Sazuna/UAT_keywords huggingface dataset:
Exploring the Formation of Resistive Pseudodisks with the GPU Code Astaroth. Pseudodisks are dense structures formed perpendicular to the direction of the magnetic field during the gravitational collapse of a molecular cloud core. Numerical simulations of the formation of pseudodisks are usually computationally expensive with conventional CPU codes. To demonstrate the proof of concept of a fast computing method for this numerically costly problem, we explore the GPU-powered MHD code Astaroth, a sixth-order finite difference method with low adjustable finite resistivity implemented with sink particles. The formation of pseudodisks is physically and numerically robust and can be achieved with a simple and clean setup for this newly adopted numerical approach for science verification. The method's potential is illustrated by evidencing the dependence on the initial magnetic field strength of specific physical features accompanying the formation of pseudodisks, e.g., the occurrence of infall shocks and the variable behavior of the mass and magnetic flux accreted on the central object. As a performance test, we measure both weak and strong scaling of our implementation to find the most efficient way to use the code on a multi-GPU system. Once suitable physics and problem-specific implementations are realized, the GPU-accelerated code is an efficient option for 3D magnetized collapse problems.

Keywords: Star formation, Magnetohydrodynamics, Magnetic fields
TESS Observations of Seven Newly Identified High-amplitude δ Scuti Stars. We report seven newly identified high-amplitude δ Scuti (HADS) stars. Among them, two stars (TIC 30977864 and TIC 387379145) exhibit pure radial pulsation without the excitation of non-radial modes. TIC 30977864 is classified as a double-mode HADS star, while the other four stars potentially show triple-mode HADS behavior. TIC 112682462 and TIC 255603395 closely resemble RR Lyrae stars based on their light curves, position in the period-luminosity diagram, and the period ratio diagram. However, without spectral observations, it is challenging to ascertain whether these two stars are HADS or RR Lyrae stars. TIC 281695001 exhibits a fundamental frequency amplitude smaller than that of the first overtone, suggesting the presence of intriguing phenomena that necessitate further analysis. We analyzed the relationship between metallicity and period using data provided by Netzel &amp; Smolec. The metallicities of the 176 stars display a broad distribution ranging from -2.0 dex to 0.5 dex, with periods spanning 0.05 to 0.20 days. This random distribution of metallicities may contribute to the dispersion observed in the P1/P0 ratio. To derive more accurate conclusions, future spectroscopic observations of a larger sample of HADS stars are crucial. These observations will provide precise rotational velocities and more accurate determinations of metallicities.

Keywords: Asteroseismology, Delta Scuti variable stars
Monster Radiative Shocks in the Perturbed Magnetospheres of Neutron Stars. Magnetospheres of neutron stars can be perturbed by star quakes, interaction in a binary system, or sudden collapse of the star. The perturbations are typically in the kilohertz band and excite magnetohydrodynamic waves. We show that compressive magnetospheric waves steepen into monster shocks, possibly the strongest shocks in the Universe. The shocks are radiative, i.e., the plasma energy is radiated before it crosses the shock. As the kilohertz wave with the radiative shock expands through the magnetosphere, it produces a bright X-ray burst. Then, it launches an approximately adiabatic blast wave, which will expand far from the neutron star. These results suggest a new mechanism for X-ray bursts from magnetars and support the connection of magnetar X-ray activity with fast radio bursts. Similar shocks may occur in magnetized neutron-star binaries before they merge, generating an X-ray precursor of the merger. Powerful radiative shocks are also predicted in the magnetosphere of a neutron star when it collapses into a black hole, producing a bright X-ray transient.

