Sazuna/UAT_keywords huggingface dataset:
Strong Coupling of Hydrodynamics and Reactions in Nuclear Statistical Equilibrium for Modeling Convection in Massive Stars. We build on the simplified spectral deferred corrections (SDC) coupling of hydrodynamics and reactions to handle the case of nuclear statistical equilibrium (NSE) and electron/positron captures/decays in the cores of massive stars. Our approach blends a traditional reaction network on the grid with a tabulated NSE state from a very large,   nuclei network. We demonstrate how to achieve second-order accuracy in the simplified-SDC framework when coupling NSE to hydrodynamics, with the ability to evolve the star on the hydrodynamics time step. We discuss the application of this method to convection in massive stars leading up to core collapse. We also show how to initialize the initial convective state from a 1D model in a self-consistent fashion. All of these developments are done in the publicly available Castro simulation code and the entire simulation methodology is fully GPU-accelerated.

Keywords: Hydrodynamical simulations, Explosive nucleosynthesis, Hydrodynamics, Nucleosynthesis, Reaction rates, GPU computing, Reaction rate equations, Supernova dynamics
Identifying New High-confidence Polluted White Dwarf Candidates Using Gaia XP Spectra and Self-organizing Maps. The identification of new white dwarfs (WDs) polluted with heavy elements is important since they provide a valuable tool for inferring the chemical properties of putative planetary systems accreting material on their surfaces. The Gaia space mission has provided us with an unprecedented amount of astrometric, photometric, and low-resolution (XP) spectroscopic data for millions of newly discovered stellar sources, among them thousands of WDs. In order to find WDs among these data and to identify which ones have metals in their atmospheres, we propose a methodology based on an unsupervised artificial intelligence technique called self-organizing maps. In our approach, a nonlinear high-dimensional data set is projected on a 2D grid map where similar elements fall into the same neuron. By applying this method, we obtained a clean sample of 66,337 WDs. We performed an automatic spectral classification analysis on them, obtaining 143 bona fide polluted WD candidates not previously classified in the literature. The majority of them are cool WDs and we identify in their XP spectra several metallic lines such as Ca, Mg, Na, Li, and K. The fact that we obtain similar precision metrics to those achieved with recent supervised techniques highlights the power of our unsupervised approach to mine the Gaia archives for hidden treasures to follow up spectroscopically with higher resolution.

Keywords: White dwarf stars, Astronomy data analysis, Catalogs
The JCMT BISTRO Survey: The Magnetic Fields of the IC 348 Star-forming Region. We present 850 μm polarization observations of the IC 348 star-forming region in the Perseus molecular cloud as part of the B-fields In STar-forming Region Observation survey. We study the magnetic properties of two cores (HH 211 MMS and IC 348 MMS) and a filamentary structure of IC 348. We find that the overall field tends to be more perpendicular than parallel to the filamentary structure of the region. The polarization fraction decreases with intensity, and we estimate the trend by power law and the mean of the Rice distribution fittings. The power indices for the cores are much smaller than 1, indicative of possible grain growth to micron size in the cores. We also measure the magnetic field strengths of the two cores and the filamentary area separately by applying the Davis–Chandrasekhar–Fermi method and its alternative version for compressed medium. The estimated mass-to-flux ratios are 0.45–2.20 and 0.63–2.76 for HH 211 MMS and IC 348 MMS, respectively, while the ratios for the filament are 0.33–1.50. This result may suggest that the transition from subcritical to supercritical conditions occurs at the core scale (∼0.05 pc) in the region. In addition, we study the energy balance of the cores and find that the relative strength of turbulence to the magnetic field tends to be stronger for IC 348 MMS than for HH 211 MMS. The result could potentially explain the different configurations inside the two cores: a single protostellar system in HH 211 MMS and multiple protostars in IC 348 MMS.

