Sazuna/UAT_keywords huggingface dataset:
Uniform Distribution of the Extremely Overionized Plasma Associated with the Supernova Remnant G359.1-0.5. We report on the results of our detailed analyses on the peculiar recombining plasma of the supernova remnant (SNR) G359.1-0.5, and the interacting CO clouds. Combining Chandra and Suzaku data, we estimated the ionization state of the plasma with a careful treatment of the background spectrum. The average spectrum showed a remarkably large deviation of the electron temperature (∼0.17 keV) from the initial temperature (&gt;16 keV), indicating that the plasma is in a highly recombination-dominant state. On the other hand, the recombination timescale (net) is comparable to those of the other recombining SNRs (∼4.2 × 1011 cm-3 s). We also searched for spatial variation of the plasma parameters, but found no significant differences. Using 12CO(J = 2-1) data obtained with NANTEN2, we found a new, plausible candidate for the interacting CO cloud, which has a line-of-sight velocity of ∼ -20 km s-1. This indicates that the SNR is located at a distance of ∼4 kpc, which is the foreground of the Galactic center, as previously reported. The associated CO cloud does not show clear spatial coincidence with the nearby GeV/TeV emission, indicating that the origins of the GeV/TeV emission are likely unrelated to G359.1-0.5.

Keywords: Supernova remnants, X-ray sources, Interstellar medium
Magnetic Fields and Afterglows of BdHNe: Inferences from GRB 130427A, GRB 160509A, GRB 160625B, GRB 180728A, and GRB 190114C. GRB 190114C is the first binary-driven hypernova (BdHN) fully observed from initial supernova (SN) appearance to the final emergence of the optical SN signal. It offers an unprecedented testing ground for the BdHN theory, which is here determined and further extended to additional gamma-ray bursts (GRBs). BdHNe comprise two subclasses of long GRBs, with progenitors a binary system composed of a carbon-oxygen star (COcore) and a neutron star (NS) companion. The COcore explodes as an SN, leaving at its center a newborn NS (νNS). The SN ejecta hypercritically accretes on both the νNS and the NS companion. BdHNe I are very tight binaries, where the accretion leads the companion NS to gravitationally collapse into a black hole (BH). In BdHN II, the accretion rate onto the NS is lower, so there is no BH formation. We observe the same afterglow structure for GRB 190114C and other selected examples of BdHNe I (GRB 130427A, GRB 160509A, GRB 160625B) and for BdHN II (GRB 180728A). In all cases, the afterglows are explained via the synchrotron emission powered by the νNS, and their magnetic field structures and their spin are determined. For BdHNe I, we discuss the properties of the magnetic field embedding the newborn BH, which was inherited from the collapsed NS and amplified during the gravitational collapse process, and surrounded by the SN ejecta.

Keywords: Black hole physics, Gamma-ray bursts, High energy astrophysics
A Hard X-Ray Test of HCN Enhancements As a Tracer of Embedded Black Hole Growth. Enhanced emission from the dense gas tracer HCN (relative to HCO+) has been proposed as a signature of active galactic nuclei (AGN). In a previous single-dish millimeter line survey we identified galaxies with HCN/HCO+ (1-0) intensity ratios consistent with those of many AGN but whose mid-infrared spectral diagnostics are consistent with little to no (≲15%) contribution of an AGN to the bolometric luminosity. To search for putative heavily obscured AGN, we present and analyze NuSTAR hard X-ray (3-79 keV) observations of four such galaxies from the Great Observatories All-sky LIRG Survey. We find no X-ray evidence for AGN in three of the systems and place strong upper limits on the energetic contribution of any heavily obscured ( ${N}_{{\rm{H}}}\gt {10}^{24}$ ${\mathrm{cm}}^{-2}$ ) AGN to their bolometric luminosity. The upper limits on the X-ray flux are presently an order of magnitude below what XDR-driven chemistry models predict are necessary to drive HCN enhancements. In a fourth system we find a hard X-ray excess consistent with the presence of an AGN, but contributing only ∼3% of the bolometric luminosity. It is also unclear if the AGN is spatially associated with the HCN enhancement. We further explore the relationship between HCN/HCO+ (for several Jupper levels) and ${L}_{\mathrm{AGN}}$ / ${L}_{\mathrm{IR}}$ for a larger sample of systems in the literature. We find no evidence for correlations between the line ratios and the AGN fraction derived from X-rays, indicating that HCN/HCO+ intensity ratios are not driven by the energetic dominance of AGN, nor are they reliable indicators of ongoing supermassive black hole accretion.