Keywords: Neutron stars, Plasma astrophysics, X-ray transient sources, Radio bursts, Radiative processes, Magnetars
Probing Cosmology with Baryon Acoustic Oscillations Using Gravitational Waves. The third-generation (3G) gravitational wave (GW) detectors such as the Einstein Telescope or Cosmic Explorer are expected to play an important role in cosmology. With the help of 3G detectors, we will be able to probe large-scale structure features such as baryon acoustic oscillations (BAO), galaxy bias, etc. We explore the possibility to do precision cosmology, with the 3G GW detectors by measuring the angular BAO scale using localization volumes of compact binary merger events. Through simulations, we show that with a 3G detector network, by probing the angular BAO scale using purely GW observations, we can constrain the Hubble constant for the standard model of cosmology (ΛCDM) with 90% credible regions as ${H}_{0}={59.4}_{-17.7}^{+33.9}\,\mathrm{km}\,{{\rm{s}}}^{-1}\,{\mathrm{Mpc}}^{-1}$ . When combined with BAO measurements from galaxy surveys, we show that it can be used to constrain various models of cosmology such as parameterized models for dark energy equations of state. We also show how cosmological constraints using BAO measurements from GW observations in the 3G era will complement the same from spectroscopic surveys.

Keywords: Cosmology, Baryon acoustic oscillations, Gravitational wave detectors, Gravitational waves
JWST Reveals Widespread CO Ice and Gas Absorption in the Galactic Center Cloud G0.253+0.016. We report JWST NIRCam observations of G0.253+0.016, the molecular cloud in the Central Molecular Zone known as "The Brick," with the F182M, F187N, F212N, F410M, F405N, and F466N filters. We catalog 56,146 stars detected in all six filters using the crowdsource package. Stars within and behind The Brick exhibit prodigious absorption in the F466N filter that is produced by a combination of CO ice and gas. In support of this conclusion, and as a general resource, we present models of CO gas and ice and CO2 ice in the F466N, F470N, and F410M filters. Both CO gas and ice contribute to the observed stellar colors. We show, however, that CO gas does not absorb the Pfβ and Huϵ lines in F466N, but that these lines show excess absorption, indicating that CO ice is present and contributes to observed F466N absorption. The most strongly absorbed stars in F466N are extincted by ~2 mag, corresponding to &gt;80% flux loss. This high observed absorption requires very high column densities of CO, and thus a total CO column that is in tension with standard CO abundance and/or gas-to-dust ratios. This result suggests the CO/H2 ratio and dust-to-gas ratio are greater in the Galactic Center than in the Galactic disk. Ice and/or gas absorption is observed even in the cloud outskirts, implying that additional caution is needed when interpreting stellar photometry in filters that overlap with ice bands throughout galactic centers.

Keywords: Ice composition, Infrared dark clouds
Multiwavelength Study of Dark Globule DC 314.8-5.1: Point-source Identification and Diffuse Emission Characterization. We present an analysis of multiwavelength observations of the dark globule DC 314.8-5.1, using data from the Gaia optical, Two Micron All Star Survey near-infrared, and Wide-field Infrared Survey Explorer mid-infrared surveys, dedicated imaging with the Spitzer Space Telescope, and X-ray data obtained with the Swift X-Ray Telescope (XRT). The main goal was to identify possible pre-main-sequence stars (PMSs) and young stellar objects (YSOs) associated with the globule. For this, we studied the infrared colors of all point sources within the boundaries of the cloud. After removing sources with nonstellar spectra, we investigated the Gaia parallaxes for the YSO candidates and found that none are physically related to DC 314.8-5.1. In addition, we searched for X-ray emission from PMSs with Swift-XRT, and found no 0.5-10 keV emission down to a luminosity level ≲1031 erg s-1, typical of a PMS with mass ≥2 M ⊙. Our detailed inspection therefore supports a very young, "prestellar core" evolutionary stage for the cloud. Based on archival Planck and IRAS data, we moreover identify the presence of hot dust, with temperatures ≳100 K, in addition to the dominant dust component at 14 K, originating with the associated reflection nebula.

Keywords: X-ray astronomy, Molecular clouds, Infrared astronomy, Young stellar objects, Pre-main sequence stars, Interstellar medium
A Systematic Survey of Moon-forming Giant Impacts. I. Nonrotating Bodies. In the leading theory of lunar formation, known as the giant impact hypothesis, a collision between two planet-size objects resulted in a young Earth surrounded by a circumplanetary debris disk from which the Moon later accreted. The range of giant impacts that could conceivably explain the Earth-Moon system is limited by the set of known physical and geochemical constraints. However, while several distinct Moon-forming impact scenarios have been proposed-from small, high-velocity impactors to low-velocity mergers between equal-mass objects-none of these scenarios have been successful at explaining the full set of known constraints, especially without invoking controversial post-impact processes. In order to bridge the gap between previous studies and provide a consistent survey of the Moon-forming impact parameter space, we present a systematic study of simulations of potential Moon-forming impacts. In the first paper of this series, we focus on pairwise impacts between nonrotating bodies. Notably, we show that such collisions require a minimum initial angular momentum budget of approximately 2 J EM in order to generate a sufficiently massive protolunar disk. We also show that low-velocity impacts (v ∞ ≲ 0.5 v esc) with high impactor-to-target mass ratios (γ → 1) are preferred to explain the Earth-Moon isotopic similarities. In a follow-up paper, we consider impacts between rotating bodies at various mutual orientations.

