Sazuna/UAT_keywords huggingface dataset:
A Unique Resource for Solar Flare Diagnostic Studies: The SMM Bent Crystal Spectrometer. The Bent Crystal Spectrometer (BCS) on the NASA Solar Maximum Mission spacecraft observed the X-ray spectra of numerous solar flares during the periods 1980 February-November and 1984-1989. The instrument, the first of its kind to use curved crystal technology, observed the resonance lines of He-like Ca (Ca XIX) and Fe (Fe XXV), and neighboring satellite lines, allowing the study of the rapid evolution of flare plasma temperature, turbulence, mass motions etc. To date there has not been a solar X-ray spectrometer with comparable spectral and time resolution, while subsequent solar cycles have delivered far fewer and less intense flares. The BCS data archive thus offers an unparalleled resource for flare studies. A recent reassessment of the BCS calibration and its operations is extended here by using data during a spacecraft scan in the course of a flare on 1980 November 6 that highlights small deformations in the crystal curvature of the important channel 1 (viewing lines of Ca XIX and satellites). The results explain long-standing anomalies in spectral line ratios which have been widely discussed in the past. We also provide an in-flight estimation of the BCS collimator field of view which improves the absolute intensity calibration of the BCS. The BCS channel 1 background is shown to be entirely due to solar continuum radiation, confirming earlier analyses implying a time-variable flare abundance of Ca. We suggest that BCS high-resolution Ca XIX and Fe XXV line spectra be used as templates for the analysis of X-ray spectra of nonsolar sources.

Keywords: Solar x-ray emission, Solar x-ray flares
CHAOS V: Recombination Line Carbon Abundances in M 101. The CHemical Abundances Of Spirals (CHAOS) project is building a large database of Large Binocular Telescope (LBT) H II region spectra in nearby spiral galaxies to use direct abundances to better determine the dispersion in metallicity as a function of galactic radius. Here, we present CHAOS LBT observations of C II λ4267 emission detected in 10 H II regions in M 101, and using a new photoionization model-based ionization correction factor, we convert these measurements into total carbon abundances. A comparison with M 101 C II recombination line observations from the literature shows excellent agreement, and we measure a relatively steep gradient in log(C/H) of -0.37 ± 0.06 dex ${R}_{e}^{-1}$ . The C/N observations are consistent with a constant value of log(C/N) = 0.84 with a dispersion of only 0.09 dex, which, given the different nucleosynthetic sources of C and N, is challenging to understand. We also note that when plotting N/O versus O/H, all of the H II regions with detections of C II λ4267 present N/O abundances at the minimum of the scatter in N/O at a given value of O/H. If the high surface brightness necessary for the detection of the faint recombination lines is interpreted as an indicator of H II region youth, then this may point to a lack of nitrogen pollution in the youngest H II regions. In the future, we anticipate that the CHAOS project will significantly increase the total number of C II λ4267 measurements in extragalactic H II regions.

Keywords: Spiral galaxies, H II regions, Chemical abundances, Interstellar medium
An Extreme Ultraviolet Wave Associated with a Solar Filament Activation. Extreme ultraviolet (EUV) waves are impressive coronal propagating disturbances. They are closely associated with various eruptions and can be used for global coronal seismology and the acceleration of solar energetic particles. Hence, the study of EUV waves plays an important role in solar eruptions and space weather. Here we present an EUV wave associated with a filament activation that did not evolve into any eruption. Due to the continuous magnetic flux emergence and cancellation around its one end, the filament rose with untwisting motion, and the filament mass flowed toward another end along the rising fields. Intriguingly, following the filament activation, an EUV wave formed with a fast constant speed (∼500 km s-1) ahead of the mass flow, and the overlying coronal loops expanded in both lateral and radial directions. Excluding the possibility of a remote flare and an absent coronal mass ejection, we suggest that the EUV wave was only closely associated with the filament activation. Furthermore, their intimate spatial and temporal relationship indicates that the EUV wave was likely directly triggered by the lateral expansion of overlying loops. We propose that the EUV wave can be interpreted as a linear fast-mode wave, and the most vital key for the successful generation of the EUV wave is the impulsive early phase lateral expansion of overlying loops that was driven by the activated filament mass flow without any eruption.

