Sazuna/UAT_keywords huggingface dataset:
What Physical Factors Influence the Transformation between Blue Supergiants and Red Supergiants?. The post-main-sequence evolution of massive stars is highly sensitive to key stellar model parameters, particularly initial rotational velocity and metallicity. Using the MESA code, we computed stellar models with initial masses of 16─32 M⊙, metallicities of Z = 0.0047─0.025, and initial rotational velocities of 0.0─400 km s−1. Our results demonstrate that the evolutionary trajectory toward red or blue supergiants is primarily regulated by the parameter ϵgrav, which is the rate of generation or absorption of gravitational energy in the energy conservation equation. Three main factors drive the evolution toward lower effective temperatures (to produce the reduced blue-to-red supergiant ratio, B/R) during central helium burning: (1) an increase in helium and CNO abundances in the hydrogen-burning shell, (2) an increase in the core mass ratio, and (3) a decrease in central helium abundance during the latter half of core helium burning. Rotation amplifies the core mass during the core He-burning phase, inducing atmospheric inflation, stronger mass loss, and redward evolution. Consequently, rapid rotation leads to a lower B/R supergiant ratio. A thinner envelope induced by strong winds favors a higher B/R supergiant ratio. The minimum envelope mass required for stars to transition from a red to a blue supergiant decreases with higher metallicity and higher initial rotational velocity. High-metallicity stars undergo an extended blue excursion after the red supergiant phase, increasing the B/R supergiant ratio. A higher B/R supergiant ratio is strongly linked to the presence of an intermediate convective region during the first crossing of the Hertzsprung gap.

Keywords: Stellar abundances, Stellar rotation, Stellar structures, Stellar evolution
On the Origin of Neutron-capture Elements in r-I and r-II Stars: A Differential-abundance Analysis. We present a strictly line-by-line differential analysis of a moderately r-process-enhanced star (r-I: HD 107752) with respect to a strongly r-process-enhanced star (r-II: CS 31082-0001) to investigate the possible common origin of their heavy-element nucleosynthesis with high-precision abundances. This study employs European Southern Observatory data archive high-resolution and high-signal-to-noise spectra taken with the Ultraviolet and Visual Echelle Spectrograph Very Large Telescope spectrograph. Considering only the lines in common in both spectra, we estimate differential abundances of 16 light/Fe-peak elements and 15 neutron-capture elements. Abundances of O, Al, Pr, Gd, Dy, Ho, Er, and a detection of Tm in HD 107752, are presented for the first time. We found three distinct features in the differential-abundance pattern. Nearly equal abundances of light elements up to Zn are present in both stars, indicating a common origin for these elements; in addition to no noticable odd─even differential pattern. Regarding the neutron-capture elements, the r-I star exhibits mildly depleted light r-process elements and more depleted heavier r-process elements relative to r-II star. We also show that, among the r-I and r-II stars, the ratio of lighter-to-heavier r-process elements (e.g., [(Sr, Y, Zr)/Eu]) exhibits a decreasing trend with respect to the overall r-process enhancement, forming a continuous sequence from the r-I to the r-II stars. Finally, we discuss the necessity of multiple sites for the formation of r-I stars.

Keywords: Stellar populations, Galactic archaeology, Chemical abundances, Stellar astronomy, Spectroscopy
Prestellar Cores in Turbulent Clouds: Observational Perspectives on Structure, Kinematics, and Lifetime. We analyze an ensemble of simulated prestellar cores to facilitate an interpretation of structure, kinematics, and lifetime of observed cores. While our theory predicts a "characteristic" density for star formation, it also predicts that the individual critical density varies among cores; any observed sample thus contains cores at various evolutionary stages within a given density bin. By analyzing the remaining lifetime, we find cores undergoing a quasi-equilibrium collapse evolve on a timescale of twice the freefall time throughout most of their life. Our analysis shows that the central column density and the associated full width at half-maximum provide a reasonably accurate observational estimator of the central volume density, and therefore the freefall time; this does, however, require resolving the central column density plateau. Observations with a finite beam size tend to underestimate densities of evolved cores, and this makes observed lifetimes appear to decrease more steeply than the apparent freefall time. We measure from our simulations the ratio of the prestellar duration to the envelope infall time, and find this is consistent with the observed relative number of prestellar cores and embedded protostars. Yet, the absolute core lifetime in our simulations is significantly shorter than would be expected from empirical measurements of the relative numbers of prestellar cores and Class II sources; we discuss several possible reasons for this discrepancy. Finally, our simulated cores have nearly constant line-of-sight velocity dispersion within the emitting region in the sky plane, resembling observed "coherent cores." We show that this "coherence" is a consequence of projection effects, which mask the intrinsic power-law velocity structure function. We discuss possible ways to estimate line-of-sight path lengths.

