Sazuna/UAT_keywords huggingface dataset:
Starspots as an Explanation for the Mysterious IYJ Continuum Excess Emission in Classical T Tauri Stars. An accurate estimation of the continuum excess emission from accretion spots and inner circumstellar disk regions is crucial for a proper derivation of fundamental stellar parameters in accreting systems. However, the presence of starspots can make disentangling the complicated multicomponent emission in these systems challenging. Subtraction of a single-temperature spectral template is insufficient to account for the composite stellar emission, as we demonstrated in a recent campaign involving weak-lined T Tauri stars. Here, we model the moderate-resolution near-infrared spectra of classical T Tauri stars, presenting new spectral models that incorporate spotted stars plus emission from accretion hot spots and a warm inner disk, allowing us to simultaneously reconstruct the entire 0.8–2.4 μm spectrum of our 16 targets. Using these models, we re-derive the continuum excess emission. Our results indicate that accounting for starspots resolves the need to include a previously proposed intermediate-temperature component in the IYJ excess and highlights the importance of a proper treatment of starspots in studies of accreting low-mass stars.

Keywords: Starspots, Early stellar evolution, Pre-main sequence stars, Star formation, Stellar accretion
Globular Cluster Counts around 700 Nearby Galaxies. Empirically, the total number (or total mass) of globular clusters (GCs) bound in a single galactic system correlates with the virial mass of the system. The form of this relation and its intrinsic scatter are potentially valuable constraints on theories of GC formation and galaxy evolution. In this work, we use the DESI Legacy Imaging Survey (DESI-LS) to make a large-scale, homogeneous estimate of GC abundance around 707 galaxies at distances ≲30 Mpc with luminosities  . The combination of depth and sky coverage in DESI-LS allow us to extend the techniques used by previous ground-based photometric GC surveys to a larger and potentially more representative sample of galaxies. We find average GC counts and radial profiles that are broadly consistent with the literature on individual galaxies, including good agreement with the distribution of GCs in the Milky Way, demonstrating the viability of DESI-LS images for this purpose. We find a relation between GC counts and virial mass in agreement with previous estimates based on heterogenous data sets, except at the lowest masses we probe, where we find a larger scatter in the number of cluster candidates and a slightly higher average count.

Keywords: Globular star clusters, Extragalactic astronomy
JWST Captures a Sudden Stellar Outburst and Inner Disk Wall Destruction. We analyze JWST/MIRI observations of T Cha, a highly variable (ΔV ∼ 3–5 mag) accreting Sun-like star surrounded by a disk with a large (∼15 au) dust gap. We find that the JWST mid-IR spectrum is significantly different from the Spitzer spectrum obtained 17 yr before—the emission at short wavelengths (5–10 μm) has decreased by ∼2/3 while that at longer wavelengths (15–25 μm) has increased by up to a factor of ∼3. The JWST spectrum is contemporaneous with a fairly constant higher optical emission captured by the All Sky Automated Survey. After analyzing and modeling both spectral energy distributions, we propose that JWST caught the star during an outburst that partly destroyed and significantly reduced the height of the asymmetric inner disk wall responsible for the high optical variability and lower 15–25 μm emission during the Spitzer period. The dust mass lost during this outburst is estimated to be comparable (∼1/5) to the upper limit of the total micron-sized dust mass in the inner disk of T Cha now. Monitoring this system during possible future outbursts and more observations of its quiescent state will reveal if the inner disk can be replenished or will continue to be depleted and vanish.

