Sazuna/UAT_keywords huggingface dataset:
Detection of Coronal Mass Ejections at L1 and Forecast of Their Geoeffectiveness. A novel tool aimed to detect solar coronal mass ejections (CMEs) at the Lagrangian point L1 and to forecast their geoeffectiveness is presented in this paper. This approach is based on the analysis of in situ magnetic field and plasma measurements to compute some important magnetohydrodynamic quantities of the solar wind (the total pressure, the magnetic helicity, and the magnetic and kinetic energy), which are used to identify the CME events, that is their arrival and transit times, and to assess their likelihood for impacting the Earths magnetosphere. The method is essentially based on the comparison of the topological properties of the CME magnetic field configuration and of the CME energetic budget with those of the quasi-steady ambient solar wind. The algorithm performances are estimated by testing the tool on solar wind data collected in situ by the Wind spacecraft from 2005 to 2016. In the scanned 12 yr time interval, it results that (i) the procedure efficiency is of 86% for the weakest magnetospheric disturbances, increasing with the level of the geomagnetic storming, up to 100% for the most intense geomagnetic events, (ii) zero false positive predictions are produced by the algorithm, and (iii) the mean delay between the potentially geoeffective CME detection and the geomagnetic storm onset if of 4 hr, with a 98% 2-8 hr confidence interval. Hence, this new technique appears to be very promising in forecasting space weather phenomena associated to CMEs.

Keywords: Interplanetary medium, Magnetohydrodynamics, Heliosphere, Solar coronal mass ejections, Wavelet analysis, Solar-terrestrial interactions, Solar storm, Time series analysis
Measurement of the Nuclear Symmetry Energy Parameters from Gravitational-wave Events. The nuclear symmetry energy plays a role in determining both the nuclear properties of terrestrial matter as well as the astrophysical properties of neutron stars. The first measurement of the neutron star tidal deformability, from gravitational-wave event GW170817, provides a new way of probing the symmetry energy. In this work, we report on new constraints on the symmetry energy from GW170817. We focus in particular on the low-order coefficients: namely, the value of the symmetry energy at the nuclear saturation density, S 0, and the slope of the symmetry energy, L 0. We find that the gravitational-wave data are relatively insensitive to S 0, but that they depend strongly on L 0 and point to lower values of L 0 than have previously been reported, with a peak likelihood near L 0 ∼ 23 MeV. Finally, we use the inferred posteriors on L 0 to derive new analytic constraints on higher-order nuclear terms.

Keywords: Neutron stars, Nuclear astrophysics, Gravitational waves, Nuclear physics
The Relationship of Magnetic Twist and Plasma Motion in a Magnetic Cloud. Our recent investigations indicate that interplanetary magnetic clouds (MCs) have a high-twist core and a weak-twist outer shell. Utilizing the velocity-modified uniform-twist force-free flux rope model, we further investigate the relationship between the twist profile of magnetic field lines and the distribution of the plasma poloidal angular velocity inside an MC. The poloidal velocity in the MC is 11 km s-1. There are evidently positive correlations between the absolute value of the twist and the plasma poloidal angular velocity in peeled flux ropes or flux rope layers, although the correlation coefficients in flux rope layers are less than those in peeled flux ropes. This finding suggests that plasma flows are frozen-in magnetic field lines as we expected for interplanetary medium, of which the magnetic Reynolds number is large. Furthermore, based on this picture, we infer the axial velocity in the MC frame, which is less than 10 km s-1 and almost uniform in the cross section of the MC. Besides, it is inferred that the plasma flows velocity in the MC is much less than the local Alfvén speed.

Keywords: Interplanetary magnetic fields
Isotopes of Barium as a Chronometer for Supernova Dust Formation. Ejecta from the explosion of massive stars (core-collapse supernovae) make an important contribution to dust in the interstellar medium. However, dust formation around supernovae is not a simple process, with the formation of several components over time. In particular, the exact timing is a matter of debate. Here, we demonstrate that the isotopic composition of barium in supernova grains that survived in primitive meteorites constitutes a potential chronometer. For a subset of supernova silicon carbide grains (X1 grains), the Ba isotopes indicate that they formed at roughly the same time, and that, at this time, a substantial fraction of the freshly produced unstable 137Cs (half-life 30 yr) had already decayed into 137Ba. Application to the 137Cs/137Ba system of nucleosynthesis models that replicate the abundance patterns of stable neutron capture isotopes in these grains indicates a surprisingly late (∼20 yr) timescale for condensation, a conclusion that naturally rests on the reliability of these models.

