Sazuna/UAT_keywords huggingface dataset:
3D Radiation-hydrodynamical Simulations of Shadows on Transition Disks. Shadows are often observed in transition disks, which can result from obscuring by materials closer to the star, such as a misaligned inner disk. While shadows leave apparent darkened emission as observational signatures, they have significant dynamical impact on the disk. We carry out 3D radiation-hydrodynamical simulations to study shadows in transition disks and find that the temperature drop due to the shadow acts as an asymmetric driving force, leading to spirals in the cavity. These spirals have zero pattern speed following the fixed shadow. The pitch angle is given by tan−1(c  s /v  ϕ ) (6° if h/r = 0.1). These spirals transport mass through the cavity efficiently, with α ∼ 10−2 in our simulation. Besides spirals, the cavity edge can also form vortices and flocculent streamers. When present, these features could disturb the shadow-induced spirals. By carrying out Monte Carlo radiative transfer simulations, we show that these features resemble those observed in near-infrared scattered light images. In the vertical direction, the vertical gravity is no longer balanced by the pressure gradient alone. Instead, an azimuthal convective acceleration term balances the gravity─pressure difference, leading to azimuthally periodic upward and downward gas motion reaching 10% of the sound speed, which can be probed by Atacama Large Millimeter/submillimeter Array line observations.

Keywords: Accretion, Hydrodynamical simulations, Radiative magnetohydrodynamics, Protoplanetary disks, Radiative transfer
Tidal Spin-up of Subdwarf B Stars. Hot subdwarf B (sdB) stars are stripped helium-burning stars that are often found in close binaries, where they experience strong tidal interactions. The dissipation of tidally excited gravity waves alters their rotational evolution throughout the sdB lifetime. While many sdB binaries have well-measured rotational and orbital frequencies, there have been few theoretical efforts to accurately calculate the tidal torque produced by gravity waves. In this work, we directly calculate the tidal excitation of internal gravity waves in realistic sdB stellar models and integrate the coupled spin–orbit evolution of sdB binaries. We find that for canonical sdB (M sdB = 0.47 M ⊙) binaries, the transitional orbital period below which they could reach tidal synchronization in the sdB lifetime is ∼0.2 day, with weak dependence on the companion masses. For low-mass sdBs (M sdB = 0.37 M ⊙) formed from more massive progenitor stars, the transitional orbital period becomes ∼0.15 day. These values are very similar to the tidal synchronization boundary (∼0.2 day) evident from observations. We discuss the dependence of tidal torques on stellar radii, and we make predictions for the rapidly rotating white dwarfs formed from synchronized sdB binaries.

Keywords: Tidal interaction, Stellar oscillations, Stellar rotation, B subdwarf stars
Stellar Metallicities and Gradients in the Faint M31 Satellites Andromeda XVI and Andromeda XXVIII. We present ∼300 stellar metallicity measurements in two faint M31 dwarf galaxies, Andromeda XVI (M  V  = ‑7.5) and Andromeda XXVIII (M  V  = –8.8), derived using metallicity-sensitive calcium H and K narrowband Hubble Space Telescope imaging. These are the first individual stellar metallicities in And XVI (95 stars). Our And XXVIII sample (191 stars) is a factor of ∼15 increase over literature metallicities. For And XVI, we measure  &lt;[Fe/H]&gt;=‑2.17‑0.05+0.05 ,  σ[Fe/H]=0.33‑0.07+0.07 , and ∇[Fe/H] = ‑0.23 ± 0.15 dex  Re‑1 . We find that And XVI is more metal-rich than Milky Way ultrafaint dwarf galaxies of similar luminosity, which may be a result of its unusually extended star formation history. For And XXVIII, we measure  &lt;[Fe/H]&gt;=‑1.95‑0.04+0.04 ,  σ[Fe/H]=0.34‑0.05+0.05 , and ∇[Fe/H]= ‑0.46 ± 0.10 dex  Re‑1 , placing it on the dwarf galaxy mass–metallicity relation. Neither galaxy has a metallicity distribution function (MDF) with an abrupt metal-rich truncation, suggesting that star formation fell off gradually. The stellar metallicity gradient measurements are among the first for faint (L ≲ 106 L ⊙) galaxies outside the Milky Way halo. Both galaxies' gradients are consistent with predictions from the FIRE simulations, where an age–gradient strength relationship is the observational consequence of stellar feedback that produces dark matter cores. We include a catalog for community spectroscopic follow-up, including 19 extremely metal-poor ([Fe/H] &lt; –3.0) star candidates, which make up 7% of And XVI's MDF and 6% of And XXVIII's.

