Sazuna/UAT_keywords huggingface dataset:
Eclipsing Binaries Found by the EREBOS Project: Gaia DR2 6097540197980557440-a Deeply Eclipsing sdB+dM System. We present time-series spectroscopy and photometry of Gaia DR2 6097540197980557440, a new deeply eclipsing hot subdwarf B (sdB) + M dwarf (dM) binary. We discovered this object during the course of the Eclipsing Reflection Effect Binaries from Optical Surveys (EREBOS) project, which aims to find new eclipsing sdB+dM binaries (HW Vir systems) and increase the small sample of studied systems. In addition to the primary eclipse, which is in excess of ~5 mag in the optical, the light curve also shows features typical for other HW Vir binaries such as a secondary eclipse and strong reflection effect from the irradiated, cool companion. The orbital period is 0.127037 days (~3 hr), falling right at the peak of the orbital period distribution of known HW Vir systems. Analysis of our time-series spectroscopy yields a radial velocity semiamplitude of KsdB = 100.0 ± 2.0 km s-1, which is among the fastest line-of-sight velocities found to date for an HW Vir binary. State-of-the-art atmospheric models that account for deviations from local thermodynamic equilibrium are used to determine the atmospheric parameters of the sdB. Although we cannot claim a unique light-curve modeling solution, the best-fitting model has an sdB mass of MsdB = 0.47 ± 0.03 M⊙ and a companion mass of MdM = 0.18 ± 0.01 M⊙. The radius of the companion appears to be inflated relative to theoretical mass-radius relationships, consistent with other known HW Vir binaries. Additionally, the M dwarf is one of the most massive found to date among this type of binary.

Keywords: Eclipsing binary stars, B subdwarf stars, Fundamental parameters of stars
The CaFe Project: Optical Fe II and Near-infrared Ca II Triplet Emission in Active Galaxies. II. The Driver(s) of the Ca II and Fe II and Its Potential Use as a Chemical Clock. In this second paper in the series, we carefully analyze the observational properties of the optical Fe II and near-IR Ca II triplet in active galactic nuclei (AGNs), as well as the luminosity, black hole mass, and Eddington ratio in order to define the driving mechanism behind the properties of our sample. The Ca II shows an inverse Baldwin effect, bringing out the particular behavior of this ion with respect to the other low-ionization lines such as Hβ. We performed a principal component analysis, where 81.2% of the variance can be explained by the first three principal components drawn from the FWHMs, luminosity, and equivalent widths. The first principal component (PC1) is primarily driven by the combination of black hole mass and luminosity with a significance over 99.9%, which in turn is reflected in the strong correlation of the PC1 with the Eddington ratio. The observational correlations are better represented by the Eddington ratio; thus, it could be the primary mechanism behind the strong correlations observed in the Ca II-Fe II sample. Since calcium belongs to the α-elements, the Fe II/Ca II flux ratio can be used as a chemical clock for determining the metal content in AGNs and trace the evolution of the host galaxies. We confirm the de-enhancement of the ratio Fe II/Ca II by the Eddington ratio, suggesting a metal enrichment of the BLR in intermediate-z with respect to low-z objects. A larger sample, particularly at z &gt; 2, is needed to confirm the present results.

Keywords: Supermassive black holes, Active galactic nuclei, Spectroscopy, Quasars
Fermi-LAT Observations of Sagittarius A*: Imaging Analysis. Sagittarius A* (Sgr A*)-the supermassive black hole (SMBH) in the center of our galaxy-has been observed in most of the electromagnetic spectrum, from radio to X-rays. Diffuse γ-ray emission has been observed around Sgr A* and a γ-ray point source has been detected coinciding with the SMBH's position, although there is no definitive association between the two. In this work, we have used ~11 yr of Fermi Large Area Telescope observations of the point source 4FGL J1745.6-2859 and performed a detailed imaging analysis across four energy bands. Our goal is to elucidate the nature of the γ-ray emission at the Galactic Center (GC) and whether it is associated with the SMBH. We find that the centroid of the emission approaches Sgr A*'s location as the energy increases. Assuming that the γ-ray point source is located at the GC, we estimate a luminosity of 2.61 × 1036 erg s-1 in the 100 MeV to 500 GeV energy range. This is consistent with Sgr A*'s bolometric luminosity. Based on the point source properties, we ruled out several potential candidates for its nature and favor a cosmic-ray origin either from protons, electrons, or both, accelerated by-or in the vicinity of-the SMBH. Our results indicate that the point source at the GC is indeed the γ-ray counterpart of Sgr A* in the GeV range.