Keywords: Interstellar filaments, Molecular clouds, Interstellar magnetic fields, Star formation, Interstellar medium, Submillimeter astronomy, Polarimetry
Sun-as-a-Star Spectral Line Variability in the 300–2390 nm Wavelength Range. Combining the near-daily Ozone Monitoring Instrument (OMI) and Tropospheric Monitoring Instrument (TROPOMI) measurements of solar spectra, we construct line indices (line-core to line-flanks ratios) for various transitions (mainly Fe I) in the 300–2390 nm spectral domain. The indices are supplemented by the wavelength-binned fluxes from OMI and Total and Spectral Solar Irradiance Sensor (TSIS-1). To study the short-term (solar-rotational) patterns, we normalize the indices and fluxes to the minimum-activity epoch, then de-trend them with 81 day running means. Comparisons of the de-trended TSIS-1 and OMI fluxes with the NASA-NOAA-LASP SSI (NNLSSI1) model show excellent agreement, to (0.5–2.2) × 10‑4 in the normalized and de-trended data. The data are subjected to a multiregression analysis against quantities representing the facular brightening and the sunspot darkening. The de-trended line indices and average fluxes show different sensitivities to these two solar magnetic-activity manifestations, with the fluxes being far more susceptible to the sunspot component. The de-trended line indices experience a rapid drop of activity levels towards longer wavelengths, albeit with a large rebound in the short-wave infrared (SWIR) domain that is caused by the ubiquitous, temperature-sensitive CO transitions. The wavelength-dependent activity also falls, however much slower, in the de-trended average fluxes. Qualitatively similar behavior is captured by semiempirical models.

Keywords: Solar cycle, Solar spectral irradiance, Sunspots, Solar active regions, Solar activity
Evolution of Cataclysmic Variables with Binary-driven Mass Loss during Nova Eruptions. The discrepancies between observations and theoretical predictions of cataclysmic variables (CVs) suggest that there exists unknown angular-momentum-loss mechanism(s) besides magnetic braking and gravitational radiation. Mass loss due to nova eruptions belongs to the most likely candidates. While standard theory assumes that mass is lost in the form of radiation-driven, optically thick wind (fast wind), recent numerical simulations indicate that most of the mass loss is initiated and shaped by binary interaction. We explore the effect of this binary-driven mass loss (BDML) on the CV evolutions assuming a major fraction of the lost mass leaves the system from the outer Lagrangian point. Different from the traditional continuous wind picture, we consider the mass loss process to be instantaneous because the duration of nova eruptions is much shorter than the binary evolutionary timescale. Our detailed binary evolution calculations reveal the following results. (1) BDML seems able to provide extra angular momentum loss below the period gap. The mass transfer rates at a given orbital period occupy a large range, in agreement with the observed secular mass transfer rate distribution in CVs. (2) The enhanced mass transfer rates do not lead to a runaway mass transfer process and allow the white dwarfs to grow mass ≲0.1 M ☉. (3) BDML can cause both positive and negative variations in the orbital period induced by nova eruptions, in line with observations, and can potentially explain the properties of some peculiar supersoft X-ray sources likely CAL 87, 1E 0035.4‑7230, and RX J0537.7‑7034.

Keywords: White dwarf stars, Cataclysmic variable stars
A Buddy for Betelgeuse: Binarity as the Origin of the Long Secondary Period in α Orionis. We predict the existence of α Ori B, a low-mass companion orbiting Betelgeuse. This is motivated by the presence of a 2170 day long secondary period (LSP) in Betelgeuse's lightcurve, a periodicity that is ≈5 times longer than the star's 416 day fundamental radial pulsation mode. While binarity is currently the leading hypothesis for LSPs in general, the LSP and the radial velocity (RV) variations observed in Betelgeuse, taken together, necessitate a revision of the prevailing physical picture. Specifically, the lightcurve–RV phase difference requires a companion to be behind Betelgeuse at the LSP luminosity minimum, ≈180° out of phase with the system orientation associated with occultation. We demonstrate the consistency of this model with available observational constraints and identify tensions in all other proposed LSP hypotheses. Within this framework, we calculate a mass for α Ori B of   and an orbital separation of 1850 ± 70 R ⊙, or   times the radius of Betelgeuse. We then describe the features of the companion as constrained by the fundamental parameters of Betelgeuse and its orbital system, and discuss what would be required to confirm the companion's existence observationally.