Keywords: Interstellar dust, Core-collapse supernovae, Circumstellar grains, Circumstellar disks, Meteorites
A Supernova Remnant Counterpart for HESS J1832-085. We examine the new Galactic supernova remnant (SNR) candidate, G23.11+0.18, as seen by the Murchison Widefield Array radio telescope. We describe the morphology of the candidate and find a spectral index of -0.63 ± 0.05 in the 70-170 MHz domain. Coincident TeV gamma-ray detection in High Energy Stereoscopic System (HESS) data supports the SNR nature of G23.11+0.18 and suggests that G23.11+0.18 is accelerating particles beyond TeV energies, thus making this object a promising new cosmic-ray hadron source candidate. The remnant cannot be seen in current optical, infrared and X-ray data sets. We do find, however, a dip in CO-traced molecular gas at a line-of-sight velocity of ∼85 km s-1, suggesting the existence of a G23.11+0.18 progenitor wind-blown bubble. Furthermore, the discovery of molecular gas clumps at a neighboring velocity toward HESS J1832-085 adheres to the notion that a hadronic gamma-ray production mechanism is plausible toward the north of the remnant. Based on these morphological arguments, we propose an interstellar medium association for G23.11+0.18 at a kinematic distance of 4.6 ± 0.8 kpc.

Keywords: Interstellar molecules, Gamma-ray sources, Supernova remnants, Galactic cosmic rays, Interstellar medium
Trigonometric Parallaxes of High-mass Star-forming Regions: Our View of the Milky Way. We compile and analyze approximately 200 trigonometric parallaxes and proper motions of molecular masers associated with very young high-mass stars. Most of the measurements come from the BeSSeL Survey using the VLBA and the Japanese VERA project. These measurements strongly suggest that the Milky Way is a four-arm spiral, with some extra arm segments and spurs. Fitting log-periodic spirals to the locations of the masers, allowing for “kinks” in the spirals and using well-established arm tangencies in the fourth Galactic quadrant, allows us to significantly expand our view of the structure of the Milky Way. We present an updated model for its spiral structure and incorporate it into our previously published parallax-based distance-estimation program for sources associated with spiral arms. Modeling the three-dimensional space motions yields estimates of the distance to the Galactic center, {R}0=8.15+/- 0.15 {kpc}, the circular rotation speed at the Sun's position, {{{\Theta }}}0=236+/- 7 km s-1, and the nature of the rotation curve. Our data strongly constrain the full circular velocity of the Sun, {{{\Theta }}}0+{V}⊙ =247+/- 4 km s-1, and its angular velocity, ({{{\Theta }}}0+{V}⊙ )/{R}0=30.32+/- 0.27 km s-1 kpc-1. Transforming the measured space motions to a Galactocentric frame which rotates with the Galaxy, we find non-circular velocity components typically ≲10 km s-1. However, near the Galactic bar and in a portion of the Perseus arm we find significantly larger non-circular motions. Young high-mass stars within 7 kpc of the Galactic center have a scale height of only 19 pc, and thus are well suited to define the Galactic plane. We find that the orientation of the plane is consistent with the IAU-defined plane to within ±0.°1, and that the Sun is offset toward the north Galactic pole by {Z}⊙ =5.5+/- 5.8 pc. Accounting for this offset places the central supermassive black hole, Sgr A*, in the midplane of the Galaxy. The measured motions perpendicular to the plane of the Galaxy limit precession of the plane to ≲4 km s-1 at the radius of the Sun. Using our improved Galactic parameters, we predict the Hulse-Taylor binary pulsar to be at a distance of 6.54 ± 0.24 kpc, assuming its orbital decay from gravitational radiation follows general relativity.

