Sazuna/UAT_keywords huggingface dataset:
The Role of Inhomogeneities in Supernova Shock Breakout Emission. The breakout of a supernova blast wave from its progenitor star provides strong constraints on the star and its immediate surroundings. These surroundings are shaped by mass loss from the star and can include a wide variety of inhomogeneities. Here we present results of multidimensional radiation-hydrodynamics calculations of the interactions of the supernova blast wave with inhomogeneities in the immediate surroundings of a massive Wolf-Rayet star, calculating the effect these interactions have on the shock breakout signal from supernovae.

Keywords: Transient sources, Stellar dynamics, Supernovae, X-ray sources
On the Measurement of Handedness in Fermi Large Area Telescope Data. A handedness in the arrival directions of high-energy photons from outside our Galaxy can be related to the helicity of an intergalactic magnetic field. Previous estimates by Tashiro et al. and Chen et al. showed a hint of a signal present in the photons observed by the Fermi Large Area Telescope (LAT). An update on the measurement of handedness in Fermi-LAT data is presented using more than 10 yr of observations. Simulations are performed to study the uncertainty of the measurements, taking into account the structure of the exposure caused by the energy-dependent instrument response and its observing profile, as well as the background from the interstellar medium. The simulations are required to accurately estimate the uncertainty and to show that previously the uncertainty was significantly underestimated. The apparent signal in the earlier analysis of Fermi-LAT data is rendered nonsignificant.

Keywords: Gamma-rays, Extragalactic magnetic fields
Ns 1987A in SN 1987A. The possible detection of a compact object in the remnant of SN 1987A presents an unprecedented opportunity to follow its early evolution. The suspected detection stems from an excess of infrared emission from a dust blob near the compact object's predicted position. The infrared excess could be due to the decay of isotopes like 44Ti, accretion luminosity from a neutron star or black hole, magnetospheric emission or a wind originating from the spin down of a pulsar, or to thermal emission from an embedded, cooling neutron star (NS 1987A). It is shown that the last possibility is the most plausible as the other explanations are disfavored by other observations and/or require fine-tuning of parameters. Not only are there indications that the dust blob overlaps the predicted location of a kicked compact remnant, but its excess luminosity also matches the expected thermal power of a 30 yr old neutron star. Furthermore, models of cooling neutron stars within the minimal cooling paradigm readily fit both NS 1987A and Cas A, the next-youngest known neutron star. If correct, a long heat transport timescale in the crust and a large effective stellar temperature are favored, implying relatively limited crustal n-1S0 superfluidity and an envelope with a thick layer of light elements, respectively. If the locations do not overlap, then pulsar spin down or accretion might be more likely, but the pulsar's period and magnetic field or the accretion rate must be rather finely tuned. In this case, NS 1987A may have enhanced cooling and/or a heavy-element envelope.

Keywords: Neutron stars, Supernovae
Tracking and Seismological Analysis of Multiple Coronal Loops in an Active Region. We present a new method to track the position and evolution of coronal loops designed for observations such as active regions in which multiple loops appear in close proximity or overlap with each other along the observational line of sight. The method is based on modeling a time-distance map containing one or more loops and fitting the modeled map to observational data, as opposed to the commonly used technique of analyzing each frame independently. This allows us to control the variability of the model, informed by our physical interpretation, and use the trends present to help constrain the model parameters. We apply our method to an observation of a bundle of coronal loops previously investigated using a spatiotemporal autocorrelation method and compare our results. A benefit of our method is that it provides the time series for the position of the loops that may be used for further analysis using established seismological techniques. We demonstrate this by modeling the oscillation of several loops in response to flaring energy releases that occur during the observation, and we find evidence of loop evolution consistent with the Kelvin-Helmholtz instability.

