Sazuna/UAT_keywords huggingface dataset:
The Width, Density, and Outflow of Solar Coronal Streamers. Characterizing the large-scale structure and plasma properties of the inner corona is crucial to understanding the source and subsequent expansion of the solar wind and related space weather effects. Here, we apply a new coronal rotational tomography method, along with a method to narrow streamers and refine the density estimate, to COR2A/Solar Terrestrial Relations Observatory observations from a period near solar minimum and maximum, gaining density maps for heights between 4 and 8R⊙. The coronal structure is highly radial at these heights, and the streamers are very narrow: in some regions, only a few degrees in width. The mean densities of streamers is almost identical between solar minimum and maximum. However, streamers at solar maximum contain around 50% more total mass due to their larger area. By assuming a constant mass flux, and constraints on proton flux measured by Parker Solar Probe (PSP), we estimate an outflow speed within solar minimum streamers of 50-120 kms-1 at 4R⊙, increasing to 90-250 kms-1 at 8R⊙. Accelerations of around 6 ms-2 are found for streamers at a height of 4R⊙, decreasing with height. The solar maximum slow wind shows a higher acceleration to extended distances compared with solar minimum. To satisfy the solar wind speeds measured by PSP, there must be a mean residual acceleration of around 1-2 ms-2 between 8 and 40R⊙. Several aspects of this study strongly suggest that the coronal streamer belt density is highly variable on small scales, and that the tomography can only reveal a local spatial and temporal average.

Keywords: Computational astronomy, Optical astronomy, Solar wind, Coronagraphic imaging, Solar physics, Quiet solar corona, Solar corona, Solar coronal streamers, Astronomical methods
Follow-up Ground-based Observations of the Dwarf Nova KZ Gem. We present spectroscopy of stars in the immediate vicinity of the dwarf nova (DN) KZ Gem to confirm its identification, which is ambiguous in the literature. Analysis of 73 radial velocities spanning from 2014 to 2019 provides a high-precision orbital period of 0.2224628(2) days (∼5.34 hr) and shows KZ Gem to be a double-lined DN. Time series photometry taken from 2016 to 2018 shows a variable double-hump modulation with a full amplitude of ∼0.3 mag, along with five Gaussian-like transient events lasting ∼30 minutes or more. Using the light-curve code XRBinary and nonlinear fitting code NMfit, we obtain an optimized binary model of the dwarf nova (DN) KZ Gem, from time series photometry, consisting of a Roche-lobe-filling K-type dwarf with a mass transfer rate of (2.7-7.9) × 10-10 M⊙ yr-1 to a large, cool, and thick disk surrounding a white dwarf, in an orbit with an inclination of 51°6(±1°4). Two hotspots on the disk are demonstrated to cause the observed variations in the ellipsoidal modulations from the secondary star. This physical model is compatible with the Gaia distance of KZ Gem.

Keywords: Close binary stars, Interacting binary stars, Dwarf novae, Novae, Semi-detached binary stars, Cataclysmic variable stars
Inelastic Processes in Low-energy Sulfur-Hydrogen Collisions. The cross sections and rate coefficients for inelastic processes in low-energy collisions of sulfur atoms and positive ions with hydrogen atoms and negative ions are calculated for the collisional energy range ${10}^{-4}\mbox{--}100\,\mathrm{eV}$ and for the temperature range 1000-10,000 K. Fifty-five covalent states and two ionic ones are considered. The ground ionic state ${{\rm{S}}}^{+}(3{p}^{3}{}^{4}S^\circ )+{{\rm{H}}}^{-}(1{s}^{2}{}^{1}S)$ provides only ${}^{4}{{\rm{\Sigma }}}^{-}$ molecular symmetry, while the first-excited ionic state ${{\rm{S}}}^{+}(3{p}^{3}{}^{2}D^\circ )+{{\rm{H}}}^{-}(1{s}^{2}{}^{1}S)$ provides three molecular symmetries: ${}^{2}{{\rm{\Sigma }}}^{-}$ , ${}^{2}{\rm{\Pi }}$ , and ${}^{2}{\rm{\Delta }}$ . The study of sulfur-hydrogen collisions is performed by the quantum model methods within the Born-Oppenheimer formalism. The electronic structure of the collisional quasimolecule is calculated by the semiempirical asymptotic method for each considered molecular symmetry. For nuclear dynamic calculations, the multichannel formula in combination with the Landau-Zener model is used. Nuclear dynamics within each considered symmetry is treated separately, and the total rate coefficients for each inelastic process have been summed over all symmetries. The largest values of the rate coefficients (exceeding ${10}^{-8}\,{\mathrm{cm}}^{3}\ {{\rm{s}}}^{-1}$ ) correspond to the mutual neutralization processes in ${{\rm{S}}}^{+}(3{s}^{2}3{p}^{3}{}^{4}S^\circ )\,+{{\rm{H}}}^{-}(1{s}^{2}{}^{1}S)$ (the ground ionic state being the initial state), as well as in ${{\rm{S}}}^{+}(3{p}^{3}{}^{2}D^\circ )+{{\rm{H}}}^{-}(1{s}^{2}{}^{1}S)$ (the first-excited ionic state being the initial state) collisions. At the temperature 6000 K, the rate coefficients with large magnitudes have the values from the ranges $(1.08\mbox{--}4.48)\times {10}^{-8}\,{\mathrm{cm}}^{3}\,{{\rm{s}}}^{-1}$ and $(1.19\mbox{--}5.05)\times {10}^{-8}\,{\mathrm{cm}}^{3}\,{{\rm{s}}}^{-1}$ , respectively. The calculated rate coefficients with large and moderate values are important for NLTE stellar atmosphere modeling.