Keywords: Gamma-ray sources, Gamma-ray astronomy, Galactic center, Supermassive black holes
Numerical MHD Simulations of the 3D Morphology and Kinematics of the 2017 September 10 CME-driven Shock from the Sun to Earth. A global, three-dimensional (3D) numerical simulation model has been employed to study the 3D morphology and kinematics of the large shock driven by the 2017 September 10 coronal mass ejection (CME). Based on actual solar observations, which include the photospheric magnetic field and the CME's speed and source location, the simulation result is delicately tuned by matching with coronal polarized brightness observations and in situ solar-wind measurements at 1 au. The simulation reproduces well the shock's shape and position in coronagraphic images. The shock's physical parameters at 1 au are similar to those constrained from the observations, with the simulated transit time being nearly the same as the observed one. The simulation reveals that the shock around the backward direction keeps propagating away from the Sun, and despite its large extent, the shock cannot be seen as a spherical structure forming a 360° envelope around the Sun. Identified as a fast forward shock, the shock has a sharp velocity jump and a large density compression with a Mach number larger than one from the nose toward the lateral parts, consistent with a driven shock all across the front. Compared to the nose, the right flank of the shock has a weak compression ratio, but probably yields enhanced energetic particles for observers aligned with it. It follows that large CME-driven shocks have the potential to accelerate energetic particles over a wide longitudinal separation and are likely responsible for the production of these particles in the inner heliosphere.

Keywords: Solar coronal mass ejection shocks, Solar wind, Magnetohydrodynamical simulations
Exploring the 100 au Scale Structure of the Protobinary System NGC 2264 CMM3 with ALMA. We have observed the young protostellar system NGC 2264 CMM3 in the 1.3 mm and 2.0 mm bands at a resolution of about 0"1 (70 au) with ALMA. The structures of two distinct components, CMM3A and CMM3B, are resolved in the continuum images of both bands. CMM3A has an elliptical structure extending along the direction almost perpendicular to the known outflow, while CMM3B reveals a round shape. We have fitted two 2D Gaussian components to the elliptical structure of CMM3A and CMM3B and have separated the disk and envelope components for each source. The spectral index α between 2.0 and 0.8 mm is derived to be 2.4-2.7 and 2.4-2.6 for CMM3A and CMM3B, respectively, indicating optically thick dust emission and/or grain growth. A velocity gradient in the disk/envelope direction is detected for CMM3A in the CH3CN, CH3OH, and 13CH3OH lines detected in the 1.3 mm band, which can be interpreted as the rotation of the disk/envelope system. From this result, the protostellar mass of CMM3A is roughly evaluated to be 0.1-0.5 M⊙ by assuming Keplerian rotation. The mass accretion rate is thus estimated to be 5 × 10-5 - 4 × 10-3 M⊙ yr-1, which is higher than the typical mass accretion rate of low-mass protostars. The OCS emission line shows a velocity gradient in both outflow direction and disk/envelope direction. A hint of outflow rotation is found, and the specific angular momentum of the outflow is estimated to be comparable to that of the disk. These results provide us with novel information on the initial stage of a binary/multiple system.

Keywords: Interstellar molecules, Young stellar objects, Star formation, Interstellar medium, Protostars
Dynamics in the Transition Region beneath Active Region Upflows Viewed by IRIS. Coronal upflows at the edges of active regions (ARs), which are a possible source of slow solar wind, have been found to connect with dynamics in the transition region. To infer at what scale transition region dynamics connect to AR upflows, we investigate the statistical properties of the small-scale dynamics in the transition region underneath the upflows at the edge of NOAA Active Region 11934. With observations from the Interface Region Imaging Spectrograph (IRIS), we found that the Si IV 1403 Å Doppler map consists of numerous blueshifted and redshifted patches mostly with sizes less than 1 Mm2. The blueshifted structures in the transition region tend to be brighter than the redshifted ones, but their nonthermal velocities have no significant difference. With the SWAMIS feature-tracking procedure, we found in IRIS slit-jaw 1400 Å images that dynamic bright dots with an average size of about 0.3 Mm2 and lifetimes of mostly less than 200 s were spread all over the region. Most of the bright dots appear to be localized, without a clear signature of plasma propagation to a long distance on the projection plane. Surge-like motions with speeds of about 15 km s-1 could be seen in some events at the boundaries of the upflow region, where the magnetic field appeared to be inclined. We conclude that the transition region dynamics connecting to coronal upflows should occur in at a very fine scale, suggesting that the corresponding coronal upflows should also be highly structured. It is also plausible that the transition region dynamics might just act as stimulation at the coronal base, which then drives the upflows in the corona.