Keywords: Molecular gas, Starburst galaxies, X-ray active galactic nuclei, Active galactic nuclei, Luminous infrared galaxies
Common Envelope Shaping of Planetary Nebulae. II. Magnetic Solutions and Self-collimated Outflows. Magnetic fields of order 101-102 Gauss that are present in the envelopes of red giant stars are ejected in common envelope scenarios. These fields could be responsible for the launching of magnetically driven winds in protoplanetary nebulae. Using 2D simulations of magnetized winds interacting with an envelope drawn from a 3D simulation of the common envelope phase, we study the confinement, heating, and magnetic field development of post-common envelope winds. We find that the ejected magnetic field can be enhanced via compression by factors up to ∼104 in circumbinary disks during the self-regulated phases. We find values for the kinetic energy of the order of 1046 erg that explain the large values inferred in protoplanetary nebula outflows. We show that the interaction of the formed circumbinary disk with a spherical, stellar wind produces a "tapered" flow that is almost indistinguishable from an imposed tapered flow. This increases the uncertainty of the origin of protoplanetary nebula winds, which could be either stellar, circumstellar (stellar accretion disk), circumbinary (circumbinary accretion disk), or a combination of all three. Within this framework, a scenario for self-collimation of weakly magnetized winds is discussed, which can explain the two objects where the collimation process is observationally resolved, HD 101584 and Hen 3-1475. An explanation for the equatorial, molecular hydrogen emission in CRL 2688 is also presented.

Keywords: Hydrodynamical simulations, Magnetohydrodynamical simulations, Planetary nebulae, Protoplanetary disks, Circumstellar disks, Common envelope evolution, Common envelope binary stars
Gravitational Waves from the Phase Transition of NS to QS. In this article, we study the combustion of a neutron star to a hybrid star. We assume that a sudden density fluctuation at the center of the neutron star initiates a shock discontinuity near the center of the star. This shock discontinuity deconfines nuclear matter to two-flavor quark matter, initiating the combustion of the star. This combustion front propagates from the center to the surface, converting nuclear matter to two-flavor quark matter. This combustion stops at some radial point inside the star, as at this density the shock wave becomes rather weak. Although the combustion stops, a simple shock wave propagates to the surface. We study the gravitational-wave signal for such a phase transition of a neutron star to a hybrid star. We find that such a phase transition has a unique gravitational-wave strain of amplitude 10-21. These signals last for few tens of μs and show small oscillating behavior where the phase transition stops. The power spectrum consists of peaks at the fairly high-frequency range. The conversion from neutron star to hybrid star has a unique signature in the gravitational-wave signal, which could help with defining the phase transition and the fate of the neutron star.

Keywords: Neutron stars, Shocks, Neutron star cores, Gravitational waves
Small-scale Structure Traced by Neutral Hydrogen Absorption in the Direction of Multiple-component Radio Continuum Sources. We have studied the small-scale distribution of atomic hydrogen (H I) using 21 cm absorption spectra against multiple-component background radio continuum sources from the 21-SPONGE survey and the Millennium Arecibo Absorption-Line Survey. We have found &gt;5σ optical depth variations at a level of ∼0.03-0.5 between 13 out of 14 adjacent sightlines separated by a few arcseconds to a few arcminutes, suggesting the presence of neutral structures on spatial scales from a few to thousands of au (which we refer to as tiny-scale atomic structure, TSAS). The optical depth variations are strongest in directions where the H I column density and the fraction of H I in the cold neutral medium (CNM) are highest, which tend to be at low Galactic latitudes. By measuring changes in the properties of Gaussian components fitted to the absorption spectra, we find that changes in both the peak optical depth and the linewidth of TSAS absorption features contribute to the observed optical depth variations, while changes in the central velocity do not appear to strongly impact the observed variations. Both thermal and turbulent motions contribute appreciably to the linewidths, but the turbulence does not appear strong enough to confine overpressured TSAS. In a majority of cases, the TSAS column densities are sufficiently high that these structures can radiatively cool fast enough to maintain thermal equilibrium with their surroundings, even if they are overpressured. We also find that a majority of TSAS is associated with the CNM. For TSAS in the direction of the Taurus molecular cloud and the local Leo cold cloud, we estimate densities over an order of magnitude higher than typical CNM densities.