Keywords: Binary stars, Red supergiant stars, Stellar pulsations, Massive stars, Long period variable stars, Pulsation modes, Circumstellar dust
GOALS-JWST: The Warm Molecular Outflows of the Merging Starburst Galaxy NGC 3256. We present James Webb Space Telescope (JWST) integral-field spectrograph observations of NGC 3256, a local infrared-luminous late-stage merging system with two nuclei roughly 1 kpc apart, both of which have evidence of cold molecular outflows. Using JWST/NIRSpec and Mid-Infrared Instrument data sets, we investigate this morphologically complex system on spatial scales of &lt;100 pc, where we focus on the warm molecular H2 gas surrounding the nuclei. We detect collimated outflowing warm H2 gas originating from the southern nucleus, though we do not find significant outflowing H2 gas surrounding the northern nucleus. We measure maximum intrinsic outflow velocities of ∼1000 km s−1, which extend out to a distance of 0.7 kpc. Based on H2 S(7)/S(1) ratios, we find a larger fraction of warmer gas near the southern nucleus, which decreases with increasing distance from the nucleus, signifying the southern nucleus as a primary source of H2 heating. The gas mass of the warm H2 outflow component is estimated to be M warm ,out = (1.4 ± 0.2) × 106 M ⊙, as much as 6% of the cold H2 mass estimated using Atacama Large Millimeter/submillimeter Array CO data. The outflow timescale is about 7 × 105 yr, resulting in a mass outflow rate   and kinetic power P warm,out ∼ 4 × 1041 erg s−1. Lastly, regions within our 3.″0 × 3.″0 NIRSpec data, where the outflowing gas reside show high [Fe II]/Paβ and H2/Brγ line ratios, indicate enhanced mechanical heating caused by the outflows. The fluxes and ratios of polycyclic aromatic hydrocarbons (PAHs) in these regions are not significantly different compared to those elsewhere in the disk, suggesting the outflows may not significantly alter the PAH ionization state or grain size.

Keywords: Molecular gas, Infrared astronomy, Galaxy winds, Galaxy mergers, Infrared sources, Luminous infrared galaxies
Turbulent Pressure Heats Gas and Suppresses Star Formation in Galactic Bar Molecular Clouds. The Central Molecular Zone (CMZ) of the Milky Way is fed by gas inflows from the Galactic disk along almost radial trajectories aligned with the major axis of the Galactic bar. However, despite being fundamental to all processes in the nucleus of the Galaxy, these inflows have been studied significantly less than the CMZ itself. We present observations of various molecular lines between 215 and 230 GHz for 20 clouds with ∣ℓ∣ &lt; 10°, which are candidates for clouds in the Galactic bar due to their warm temperatures and broad lines relative to typical Galactic disk clouds, using the Atacama Large Millimeter/submillimeter Array Atacama Compact Array. We measure gas temperatures, shocks, star formation rates, turbulent Mach numbers, and masses for these clouds. Although some clouds may be in the Galactic disk despite their atypical properties, nine clouds are likely associated with regions in the Galactic bar, and in these clouds, turbulent pressure is suppressing star formation. In clouds with no detected star formation, turbulence is the dominant heating mechanism, whereas photoelectric processes heat the star-forming clouds. We find that the ammonia (NH3) and formaldehyde (H2CO) temperatures probe different gas components, and in general, each transition appears to trace different molecular gas phases within the clouds. We also measure the CO-to-H2 X-factor in the bar to be an order of magnitude lower than the typical Galactic value. These observations provide evidence that molecular clouds achieve CMZ-like properties before reaching the CMZ.

Keywords: Molecular clouds, Star formation, Interstellar medium, Milky Way Galaxy, Galactic bar
Neural Network Constraints on the Cosmic-Ray Ionization Rate and Other Physical Conditions in NGC 253 with ALCHEMI Measurements of HCN and HNC. We use a neural network model and Atacama Large Millimeter/submillimeter Array (ALMA) observations of HCN and HNC to constrain the physical conditions, most notably the cosmic-ray ionization rate (CRIR, ζ), in the Central Molecular Zone (CMZ) of the starburst galaxy NGC 253. Using output from the chemical code UCLCHEM, we train a neural network model to emulate UCLCHEM and derive HCN and HNC molecular abundances from a given set of physical conditions. We combine the neural network with radiative transfer modeling to generate modeled integrated intensities, which we compare to measurements of HCN and HNC from the ALMA Large Program ALCHEMI. Using a Bayesian nested sampling framework, we constrain the CRIR, molecular gas volume and column densities, kinetic temperature, and beam-filling factor across NGC 253's CMZ. The neural network model successfully recovers UCLCHEM molecular abundances with ∼3% error and, when used with our Bayesian inference algorithm, increases the parameter-inference speed tenfold. We create images of these physical parameters across NGC 253's CMZ at 50 pc resolution and find that the CRIR, in addition to the other gas parameters, is spatially variable with ζ ∼ a few ×10−14 s−1 at r ≳ 100 pc from the nucleus, increasing to ζ &gt; 10−13 s−1 at its center. These inferred CRIRs are consistent within 1 dex with theoretical predictions based on nonthermal emission. Additionally, the high CRIRs estimated in NGC 253's CMZ can be explained by the large number of cosmic-ray-producing sources as well as a potential suppression of cosmic-ray diffusion near their injection sites.