Keywords: Hydrodynamical simulations, Earth-moon system, Lunar origin
A JWST/NIRSpec First Census of Broad-line AGNs at z = 4-7: Detection of 10 Faint AGNs with M <SUB>BH</SUB> 10<SUP>6</SUP>-10<SUP>8</SUP> M <SUB>⊙</SUB> and Their Host Galaxy Properties. We present the first statistical sample of faint type 1 AGNs at z &gt; 4 identified by JWST/NIRSpec deep spectroscopy. Among the 185 galaxies at z spec = 3.8-8.9 confirmed with NIRSpec, our systematic search for broad-line emission reveals 10 type 1 AGNs at z = 4.015-6.936 whose broad component is only seen in the permitted Hα line and not in the forbidden [O III]λ5007 line that is detected with greater significance than Hα. The broad Hα line widths of FWHM ≃ 1000-6000 km s-1 suggest that the AGNs have low-mass black holes with M BH ~ 106-108 M ⊙, remarkably lower than those of low-luminosity quasars previously identified at z &gt; 4 with ground-based telescopes. JWST and Hubble Space Telescope high-resolution images reveal that the majority of them show extended morphologies indicating significant contribution to the total lights from their host galaxies, except for three compact objects two of which show red spectral energy distributions, probably in a transition phase from faint AGNs to low luminosity quasars. Careful AGN-host decomposition analyses show that their host's stellar masses are systematically lower than the local relation between the black hole mass and the stellar mass, implying a fast black hole growth consistent with predictions from theoretical simulations. A high fraction of the broad-line AGNs (~5%), higher than z ~ 0, indicates that the number density of such faint AGNs is higher than an extrapolation of the quasar luminosity function, implying a large population of AGNs in the early universe. Such faint AGNs contribute to cosmic reionization, while the total contribution is not large, up to ~50% at z ~ 6, because of their faint nature.

Keywords: AGN host galaxies, Galaxy formation, Active galactic nuclei, Galaxy evolution
Diagnostics from Polarization of Scattered Optical Light from Galactic Infrared Cirrus. We propose polarization of scattered optical light from intermediate Galactic latitude infrared cirrus as a new diagnostic to constrain models of interstellar dust and the anisotropic interstellar radiation field (aISRF). For single scattering by a sphere, with Mie scattering phase functions for intensity and polarized intensity for a dust model at a given wavelength (Sloan r and g bands), and with models of anisotropic illumination from the entire sky (represented in HEALPix), we develop the formalism for calculating useful summary parameters for an integrated flux nebula (IFN): the average of the phase function weighted by the illumination, polarization angle (ψ), and polarization fraction (p). To demonstrate the diagnostic discrimination of polarization from scattered light, we report on the effects of different anisotropic illumination models and different dust models on the summary parameters for the Spider IFN. The summary parameters are also sensitive to the IFN location, as we illustrate using FRaNKIE illumination models. For assessing the viability of dust and aISRF models, we find that observations of ψ and p of scattered light are indeed powerful new diagnostics to complement joint modeling of the intensity of scattered light (related to the average phase function) and the intensity of thermal dust emission. However, optically thin IFNs that can be modeled using single scattering are faint and p is not large, as it could be with Rayleigh scattering, and so these observations need to be carried out with care and precision. Results for the Draco nebula compared to the Spider illustrate the challenge.