Keywords: Solar coronal loops, Solar coronal waves, Solar filaments, Solar magnetic flux emergence
On the Contribution of Quiet-Sun Magnetism to Solar Irradiance Variations: Constraints on Quiet-Sun Variability and Grand-minimum Scenarios. While the quiet-Sun magnetic field shows only little variation with the solar cycle, long-term variations cannot be completely ruled out from first principles. We investigate the potential effect of quiet-Sun magnetism on spectral solar irradiance through a series of small-scale dynamo simulations with zero vertical flux imbalance ( $\langle {B}_{z}\rangle =0$) and varying levels of small-scale magnetic field strength, and one weak network case with an additional flux imbalance corresponding to a flux density of $\langle {B}_{z}\rangle =100$ G. From these setups, we compute the dependence of the outgoing radiative energy flux on the mean vertical magnetic field strength in the photosphere at a continuum optical depth τ = 1 ( $\langle | {B}_{z}| {\rangle }_{\tau =1}$). We find that a quiet-Sun setup with a mean vertical field strength of $\langle | {B}_{z}| {\rangle }_{\tau =1}=69$ G is about 0.6% brighter than a non-magnetic reference case. We find a linear dependence of the outgoing radiative energy flux on the mean field strength $\langle | {B}_{z}| {\rangle }_{\tau =1}$ with a relative slope of 1.4 × 10-4 G-1. With this sensitivity, only a moderate change of the quiet-Sun field strength by 10% would lead to a total solar irradiance variation comparable to the observed solar cycle variation. While this does provide strong indirect constraints on possible quiet-Sun variations during a regular solar cycle, it also emphasizes that potential variability over longer timescales could make a significant contribution to longer-term solar irradiance variations.

Keywords: Radiative magnetohydrodynamics, Solar photosphere, Quiet sun, Solar spectral irradiance, Solar granulation, Radiative transfer, Solar magnetic fields
Universal Transition Diagram from Dormant to Actively Accreting Supermassive Black Holes. The vast majority of supermassive black holes (SMBHs) in the local universe exhibit levels of activity much lower than those expected from gas supplying rates onto the galactic nuclei, and only a small fraction of silent SMBHs can turn into active galactic nuclei. Revisiting observational data of very nearby SMBHs whose gravitational spheres of influence are spatially reached by the Chandra X-ray satellite, we find that the level of BH activity drastically increases from the quiescent phase when the inflow rate outside of the BH influence radius is higher than 0.1% of the Eddington accretion rate. We also show that the relation between the nuclear luminosity and gas accretion rate from the BH influence radius measured from X-ray observations is well described by the universal state transition of accreting SMBHs, as predicted by recent hydrodynamical simulations with radiative cooling and BH feedback. After the state transition, young massive stars should form naturally in the nucleus, as observed in the case of the nearest SMBH, Sagittarius A*, which is currently quiescent but was recently active.

Keywords: Supermassive black holes, Seyfert galaxies, Galaxy nuclei
The Warm Gas in the MW: A Kinematical Model. We develop a kinematical model for the Milky Way Si IV-bearing gas to determine its density distribution and kinematics. This model is constrained by a column density line-shape sample extracted from the Hubble Space Telescope/Cosmic Origins Spectrograph archival data, which contains 186 active galactic nucleus sight lines. We find that the Si IV ion density distribution is dominated by an extended disk along the z-direction (above or below the midplane), I.e., $n{(z)={n}_{0}\exp (-(z/{z}_{0})}^{0.82})$ , where z0 is the scale height of ${6.3}_{-1.5}^{+1.6}$ kpc (northern hemisphere) and ${3.6}_{-0.9}^{+1.0}$ kpc (southern hemisphere). The density distribution of the disk in the radial direction shows a sharp edge at 15-20 kpc given by, $n{({r}_{\mathrm{XY}})={n}_{0}\exp (-({r}_{\mathrm{XY}}/{r}_{0})}^{3.36})$ , where r0 ≈ 12.5 ± 0.6 kpc. The difference of density distributions over rXY and z directions indicates that the warm gas traced by Si IV is mainly associated with disk processes (e.g., feedback or cycling gas) rather than accretion. We estimate the mass of the warm gas (within 50 kpc) is $\mathrm{log}(M(50\mathrm{kpc})/{M}_{\odot })\approx 8.1$ (assuming Z ≈ 0.5 Z⊙), and a 3σ upper limit of $\mathrm{log}(M(250\mathrm{kpc})/{M}_{\odot })\approx 9.1$ (excluding the Magellanic system). Kinematically, the warm gas disk is nearly co-rotating with the stellar disk at ${V}_{\mathrm{rot}}=215\pm 3\,\mathrm{km}\,{{\rm{s}}}^{-1}$ , which lags the midplane rotation by about $8\,\mathrm{km}\,{{\rm{s}}}^{-1}\,{\mathrm{kpc}}^{-1}$ (within 5 kpc). Meanwhile, we note that the warm gas in the northern hemisphere has significant accretion with Vacc of 69 ± 7 $\mathrm{km}\,{{\rm{s}}}^{-1}$ at 10 kpc (an accretion rate of $-{0.60}_{-0.13}^{+0.11}\,{M}_{\odot }\,{\mathrm{yr}}^{-1}$), while in the southern hemisphere, there is no measurable accretion, with an upper limit of 0.4 M⊙ yr-1.