Keywords: Magnetohydrodynamics, Solar extreme ultraviolet emission, Solar coronal loops, Astronomy data analysis, Solar coronal waves, Solar corona, Solar coronal seismology
Semianalytic Expressions for the Isolation and Coupling of Mixed Modes. In the oscillation spectra of giant stars, nonradial modes may be seen to undergo avoided crossings, which produce a characteristic "mode bumping" of the otherwise uniform asymptotic p- and g-mode patterns in their respective echelle diagrams. Avoided crossings evolve very quickly relative to typical observational errors and are therefore extremely useful in determining precise ages of stars, particularly in subgiants. This phenomenon is caused by coupling between modes in the p- and g-mode cavities that are near resonance with each other. Most theoretical analyses of the coupling between these mode cavities rely on the Jeffreys-Wentzel-Kramers-Brillouin approach, which is strictly speaking inapplicable to the low-order g modes observed in subgiants or the low-order p modes seen in very evolved red giants. We present both a nonasymptotic prescription for isolating the two mode cavities, as well as a perturbative (and also nonasymptotic) description of the coupling between them, which we show to hold good for the low-order g and p modes in these physical situations. Finally, we discuss how these results may be applied to modeling subgiant stars and determining their global properties from oscillation frequencies. We also make our code for all of these computations publicly available.

Keywords: Stellar oscillations, Computational methods, Asteroseismology
Mapping Outflowing Gas in the Fermi Bubbles: A UV Absorption Survey of the Galactic Nuclear Wind. Using new ultraviolet (UV) spectra of five background quasars from the Cosmic Origins Spectrograph on the Hubble Space Telescope, we analyze the low-latitude ( $| b| =20^\circ \mbox{--}30^\circ $ ) regions of the Fermi Bubbles, the giant gamma-ray-emitting lobes at the Galactic Center. We combine these data with previous UV and atomic hydrogen (H I) data sets to build a comprehensive picture of the kinematics and metal column densities of the cool outflowing clouds entrained in the Fermi Bubbles. We find that the number of UV absorption components per sight line decreases as a function of increasing latitude, suggesting that the outflowing clouds become less common with increasing latitude. The Fermi Bubble H I clouds are accelerated up to b ∼ 7°, whereas when we model the UV Fermi Bubbles clouds' deprojected flow velocities, we find that they are flat or even accelerating with distance from the Galactic center. This trend, which holds in both the northern and southern hemispheres, indicates that the nuclear outflow accelerates clouds throughout the Fermi Bubbles or has an acceleration phase followed by a coasting phase. Finally, we note the existence of several blueshifted high-velocity clouds at latitudes exceeding ∼30°, whose velocities cannot be explained by gas clouds confined to the inside of the gamma-ray-defined Fermi Bubbles. These anomalous-velocity clouds are likely in front of the Fermi Bubbles and could be remnants from past nuclear outflows. Overall, these observations form a valuable set of empirical data on the properties of cool gas in nuclear winds from star-forming galaxies. * Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. These observations are associated with program 15339.

Keywords: Milky Way evolution, High-velocity clouds, Milky Way Galaxy, Galactic center
A Mid-infrared Flare in the Active Galaxy MCG-02-04-026: Dust Echo of a Nuclear Transient Event. We report the discovery of a mid-infrared (MIR) flare using Wide field Infrared Survey Explorer data in the center of the nearby Seyfert 1.9 galaxy MCG-02-04-026. The MIR flare began in the first half of 2014, peaked around the end of 2015, and faded in 2017. During these years, energy of more than 7 × 1050 erg was released in the infrared, and the flare's MIR color was generally turning red. We detected neither optical nor ultraviolet (UV) variation corresponding to the MIR flare based on available data. We explained the MIR flare using a dust echo model in which the radiative transfer is involved. The MIR flare can be well explained as thermal reradiation from dust heated by UV-optical photons of a primary nuclear transient event. Although the transient event was not seen directly owing to dust obscuration, we can infer that it may produce a total energy of at least ∼1051 erg, most of which was released in less than ∼3 yr. The nature of the transient event could be a stellar tidal disruption event by the central supermassive black hole (SMBH), or a sudden enhancement of the existing accretion flow onto the SMBH, or a supernova that was particularly bright.