Keywords: Interstellar dust, Dust composition, Interstellar radiation field, Diffuse nebulae, Dust continuum emission, Interstellar clouds, Interstellar medium, Interstellar scattering, Reflection nebulae
Magnetohydrodynamical Torsional Oscillations from Thermoresistive Instability in Hot Jupiters. Hot Jupiter atmospheres may be subject to a thermoresistive instability where an increase in the electrical conductivity due to ohmic heating results in runaway of the atmospheric temperature. We introduce a simplified one-dimensional model of the equatorial substellar region of a hot Jupiter that includes the temperature dependence and time dependence of the electrical conductivity, as well as the dynamical back-reaction of the magnetic field on the flow. This model extends our previous one-zone model to include the radial structure of the atmosphere. Spatial gradients of electrical conductivity strongly modify the radial profile of Alfvénic oscillations, leading to steepening and downward transport of magnetic field, enhancing dissipation at depth. We find unstable solutions that lead to self-sustained oscillations for equilibrium temperatures in the range T eq ≈ 1000-1200 K and radial magnetic field strength in the range ≈10-100 G. For a given set of parameters, self-sustained oscillations occur in a narrow range of equilibrium temperatures that allow the magnetic Reynolds number to alternate between large and small values during an oscillation cycle. With our simplified geometry, outside of this temperature window the system reaches a steady state in which the effect of the magnetic field can be approximated as a magnetic drag term. Our results show that thermoresistive instability is a possible source of variability in magnetized hot Jupiters at colder temperatures and emphasize the importance of including the temperature dependence of electrical conductivity in models of atmospheric dynamics.

Keywords: Exoplanet atmospheric dynamics, Magnetohydrodynamics, Exoplanet atmospheric variability, Astrophysical fluid dynamics
Rapid Localization of Gravitational Wave Sources from Compact Binary Coalescences Using Deep Learning. The mergers of neutron star-neutron star and neutron star-black hole binaries (NSBHs) are the most promising gravitational wave (GW) events with electromagnetic (EM) counterparts. The rapid detection, localization, and simultaneous multimessenger follow-up of these sources are of primary importance in the upcoming science runs of the LIGO-Virgo-KAGRA Collaboration. While prompt EM counterparts during binary mergers can last less than 2 s, the timescales of existing localization methods that use Bayesian techniques, vary from seconds to days. In this paper, we propose the first deep learning-based approach for rapid and accurate sky localization of all types of binary coalescences, including neutron star-neutron star and NSBHs for the first time. Specifically, we train and test a normalizing flow model on matched-filtering output from GW searches to obtain sky direction posteriors in around 1 s using a single P100 GPU, which is several orders of magnitude faster than full Bayesian techniques.

Keywords: Convolutional neural networks, Gravitational waves, Gravitational wave sources, Neural networks
RZ Piscium Hosts a Compact and Highly Perturbed Debris Disk. RZ Piscium (RZ Psc) is well known in the variable star field because of its numerous irregular optical dips in the past 5 decades, but the nature of the system is heavily debated in the literature. We present multiyear infrared monitoring data from Spitzer and WISE to track the activities of the inner debris production, revealing stochastic infrared variability as short as weekly timescales that is consistent with destroying a 90 km sized asteroid every year. ALMA 1.3 mm data combined with spectral energy distribution modeling show that the disk is compact (~0.1-13 au radially) and lacks cold gas. The disk is found to be highly inclined and has a significant vertical scale height. These observations confirm that RZ Psc hosts a close to edge-on, highly perturbed debris disk possibly due to migration of recently formed giant planets that might be triggered by the low-mass companion RZ Psc B if the planets formed well beyond the snowlines.

Keywords: Extrasolar rocky planets, Exoplanet migration, Infrared excess, Circumstellar matter, Debris disks
Identifying the Physical Origin of Gamma-Ray Bursts with Supervised Machine Learning. The empirical classification of gamma-ray bursts (GRBs) into long and short GRBs based on their durations is already firmly established. This empirical classification is generally linked to the physical classification of GRBs originating from compact binary mergers and GRBs originating from massive star collapses, or Type I and II GRBs, with the majority of short GRBs belonging to Type I and the majority of long GRBs belonging to Type II. However, there is a significant overlap in the duration distributions of long and short GRBs. Furthermore, some intermingled GRBs, i.e., short-duration Type II and long-duration Type I GRBs, have been reported. A multiparameter classification scheme of GRBs is evidently needed. In this paper, we seek to build such a classification scheme with supervised machine-learning methods, chiefly XGBOOST. We utilize the GRB Big Table and Greiner's GRB catalog and divide the input features into three subgroups: prompt emission, afterglow, and host galaxy. We find that the prompt emission subgroup performs the best in distinguishing between Type I and II GRBs. We also find the most important distinguishing features in prompt emission to be T 90, the hardness ratio, and fluence. After building the machine-learning model, we apply it to the currently unclassified GRBs to predict their probabilities of being either GRB class, and we assign the most probable class of each GRB to be its possible physical class.