Keywords: Star formation, Molecular clouds, Interstellar medium
Study of H I Turbulence in the SMC Using Multipoint Structure Functions. Turbulence in the interstellar medium (ISM) plays an important role in many physical processes, including forming stars and shaping complex ISM structures. In this work, we investigate the H I turbulence properties of the Small Magellanic Cloud (SMC) to reveal what physical mechanisms drive the turbulence and at what scales. Using high-resolution H I data from the Galactic ASKAP survey and multipoint structure functions (SFs), we perform a statistical analysis of H I turbulence in 34 subregions of the SMC. The two-point SFs tend to show a linear trend, and their slope values are relatively uniform across the SMC, suggesting that large-scale structures exist and are dominant in the two-point SFs. On the other hand, seven-point SFs enable us to probe small-scale turbulence by removing large-scale fluctuations, which is difficult to achieve with the two-point SFs. In the seven-point SFs, we find break features at scales of 34─84 pc, with a median scale of ∼50 pc. This result indicates the presence of small-scale turbulence fluctuations in the SMC and quantifies their scale. In addition, we find strong correlations between the slope values of the seven-point SFs and stellar-feedback-related quantities (e.g., Hα intensity, the number of young stellar objects, and the number of H I shells), suggesting that stellar feedback may affect the small-scale turbulence properties of the H I gas in the SMC. Lastly, the estimated sonic Mach numbers across the SMC are subsonic, which is consistent with the fact that the H I gas of the SMC primarily consists of a warm neutral medium.

Keywords: Radio astronomy, Small Magellanic Cloud, Interstellar medium, Interstellar atomic gas
Molecular Observations of the Protoplanetary Nebula Frosty Leo: A Unique Window into Superoxygen Chemistry. Molecular observations were conducted of the protoplanetary nebula (PPN) Frosty Leo (IRAS 09371+1212) using the 12 m antenna and the Submillimeter Telescope of the Arizona Radio Observatory at 1─3 mm. In addition to CO, multiple transitions were detected of the sulfur—containing molecules CS (J = 2 → 1, 3 → 2, 5 → 4), SO (NJ = 23 → 12, 33 → 22, 34 → 23, 43 → 32, 44 → 33, 56 → 45, 65 → 54), SO2 (JKa,Kc = 31,3 → 20,2, 51,5 → 40,4, 42,2 → 41,3, 32,2 → 31,3, 52,4 → 51,5, 71,7 → 60,6), and H2S,  H233S , and  H234S  (JKa,Kc = 11,0 → 10,1). The J = 2 → 1 and 3 → 2 lines of SiO were also measured, but the carbon-bearing species HCN and HCO+ were not detected despite intensive searches. Aside from SO, these identifications are new for this source. The observed line profiles appear broad but mostly symmetric, consistent with an origin in the so-called central ring. From a radiative transfer analysis, fractional abundances, relative to H2, were determined. H2S was found to be the most abundant S-bearing species, with f ∼ 1.4 × 10−6, followed by SO (f ∼ 2.1 × 10−7) and SO2 (f ∼ 8.6 × 10−8). CS and SiO had lower values of f ∼ 2.2─2.9 × 10−8. From H2S, unusually low sulfur isotope ratios were determined, with 32S/33S = 21.6 ± 7.4 and 32S/34S = 6.6 ± 1.3. The striking absence of HCN and HCO+, commonly found in O-rich environments, and the prevalence of S-bearing molecules, suggests this PPN has a unique oxygen-driven chemistry and may explain the strong crystalline ice features observed.