Keywords: Planetary system formation, Infrared astronomy, Pre-main sequence stars, Protoplanetary disks, Circumstellar disks
Diversity in Hydrogen-rich Envelope Mass of Type II Supernovae. I. Plateau Phase Light-curve Modeling. We present a systematic study of Type II supernovae (SNe II) originating from progenitors with effective temperatures (T eff) and luminosities closely resembling red supergiants (RSGs) observed in pre-supernova (SN) images and in the Galaxy. Using Modules for Experiments in Stellar Astrophysics, we compute a large grid of massive stars with T eff ranging from 3200 to 3800 K at their RSG phases, with hydrogen envelopes artificially stripped to varying extents (3–10 M ⊙). The light curves of SNe IIP resulting from the explosions of these Galactic-RSG–like progenitors are modeled using STELLA. Our survey of the light curves reveals that partial stripping of the hydrogen envelope creates diversity in the magnitude and duration of SNe IIP light curves, without affecting the position of the RSG progenitor on the Hertzsprung–Russell diagram. For these Galactic-RSG-like progenitor models, we establish an indicator based on the light-curve properties to estimate the hydrogen envelope mass. Additionally, we discuss the effects of material mixing and 56Ni heating. Applying our model grid to a large sample of approximately 100 observed SNe IIP reveals a considerably broader range of hydrogen-rich envelope masses than predicted by standard stellar wind models. This finding suggests that if SNe IIP are explosions of Galactic-like RSGs to explain the diversity in the observed light curves, a significant fraction of them must have experienced substantial mass loss beyond the standard mass-loss prescription prior to their explosions. This finding highlights the uncertainties involved in massive star evolution and the pre-SN mass-loss mechanism.

Keywords: Hydrodynamics, Core-collapse supernovae, Type II supernovae, Radiative transfer, Stellar evolution
Diversity in Hydrogen-rich Envelope Mass of Type II Supernovae. II. SN 2023ixf as Explosion of Partially Stripped Intermediate Massive Star. SN 2023ixf is one of the most well-observed core-collapse supernovae in recent decades, yet there is inconsistency in the inferred zero-age main-sequence (ZAMS) mass M ZAMS of its progenitor. Direct observations of the pre-supernova (SN) red supergiant (RSG) estimate M ZAMS spanning widely from 11 to 18 M ⊙. Additional constraints, including the host environment and the pulsation of its progenitor RSG, suggest a massive progenitor with M ZAMS &gt; 17 M ⊙. However, the analysis of the SN properties, from light-curve modeling to late-phase spectroscopy, favors a relatively low-mass scenario (M ZAMS &lt; 15 M ⊙). In this work, we conduct a systematic analysis of SN 2023ixf, from the RSG progenitor, plateau phase light curve to late-phase spectroscopy. Using MESA+STELLA to simulate the RSG progenitor and their explosions, we find that a range of the RSG models having M ZAMS that vary from 12 to 17.5 M ⊙ can reproduce its multiband light curves if the hydrogen-rich envelope mass and the explosion energy are allowed to vary. Using late-phase spectroscopy as an independent measurement, the oxygen line [O I] indicates an intermediate-massive progenitor (M ZAMS ∼ 16.0 M ⊙). By incorporating the velocity structure derived from the light-curve modeling into an axisymmetric model, we generated [O I] line profiles that are consistent with the [O I] line observed in late-phase spectroscopy of SN 2023ixf. Bringing these analyses together, we conclude that SN 2023ixf is the aspherical explosion of an intermediate-massive star (M ZAMS = 15–16 M ⊙), with the hydrogen envelope being stripped to 4–5 M ⊙ prior to its explosion.

Keywords: Type II supernovae, Red supergiant stars, Supernova dynamics, Core-collapse supernovae
Bar Formation and Destruction in the FIRE-2 Simulations. The physical mechanisms responsible for bar formation and destruction in galaxies remain a subject of debate. While we have gained valuable insight into how bars form and evolve from isolated idealized simulations, in the cosmological domain, galactic bars evolve in complex environments, with mergers and gas accretion events occurring in the presence of the turbulent interstellar medium with multiple star formation episodes, in addition to coupling with their host galaxies' dark matter halos. We investigate the bar formation in 13 Milky Way–mass galaxies from the Feedback in Realistic Environments (FIRE-2) cosmological zoom-in simulations. 8 of the 13 simulated galaxies form bars at some point during their history: three from tidal interactions and five from internal evolution of the disk. The bars in FIRE-2 are generally shorter than the corotation radius (mean bar radius ∼1.53 kpc), have a wide range of pattern speeds (36–97 km s‑1 kpc‑1), and live for a wide range of dynamical times (2–160 bar rotations). We find that the bar formation in FIRE-2 galaxies is influenced by satellite interactions and the stellar-to-dark-matter mass ratio in the inner galaxy, but neither is a sufficient condition for bar formation. Bar formation is more likely to occur, with the bars formed being stronger and longer-lived, if the disks are kinematically cold; galaxies with high central gas fractions and/or vigorous star formation, on the other hand, tend to form weaker bars. In the case of the FIRE-2 galaxies, these properties combine to produce ellipsoidal bars with strengths A 2/A 0 ∼ 0.1–0.2.