Keywords: Molecular gas, Starburst galaxies, Stellar feedback, Neural networks, Star forming regions, Cosmic ray astronomy, Astrochemistry, Galaxy nuclei, Interstellar medium
Radial Evolution of Non-Maxwellian Electron Populations Derived from Quasi-thermal Noise Spectroscopy: Parker Solar Probe Observations. Understanding the transport of energy within space plasmas, particularly in the solar wind, remains a complex challenge. Accurate measurement of electron temperatures and their nonthermal characteristics is crucial for comprehending energy transport properties in plasmas. Quasi-thermal-noise (QTN) spectroscopy has emerged as a dependable tool for precise electron parameters assessment as it is less susceptible to spacecraft effects than particle detectors. In this study, we apply a QTN spectroscopy fitting method to analyze data from the Parker Solar Probe FIELDS radio instrument obtained during Encounters 2 through 13, under unbiased antenna conditions. We use the kappa function to characterize the electron velocity distribution and employ a fitting technique to derive the changes in each parameter across heliocentric distances ranging from 12 Rs to 76 Rs. Specifically, we find that the electron density scales as n  e  ∝ r ‑2.09±0.04 and the T  e  ∝ r ‑0.65±0.02. The distribution of the kappa index has three distinct regions as a function of radial distance from the Sun. Furthermore, we conduct a statistical analysis of solar wind energy flux which we finds follows a power-law relationship w total ∝ r ‑1.92±0.04.

Keywords: Space probes
Investigating the Potential of LS 5039 as a Triple System Using Fermi-LAT Data. LS 5039 is one of a handful of γ-ray binary systems in the milky Way, comprising a pulsar and a massive O-type companion star with an orbital period of 3.9 days. Recently, we conducted a data analysis using approximately 16 yr of Fermi Large Area Telescope observations, spanning from 2008 August 4 to 2024 July 8. In our timing analysis, we discovered two new periodic signals with frequencies higher and lower than the known orbital period. The higher-frequency signal has a period of 3.63819 days with a 7.1σ confidence level, while the lower-frequency signal has a period of 4.21654 days with a 6.3σ confidence level. Additionally, in data from the High Energy Stereoscopic System of Cherenkov telescopes, two potential signals are found with periods similar to the two newly discovered ones. Considering that these two signals fall within the same frequency interval as the orbital period, we suggest the possibility of a third body orbiting the barycenter of the LS 5039 binary system, with the new periodic signals arising from specific frequency combinations of the two orbital periods.

Keywords: Gamma-ray sources, Periodic variable stars, Gamma-rays
Astrophysical Properties of the Sirius Binary System Modeled with MESA. Sirius is the brightest star in the night sky and, despite its proximity, this binary system still imposes intriguing questions about its current characteristics and past evolution. H. E. Bond et al. published decades of astronometric measurements of the Sirius system, determining the dynamical masses for Sirius A and B, and the orbital period. We have used these determinations, combined with photometric determinations for luminosity and spectroscopic determinations of effective temperature (T eff) and metallicity, to model the evolution of the Sirius system using Modules for Experiments in Stellar Astrophysics. We have constructed a model grid calculated especially for this system and were able to obtain, for Sirius B, a progenitor mass of 6.0 ± 0.6 M ⊙, yielding a white dwarf mass of 1.015 ± 0.189 M ⊙. Our best determination for the age of the system is 203.6 ± 45 Myr with a metallicity of 0.0124. We have compared our best-fit models with the ones computed using TYCHO, YREC, and PARSEC, establishing external uncertainties. Our results are consistent with the observations and support a noninteracting past.