Keywords: Local Group, Stellar abundances, Dwarf galaxies, HST photometry
Numerical Experiment on the Influence of Granulation-induced Waves on Solar Chromosphere Heating and Plasma Outflows in a Magnetic Arcade. This paper offers a fresh perspective on solar chromosphere heating and plasma outflows, focusing on the contribution of waves generated by solar granulation. Utilizing a 2.5D numerical experiment for the partially ionized lower solar atmosphere, we investigate the dissipation of these waves and their impact on plasma outflows and chromospheric heating via ion-neutral collisions. Employing the JOint ANalytical and Numerical Approach code, we adopt two-fluid model equations, examining partially ionized hydrogen plasma dynamics, including protons+electrons and neutrals, treated as two separate fluids that are coupled through ion-neutral collisions. Our investigation focuses on a quiet solar chromosphere region characterized by gravitational stratification and magnetic confinement by an initially set single magnetic arcade. The primary source of the waves is the solar convection beneath the photosphere. Our results demonstrate that ion-neutral collisions result in the dissipation of such waves, releasing thermal energy that heats the chromosphere plasma. Notably, this is accompanied by upward-directed plasma flows. Finally, we conclude that wave dissipation due to ion-neutral collisions in the two-fluid plasma model induces chromosphere heating and plasma outflows.

Keywords: Magnetohydrodynamics, Solar photosphere, The Sun, Solar wind, Solar physics, Solar chromosphere
The Peculiar Disk Evolution of 4U 1630-472 Observed by Insight-HXMT During its 2022 and 2023 Outbursts. We study the spectral properties of the black hole X-ray transient binary 4U 1630–472 during its 2022 and 2023 outbursts with Insight-HXMT observations. We find that the outbursts are in peculiar soft states. The effect of the hardening factor on the disk temperature is taken into account by the kerrbb model, and the flux and temperature of the disk are found to follow  F∝Teff3.92±0.13  and  F∝Teff4.91±1.00  for the two outbursts, respectively. The flux–temperature relation is roughly consistent with a standard disk. By fitting with a p-free model, the p-value, the exponent of the radial dependence of the disk temperature, is found to have an anticorrelation with disk temperature. Combining a joint diagnostic analysis with a diagram of the relation between the nonthermal fraction and luminosity, we find a possible scenario that the disk evolves from 2022 to 2023 toward a slim one with a decreasing radiation efficiency, where such an evolution may depend on the fraction of the nonthermal emission in the high soft state.

Keywords: Low-mass x-ray binary stars
The Dark Energy Survey Supernova Program: Light Curves and 5 Yr Data Release. We present griz photometric light curves for the full 5 yr of the Dark Energy Survey Supernova (DES-SN) program, obtained with both forced point-spread function photometry on difference images (DiffImg) performed during survey operations, and scene modelling photometry (SMP) on search images processed after the survey. This release contains 31,636 DiffImg and 19,706 high-quality SMP light curves, the latter of which contain 1635 photometrically classified SNe that pass cosmology quality cuts. This sample spans the largest redshift (z) range ever covered by a single SN survey (0.1 &lt; z &lt; 1.13) and is the largest single sample from a single instrument of SNe ever used for cosmological constraints. We describe in detail the improvements made to obtain the final DES-SN photometry and provide a comparison to what was used in the 3 yr DES-SN spectroscopically confirmed Type Ia SN sample. We also include a comparative analysis of the performance of the SMP photometry with respect to the real-time DiffImg forced photometry and find that SMP photometry is more precise, more accurate, and less sensitive to the host-galaxy surface brightness anomaly. The public release of the light curves and ancillary data can be found at github.com/des-science/DES-SN5YR and doi:10.5281/zenodo.12720777.