Keywords: Hydrodynamical simulations, Galaxy interactions, Dark matter, Galaxy bars
Self-interacting Dark Matter, Core Collapse, and the Galaxy–Galaxy Strong-lensing Discrepancy. Gravitational lensing by galaxy clusters has emerged as a powerful tool to probe the standard cold dark matter (CDM) paradigm of structure formation in the Universe. Despite the remarkable explanatory power of CDM on large scales, tensions with observations on small scales have been reported. Recent studies find that the observational cross section for galaxy–galaxy strong lensing (GGSL) in clusters exceeds the CDM prediction by more than an order of magnitude and persists even after rigorous examination of various possible systematics. We investigate the impact of modifying the internal structure of cluster dark matter subhalos on GGSL and report that altering the inner density profile, given by rγ, to steeper slopes with γ &gt; 2.5 can alleviate the GGSL discrepancy. This is steeper than slopes obtained with the inclusion of the contribution of baryons to the inner regions of these subhalos. Deviating from the γ ~ 1.0 cusps that CDM predicts, these steeper slopes could arise in models of self-interacting dark matter undergoing core collapse. Our results motivate additional study of subhalo core collapse in dense cluster environments.

Keywords: Cosmology, Galaxy dark matter halos, Galaxy clusters, Strong gravitational lensing, Dark matter
Stellar Metallicities from DECam u-band Photometry: A Study of Milky Way Ultra-faint Dwarf Galaxies. We conducted an in-depth analysis of candidate member stars located in the peripheries of three ultra-faint dwarf (UFD) galaxy satellites of the Milky Way (MW): Boötes I (Boo1), Boötes II (Boo2), and Segue I (Seg1). Studying these peripheral stars has previously been difficult due to contamination from the MW foreground. We used u-band photometry from the Dark Energy Camera (DECam) to derive metallicities to efficiently select UFD candidate member stars. This approach was validated on Boo1, where we identified both previously known and new candidate member stars beyond five half-light radii. We then applied a similar procedure to Boo2 and Seg1. Our findings hinted at evidence for tidal features in Boo1 and Seg1, with Boo1 having an elongation consistent with its proper motion and Seg1 showing some distant candidate stars, a few of which are along its elongation and proper motion. We find two Boo2 stars at large distances consistent with being candidate member stars. Using a foreground contamination rate derived from the Besançon Galaxy model, we ascribed purity estimates to each candidate member star. We recommend further spectroscopic studies on the newly identified high-purity members. Our technique offers promise for future endeavors to detect candidate member stars at large radii in other systems, leveraging metallicity-sensitive filters with the Legacy Survey of Space and Time and the new, narrowband Ca HK filter on DECam.

Keywords: Stellar populations, Dwarf galaxies, Galaxy evolution
On the Nature of the Dark Cavity of Solar Coronal Mass Ejections. Earlier studies have shown that less than one-third of coronal mass ejections (CMEs) possess the archetypical three-part (bright core, dark cavity, and bright front) structure in the outer corona (e.g., 2–6 R⊙). In the traditional opinion, the core, cavity, and front correspond to the erupted filament, magnetic flux rope (MFR), and plasma pileup along the MFR border, respectively. Recent studies have demonstrated that nearly 100% of normal CMEs have a three-part structure in the inner corona (&lt;2 R⊙), agreeing with the prediction of a new explanation of the nature of the three-part structure. In the new opinion, the core and front correspond to the MFR plasma and plasma pileup along the coronal loops, respectively. The cavity is either a part of the MFR, or a low-density zone between the front and the MFR. In this paper, we revisit a textbook case of an eruption that occurred on 2017 September 10. In the inner corona, the CME exhibited a clear three-part appearance in the extreme-ultraviolet images and had a smooth-curved front, while, in the outer corona, the CME loses the three-part feature as the core expands and the cavity disappears. Meanwhile, a bulge appears at the CME front as the core moves faster than the front and protrudes from its bottom. It is difficult to understand the disappearance of the cavity and the appearance of the bulge if assuming the cavity as being a part of the MFR. Therefore, we suggest that the dark cavity represents a low-density zone between the front and MFR in the early eruption stage.