Keywords: Slow solar wind, Solar atmosphere, Solar active region velocity fields, Solar coronal transients, Solar active regions, Solar corona, Solar transition region, Doppler shift
The Final Months of Massive Star Evolution from the Circumstellar Environment around SN Ic 2020oi. We present the results of Atacama Large Millimeter/submillimeter Array (ALMA) band 3 observations of the nearby type Ic supernova (SN) 2020oi. Under the standard assumptions on the SN-circumstellar medium (CSM) interaction and the synchrotron emission, the data indicate that the CSM structure deviates from a smooth distribution expected from the steady-state mass loss in the very vicinity of the SN (≲1015 cm), which is then connected to the outer smooth distribution (≳1016 cm). This structure is further confirmed through the light-curve modeling of the whole radio data set as combined with the previously reported data at lower frequency. Because this is an explosion of a bare carbon-oxygen (C+O) star with a fast wind, we can trace the mass-loss history of the progenitor of SN 2020oi in the final year. The inferred nonsmooth CSM distribution corresponds to fluctuations on the subyear timescale in the mass-loss history toward the SN explosion. Our finding suggests that the pre-SN activity is likely driven by the accelerated change in the nuclear burning stage in the last moments just before the massive star's demise. The structure of the CSM derived in this study is beyond the applicability of the other methods at optical wavelengths, highlighting the importance and uniqueness of quick follow-up observations of SNe by ALMA and other radio facilities.

Keywords: Millimeter astronomy, Circumstellar matter, Supernovae, Radio sources, Stellar evolution
Numerical Study of Two Injection Methods for the 2007 November 15 Coronal Mass Ejection in the Inner Heliosphere. In this paper, we use two injection methods, i.e., coronal mass ejection (CME) with and without radial compression, to investigate the propagation of the 2007 November 15 CME in the inner heliosphere with a three-dimensional, time-dependent, numerical magnetohydrodynamic model. In order to reproduce the large-scale interplanetary magnetic field associated with the CME, the spheromak model is used to provide the intrinsic magnetic field structure of the CME. The modeled results also suggest that the CME without radial compression propagates in interplanetary space with a lower velocity and arrives at 1 au later. We interpret these differences as a result of different Lorentz forces acting on the two injection methods, which lead to different CME expansions in the heliosphere. Additionally, the model of a CME without radial compression tends to overestimate the radial extension at 1 au due to an overestimation of the CME radial size in the simulation and the modeled magnetic fields at 1 au are lower compared to the model of a CME with radial compression. The above results are all useful in understanding the dynamic process occurring between the CME and the solar wind.

Keywords: Solar coronal mass ejections
Associated Molecular and Atomic Clouds with X-Ray Shell of Superbubble 30 Doradus C in the LMC. 30 Doradus C is a superbubble that emits the brightest non-thermal X- and TeV gamma-rays in the Local Group. To explore the detailed connection between the high-energy radiation and the interstellar medium, we have carried out new CO and HI observations using the Atacama Large Millimeter/Submillimeter Array (ALMA), Atacama Submillimeter Telescope Experiment, and the Australia Telescope Compact Array with resolutions of up to 3 pc. The ALMA data of 12CO(J = 1-0) emission revealed 23 molecular clouds, with typical diameters of ~6-12 pc and masses of ~600-10,000 M☉. A comparison with the X-rays of XMM-Newton at ~3 pc resolution shows that X-rays are enhanced toward these clouds. The CO data were combined with the HI to estimate the total interstellar protons. A comparison of the interstellar proton column density and the X-rays revealed that the X-rays are enhanced with the total proton column density. These are most likely to be caused by the shock-cloud interaction, which is modeled by magnetohydrodynamical simulations (Inoue et al. 2012). We also note a trend for the X-ray photon index to vary with distance from the center of the high-mass star cluster. This suggests that the cosmic-ray electrons are accelerated by one or multiple supernovae in the cluster. Based on these results, we discuss the role of the interstellar medium in cosmic-ray particle acceleration.