Keywords: Cosmology, Type Ia supernovae, Dark energy
Ultraviolet Flux and Spectral Variability Study of Blazars Observed with UVIT/AstroSat. Blazars, the peculiar class of active galactic nuclei, are known to show flux variations across the accessible electromagnetic spectrum. Though they have been studied extensively for their flux variability characteristics across wavelengths, information on their ultraviolet (UV) flux variations on timescales of hours is very limited. Here, we present the first UV flux variability study on intraday timescales of a sample of ten blazars comprising two flat-spectrum radio quasars (FSRQs) and eight BL Lacertae objects (BL Lacs). These objects, spanning a redshift (z) range of 0.034 ≤ z ≤ 1.003, were observed in the far-UV (1300‑1800 Å) and near-UV (2000‑3000 Å) wavebands using the ultraviolet imaging telescope on board AstroSat. UV flux variations on timescales of hours were detected in nine sources out of the observed ten blazars. The spectral variability analysis showed a bluer-when-brighter trend with no difference in the UV spectral variability behavior between the studied sample of FSRQs and BL Lacs. The observed UV flux and spectral variability in our sample of both FSRQs and BL Lacs revealed that the observed UV emission in them is dominated by jet synchrotron process.

Keywords: BL Lacertae objects, Blazars, Flat-spectrum radio quasars, Active galactic nuclei, Ultraviolet photometry
Identifying Subcomponents of Mean Pulse Profiles of PSR B1822–09 with Single Pulses. Using observational data obtained with the Five-hundred-meter Aperture Spherical radio Telescope, we succeeded in identifying subcomponents of different pulse profile components of PSR B1822‑09 by the phase-to-phase cross correlations between intensity sequences of single pulses. The determined number of the subcomponents and edges of the subcomponents are consistent with the results of Gaussian fitting on the mean pulse profiles of PSR B1822‑09. According to the results, the main pulse (MP) in both the radio burst mode (B mode) and the radio-quiet mode (Q mode), the precursor (PC), and the interpulse (IP) of PSR B1822‑09 are all composed of three subcomponents. The correlation coefficients between intensity sequences at different pulse phases reveal a positive correlation between the subcomponent C8 of the MP and C3 of the IP in the Q mode, and a positive correlation between C5 of the PC and C2 of the IP during the switching process from the B mode to the Q mode. These complex correlations present a challenge for the existing scenarios that describe relations between different pulse profile components. We proposed a hypothesis that different subcomponents correspond to different subpatches on the pulsar surface, and emissions from a subpatch reveal responses of the subpatch to some variations like the voltage in the magnetosphere. Therefore, correlations between different subcomponents depend on the responses of the subpatches to the variations.

Keywords: Radio pulsars, Pulsars
Predicting the Energetic Proton Flux with a Machine Learning Regression Algorithm. The need for real-time monitoring and alerting systems for space weather hazards has grown significantly in the last two decades. One of the most important challenges for space mission operations and planning is the prediction of solar proton events (SPEs). In this context, artificial intelligence and machine learning techniques have opened a new frontier, providing a new paradigm for statistical forecasting algorithms. The great majority of these models aim to predict the occurrence of an SPE, i.e., they are based on the classification approach. This work is oriented toward the successful implementation of onboard prediction systems, which is essential for the future of space exploration. We present a simple and efficient machine learning regression algorithm that is able to forecast the energetic proton flux up to 1 hr ahead by exploiting features derived from the electron flux only. This approach could be helpful in improving monitoring systems of the radiation risk in both deep space and near-Earth environments. The model is very relevant for mission operations and planning, especially when flare characteristics and source location are not available in real time, as at Mars distance.