Keywords: Infrared astronomy, Active galaxies, Transient sources
A Global Nonhydrostatic Atmospheric Model with a Mass- and Energy-conserving Vertically Implicit Correction (VIC) Scheme. Global nonhydrostatic atmospheric models are becoming increasingly important for studying the climates of planets and exoplanets. However, such models suffer from computational difficulties due to the large aspect ratio between the horizontal and vertical directions. To overcome this problem, we developed a global model using a vertically implicit correction (VIC) scheme in which the integration time step is no longer limited by the vertical propagation of acoustic waves. We proved that our model, based on the Athena++ framework and its extension for planetary atmospheres—SNAP (Simulating Nonhydrostatic Atmospheres on Planets), rigorously conserves mass and energy in finite-volume simulations. We found that traditional numerical stabilizers such as hyperviscosity and divergence damping are not needed when using the VIC scheme, which greatly simplifies the numerical implementation and improves stability. We present simulation results ranging from 1D linear waves to 3D global circulations with and without the VIC scheme. These tests demonstrate that our formulation correctly tracks local turbulent motions, produces Kelvin-Helmholtz instability, and generates a super-rotating jet on hot Jupiters. Employing this VIC scheme improves the computational efficiency of global simulations by more than two orders of magnitude compared to an explicit model and facilitates the capability of simulating a wide range of planetary atmospheres both regionally and globally.

Keywords: Computational methods, Planetary atmospheres, Exoplanet atmospheres, Atmospheric science
A 3 mm Chemical Exploration of Small Organics in Class I YSOs. There is mounting evidence that the composition and structure of planetary systems are intimately linked to their birth environments. During the past decade, several spectral surveys probed the chemistry of the earliest stages of star formation and late planet-forming disks. However, very little is known about the chemistry of intermediate protostellar stages, i.e., class I young stellar objects (YSOs), where planet formation may have already begun. We present here the first results of a 3 mm spectral survey performed with the IRAM 30 m telescope to investigate the chemistry of a sample of seven class I YSOs located in the Taurus star-forming region. These sources were selected to embrace the wide diversity identified for low-mass protostellar envelope and disk systems. We present detections and upper limits of 13 small (Natoms ≤ 3) C, N, O, and S carriers—namely, CO, HCO+, HCN, HNC, CN, N2H+, C2H, CS, SO, HCS+, C2S, SO2, and OCS—and some of their D, 13C, 15N, 18O, 17O, and 34S isotopologues. Together, these species provide constraints on gas-phase C/N/O ratios, D and 15N fractionation, source temperature, and UV exposure, as well as the overall S chemistry. We find substantial evidence of chemical differentiation among our source sample, some of which can be traced back to class I physical parameters, such as the disk-to-envelope mass ratio (proxy for class I evolutionary stage), source luminosity, and UV field strength. Overall, these first results allow us to start investigating the astrochemistry of class I objects; however, interferometric observations are needed to differentiate envelope versus disk chemistry.

Keywords: Interstellar molecules, Millimeter astronomy, Surveys, Astrochemistry, Young stellar objects, Radio observatories
The Decaying and Scattering Properties of the d*(2380) Hexaquark Bose-Einstein Condensate Dark Matter. Recently, a study has shown that the Bose-Einstein condensates (BECs) formed by the d*(2380) hexaquarks (d*(2380)-BECs) can be thermally produced in the early universe and they are stable enough to be a competitive candidate for dark matter. Searching for the decaying signature of d*(2380)-BECs is a possible way to verify this dark matter model. In this article, we discuss the scattering and decaying properties of the d*(2380)-BECs and we show that the decay rate of the d*(2380)-BECs is correlated with the TeV cosmic-ray flux. The predicted average decay rate in our Galaxy is several orders of magnitude larger than the current observed upper limit. Therefore, it would be very difficult for us to search for the decaying signature of the d*(2380)-BEC dark matter model. Nevertheless, the size of the d*(2380)-BECs may be large enough to have self-interaction so that we can possibly detect them in the future.