Keywords: White dwarf stars, Computational astronomy, DA stars
Neutrino Detection Rates from Lepto-hadronic Model Simulations of Bright Blazar Flares. There is mounting evidence that blazars are the sources of part of the very-high-energy astrophysical neutrino flux detected by IceCube. In particular, there have been several spatial and temporal coincidences of individual IceCube neutrino events with flaring blazars, the most prominent of them being IceCube-170922A, coincident with a multiwavelength flare of TXS 0506+056. Motivated by this, we used the time-dependent lepto-hadronic code OneHaLe to model the spectral energy distributions and light curves of a sample of bright γ-ray flares of blazars detected by Fermi-Large Area Telescope, for which Kreter et al. provided calorimetric estimates of the expected neutrino detection rates. Flares were modeled with temporal changes of the proton injection spectra. Our analysis shows that the calorimetric approach overestimates the increase in neutrino production by a factor of typically ∼10 if the γ-ray emission is dominated by proton-synchrotron radiation.

Keywords: Blazars, Neutrino astronomy, Gamma-ray astronomy, Active galactic nuclei
Absolute Dimensions of the Interferometric Binary HD 174881: A Test of Stellar Evolution Models for Evolved Stars. We report high-resolution spectroscopic monitoring and long-baseline interferometric observations with the Palomar Testbed Interferometer (PTI) of the 215 day binary system HD 174881 (K1 II-III), composed of two giant stars. The system is spatially resolved with the PTI, as well as in archival measurements with the CHARA Array. Our analysis of these observations, along with an analysis of the spectral energy distribution, have allowed us to infer accurate values for the absolute masses (  and  ), radii (34.0 ± 1.3 and 22.7 ± 1.8 R ☉), effective temperatures (4620 ± 100 and 4880 ± 150 K), and bolometric luminosities of both components, as well as other properties including the orbital parallax (distance). These provide valuable tests of stellar evolution models for evolved stars, which are still relatively uncommon compared to the situation for main-sequence stars. We find generally good agreement of all of these properties of HD 174881 with two sets of recent models (MIST and PARSEC) at compositions near solar, for ages of 255–273 Myr. We also find evidence of an infrared excess, based largely on the flux measurements from IRAS at 60 and 100 μm.

Keywords: Giant stars, Stellar evolutionary models, Spectroscopic binary stars, Interferometric binary stars, Stellar evolution
Post-Keplerian Perturbations of the Hyperbolic Motion in the Field of a Rotating Massive Object: Analysis in Terms of Osculating and Nonosculating (Contact) Elements. The perturbations of the hyperbolic motion of a test particle due to the general relativistic gravitoelectromagnetic Schwarzschild and Lense–Thirring components of the gravitational field of a rotating massive body are analytically worked out to the first post-Newtonian level in terms of the osculating Keplerian orbital elements. To the Newtonian order, the impact of the quadrupole mass moment of the source is calculated as well. The resulting analytical expressions are valid for a generic orientation in space of both the orbital plane of the probe and the spin axis of the primary, and for arbitrary values of the eccentricity. They are applied to 'Oumuamua, an interstellar asteroid which recently visited our solar system along an unbound heliocentric orbit, and to the Near Earth Asteroid Rendezvous spacecraft during its flyby of the Earth. The calculational approach developed can be straightforwardly extended to any alternative models of gravity as well.

Keywords: Celestial mechanics, General relativity, Planetary probes
Detection of Diffuse Hot Gas around the Young, Potential Superstar Cluster H72.97–69.39. We present the first Chandra X-ray observations of H72.97–69.39, a highly embedded, potential superstar cluster in its infancy located in the star-forming complex N79 of the Large Magellanic Cloud. We detect particularly hard, diffuse X-ray emission that is coincident with the young stellar objects identified with JWST, and the hot gas fills cavities in the dense gas mapped by the Atacama Large Millimeter/submillimeter Array. The X-ray spectra are best fit with either a thermal plasma or power-law model, and assuming the former, we show that the X-ray luminosity of L X = (1.0 ± 0.3) × 1034 erg s‑1 is a factor of ∼20 below the expectation for a fully confined wind bubble. Our results suggest that stellar wind feedback produces diffuse hot gas in the earliest stages of massive star cluster formation and that wind energy can be lost quickly via either turbulent mixing followed by radiative cooling or by physical leakage.

Keywords: Young star clusters, H II regions, Stellar wind bubbles