblate photosphere using intensity interferometry.

Keywords: Astronomy data modeling, Stellar radii, Long baseline interferometry, Stellar rotation, Nonclassical interferometry, High angular resolution
Discovery of a ∼208 day Quasiperiodic Oscillation in the X-Ray Emission of the TeV Blazar 1ES 1959+650. We report the discovery of a significant quasiperiodic oscillation (QPO) in the X-ray emission of the TeV blazar 1ES 1959+650 through a detailed timing analysis of long-term Swift X-ray Telescope data. The detected QPO has a period of ∼208 days with a high local confidence level (&gt;5.0σ) and a global confidence level around 3.7σ that persists for over 20 cycles across both high- and low-flux states. The overall variability is composed of this stable QPO superimposed on a slow, long-term trend. Furthermore, we demonstrate that a helical trajectory model for a propagating plasma blob in the jet compellingly reproduces the observed light curve, providing strong support for this physical interpretation.

Keywords: Blazars, Active galactic nuclei, Flat-spectrum radio quasars, BL Lacertae objects