Keywords: Particle astrophysics, Dark matter, Particle physics
Emergence of an Ultrared, Ultramassive Galaxy Cluster Core at z = 4. Recent simulations and observations of massive galaxy cluster evolution predict that the majority of stellar mass buildup happens within cluster members by z = 2, before cluster virialization. Protoclusters rich with dusty, star-forming galaxies (DSFGs) at z &gt; 3 are the favored candidate progenitors for these massive galaxy clusters at z ∼ 0. We present here the first study analyzing stellar emission along with cold dust and gas continuum emission in a spectroscopically confirmed z = 4.002 protocluster core rich with DSFGs, the Distant Red Core (DRC). We combine new Hubble Space Telescope and Spitzer data with existing Gemini, Herschel, and Atacama Large Millimeter/submillimeter Array observations to derive individual galaxy-level properties and compare them to coeval field and other protocluster galaxies. All of the protocluster members are massive (&gt;1010 M☉), but not significantly more so than their coeval field counterparts. Within uncertainty, all are nearly indistinguishable from galaxies on the star-forming versus stellar mass main-sequence relationship and the star formation efficiency plane. Assuming no future major influx of fresh gas, we estimate that these gaseous DSFGs will deplete their gas reservoirs in ∼300 Myr, becoming the massive quiescent ellipticals dominating cluster cores by z ∼ 3. Using various methodologies, we derive a total z = 4 halo mass of ∼1014 M☉ and estimate that the DRC will evolve to become an ultramassive cluster core of mass ≳1015 M☉ by z = 0.

Keywords: Galaxy evolution, Galaxy clusters, Infrared galaxies, High-redshift galaxy clusters
Non-LTE Calculations of the Mg I 12.32 μm Line in a Flaring Atmosphere. The infrared Mg I lines near 12 μm are a pair of emission lines that are magnetically sensitive and have been used to measure solar magnetic fields. Here we calculate the response of the Mg I 12.32 μm line during a flare and find that in our modeling this line has a complicated behavior. At the beginning of the flare heating, this line shows an intensity dimming at the line center. The intensity then increases when heating continues, with increasing contributions from the heated layers in the chromosphere. The line formation height and the line width also increase as a result. As for the polarized line profiles, we find that flare heating tends to decrease the Zeeman splitting width and attenuates the Stokes V lobe intensity. The wider features in the Stokes V profiles are more pronounced during flare heating, which should be considered when performing magnetic field inversions.

Keywords: Solar photosphere, Solar flare spectra, Infrared astronomy, Radiative transfer simulations, Solar chromosphere
Heuristic Description of Perpendicular Particle Transport in Turbulence with Super-diffusive Magnetic Field Lines. Recently a heuristic description of collisionless perpendicular diffusion of energetic particles was presented. The latter approach describes the transport of energetic particles across a mean magnetic field based on simple physical arguments. Although this approach was developed with the intention to improve our understanding of perpendicular diffusion, this heuristic approach also provided some interesting quantitative results such as an explanation of the factor a2 used in the past to balance out inaccuracies of systematic analytical theories. However, the aforementioned heuristic approach is based on the assumption that magnetic field lines become diffusive after overcoming the initial free-streaming regime. In the current paper we alter the heuristic approach to make it applicable for turbulence spectra leading to super-diffusive magnetic fields lines. It is argued that particle diffusion is still restored in the late time limit. In the high-energy limit this recovery of diffusion is based on a hybrid model in which particles move half ballistically and half diffusively in the parallel direction. Furthermore, this leads to the relation ${\lambda }_{\perp }\propto {\lambda }_{\parallel }^{1/3}$ between perpendicular and parallel mean free paths of the energetic particles. This type of transport was obtained in the past from test-particle simulations as well as systematic analytical theories. In the current paper we present the first time an explanation of this behavior based on simple physical arguments.