Keywords: Gamma-ray bursts, Astronomy data analysis
Degenerate Interpretations of O<SUB>3</SUB> Spectral Features in Exoplanet Atmosphere Observations Due to Stellar UV Uncertainties: A 3D Case Study with TRAPPIST-1 e. TRAPPIST-1 e is a potentially habitable terrestrial exoplanet orbiting an ultracool M dwarf star and is a key target for observations with the James Webb Space Telescope. One-dimensional photochemical modeling of terrestrial planetary atmospheres has shown the importance of the incoming stellar UV flux in modulating the concentration of chemical species, such as O3 and H2O. In addition, three-dimensional (3D) modeling has demonstrated anisotropy in chemical abundances due to transport in tidally locked exoplanet simulations. We use the Whole Atmosphere Community Climate Model Version 6 (WACCM6), a 3D Earth system model, to investigate how uncertainties in the incident UV flux, combined with transport, affect observational predictions for TRAPPIST-1 e (assuming an initial Earth-like atmospheric composition). We use two semiempirical stellar spectra for TRAPPIST-1 from the literature. The UV flux ratio between them can be as large as a factor of 5000 in some wavelength bins. Consequently, the photochemically produced total O3 columns differ by a factor of 26. Spectral features of O3 in both transmission and emission spectra vary between these simulations (e.g., differences of 20 km in the transmission spectrum effective altitude for O3 at 0.6 μm). This leads to potential ambiguities when interpreting observations, including overlap with scenarios that assume alternative O2 concentrations. Hence, to achieve robust interpretations of terrestrial exoplanetary spectra, characterization of the UV spectra of their host stars is critical. In the absence of such stellar measurements, atmospheric context can still be gained from other spectral features (e.g., H2O), or by comparing direct imaging and transmission spectra in conjunction.

Keywords: Exoplanets, Exoplanet atmospheric composition , Exoplanet atmospheres, Transmission spectroscopy
Ab-initio General-relativistic Neutrino-radiation Hydrodynamics Simulations of Long-lived Neutron Star Merger Remnants to Neutrino Cooling Timescales. We perform the first 3D ab-initio general-relativistic neutrino-radiation hydrodynamics of a long-lived neutron star merger remnant spanning a fraction of its cooling timescale. We find that neutrino cooling becomes the dominant energy loss mechanism after the gravitational-wave dominated phase (∼20 ms postmerger). Electron flavor antineutrino luminosity dominates over electron flavor neutrino luminosity at early times, resulting in a secular increase of the electron fraction in the outer layers of the remnant. However, the two luminosities become comparable ∼20─40 ms postmerger. A dense gas of electron antineutrinos is formed in the outer core of the remnant at densities ∼1014.5 g cm−3, corresponding to temperature hot spots. The neutrinos account for ∼10% of the lepton number in this region. Despite the negative radial temperature gradient, the radial entropy gradient remains positive, and the remnant is stably stratified according to the Ledoux criterion for convection. A massive accretion disk is formed from the material squeezed out of the collisional interface between the stars. The disk carries a large fraction of the angular momentum of the system, allowing the remnant massive neutron star to settle to a quasi-steady equilibrium within the region of possible, stable, rigidly rotating configurations. The remnant is differentially rotating, but it is stable against the magnetorotational instability. Other MHD mechanisms operating on longer timescales are likely responsible for the removal of the differential rotation. Our results indicate the remnant massive neutron star is thus qualitatively different from a protoneutron stars formed in core-collapse supernovae.

Keywords: Neutron stars, Stellar structures, Gravitational waves, Stellar mergers