Keywords: Interstellar molecules, Protoplanetary nebulae, Molecular spectroscopy, Astrochemistry, Radio astronomy
Cross-correlating the Patchy Screening and Kinetic Sunyaev─Zel'dovich Effects as a New Probe of Reionization. The kinetic Sunyaev─Zel'dovich effect (kSZ) and patchy screening effect are two complementary cosmic microwave background (CMB) probes of the reionization era. The kSZ effect is a relatively strong signal, but is difficult to disentangle from other sources of temperature anisotropy, whereas patchy screening is weaker but can be reconstructed using the cleaner polarization channel. Here, we explore the potential of using upcoming CMB surveys to correlate a reconstructed map of patchy screening with (the square of) the kSZ map, and what a detection of this cross correlation would mean for reionization science. To do this, we use simulations and theory to quantify the contributions to this signal from different redshifts. We then use the expected survey properties for CMB-S4 and CMB-HD to make detection forecasts. We find that, for our fiducial reionization scenario, CMB-S4 will obtain a hint of this signal at up to 1.8σ, and CMB-HD will detect it at up to 14σ. We explore the physical interpretation of the signal and find that it is uniquely sensitive to the first half of reionization and to the bispectrum of the ionized gas distribution.

Keywords: Observational cosmology, Cosmic microwave background radiation, Sunyaev-Zeldovich effect, Circumgalactic medium, Reionization
Millimeter-wave Spectrum Analysis and Searches for 2-aminopropenenitrile (<inline-formula> <mml:math><mml:msub><mml:mi>H</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mi>C</mml:mi><mml:mtext>=</mml:mtext><mml:mi>C</mml:mi><mml:mo>(</mml:mo><mml:msub><mml:mi>NH</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mo>)</mml:mo><mml:mi>CN</mml:mi></mml:math> </inline-formula>) toward the Galactic Center Sources Sgr B2(N1) and G+0.693─0.027. We present an analysis of the millimeter-wave spectra of 2-aminopropenenitrile ( H2C=C(NH2)CN ), an α-aminonitrile of plausible prebiotic and astrophysical relevance. The molecule has a rotational spectrum that is in harmony with a large-amplitude motion of the amino group. Accurate rest transition frequencies are reported in selected regions between 158 and 324 GHz, along with extended and improved sets of molecular parameters for the ground state. In addition, several vibrational satellites were identified for the first time. Experimental results were used to search for 2-aminopropenenitrile toward two chemically rich interstellar sources in the Sgr B2 region of the Galactic center: the hot molecular core Sgr B2(N1S) and the molecular cloud G+0.693─0.027. We also searched for the reduced derivative, 2-aminopropionitrile ( CH3CH(NH2)CN ), in the former source. None of the molecules were detected, and the upper limits of their column densities were obtained.

Keywords: Rotational spectroscopy, Experimental data, Molecular spectroscopy, Millimeter-wave spectroscopy, Interstellar medium, Radio astronomy, Catalogs
The Relative Contributions of Accretion Disk versus Jet to the Optical and Mid-infrared Variability of Seyfert Galaxies. We performed a comprehensive analysis of flux and color variability in a redshift-matched sample of Seyfert galaxies, comprising 23 gamma-ray-detected narrow-line Seyfert 1 galaxies (gNLS1s), 190 non-gamma-ray-detected narrow-line Seyfert 1 galaxies (ngNLS1s), and 10 gamma-ray-detected broad-line Seyfert 1 galaxies (gBLS1s). Utilizing multiband light curves from the Zwicky Transient Facility in the g, r, and i bands, along with mid-infrared (MIR) observations in the W1 and W2 bands from the Wide-field Infrared Survey Explorer, we observed that gBLS1s exhibit more significant variability than gNLS1s, while ngNLS1s display minimal variability across both optical and MIR wavelengths. The pronounced variability in gBLS1s may be attributed to a more closely aligned jet relative to the observer's line of sight or their comparatively lower accretion rates. In contrast, the subdued variability in ngNLS1s suggests that their flux changes are primarily driven by accretion disk instabilities. A strong correlation between optical and MIR variability amplitudes across different timescales supports the reprocessing scenario, where accretion disk emission is reemitted by surrounding dust. Furthermore, our long-term color variability analysis revealed both stronger bluer-when-brighter and redder-when-brighter (RWB) trends in the current sample, but a stronger RWB in approximately 50%, 49%, and 50% of gNLS1s, ngNLS1s, and gBLS1s, respectively, at longer optical wavelengths, and 55%, 28%, and 30% at MIR wavelengths, strengthen the reprocessing scenario. The prevalent RWB trends observed at both optical and MIR wavelengths from the current sample on longer timescales are likely associated with accretion disk instabilities.