Keywords: Collision physics, Stellar abundances, Atomic data benchmarking, Atomic physics
Early Low-mass Galaxies and Star-cluster Candidates at z ∼ 6-9 Identified by the Gravitational-lensing Technique and Deep Optical/Near-infrared Imaging. We present very faint dropout galaxies at z ∼ 6-9 with a stellar mass M⋆ down to ${M}_{\star }\sim {10}^{6}\,{M}_{\odot }$ that are found in deep optical/near-infrared (NIR) images of the full data sets of the Hubble Frontier Fields (HFF) program in conjunction with deep ground-based and Spitzer images and gravitational-lensing magnification effects. We investigate stellar populations of the HFF dropout galaxies with the optical/NIR photometry and BEAGLE models made of self-consistent stellar population synthesis and photoionization models, carefully including strong nebular emission impacting on the photometry. We identify 453 galaxies with ${M}_{\star }\sim {10}^{6}\mbox{--}{10}^{9}\,{M}_{\odot }$ . Our best-estimate ${M}_{\star }/{L}_{\mathrm{UV}}$ function is comparable to a model of star formation duration time of 100 Myr that is assumed in Bouwens et al. We derive the galaxy stellar mass functions (GSMFs) at z ∼ 6-9 that agree with those obtained by previous studies at ${M}_{\star }\gtrsim {10}^{8}\,{M}_{\odot }$ , and that extend to ${M}_{\star }\sim {10}^{6}\,{M}_{\odot }$ . Estimating the stellar mass densities ${\rho }_{\star }$ with the GSMFs, we find a very slow evolution from z ∼ 9 to z ∼ 6-7, which is consistent with the one estimated from star formation rate density measurements. In conjunction with the estimates of the galaxy effective radii Re on the source plane, we have pinpointed four objects with low stellar masses ( ${M}_{\star }\leqslant {10}^{7}\,{M}_{\odot }$ ) and very compact morphologies ( ${R}_{{\rm{e}}}\leqslant 40$ pc) that are comparable with those of globular clusters (GCs) in the Milky Way today. These objects are candidates of star clusters, some of which may be related to GCs today.

Keywords: Globular star clusters, Galaxy formation, Strong gravitational lensing, Stellar mass functions, High-redshift galaxies
Constraints on the Muon Fraction and Density Profile in Neutron Stars. Muons in neutron stars (NSs) play especially important roles in addressing several interesting new physics questions associated with detecting as well as understanding interactions and astrophysical effects of muonphilic dark matter particles. The key model inputs for studying the latter are the total muon mass Mμ, the muon mass fraction Mμ/MNS over the NS mass MNS, and the muon radial density profile ρμ(r) in NSs of varying masses. We investigate these quantities within a minimum model for the core of NSs consisting of neutrons, protons, electrons, and muons using an explicitly isospin-dependent parametric equation of state (EOS) constrained by available nuclear laboratory experiments and the latest astrophysical observations of NS masses, radii, and tidal deformabilities. We found that the absolutely maximum muon mass Mμ and its mass fraction Mμ/MNS in the most massive NSs allowed by causality are about 0.025 M⊙ and 1.1%, respectively. For the most massive NS of mass 2.14 M⊙ observed so far, they reduce to about 0.020 M⊙ and 0.9%, respectively. We also study respective effects of individual parameters describing the EOS of high-density neutron-rich nucleonic matter on the muon contents in NSs with varying masses. We found that the most important but uncertain nuclear physics ingredient for determining the muon contents in NSs is the high-density nuclear symmetry energy.