Keywords: Interplanetary turbulence, Solar energetic particles, Galactic cosmic rays
KIC 12268220: A δ Scuti Pulsating Star and an Active Protohelium White Dwarf in an Eclipsing Binary System. We present a photometric, spectroscopic, asteroseismic, and evolutionary analysis of the Algol-type eclipsing binary KIC 12268220. We find the O'Connell effect and anticorrelated eclipse timing variations in the Kepler light curve, revealing the presence of large starspots. Radial velocities and atmospheric parameters are obtained from ground-based spectroscopic observations. Combined with the radial velocity measurements and Gaia-derived total luminosity, our light-curve modeling yields the solution of the physical parameters for both the primary and secondary components. We find 14 independent frequencies arising from the δ Scuti primary, and the observed frequencies agree with the frequency range of unstable modes from nonadiabatic calculations. Based on the conclusion from previous literature, we run a grid of models to study the evolution process of our system. The evolutionary tracks of our model suggest that the low-mass ( $\sim 0.23\,{M}_{\odot }$ ) evolved secondary shows a similar evolutionary state to the R CMa-type system, which might evolve to an EL CVn system.

Keywords: Eclipsing binary stars, White dwarf stars, Delta Scuti variable stars, Stellar evolution
Solar Vortex Tubes: Vortex Dynamics in the Solar Atmosphere. In this work, a state-of-the-art vortex detection method, Instantaneous Vorticity Deviation, is applied to locate three-dimensional vortex tube boundaries in numerical simulations of solar photospheric magnetoconvection performed by the MURaM code. We detected three-dimensional vortices distributed along intergranular regions and displaying coned shapes that extend from the photosphere to the low chromosphere. Based on a well-defined vortex center and boundary, we were able to determine averaged radial profiles and thereby investigate the dynamics across the vortical flows at different height levels. The solar vortex tubes present nonuniform angular rotational velocity, and, at all height levels, there are eddy viscosity effects within the vortices, which slow down the plasma as it moves toward the center. The vortices impact the magnetic field as they help to intensify the magnetic field at the sinking points, and in turn, the magnetic field ends up playing an essential role in the vortex dynamics. The magnetic field was found to be especially important to the vorticity evolution. On the other hand, it is shown that, in general, kinematic vortices do not give rise to magnetic vortices unless their tangential velocities at different height levels are high enough to overcome the magnetic tension.

Keywords: Solar atmosphere, Solar convective zone, Solar granulation, Magnetohydrodynamical simulations
Synchrotron Self-Compton Scattering in Sgr A* Derived from NIR and X-Ray Flare Statistics. The flaring activity of Sagittarius A* (Sgr A*) can be analyzed by statistical means to test emission models for its accretion flow. A particular modeling question is whether the observed X-ray flares are the high-energy end of a synchrotron spectrum or if they arise from self-Comptonized photons of a lower-energy synchrotron process. We use already published Chandra X-ray Visionary Project data to statistically investigate the X-ray count-rate distribution of Sgr A*. Two previous workgroups have already undertaken such an analysis on that data. They modeled the flaring part of the emission with a bounded power law, i.e., a power-law distribution with a hard cutoff at the highest measured count rate. With this model, both teams obtain a power-law index ${\alpha }_{X}\sim 2$ . We show that the flare count-rate distribution can also be well described by a truncated, i.e., an exponentially decaying power law. We argue that an exponential truncation is a more natural model than a hard cutoff. With this alternate model, our fit yields a power-law index ${\alpha }_{X}\sim 1.66$ . We find that this slope can be canonically explained by a synchrotron self-Compton (SSC) process. Therefore, we argue that SSC models are the best ones suitable to explain the observed X-ray count-rate distribution.

Keywords: Supermassive black holes, Galactic center, Active galactic nuclei, X-ray active galactic nuclei