Keywords: Solar activity, Solar flares, Solar coronal mass ejections
Analysis of Solar Eruptions Deflecting in the Low Corona: Influence of the Magnetic Environment. Coronal mass ejections (CMEs) can exhibit nonradial evolution. The background magnetic field is considered the main driver for the trajectory deviation relative to the source region. The influence of the magnetic environment has been largely attributed to the gradient of the magnetic pressure. In this work, we propose a new approach for investigating the role of topology on CME deflection and for quantifying and comparing the action between the magnetic field gradient ("gradient" path) and the topology ("topological" path). We investigate eight events simultaneously observed by the Solar Orbiter, STEREO-A, and the Solar Dynamics Observatory; and, with a new tracking technique, we reconstruct the 3D evolution of the eruptions. Then, we compare their propagation with the predictions from the two magnetic drivers. We find that the "topological" path describes the CME actual trajectory much better than the more traditional "gradient path." Our results strongly indicate that the ambient topology may be the dominant driver for deflections in the low corona, and that this presents a promising method for estimating the direction of propagation of CMEs early in their evolution.

Keywords: Solar magnetic fields, Solar filament eruptions, Solar coronal mass ejections, Solar-terrestrial interactions
Chemical Links between a Young M-type T Tauri Star and Its Substellar Companion: Spectral Analysis and C/O Measurement of DH Tau A. The chemical abundance measurements of host stars and their substellar companions provide a powerful tool to trace the formation mechanism of the planetary systems. We present a detailed high-resolution spectroscopic analysis of a young M-type star, DH Tau A, which is located in the Taurus molecular cloud belonging to the Taurus-Auriga star-forming region. This star is host to a low-mass companion, DH Tau b, and both the star and the companion are still in their accreting phase. We apply our technique to measure the abundances of carbon and oxygen using carbon- and oxygen-bearing molecules, such as CO and OH, respectively. We determine a near-solar carbon-to-oxygen abundance ratio of C/O = 0.555 ± 0.063 for the host star DH Tau A. We compare this stellar abundance ratio with that of the companion from our previous study ( ), which also has a near-solar value. This confirms the chemical homogeneity in the DH Tau system, which suggests a formation scenario for the companion consistent with a direct and relatively fast gravitational collapse rather than a slow core accretion process.

Keywords: M dwarf stars
Spectral Energy Distribution Modeling of BL Lacertae during a Large Submillimeter Outburst and Low X-Ray Polarization State. In 2023 October–November, the blazar BL Lacertae underwent a very large-amplitude submillimeter outburst. The usual single-zone leptonic model with the lower-energy peak of the spectral energy distribution (SED) fit by the synchrotron emission from one distribution of relativistic electrons in the jet and inverse-Compton (IC) scattering of lower-energy photons from the synchrotron radiation in the jet itself (synchrotron self-Compton or SSC) or those from the broad-line region and torus by the same distribution of electrons cannot satisfactorily fit the broadband SED with simultaneous data at submillimeter, optical, X-ray, and GeV energies. Furthermore, simultaneous observations with IXPE indicate the X-ray polarization is undetected. We consider two different synchrotron components, one for the high flux in the submillimeter wavelengths and another for the data at the optical band, which are supposedly due to two separate distributions of electrons. In that case, the optical emission is dominated by the synchrotron radiation from one electron distribution, while the X-rays are mostly due to SSC process by another, which may result in low polarization fraction due to the IC scattering. We show that such a model can fit the broadband SED satisfactorily as well as explain the low polarization fraction at the X-rays.