Keywords: CCD photometry, Sky surveys, Multi-color photometry, Optical astronomy, Active galaxies, Galaxy jets, Seyfert galaxies, Low-luminosity active galactic nuclei, Gamma-rays, Infrared photometry
Mapping the z ∼ 2 Circumgalactic Medium with KBSS Galaxy Pairs<SUP></SUP>. We present new results on the spatial structure and kinematics of the circumgalactic medium (CGM) of z ∼ 2 star-forming galaxies drawn from the Keck Baryonic Structure Survey, using Lyα and metallic ion absorption recorded in spectra of background galaxies whose sight lines are projected within θ ∼ 30″ (physical distances Dtran ≲ 250 kpc) of the foreground galaxy. The sample of 1033 foreground galaxies (&lt;zfg&gt; = 2.03 ± 0.36;  8≲log(M*/M⊙)≲11 ) is probed by the spectra of 736 background galaxies obtained using Keck/KCWI (R ∼ 1800) and Keck/LRIS (R ∼ 1200). Using the galaxy pair ensemble, we present measurements of absorption strength (Wλ) and line-of-sight velocity dispersion (σ) as a function of Dtran, which together with "down-the-barrel" spectra of the foreground galaxies provide unprecedented maps of neutral hydrogen and ionized metals throughout the CGM of star-forming galaxies at "cosmic noon." A 2D map of Lyα absorption depth (versus line-of-sight velocity and Dtran) for the full ensemble shows a distinct transition near Dtran ∼ 80 kpc (close to the virial radius of the average foreground galaxy) where the line-of-sight velocity dispersion reaches a minimum, and beyond which the Lyα absorption depth flattens. Splitting the sample into subsets based on properties of the foreground galaxies, we find a strong and monotonic correlation of both Wλ(C IV) and σ(C IV) with stellar mass (M*) at all Dtran including DTB (i.e., Dtran ∼ 0─250 kpc). Taken together, our results suggest that the kinematics, covering fraction, and spatial extent of CGM gas traced by Lyα and (especially) C IV are modulated primarily by halo mass, and that a significant fraction of the CGM gas may be unbound. *Based on data obtained at W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

Keywords: High-redshift galaxies, Galaxy pairs, Galaxy evolution, Circumgalactic medium
Deciphering the Nature of Virgil: An Obscured Active Galactic Nucleus Lurking within an Apparently Normal Lyα Emitter during Cosmic Reionization. We present a comprehensive analysis of the MIRI Extremely Red Object Virgil, a Lyα emitter at zspec = 6.6379 ± 0.0035 with the photometric properties of a Little Red Dot. Leveraging new JWST/MIRI imaging from the MIDIS and PAHSPECS programs, we confirm Virgil's extraordinary nature among galaxies in JADES/GOODS-South, exhibiting a strikingly red NIRCam-to-MIRI color (F444W─F1500W = 2.84 ± 0.04 mag). Deep NIRSpec/PRISM spectroscopy from the OASIS program offers key insights into the host galaxy, revealing properties of an average star-forming galaxy during Cosmic Reionization, such as a subsolar metallicity, low-to-moderate dust content, and a relatively high ionization parameter and electron temperature. By estimating the star formation rate of Virgil from UV and Hα, we find evidence that the galaxy is either entering or fading out of a bursty episode. Although line-ratio diagnostics employed at high z would classify Virgil as an active galactic nucleus (AGN), this classification becomes ambiguous once redshift evolution is considered. Nonetheless, Virgil occupies the same parameter space as recently confirmed AGNs at similar redshifts. The new deep MIRI data at 15 μm reinforce the AGN nature of Virgil, as inferred from multiple spectral energy distribution (SED) fitting codes. Virgil's rising infrared SED and UV excess resemble those of Dust-Obscured Galaxies (DOGs) studied with Spitzer at Cosmic Noon, particularly blue-excess HotDOGs. Our results highlight the need for a multiwavelength approach incorporating MIRI to uncover such extreme sources at z ≳ 6 and to shed light on the interplay between galaxy evolution and early black hole growth during Cosmic Reionization.