Keywords: Neutron stars, High energy astrophysics, Nuclear astrophysics, Dark matter, Nuclear physics
Higher Radial Harmonics of Sausage Oscillations in Coronal Loops. Impulsively excited sausage oscillations of a plasma cylinder with a smooth radial profile of Alfvén speed are analyzed with a numerical solution of the initial-value problem for a partial differential equation of the Klein-Gordon type, describing linear magnetoacoustic oscillations with a fixed axial wavelength and an azimuthal mode number. The range of analyzed ratios of Alfvén speeds outside and inside the cylinder is from 2 to 10. Both trapped and leaky regimes of the oscillations are considered. It is shown that even in the long-wavelength limit, I.e., for axial wavenumbers much smaller than the cutoff values, damping times of higher radial sausage harmonics could be significantly greater than the oscillation periods, I.e., several oscillation cycles could be present in the signal. The quality factors decrease with decfreasing ratios of Alfvén speeds outside and inside the cylinder. Oscillation periods of the second and third radial harmonics remain practically independent of the axial wavelength even when the wavelength is shorter than the radius of the cylinder. The ratios of oscillation periods of fundamental and higher radial and axial harmonics are found to be significantly different, up to a factor of two in the long-wavelength limit. It is concluded that higher radial harmonics could be responsible for the departure of observed sausage oscillation signals from a harmonic shape, especially during the first several cycles of the oscillation. Even in the absence of spatially resolved data, higher axial and radial harmonics can be distinguished from each other by the period ratios.

Keywords: Solar oscillations, Magnetohydrodynamics, Solar flares
Physical Conditions and Kinematics of the Filamentary Structure in Orion Molecular Cloud 1. We have studied the structure and kinematics of the dense molecular gas in the Orion Molecular Cloud 1 (OMC1) region with the N2H+ 3-2 line. The 6' × 9' (∼0.7 × 1.1 pc) region surrounding the Orion Kleinmann-Low (KL) core has been mapped with the Submillimeter Array (SMA) and the Submillimeter Telescope (SMT). The combined SMA and SMT image, with a resolution of ∼5"4 (∼2300 au), reveals multiple filaments with a typical width of 0.02-0.03 pc. On the basis of the non-local thermodynamic equilibrium analysis using the N2H+ 3-2 and 1-0 data, the density and temperature of the filaments are estimated to be ∼107 cm-3 and ∼15 K-20 K, respectively. The core fragmentation is observed in three massive filaments, one of which shows the oscillations in the velocity and intensity that could be the signature of core-forming gas motions. The gas kinetic temperature is significantly enhanced in the eastern part of OMC1, likely due to the external heating from the high-mass stars in M42 and M43. In addition, the filaments are colder than their surrounding regions, suggesting shielding from the external heating due to the dense gas in the filaments. The OMC1 region consists of three subregions, I.e., north, west, and south of Orion KL, having different radial velocities with sharp velocity transitions. There is a north-to-south velocity gradient from the western to the southern regions. The observed velocity pattern suggests that dense gas in OMC1 is collapsing globally toward the high-mass star-forming region, Orion Nebula Cluster.

Keywords: Interstellar filaments, Star formation, Molecular clouds
Coronal Bright Points as Possible Sources of Density Variations in the Solar Corona. Recent analysis of high-cadence white-light images taken by the Solar-Terrestrial RElations Observatory near solar maximum has revealed that outflowing density structures are released in a ubiquitous manner in the solar wind. The present study investigates whether these density fluctuations could originate from the transient heating of the low corona observed during coronal bright points (CBPs). We assume that part of the intense heating measured during CBPs occurs at the coronal base of open magnetic fields that channel the forming solar wind. We employ the solar wind model MULTI-VP to quantify the plasma compression induced by transient heating and investigate how the induced perturbation propagates to the upper corona. We show that for heating rates with statistics comparable to those observed during CBPs, the compressive wave initially increases the local plasma density by a factor of up to 50% at 5 R⊙. The wave expands rapidly beyond 30 solar radii and the local enhancement in density decreases beyond. Based on the occurrence rates of CBPs measured in previous studies, we impose transient heating events at the base of thousands of open magnetic field lines to study the response of the entire 3D corona. The simulated density cubes are then converted into synthetic white-light imagery. We show that the resulting brightness variations occupy all position angles in the images on timescales of hours. We conclude that a significant part of the ubiquitous brightness variability of the solar corona could originate in the strong transient heating of flux tubes induced by CBPs.