Keywords: Solar energetic particles, Space weather, Interplanetary physics, Solar radiation
Up, Up, and Away: Winds and Dynamical Structure as a Function of Altitude in the Ultrahot Jupiter WASP-76b. Due to the unprecedented signal strengths offered by the newest high-resolution spectrographs on 10 m class telescopes, exploring the 3D nature of exoplanets is possible with an unprecedented level of precision. In this paper, we present a new technique to probe the vertical structure of exoplanetary winds and dynamics using ensembles of planet absorption lines of varying opacity, and apply it to the well-studied ultrahot Jupiter WASP-76b. We then compare these results to state-of-the-art global circulation models (GCMs) with varying magnetic drag prescriptions. We find that the known asymmetric velocity shift in Fe I absorption during transit persists at all altitudes, and observe tentative trends for stronger blueshifts and more narrow line profiles deeper in the atmosphere. By comparing three different model prescriptions (a hydrodynamical model with no drag, a magnetic drag model, and a uniform drag model) we are able to rule out the uniform drag model due to inconsistencies with observed trends in the data. We find that the magnetic model is slightly favored over the the hydrodynamic model, and note that this 3-Gauss kinematic magnetohydrodynamical GCM is also favored when compared to low-resolution data. Future generation high-resolution spectrographs on extremely large telescopes will greatly increase signals and make methods like these possible with higher precision and for a wider range of objects.

Keywords: Exoplanet atmospheric dynamics, Exoplanet atmospheres, Exoplanet atmospheric structure
Self-similar Solutions of Oscillatory Reconnection: Parameter Study of Magnetic Field Strength and Background Temperature. Oscillatory reconnection is a specific type of time-dependent reconnection which involves periodic changes in the magnetic topology of a null point. The mechanism has been reported for a variety of magnetic field strengths and configurations, background temperatures, and densities. All these studies report an oscillation in the current density at the null point, but also report a variety of periods, amplitudes, and overall behaviors. We conduct a parametric study for equilibrium magnetic field strength and initial background temperature, solving two-dimensional resistive magnetohydrodynamic equations around a magnetic X-point. We introduce a parameter space for the ratio of internal to magnetic energy and find self-similar solutions for simulations where this ratio is below 0.1 (which represents a magnetically dominated environment or, equivalently, a low-beta plasma). Self-similarity can be seen in oscillations in the current density at the null (including amplitude and period), ohmic heating, and the temperature generated via reconnection jets. The parameter space of energy ratios also allows us to contextualize previous studies of the oscillatory reconnection mechanism and bring those different studies together into a single unified understanding.

Keywords: Solar coronal transients, Magnetohydrodynamics, Solar magnetic reconnection, Solar coronal heating, Solar physics
Energy Evolution in the Progenitor of Galaxy Shells: A Semi-analytical Model. The stellar shells surrounding an elliptical galaxy, as remnants of a dwarf galaxy disrupted during merging, reveal the distribution of energy and angular momentum of the progenitor dwarf galaxy. We develop a semi-analytical model to describe the changes in energy ΔE  i  and angular momentum ΔLz  i  for particles during the first infall. We show that these changes, induced by the self-gravity of the progenitor, are important in broadening the initial energy distribution of the Plummer or Hernquist progenitor model. Consequently, these changes are crucial in shaping the shells. In the freefall stage following the disintegration of the progenitor potential, particles are no longer bound by self-gravity but move within the gravitational potential of the target galaxy. We investigate the relationship between the radial period and the energy of particles undergoing radial motion. We show that an accurate model of the energy range of the dwarf galaxy at disruption is essential to predict the number of observable shells.

Keywords: Stellar streams, Galaxy dynamics, Galaxy mass distribution, Galaxy mergers, Interacting galaxies, N-body simulations, Astronomical simulations
Gravitational-wave and Gravitational-wave Memory Signatures of Core-collapse Supernovae. In this paper, we calculate the energy, signal-to-noise ratio (SNR), detection range, and angular anisotropy of the matter, matter memory, and neutrino memory gravitational-wave (GW) signatures of 21 three-dimensional initially nonrotating core-collapse supernova (CCSN) models carried to late times. We find that inferred energy, SNR, and detection range are angle-dependent quantities, and that the spread of possible energy, signal to noise, and detection ranges across all viewing angles generally increases with progenitor mass. When examining the low-frequency matter memory and neutrino memory components of the signal, we find that the neutrino memory is the most detectable component of a CCSN GW signal, and that DECIGO is best equipped to detect both matter memory and neutrino memory. Moreover, we find that the polarization angle between the h + and h × strains serves as a unique identifier of matter and neutrino memory. Finally, we develop a Galactic density- and stellar mass-weighted formalism to calculate the rate at which we can expect to detect CCSN GW signals with the Advanced Laser Interferometer Gravitational-Wave Observatory (aLIGO). When considering only the matter component of the signal, the aLIGO detection rate is around 65% of the total Galactic supernova rate, but increases to 90% when incorporating the neutrino memory component. We find that all future detectors (Einstein Telescope, Cosmic Explorer, DECIGO) will be able to detect CCSN GW signals from the entire Galaxy, and for the higher-mass progenitors even into the Local Group of galaxies.