Keywords: Interstellar line absorption, Neutral hydrogen clouds, Interstellar medium, Milky Way Galaxy
Constraint on the Ejecta Mass for Black Hole-Neutron Star Merger Event Candidate S190814bv. We derive the upper limit to the ejecta mass of S190814bv, a black hole-neutron star (BH-NS) merger candidate, through radiative transfer simulations for kilonovae with realistic ejecta density profiles, as well as detailed opacity and heating rate models. The limits to the ejecta mass strongly depend on the viewing angle. For the face-on observations (≤45°), the total ejecta mass should be smaller than 0.1 M⊙ for the average distance of S190814bv (D = 267 Mpc), while a larger mass is allowed for the edge-on observations. We also derive the conservative upper limits of the dynamical ejecta mass to be 0.02, 0.03, and 0.05 M⊙ for the viewing angles ≤20°, ≤50°, and ≤90°, respectively. We show that an iz-band observation deeper than 22 mag within 2 days after the gravitational-wave trigger is crucial to detect a kilonova with a total ejecta mass of 0.06 M⊙ at a distance of D = 300 Mpc. We also show that a strong constraint on the NS mass-radius relation can be obtained if future observations put an upper limit of 0.03 M⊙ on the dynamical ejecta mass for a BH-NS event with a chirp mass smaller than ≲3 M⊙ and effective spin larger than ≳0.5.

Keywords: Gravitational wave astronomy, Neutron stars, Radiative transfer simulations, Black holes
Small-scale Dynamical Coherence Accompanied with Galaxy Conformity. The discovery of the coherence between galaxy rotation and neighbor motion in 1 Mpc scales has recently been reported. Following up on the discovery, we investigate whether the neighbors in such dynamical coherence also present galaxy conformity, using the Calar Alto Legacy Integral Field Area Survey (CALIFA) data and the NASA-Sloan Atlas catalog. We measure the correlation coefficient of g - r colors between the CALIFA galaxies and their neighbors, as a quantitative indicator of galaxy conformity. The neighbors are divided into coherently moving and anticoherently moving ones, the correlation coefficients from which are compared with each other, in various bins of relative luminosity and projected distance. In most cases, the CALIFA galaxies and their neighbors show positive correlation coefficients in g - r color, even for the anticoherent neighbors. However, we find a statistically significant (2.6σ) difference between coherent and anticoherent neighbors, when the neighbor galaxies are bright ( ${\rm{\Delta }}{M}_{r}\leqslant -1.0$ ) and close (D ≤ 400 kpc). That is, when they are bright and close to the CALIFA galaxies, the coherently moving neighbors show stronger conformity with the CALIFA galaxies than the anticoherently moving neighbors. This result supports that the small-scale dynamical coherence may originate from galaxy interactions as galaxy conformity is supposed to do, which agrees with the conclusion of the previous study.

Keywords: Galaxy environments, Companion galaxies, Galaxy dynamics, Galaxy rotation, Galaxy kinematics, Interacting galaxies
Swift Spectroscopy of the Accretion Disk Wind in the Black Hole GRO J1655-40. Chandra obtained two High Energy Transmission Grating spectra of the stellar-mass black hole GRO J1655-40 during its 2005 outburst, revealing a rich and complex disk wind. Soon after its launch, the Neil Gehrels Swift Observatory began monitoring the same outburst. Some X-ray Telescope (XRT) observations were obtained in a mode that makes it impossible to remove strong Mn calibration lines, so the Fe Kα line region in the spectra was previously neglected. However, these lines enable a precise calibration of the energy scale, facilitating studies of the absorption-dominated disk wind and its velocity shifts. Here we present fits to 15 Swift/XRT spectra, revealing variability and evolution in the outflow. The data strongly point to a magnetically driven disk wind: both the higher-velocity (e.g., $V\simeq {10}^{4}\,\mathrm{km}\,{{\rm{s}}}^{-1}$ ) and lower-velocity (e.g., $V\simeq {10}^{3}\,\mathrm{km}\,{{\rm{s}}}^{-1}$ ) wind components are typically much faster than is possible for thermally driven outflows ( $V\leqslant 200\,\mathrm{km}\,{{\rm{s}}}^{-1}$ ), and photoionization modeling yields absorption radii that are two orders of magnitude below the Compton radius that defines the typical inner extent of thermal winds. Moreover, correlations between key wind parameters yield an average absorption measure distribution that is consistent with magnetohydrodynamic wind models. We discuss our results in terms of recent observational and theoretical studies of black hole accretion disks and outflows, as well as future prospects.