Keywords: Magnetohydrodynamics, Solar wind, Solar corona
VVV Survey Microlensing: Catalog of Best and Forsaken Events. We search for microlensing events in the zero-latitude area of the Galactic Bulge using the VVV Survey near-IR data. We have discovered a total sample of N = 630 events within an area covering 20.68 deg2 between the years 2010 and 2015. In this paper, we describe the search and present the data for the final sample, including near-IR magnitudes, colors, and proper motions, as well as the standard microlensing parameters. We use the near-IR color-magnitude and color-color diagrams to select NRC = 290 events with red-clump sources to analyze the extinction properties of the sample in the central region of the Galactic plane. The timescale distribution and its dependence in the longitude axis is presented. The mean timescale decreases as we approach the Galactic minor axis (b = 0°). Finally, we give examples of special microlensing events, such as binaries, short-timescale events, and events with a strong parallax effect.

Keywords: Galaxy structure, Galaxy bulges, Galactic bulge, Gravitational microlensing, Microlensing event rate
A Scenario for Ultradiffuse Satellite Galaxies with Low Velocity Dispersions: The Case of [KKS 2000]04. A scenario for achieving a low velocity dispersion for the galaxy [KKS 2000]04 (aka NGC 1052-DF2) and similar galaxies is presented. A progenitor halo corresponding to a z = 0 halo of mass $\lesssim 5\times {10}^{10}\,{M}_{\odot }$ and a low concentration parameter (but consistent with cosmological simulations) infalls onto a Milky Way-size host at early times. Substantial removal of cold gas from the inner regions by supernova feedback and ram pressure, assisted by tidal stripping of the dark matter in the outer regions, leads to a substantial reduction of the velocity dispersion of stars within one effective radius. In this framework, the observed stellar content of [KKS 2000]04 is associated with a progenitor mass close to that inferred from the global stellar-to-halo-mass ratio. As far as the implications of kinematics are concerned, even if at a ∼20 Mpc distance, it is argued that [KKS 2000]04 is no more peculiar than numerous early type galaxies with seemingly little total dark-matter content.

Keywords: Cosmology, Dark matter, Galaxies
A Relationship between Stellar Age and Spot Coverage. We investigate starspot distributions consistent with space-based photometry of F, G, and K stars in six stellar associations ranging in age from 10 Myr to 4 Gyr. We show that a simple light-curve statistic called the "smoothed amplitude" is proportional to stellar age as t-1/2, following a Skumanich-like spin-down relation. We marginalize over the unknown stellar inclinations by forward modeling the ensemble of light curves for direct comparison with the Kepler, K2, and TESS photometry. We sample the posterior distributions for spot coverage with approximate Bayesian computation. We find typical spot coverages in the range 1%-10%, which decrease with increasing stellar age. The spot coverage is proportional to tn where n = -0.37 ± 0.16, also statistically consistent with a Skumanich-like t-1/2 decay of starspot coverage with age. We apply two techniques to estimate the spot coverage of young exoplanet-hosting stars likely to be targeted for transmission spectroscopy with the James Webb Space Telescope, and estimate the bias in exoplanet radius measurements due to varying starspot coverage.

Keywords: Stellar rotation, Starspots, Stellar photospheres, Bayesian statistics
Probing the Innermost Regions of AGN Jets and Their Magnetic Fields with RadioAstron. III. Blazar S5 0716+71 at Microarcsecond Resolution. We present RadioAstron Space VLBI imaging observations of the BL Lac object S5 0716+71 made on 2015 January 3-4 at a frequency of 22 GHz (wavelength λ = 1.3 cm). The observations were made in the framework of the AGN Polarization Key Science Program. The source was detected on projected space-ground baselines up to 70,833 km (5.6 Earth diameters) for both parallel-hand and cross-hand interferometric visibilities. We have used these detections to obtain a full-polarimetric image of the blazar at an unprecedented angular resolution of 24 μas, the highest for this source to date. This enabled us to estimate the size of the radio core to be &lt;12 × 5 μas and to reveal a complex structure and a significant curvature of the blazar jet in the inner 100 μas, which is an indication that the jet viewing angle lies inside the opening angle of the jet conical outflow. Fairly highly (15%) linearly polarized emission is detected in a jet region 19 μas in size, located 58 μas downstream from the core. The highest brightness temperature in the source frame is estimated to be &gt;2.2 × 1013 K for the blazar core. This implies that the inverse-Compton limit must be violated in the rest frame of the source, even for the largest Doppler factor δ ∼ 25 reported for 0716+714.