Keywords: Gravitational waves, Core-collapse supernovae
Pursuing Truth: Improving Retrievals on Mid-infrared Exo-Earth Spectra with Physically Motivated Water Abundance Profiles and Cloud Models. Atmospheric retrievals are widely used to constrain exoplanet properties from observed spectra. We investigate how the common nonphysical retrieval assumptions of vertically constant molecule abundances and cloud-free atmospheres affect our characterization of an exo-Earth (an Earth-twin orbiting a Sun-like star). Specifically, we use a state-of-the-art retrieval framework to explore how assumptions for the H2O profile and clouds affect retrievals. In the first step, we validate different retrieval models on a low-noise simulated 1D mid-infrared (MIR) spectrum of Earth. Thereafter, we study how these assumptions affect the characterization of Earth with the Large Interferometer For Exoplanets (LIFE). We run retrievals on LIFE mock observations based on real disk-integrated MIR Earth spectra. The performance of different retrieval models is benchmarked against ground truths derived from remote sensing data. We show that assumptions for the H2O abundance and clouds directly affect our characterization. Overall, retrievals that use physically motivated models for the H2O profile and clouds perform better on the empirical Earth data. For observations of Earth with LIFE, they yield accurate estimates for the radius, pressure–temperature structure, and the abundances of CO2, H2O, and O3. Further, at R = 100, a reliable and bias-free detection of the biosignature CH4 becomes feasible. We conclude that the community must use a diverse range of models for temperate exoplanet atmospheres to build an understanding of how different retrieval assumptions can affect the interpretation of exoplanet spectra. This will enable the characterization of distant habitable worlds and the search for life with future space-based instruments.

Keywords: Infrared spectroscopy, Exoplanet atmospheric variability, Earth (planet), Astrobiology, Space telescopes, Biosignatures
Role of Magma Oceans in Controlling Carbon and Oxygen of Sub-Neptune Atmospheres. Most exoplanets with a few Earth radii are more inflated than bare-rock planets with the same mass, indicating a substantial volatile amount. Neither the origin of the volatiles nor the planet's bulk composition can be constrained from the mass–radius relation alone, and the spectral characterization of their atmospheres is needed to solve this degeneracy. Previous studies showed that chemical interaction between accreted volatile and possible molten rocky surface (i.e., magma ocean) can greatly affect the atmospheric composition. However, a variety in the atmospheric compositions of such planets with different properties remains elusive. In this work, we examine the dependence of atmospheric H, O, and C on planetary parameters (atmospheric thickness, planetary mass, equilibrium temperature, and magma properties such as redox state) assuming nebula gas accretion on an Earth-like core, using an atmosphere-magma chemical equilibrium model. Consistent with previous work, we show that atmospheric H2O fraction on a fully molten rocky interior with an Earth-like redox state is on the order of 10‑2–10‑1 regardless of other planetary parameters. Despite the solubility difference between H- and C-bearing species, C/H increases only a few times above the nebula value except for atmospheric pressure ≲1000 bar and H2O fraction ≳10%. This results in a negative O/H–C/O trend and depleted C/O below one-tenth of the nebula gas value under an oxidized atmosphere, which could provide a piece of evidence of rocky interior and endogenic water. We also highlight the importance of constraints on the high-pressure material properties for interpreting the magma–atmospheric interaction of inflated planets.

Keywords: Extrasolar rocky planets, Exoplanet formation, Planetary interior, Exoplanet atmospheres