Keywords: Trigonometric parallax, Milky Way dynamics, Milky Way rotation, Gravitational wave sources, Star formation, Milky Way Galaxy
Can the Uranian Satellites Form from a Debris Disk Generated by a Giant Impact?. Hydrodynamic simulations of a giant impact to proto-Uranus indicated that such an impact could tilt its rotational axis and produce a circumplanetary debris disk beyond the corotation radius of Uranus. However, whether Uranian satellites can actually be formed from such a wide disk remains unclear. Herein, we modeled a wide debris disk of solids with several initial conditions inferred from the hydrodynamic simulations and performed N-body simulations to investigate in situ satellite formation from the debris disk. We also took account of orbital evolutions of satellites due to the planetary tides after the growth of satellites. We found that, in any case, the orbital distribution of the five major satellites could not be reproduced from the disk as long as the power index of its surface density is similar to that of the disk generated just after the giant impact. Satellites in the middle region obtained much larger masses than Ariel or Umbriel, while the outermost satellites did not grow to the mass of Oberon. Our results indicate that we should consider the thermal and viscous evolution of the evaporated disk after the giant impact to form the five major satellites through the in situ formation scenario. On the other hand, the small inner satellites would be formed from the rings produced by the disrupted satellites that migrated from around the corotation radius of Uranus due to the planetary tides.

Keywords: Natural satellite formation, N-body simulations, Uranian satellites
Sensitivity of Super-Kamiokande with Gadolinium to Low Energy Antineutrinos from Pre-supernova Emission. Supernova detection is a major objective of the Super-Kamiokande (SK) experiment. In the next stage of SK (SK-Gd), gadolinium (Gd) sulfate will be added to the detector, which will improve the ability of the detector to identify neutrons. A core-collapse supernova (CCSN) will be preceded by an increasing flux of neutrinos and antineutrinos, from thermal and weak nuclear processes in the star, over a timescale of hours; some of which may be detected at SK-Gd. This could provide an early warning of an imminent CCSN, hours earlier than the detection of the neutrinos from core collapse. Electron antineutrino detection will rely on inverse beta decay events below the usual analysis energy threshold of SK, so Gd loading is vital to reduce backgrounds while maximizing detection efficiency. Assuming normal neutrino mass ordering, more than 200 events could be detected in the final 12 hr before core collapse for a 15-25 solar mass star at around 200 pc, which is representative of the nearest red supergiant to Earth, α-Ori (Betelgeuse). At a statistical false alarm rate of 1 per century, detection could be up to 10 hr before core collapse, and a pre-supernova star could be detected by SK-Gd up to 600 pc away. A pre-supernova alert could be provided to the astrophysics community following gadolinium loading.

Keywords: Neutrino astronomy, Supernova neutrinos, Particle astrophysics, Silicon burning
Measurements of Low Temperature Rate Coefficients for the Reaction of CH with CH<SUB>2</SUB>O and Application to Dark Cloud and AGB Stellar Wind Models. Rate coefficients have been measured for the reaction of CH radicals with formaldehyde, CH2O, over the temperature range of 31-133 K using a pulsed Laval nozzle apparatus combined with pulsed laser photolysis and laser-induced fluorescence spectroscopy. The rate coefficients are very large and display a distinct decrease with decreasing temperature below 70 K, although classical collision rate theory fails to reproduce this temperature dependence. The measured rate coefficients have been parameterized and used as input for astrochemical models for both dark cloud and Asymptotic Giant Branch stellar outflow scenarios. The models predict a distinct change (up to a factor of two) in the abundance of ketene, H2CCO, which is the major expected molecular product of the CH + CH2O reaction.

Keywords: Circumstellar envelopes, Laboratory astrophysics, Experimental techniques, Reaction rates, Dense interstellar clouds, Astrochemistry
Nuclear Ignition of White Dwarf Stars by Relativistic Encounters with Rotating Intermediate Mass Black Holes. We present results from general relativistic calculations of nuclear ignition in white dwarf stars triggered by near encounters with rotating intermediate mass black holes with different spin and alignment parameters. These encounters create thermonuclear environments characteristic of Type Ia supernovae capable of producing both calcium and iron-group elements in arbitrary ratios, depending primarily on the proximity of the interaction which acts as a strong moderator of nucleosynthesis. We explore the effects of black hole spin and spin-orbital alignment on burn-product synthesis to determine whether they might also be capable of moderating reactive flows. When normalized to equivalent impact penetration, accounting for frame-dragging corrections, the influence of spin is weak, no more than 25% as measured by nuclear energy release and mass of burn products, even for near maximally rotating black holes. Stars on prograde trajectories approach closer to the black hole and produce significantly more unbound debris and iron-group elements than is possible by encounters with nonrotating black holes or by retrograde orbits, at more than 50% mass conversion efficiency. The debris contains several radioisotopes, most notably 56Ni, made in amounts that produce subluminous (but still observable) light curves compared to branch-normal SNe Ia.