Keywords: AGN host galaxies, Galaxy formation, Photoionization, Infrared photometry, Infrared astronomy, Active galactic nuclei, Galaxy evolution, Spectral energy distribution, High-redshift galaxies, Galaxies, Near infrared astronomy
Early Lightcurves of Type Ia Supernovae Are Consistent with Nondegenerate Progenitor Companions. If Type Ia supernovae (SNe Ia) result from a white dwarf being ignited by Roche-lobe overflow from a nondegenerate companion, then as the SN explosion runs into the companion star its ejecta will be shocked, causing an early blue excess in the lightcurve. A handful of these excesses have been found in single-object studies, but inferences about the population of SNe Ia as a whole have been limited because of the rarity of multiwavelength follow-up within days of explosion. Here we present a 3 yr investigation yielding a nearly unbiased sample of nine nearby (z &lt; 0.01) SNe Ia with exemplary early data. The data are multiwavelength, covering UBVgri and Neil Gehrels Swift Observatory UV bandpasses, and also early, with an average first epoch 16.0 days before maximum light. Of the nine objects, three show early blue excesses. We do not find enough statistical evidence to reject the null hypothesis that SNe Ia predominantly arise from Roche-lobe-overflowing single-degenerate systems (p = 0.94). When looking at the objects' colors, we find the objects are almost uniformly near-UV─blue, in contrast to earlier literature samples which found that only a third of SNe Ia are near-UV─blue, and we find a seemingly continuous range of B − V colors in the days after explosion, again in contrast with earlier claims in the literature. This study highlights the importance of early, multiwavelength, high-cadence data in determining the progenitor systems of SNe Ia and in revealing their diverse early behavior.

Keywords: Type Ia supernovae, Supernovae
Unveiling the Mixing and Transport Processes of Solar Wind and Planetary Ions in the Magnetopause Boundary Layer. Kelvin─Helmholtz (KH) vortices are widely observed in astrophysics and heliophysics, including at Jovian and terrestrial magnetopauses, the Martian sheath─ionosphere boundary, the heliopause, and within stellar accretion disks. These vortices play a critical role in transporting mass, momentum, and energy across boundary layers. Magnetized planets such as Earth exhibit a higher incidence of fully rolled-up, nonlinear KH vortices compared to nonmagnetized planets like Mars. In contrast to previous magnetohydrodynamic studies, this work adopts a kinetic point of view to quantify ion mixing rates using 3D global hybrid simulations, with Earth as a representative case. This approach enables automated identification of the KH-modulated, corrugated magnetopause. For the first time, we provide a quantitative assessment of how solar wind conditions control solar wind entry and subsequent mixing with magnetospheric ions via KH waves. We find that under northward interplanetary magnetic field (IMF) conditions, the flux of particles crossing the dayside magnetopause increases with solar wind dynamic pressure and peaks in the KH region. Notably, the KH-modulated low-latitude boundary layer thins as the dynamic pressure increases. Under southward IMF conditions, coupled reconnection and KH structures further enhance solar wind injection and boost magnetospheric ion escape in the dayside, especially near the subsolar point, where reconnection intensifies this exchange. These results also shed light on the evolution of space environments and mass transport at magnetized planets in the heliosphere and beyond.

Keywords: Heliosphere
The Hot Circumgalactic Medium in Stacked X-Rays: Observations versus Simulations. Current cosmological simulations rely on active galactic nucleus (AGN) feedback to quench star formation and match observed stellar mass distributions, but models for AGN feedback are poorly constrained. The circumgalactic medium (CGM) provides a valuable laboratory to study this process, as its metallicity, temperature, and density distributions are directly shaped by AGN activity. Recent observations from the eROSITA instrument provide constraints on the CGM through measurements of extended soft X-ray emission. In this work, we generate synthetic eROSITA observations from the EAGLE and SIMBA cosmological simulations and compare them to observations of galaxies stacked by stellar mass, halo mass, and star formation rate. SIMBA outperforms EAGLE in matching observed surface brightness profiles, but neither simulation achieves consistent agreement with observations across the full range of galaxy properties we studied. We find that variations in CGM X-ray emission between simulations are primarily driven by density differences at R ≲ 0.2R200c and temperature and metallicity changes at larger radii. These results highlight the need for further refinement of AGN feedback models in cosmological simulations and demonstrate the power of stacked X-ray observations as a tool for constraining feedback physics.

Keywords: X-ray astronomy, Hydrodynamical simulations, Galaxy environments, Quasars, Intergalactic medium, Active galactic nuclei, Circumgalactic medium, Extragalactic astronomy, Astronomical simulations