Keywords: BL Lacertae objects, Jets, Blazars, Relativistic jets, Active galactic nuclei, Interferometry
Subaru Medium-resolution Spectra of a QSO at z = 6.62: Three Reionization Tests. Investigating the Gunn-Peterson (GP) trough of high-redshift quasars (QSOs) is a powerful way to reveal the cosmic reionization. As one of such attempts, we perform a series of analyses to examine the absorption lines observed with one of the highest-redshift QSOs, PSO J006.1240+39.2219, which we previously discovered at z = 6.62. Using the Subaru telescope, we obtained medium-resolution spectrum with a total exposure time of 7.5 hr. We calculate the Lyα transmission in different redshift bins to determine the near zone radius and the optical depth at 5.6 &lt; z &lt; 6.5. We find a sudden change in the Lyα transmission at 5.75 &lt; z &lt; 5.86, which is consistent with the result from the literature. The near zone radius of the QSO is 5.79 ± 0.09 pMpc, within the scatter of the near zone radii of other QSOs measured in previous studies. We also analyze the dark gap distribution to probe the neutral hydrogen fractions beyond the saturation limit of the GP trough. We extend the measurement of the dark gaps to 5.7 &lt; z &lt; 6.3. We find that the gap widths increase with increasing redshifts, suggesting more neutral universe at higher redshifts. However, these measurements strongly depend on the continuum modeling. As a continuum model-free attempt, we also perform the dark pixel counting analysis to find the upper limit of $\langle {X}_{{\rm{H}}{\rm{I}}}\rangle \sim 0.6$ (0.8) at z &lt; 5.8 (z &gt; 5.8). All three analyses based on this QSO show increasingly neutral hydrogen toward higher redshifts, adding precious measurements up to z ∼ 6.5.

Keywords: Early universe, Quasar absorption line spectroscopy, Quasars, Observational cosmology, Intergalactic medium phases, Intergalactic medium, Reionization
Silicate Grain Growth due to Ion Trapping in Oxygen-rich Supernova Remnants like Cassiopeia A. Core-collapse supernovae can condense large masses of dust post-explosion. However, sputtering and grain-grain collisions during the subsequent passage of the dust through the reverse shock can potentially destroy a significant fraction of the newly formed dust before it can reach the interstellar medium. Here we show that in oxygen-rich supernova remnants like Cassiopeia A, the penetration and trapping within silicate grains of the same impinging ions of oxygen, silicon, and magnesium that are responsible for grain surface sputtering can significantly reduce the net loss of grain material. We model conditions representative of dusty clumps (density contrast of χ = 100) passing through the reverse shock in the oxygen-rich Cassiopeia A remnant and find that, compared to cases where the effect is neglected as well as facilitating the formation of grains larger than those that had originally condensed, ion trapping increases the surviving masses of silicate dust by factors of up to two to four, depending on initial grain radii. For higher density contrasts (χ ≳ 180), we find that the effect of gas accretion on the surface of dust grains surpasses ion trapping, and the survival rate increases to ∼55% of the initial dust mass for χ = 256.

Keywords: Hydrodynamics, Core-collapse supernovae, Astrophysical dust processes, Supernova remnants, Interstellar dust processes
Proton Perpendicular Heating in Turbulence Simulations: Determination of the Velocity Diffusion Coefficient. Numerical methods are presented that can determine the perpendicular velocity space diffusion coefficient from kinetic simulation results. The methods are applied to hybrid simulation results using particle protons and a massless, quasi-neutralizing electron fluid for a case of quasi-perpendicular turbulence. During the quasi-steady phase of the turbulence, the evolution of the grid-averaged, gyrotropic, and peculiar velocity distribution of protons with velocity components perpendicular to the background magnetic field is found to be adequately described by diffusion. The estimated diffusion coefficient varies with perpendicular proton speed. A relative maximum occurs at a speed of zero. About the thermal speed, the coefficient decreases with increasing speed consistent with a power law with index -3. A relative minimum occurs at larger speeds, and the diffusion coefficient rises among the fastest protons contained in the simulation. The functional form of the diffusion coefficient appears to be the result of two sources. At speeds less than the relative minimum, the diffusion is dominated by turbulence generated fluctuations, while at greater speeds the diffusion arises from the large-scale fluctuations that initiated the turbulent energy cascade. Results are compared with theoretical predictions for the diffusion coefficient and with results presented from a previous simulation. Implications for generating suprathermal protons from quasi-perpendicular turbulence are also discussed.

Keywords: Interplanetary turbulence, Space plasmas, Solar wind