Keywords: Black hole physics, Explosive nucleosynthesis, Black holes, Hydrodynamics, White dwarf stars
Steady Electron Runaway Model SERM: Astrophysical Alternative for the Maxwellian Assumption. A Steady Electron Runaway Model (SERM) is formulated describing plasmas in the astrophysical “condition” having finite (rather than infinitesimal) Knudsen number, {K}}}Pe}, suggesting an omnipresent leptokurtic, nonthermal, and heat-conducting electron velocity distribution function (eVDF) as the replacement for the Maxwellian ansatz typically made. The shape parameters of SERM’s eVDFs are functionals of the local dimensionless electric field, {E}}}\parallel , shown to be nearly interchangeable with the pressure Knudsen number, {K}}}Pe}. The eVDF is determined by the total density and pressure, heat flux, and {E}}}\parallel  with the Maxwellian as a special case when {E}}}\parallel =0. The nonthermal part of the eVDF is caused by local and global runaway physics and its density fraction is monotonically dependent on {E}}}\parallel . SERM explains the distinguishable conduction band of suprathermal electrons to be the result of the inhomogeneities of astroplasmas that require {E}}}\parallel \ne 0 to enforce quasi-neutrality. SERM shows that the direction of the heat flow should be that of {E}\parallel \hat{{\boldsymbol{b}}}. Almost all reported space age correlations among the shape parameters of the solar wind eVDF are reproduced by this modeling, including scaling of: (i) nonthermal spectral break energy, and (ii) partition of suprathermal density and partial pressure, with solar wind speed. SERM, together with eVDF observations, indirectly bracket 0.2&lt; {E}}}\parallel (1 {au})&lt; 0.65, producing a steady-state eVDF, consistent with in situ (i) heat flows, (ii) strahl pitch angle features in high-speed winds, (iii) {J}\parallel =0, and (iv) non-negative probability at all velocities. Because finite {K}}}Pe} is the identified prerequisite for SERM modeling, nonthermal eVDF’s are expected nearly everywhere in astrophysics where {K}}}Pe}&gt; 0.01.

Keywords: Solar wind, Solar coronal heating, Solar coronal lines, Non-Gaussianity, Stellar coronal lines
Fluorine Abundances in the Galactic Disk. The chemical evolution of fluorine is investigated in a sample of Milky Way red giant stars that span a significant range in metallicity from [Fe/H] ∼ -1.3 to 0.0 dex. Fluorine abundances are derived from vibration-rotation lines of HF in high-resolution infrared spectra near 2.335 μm. The red giants are members of the thin and thick disk/halo, with two stars being likely members of the outer disk Monoceros overdensity. At lower metallicities, with [Fe/H] &lt; -0.4 to -0.5, the abundance of F varies as a primary element with respect to the Fe abundance, with a constant subsolar value of [F/Fe] ∼ -0.3 to -0.4 dex. At larger metallicities, however, [F/Fe] increases rapidly with [Fe/H] and displays a near-secondary behavior with respect to Fe. Comparisons with various models of chemical evolution suggest that in the low-metallicity regime (dominated here by thick-disk stars), a primary evolution of 19F with Fe, with a subsolar [F/Fe] value that roughly matches the observed plateau, can be reproduced by a model incorporating neutrino nucleosynthesis in the aftermath of the core collapse in Type II supernovae. A primary behavior for [F/Fe] at low metallicity is also observed for a model including rapidly rotating low-metallicity massive stars, but this overproduces [F/Fe] at low metallicity. The thick-disk red giants in our sample span a large range of galactocentric distance (R  g  ∼ 6-13.7 kpc) yet display a roughly constant value of [F/Fe], indicating a very flat gradient (with a slope of 0.02 ± 0.03 dex kpc-1) of this elemental ratio over a significant portion of the Galaxy having | Z| &gt; 300 pc away from the Galaxy midplane.