Keywords: Cosmic rays, Supernova remnants, Interstellar clouds, Radio astronomy, Superbubbles
A New Low-beta Regime for Unstable Proton Firehose Modes in Bi-kappa-distributed Plasmas. In the solar-wind plasma an excess of kinetic temperature along the background magnetic field stimulates proton firehose modes to grow if the parallel plasma beta parameter is sufficiently high, i.e., βp∥ ≳ 1. This instability can prevent the expansion-driven anisotropy from increasing indefinitely and explain the observations. Moreover, such kinetic instabilities are expected to be even more effective in the presence of suprathermal Kappa-distributed populations, which are ubiquitous in the solar wind and are less affected by collisions than the core population but contribute with an additional free energy. In this work we use both linear and extended quasi-linear (QL) frameworks to characterize the unstable periodic proton firehose modes (propagating parallel to the magnetic field) under the influence of suprathermal protons. Linear theory predicts a systematic stimulation of the instability, suprathermals amplifying the growth rates and decreasing the instability thresholds to lower anisotropies and lower plasma betas (βp∥ &lt; 1). In perfect agreement with these results, the QL approach reveals a significant enhancement of the resulting electromagnetic fluctuations up to saturation with a stronger back reaction on protons, leading also to a faster and more efficient relaxation of the temperature anisotropy.

Keywords: Space plasmas, Solar wind
Small-scale Turbulent Motion of the Plasma in a Solar Filament as the Precursor of Eruption. A filament, a dense cool plasma supported by the magnetic fields in the solar corona, often becomes unstable and erupts. It is empirically known that the filament often demonstrates some activations such as a turbulent motion prior to eruption. In our previous study, we analyzed the Doppler velocity of an Hα filament and found that the standard deviation of the line-of-sight velocity distribution in a filament, which indicates the increasing amplitude of the small-scale motions, increased prior to the onset of the eruption. Here, we present a further analysis on this filament eruption, which initiated approximately at 03:40 UT on 2016 November 5 in the vicinity of NOAA Active Region 12605. It includes a coronal line observation and the extrapolation of the surrounding magnetic fields. We found that both the spatially averaged microturbulence inside the filament and the nearby coronal line emission increased 6 and 10 hr prior to eruption, respectively. In this event, we did not find any significant changes in the global potential field configuration preceding the eruption for the past 2 days, which indicates that there is a case in which it is difficult to predict the eruption only by tracking the extrapolated global magnetic fields. In terms of space weather prediction, our result on the turbulent motions in a filament could be used as the useful precursor of a filament eruption.

Keywords: Solar filaments, Solar magnetic fields, Solar coronal mass ejections, Quiet solar corona, Solar filament eruptions
HAWC+/SOFIA Polarimetry in L1688: Relative Orientation of Magnetic Field and Elongated Cloud Structure. We present a study of the relative orientation between the magnetic field and elongated cloud structures for the ρ Oph A and ρ Oph E regions in L1688 in the Ophiuchus molecular cloud. Combining inferred magnetic field orientation from HAWC+ 154 μm observations of polarized thermal emission with column density maps created using Herschel submillimeter observations, we find consistent perpendicular relative alignment at scales of 0.02 pc (33"6 at d ≈ 137 pc) using the histogram of relative orientations (HRO) technique. This supports the conclusions of previous work using Planck polarimetry and extends the results to higher column densities. Combining this HAWC+ HRO analysis with a new Planck HRO analysis of L1688, the transition from parallel to perpendicular alignment in L1688 is observed to occur at a molecular hydrogen column density of approximately 1021.7 cm-2. This value for the alignment transition column density agrees well with values found for nearby clouds via previous studies using only Planck observations. Using existing turbulent, magnetohydrodynamic simulations of molecular clouds formed by colliding flows as a model for L1688, we conclude that the molecular hydrogen volume density associated with this transition is approximately ~104 cm-3. We discuss the limitations of our analysis, including incomplete sampling of the dense regions in L1688 by HAWC+.