Keywords: BL Lacertae objects, Blazars, Active galaxies, Relativistic jets, Spectral energy distribution
Distinguishability of a Naked Singularity from a Black Hole in Dynamics and Radiative Signatures. Can a naked singularity (NkS) be distinguished from a black hole (BH)? We have investigated it with cutting-edge general relativistic magnetohydrodynamic simulations, followed by general relativistic radiation transfer calculation for magnetized accretion flow around NkS and BHs. Based on our simulations, the accreting matter close enough to the singularity repels due to effective potential. This prevents matter from reaching an NkS and forms a quasi-spherical symmetric density distribution around it, unlike the accretion flows around a BH. We observe 1 order of magnitude higher mass flux through the jet and much stronger wind from an NkS than a BH. We found that the jet launching mechanism in an NkS differs significantly from that in a BH. In the horizon-scale images, an NkS shows a photon arc instead of a photon ring that is shown around a BH. In summary, the flow dynamics and radiative properties around an NkS are distinctly different from a BH. These properties would be useful to either confirm or rule out such exotic compact objects through future observations.

Keywords: Accretion, Black hole physics, Magnetohydrodynamics, Naked singularities
Milky Way Dark Matter Distribution or MOND Test from Vertical Stellar Kinematics with Gaia DR3. Vertical stellar kinematics+density can be used to trace the dark matter distribution (or the equivalent phantom mass in a Modified Newtonian Dynamics (MOND) scenario) through the Jeans equations. In this paper, we want to improve this type of analysis by making use of the recent data of the 6D information from the Gaia DR3 survey in the anticenter and the Galactic poles to obtain the dynamical mass distribution near plane regions, including extended kinematics over a wide region of 8 kpc &lt; R &lt; 22 kpc, ∣z∣ &lt; 3 kpc. Our conclusions are as follows: (i) the model of the spherical dark matter halos and the MOND model are compatible with the data; (ii) the model of the disky matter (with density proportional to the gas density) is excluded; (iii) the total lack of dark matter (there is only visible matter) within Newtonian gravity is compatible with the data; for instance, at solar Galactocentric radius, we obtained Σ = 39 ± 18 M ⊙ pc‑2 for z = 1.05 kpc, compatible with the expected value for visible matter alone of 44 M ⊙ pc‑2, thus allowing zero dark matter. Similarly, for R &gt; R ⊙, z = 1.05 kpc, Σ = 28.7 ± 9.6, 23.0 ± 5.7, 16.9 ± 5.8, and 11.4 ± 6.6 M ⊙ pc‑2, respectively, for R = 10, 13, 16, and 19 kpc, compatible with visible matter alone. Larger error bars in comparison with previous works are not due to worse data or a more awkward technique but to a stricter modeling of the stellar distribution.

Keywords: Stellar kinematics, Milky Way disk, Galaxy dynamics, Dark matter
Separating Super-puffs versus Hot Jupiters among Young Puffy Planets. Discoveries of close-in young puffy (R p ≳ 6 R ⊕) planets raise the question of whether they are bona fide hot Jupiters or puffed-up Neptunes, potentially placing constraints on the formation location and timescale of hot Jupiters. Obtaining mass measurements for these planets is challenging due to stellar activity and noisy spectra. Therefore, we aim to provide independent theoretical constraints on the masses of these young planets based on their radii, incident fluxes, and ages, benchmarking to the planets of age &lt;1 Gyr detected by Kepler, K2, and the Transiting Exoplanet Survey Satellite. Through a combination of interior structure models, considerations of photoevaporative mass loss, and empirical mass–metallicity trends, we present the range of possible masses for 22 planets with an age of ∼10–900 Myr and radii of ∼6–16 R ⊕. We generally find that our mass estimates are in agreement with the measured masses and upper limits where applicable. There exist some outliers including super-puffs Kepler-51 b, c and V1298 Tau d, b, e, for which we outline their likely formation conditions. Our analyses demonstrate that most of the youngest planets (≲100 Myr) tend to be puffed-up, Neptune-mass planets, while the true hot Jupiters are typically found around stars aged at least a few hundred Myr, suggesting the dominant origin of hot Jupiters to be late-stage high-eccentricity migration.

Keywords: Exoplanet astronomy, Exoplanet evolution, Exoplanet formation, Star-planet interactions