Keywords: Stellar accretion disks, Black holes, Compact objects
Burst Properties of the Most Recurring Transient Magnetar SGR J1935+2154. We present timing and time-integrated spectral analysis of 127 bursts from SGR J1935+2154. These bursts were observed with the Gamma-ray Burst Monitor on the Fermi Gamma-ray Space Telescope and the Burst Alert Telescope on the Neil Gehrels Swift Observatory during the source's four active episodes from 2014 to 2016. This activation frequency makes SGR J1935+2154 the most burst prolific transient magnetar. We find the average duration of all the detected bursts to be much shorter than the typical, anticipated value. We fit the burst time-integrated spectra with two blackbody functions, a Comptonized model and three other simpler models. Bursts from SGR J1935+2154 exhibit similar spectral properties to other magnetars, with the exception of the power-law index from the Comptonized model, which correlates with burst fluence. We find that the durations and both blackbody temperatures of the bursts have significantly evolved across the four active episodes. We also find that the burst time history exhibits two trends, which are strongly correlated with the decay of the persistent emission in each outburst.

Keywords: Neutron stars, Transient sources, Soft gamma-ray repeaters, X-ray transient sources, Magnetars, Gamma-ray transient sources
Phase Mixing of Kink MHD Waves in the Solar Corona: Viscous Dissipation and Heating. Magnetohydrodynamic (MHD) kink waves have been observed frequently in solar coronal flux tubes, which makes them a great tool for seismology of the solar corona. Here, the effect of viscosity is studied on the evolution of kink waves. To this aim, we solve the initial value problem for the incompressible linearized viscous MHD equations in a radially inhomogeneous flux tube in the limit of long wavelengths. Using a modal expansion technique the spatio-temporal behavior of the perturbations is obtained. We confirm that for large Reynolds numbers representative of the coronal plasma the decrement in the amplitude of the kink oscillations is due to the resonant absorption mechanism that converts the global transverse oscillation to rotational motions in the inhomogeneous layer of the flux tube. We show that viscosity suppresses the rate of phase mixing of the perturbations in the inhomogeneous region of the flux tube and prevents the continuous building up of small scales in the system once a sufficiently small scale is reached. The viscous dissipation function is calculated to investigate plasma heating by viscosity in the inhomogeneous layer of the flux tube. For Reynolds numbers of the order of 106-108, the energy of the kink wave is transformed into heat in two to eight periods of the kink oscillation. For larger and more realistic Reynolds numbers, heating happens, predominantly, after the global kink oscillation is damped, and no significant heating occurs during the observable transverse motion of the flux tube.

Keywords: Magnetohydrodynamics, The Sun, Solar physics, Astrophysical fluid dynamics, Magnetohydrodynamical simulations
Heating and Eruption of a Solar Circular-ribbon Flare. We studied a circular-ribbon flare, SOL2014-12-17T04:51, with emphasis on its thermal evolution as determined by the differential emission measure (DEM) inversion analysis of the extreme ultraviolet (EUV) images of the Atmospheric Imaging Assembly instrument on board the Solar Dynamics Observatory. Both temperature and emission measure start to rise much earlier than the flare, along with an eruption and formation of a hot halo over the fan structure. In the main flare phase, another set of ribbons forms inside the circular ribbon, and expands as expected for ribbons at the footpoints of a postflare arcade. An additional heating event further extends the decay phase, which is also characteristic of some eruptive flares. The basic magnetic configuration appears to be a fan-spine topology, rooted in a minority-polarity patch surrounded by majority-polarity flux. We suggest that reconnection at the null point begins well before the impulsive phase, when the null is distorted into a breakout current sheet, and that both flare and breakout reconnection are necessary in order to explain the subsequent local thermal evolution and the eruptive activities in this confined magnetic structure. Using local DEMs, we found a postflare temperature increase inside the fan surface, indicating that the so-called EUV late phase is due to continued heating in the flare loops.