Keywords: Molecular clouds, Interstellar magnetic fields, Giant molecular clouds, Star formation, Interstellar medium
The M-dwarf Ultraviolet Spectroscopic Sample. I. Determining Stellar Parameters for Field Stars. Accurate stellar properties are essential for precise stellar astrophysics and exoplanetary science. In the M-dwarf regime, much effort has gone into defining empirical relations that can use readily accessible observables to assess physical stellar properties. Often, these relations for the quantity of interest are cast as a nonlinear function of available data; in Bayesian modeling, however, the reverse is needed. In this article, we introduce a new Bayesian framework to self-consistently and simultaneously apply multiple empirical calibrations to fully characterize the mass, luminosity, radius, and effective temperature of a field age M dwarf. This framework includes a new M-dwarf mass-radius relation with a scatter of 3.1% at fixed mass. We further introduce the M-dwarf Ultraviolet Spectroscopic Sample (MUSS), and apply our methodology to provide consistent stellar parameters for these nearby low-mass stars, selected as having available spectroscopic data in the ultraviolet. These targets are of interest largely as either exoplanet hosts or benchmarks in multiwavelength stellar activity. We use the field MUSS stars to define a low-mass main sequence in the solar neighborhood through Gaussian Process (GP) regression. These results enable us to empirically measure a feature in the GP derivative at ${{ \mathcal M }}_{b}=0.337{\pm }_{0.026}^{0.013}$ M⊙ that indicates where the MUSS transitions from fully to partly convective interiors.

Keywords: M dwarf stars, Fundamental parameters of stars, Astrostatistics
HaloSat Observations of Heliospheric Solar Wind Charge Exchange. X-ray emission from solar wind charge exchange (SWCX) produced in interplanetary space contaminates every astrophysical observation, regardless of the line of sight. Unfortunately, the primary SWCX emission lines also happen to be important diagnostics of astrophysical plasmas. Models of SWCX emission are limited by two main uncertainties: the local solar wind fluxes along the line of sight and the charge exchange cross sections. The He cone, a localized density enhancement of helium neutrals, is the only heliospheric SWCX emission feature that is small enough and bright enough to be observationally isolated from the X-ray background and the broader SWCX emission. HaloSat, an X-ray CubeSat mission, has recently completed two series of specialized observations, near and far from the ecliptic plane, during two Earth transits of the He cone. These observations were used to test the predictions of an SWCX emission model against the emission observed at low ecliptic latitude, where the solar wind data are monitored, and at high ecliptic latitude, where the solar wind data are extrapolated. The measured SWCX emission for the set of observations near the ecliptic plane was consistent with the line intensities predicted by the model but underpredicted for the set of observations at high ecliptic latitude near the south ecliptic pole. Additionally, high-temperature Galactic halo emission components are reported for both spectral sets.

Keywords: Charge exchange ionization, Milky Way dark matter halo, Solar wind, Diffuse x-ray background
Non-thermal Electron Energization During the Impulsive Phase of an X9.3 Flare Revealed by Insight-HXMT. The X9.3 flare SOL20170906T11:55 was observed by the CsI detector aboard the first Chinese X-ray observatory Hard X-ray Modulation telescope (Insight-HXMT). Using the wavelets method, we report 22 s quasiperiodic pulsations during the impulsive phase. The spectra from 100 keV to 800 keV show the evolution with the gamma-ray flux of a power-law photon index from ~1.8 before the peak, ~2.0 around the flare peak, to ~1.8 again. The gyrosynchrotron microwave spectral analysis reveals a 36"6 ± 0"6 radius gyrosynchrotron source with mean transverse magnetic field around 608.2 Gauss. The penetrated ≥10 keV non-thermal electron density is about 106.7 cm-3 at peak time. The magnetic field strength followed the evolution of high-frequency radio flux. Further gyrosynchrotron source modeling analysis implies that there exists a quite steady gyrosynchrotron source, and the non-thermal electron density and transverse magnetic field evolution are similar to higher-frequency light curves. The temporal spectral analysis reveals that those non-thermal electrons are accelerated by repeated magnetic reconnection, likely from a lower corona source.

Keywords: Solar flares