Keywords: Chemical abundances, Milky Way disk, Milky Way stellar halo, Galaxy abundances, Infrared telescopes, Spectroscopy, Red giant stars, Giant stars
On the Source Position and Duration of a Solar Type III Radio Burst Observed by LOFAR. The flux of solar type III radio bursts have a time profile of rising and decay phases at a given frequency, which has been actively studied since the 1970s. Several factors that may influence the duration of a type III radio burst have been proposed. In this work, to study the dominant cause of the duration, we investigate the source positions of the front edge, the peak, and the tail edge in the dynamic spectrum of a single and clear type III radio burst. The duration of this type III burst at a given frequency is about 3 s for decameter wave. The beam-formed observations by the LOw-Frequency ARray are used, which can provide the radio source positions and the dynamic spectra at the same time. We find that, for this burst, the source positions of the front edge, the peak, and the tail edge split with each other spatially. The radial speed of the electrons exciting the front edge, the peak, and the tail edge is 0.42c, 0.25c, and 0.16c, respectively. We estimate the influences of the corona density fluctuation and the electron velocity dispersion on the duration, and the scattering effect by comparison with a few short-duration bursts from the same region. The analysis yields that, in the frequency range of 30-41 MHz, the electron velocity dispersion is the dominant factor that determines the time duration of type III radio bursts with long duration, while scattering may play an important role in the duration of short bursts.

Keywords: Solar energetic particles, The Sun, Radio bursts, Solar radio emission, Radio sources
NuSTAR and Chandra Observations of New X-Ray Transients in the Central Parsec of the Galaxy. We report NuSTAR and Chandra observations of two X-ray transients, SWIFT J174540.7-290015 (T15) and SWIFT J174540.2-290037 (T37), which were discovered by the Neil Gehrels Swift Observatory in 2016 within r ∼ 1 pc of Sgr A*. NuSTAR detected bright X-ray outbursts from T15 and T37, likely in the soft and hard states, with 3-79 keV luminosities of 8 × 1036 and 3 × 1037 erg s-1, respectively. No X-ray outbursts have previously been detected from the two transients and our Chandra ACIS analysis puts an upper limit of L X ≲ 2 × 1031 erg s-1 on their quiescent 2-8 keV luminosities. No pulsations, significant quasi-periodic oscillations, or type I X-ray bursts were detected in the NuSTAR data. While T15 exhibited no significant red noise, the T37 power density spectra are well characterized by three Lorentzian components. The declining variability of T37 above ν ∼ 10 Hz is typical of black hole (BH) transients in the hard state. NuSTAR spectra of both transients exhibit a thermal disk blackbody, X-ray reflection with broadened Fe atomic features, and a continuum component well described by Comptonization models. Their X-ray reflection spectra are most consistent with high BH spin (a * ≳ 0.9) and large disk density (n  e  ∼ 1021 cm-3). Based on the best-fit ionization parameters and disk densities, we found that X-ray reflection occurred near the inner-disk radius, which was derived from the relativistic broadening and thermal disk component. These X-ray characteristics suggest the outbursting BH-low-mass X-ray binary scenario for both transients and yield the first BH spin measurements from X-ray transients in the central 100 pc region.

Keywords: Low-mass x-ray binary stars, X-ray transient sources, Galactic center, X-ray telescopes
Testing Stellar Evolution with Asteroseismic Inversions of a Main-sequence Star Harboring a Small Convective Core. The goal of stellar evolution theory is to predict the structure of stars throughout their lifetimes. Usually, these predictions can be assessed only indirectly, for example by comparing predicted and observed effective temperatures and luminosities. Thanks now to asteroseismology, which can reveal the internal structure of stars, it becomes possible to compare the predictions from stellar evolution theory to actual stellar structures. In this work, we present an inverse analysis of the oscillation data from the solar-type star KIC 6225718, which was observed by the Kepler space observatory during its nominal mission. As its mass is about 20% greater than solar, this star is predicted to transport energy by convection in its nuclear-burning core. We find significant differences between the predicted and actual structure of the star in the radiative interior near to the convective core. In particular, the predicted sound speed is higher than observed in the deep interior of the star, and too low at a fractional radius of 0.25 and beyond. The cause of these discrepancies is unknown, and is not remedied by known physics in the form of convective overshooting or elemental diffusion.

Keywords: Stellar interiors, Stellar convective zones, Stellar structures, Solar analogs, Stellar evolutionary models, Stellar cores, Stellar astronomy, Stellar physics, Astrophysical processes, Stellar oscillations, Asteroseismology, Stellar evolution