Keywords: The Sun, Solar physics
Flare Energy Release at the Magnetic Field Polarity Inversion Line during the M1.2 Solar Flare of 2015 March 15. II. Investigation of Photospheric Electric Current and Magnetic Field Variations Using HMI 135 s Vector Magnetograms. This work is a continuation of Paper I and is devoted to the analysis of nonthermal electron dynamics and plasma heating in the confined M1.2 class solar flare SOL2015-03-15T22:43, revealing energy release in the highly sheared interacting magnetic loops in the low corona, above the polarity inversion line (PIL). The aim of the present work is to perform the first extensive quantitative analysis of the photospheric magnetic field and photospheric vertical electric current (PVEC) dynamics in the confined flare region near the PIL using new vector magnetograms obtained with the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory with a high temporal resolution of 135 s. Data analysis reveals sharp changes of the magnetic structure and PVEC associated with flare onset near the PIL. It is found that the strongest plasma heating and electron acceleration are associated with the largest increase in the magnetic reconnection rate, total PVEC, and effective PVEC density in the flare ribbons. Observations and nonlinear force-free field extrapolations show that the magnetic field structure around the PIL is consistent with a tether-cutting magnetic reconnection (TCMR) geometry. We give a qualitative interpretation of the observed dynamics of the flare ribbons, magnetic field, PVEC, and electron acceleration within the TCMR scenario.

Keywords: Solar flares, Solar magnetic fields, Solar magnetic reconnection
Measuring Star Formation Histories, Distances, and Metallicities with Pixel Color-Magnitude Diagrams. II. Applications to Nearby Elliptical Galaxies. We present spatially resolved measurements of star formation histories (SFHs), metallicities, and distances in three nearby elliptical galaxies and the bulge of M31 derived using the pixel color-magnitude diagram (pCMD) technique. We compute pCMDs from archival Hubble Space Telescope photometry of M87, M49, NGC 3377, and M31, and we fit the data using the new code PCMDPy. We measure distances to each system that are accurate to ∼10%. The recovered nonparametric SFHs place reasonable (±1 dex) constraints on the recent (&lt;2 Gyr) star formation in M31 and NGC 3377, both of which show evidence of inside-out growth. The SFHs in M87 and M49 are constrained only at the oldest ages. The pCMD technique is a promising new avenue for studying the evolutionary history of the nearby universe and is highly complementary to existing stellar population modeling techniques.

Keywords: Star formation, Galaxy distances, Galaxy photometry, Elliptical galaxies
From Super-Earths to Mini-Neptunes: Implications of a Surface on Atmospheric Circulation. It is well known that planets with radii between that of Earth and Neptune have been the most commonly detected to date. To classify these planets as either terrestrial or gaseous, typically we turn to mass-radius relations and composition curves to determine the likelihood of such a planet being rocky or gaseous. While these methods have set a likely transition radius of approximately 1.5 R⊕, we cannot expect that any change between terrestrial and gaseous compositions will be a sharp cutoff, and composition curve predictions result in ambiguous designations for planets right near this transition radius. In this work, we present 3D general circulation models (GCMs) of transition planets, wherein we study the effects of a surface on observable quantities such as the latitudinal variations and eclipse depths. We present our updated GCM, validated on the circulation of Earth, before discussing our modeling choices for this transition planet. Finally, we discuss the results of this study and explore the prospects of detecting the presence of a surface through observations of secondary eclipses in the future.

Keywords: Extrasolar rocky planets, Super Earths, Exoplanet astronomy, Exoplanet surfaces, Mini Neptunes, Exoplanet atmospheres
Patterns in the Multiwavelength Behavior of Candidate Neutrino Blazars. Motivated by the identification of the blazar TXS 0506+056 as the first promising high-energy neutrino counterpart candidate, we search for additional neutrino blazar candidates among the Fermi-Large Area Telescope detected blazars. We investigate the multiwavelength behavior from radio to GeV gamma-rays of blazars found to be in spatial coincidence with single high-energy neutrinos and lower-energy neutrino flare candidates. In addition, we compare the average gamma-ray emission of the potential neutrino-emitting sources to the entire sample of gamma-ray blazars. We find that neutrino-emitting blazar candidates are statistically compatible with hypotheses of both a linear correlation and no correlation between neutrino and gamma-ray energy flux.

Keywords: Light curves, Blazars, Neutrino astronomy, High energy astrophysics