Keywords: Milky Way Galaxy fountains, Interstellar absorption, Quasar absorption line spectroscopy, Circumgalactic medium
Formation of Giant Planet Satellites. Recent analyses have shown that the concluding stages of giant planet formation are accompanied by the development of a large-scale meridional flow of gas inside the planetary Hill sphere. This circulation feeds a circumplanetary disk that viscously expels gaseous material back into the parent nebula, maintaining the system in a quasi-steady state. Here, we investigate the formation of natural satellites of Jupiter and Saturn within the framework of this newly outlined picture. We begin by considering the long-term evolution of solid material, and demonstrate that the circumplanetary disk can act as a global dust trap, where s• ∼ 0.1-10 mm grains achieve a hydrodynamical equilibrium, facilitated by a balance between radial updraft and aerodynamic drag. This process leads to a gradual increase in the system's metallicity, and eventually culminates in the gravitational fragmentation of the outer regions of the solid subdisk into ${ \mathcal R }\sim 100$ km satellitesimals. Subsequently, satellite conglomeration ensues via pair-wise collisions but is terminated when disk-driven orbital migration removes the growing objects from the satellitesimal feeding zone. The resulting satellite formation cycle can repeat multiple times, until it is brought to an end by photoevaporation of the parent nebula. Numerical simulations of the envisioned formation scenario yield satisfactory agreement between our model and the known properties of the Jovian and Saturnian moons.

Keywords: Galilean satellites, Saturnian satellites, Natural satellite formation
The Drivers of Active Region Outflows into the Slow Solar Wind. Plasma outflows from the edges of active regions have been suggested as a possible source of the slow solar wind. Spectroscopic measurements show that these outflows have an enhanced elemental composition, which is a distinct signature of the slow wind. Current spectroscopic observations, however, do not have sufficient spatial resolution to distinguish what structures are being measured or determine the driver of the outflows. The High-resolution Coronal Imager (Hi-C) flew on a sounding rocket in 2018 May and observed areas of active region outflow at the highest spatial resolution ever achieved (250 km). Here we use the Hi-C data to disentangle the outflow composition signatures observed with the Hinode satellite during the flight. We show that there are two components to the outflow emission: a substantial contribution from expanded plasma that appears to have been expelled from closed loops in the active region core and a second contribution from dynamic activity in active region plage, with a composition signature that reflects solar photospheric abundances. The two competing drivers of the outflows may explain the variable composition of the slow solar wind.

Keywords: Slow solar wind, Solar corona
Spatially Resolved Chandra Spectroscopy of the Large Magellanic Cloud Supernova Remnant N132D. We perform detailed spectroscopy of the X-ray-brightest supernova remnant in the Large Magellanic Cloud (LMC), N132D, using Chandra archival observations. By analyzing the spectra of the entire well-defined rim, we determine the mean abundances for O, Ne, Mg, Si, S, and Fe for the local LMC environment. We find evidence of enhanced O on the northwestern and S on the northeastern blast wave. By analyzing spectra interior to the remnant, we confirm the presence of a Si-rich, relatively hot plasma (≳1.5 keV) that is also responsible for the Fe K emission. Chandra images show that the Fe K emission is distributed throughout the interior of the southern half of the remnant but does not extend out to the blast wave. We estimate the progenitor mass to be 15 ± 5 M☉ using abundance ratios in different regions that collectively cover a large fraction of the remnant, as well as from the radius of the forward shock compared with models of an explosion in a cavity created by stellar winds. We fit ionizing and recombining plasma models to the Fe K emission and find that the current data cannot distinguish between the two, so the origin of the high-temperature plasma remains uncertain. Our analysis is consistent with N132D being the result of a core-collapse supernova in a cavity created by its intermediate-mass progenitor.

Keywords: X-ray astronomy, High resolution spectroscopy, Core-collapse supernovae, Interstellar abundances, Plasma astrophysics, Large Magellanic Cloud, Interstellar medium, X-ray observatories, Shocks, Metallicity
Toward an Accurate Description of an Accretion-induced Collapse and the Associated Ejected Mass. We revisit the accretion-induced collapse (AIC) process, in which a white dwarf collapses into a neutron star. We are motivated by the persistent radio source associated with the fast radio burst FRB 121102, which was explained by Waxman as a weak stellar explosion with a small (∼10-5 M⊙) mildly relativistic mass ejection that may be consistent with AIC. Additionally, the interaction of the relatively low ejected mass with a pre-collapse wind might be related to fast optical transients. The AIC is simulated with a one-dimensional, Lagrangian, Newtonian hydrodynamic code. We put an emphasis on accurately treating the equation of state and the nuclear burning, which is required for any study that attempts to accurately simulate AIC. We leave subjects such as neutrino physics and general relativity corrections for future work. Using an existing initial profile and our own initial profiles, we find that the ejected mass is ∼10-2 to 10-1 M⊙ over a wide range of parameters, and we construct a simple model to explain our results.

Keywords: Neutron stars, Hydrodynamical simulations, Hydrodynamics, White dwarf stars, Radio transient sources
Common-envelope Dynamics of a Stellar-mass Black Hole: General Relativistic Simulations. With the goal of providing more accurate and realistic estimates of the secular behavior of the mass accretion and drag rates in the "common-envelope" scenario encountered when a black hole or a neutron star moves in the stellar envelope of a red supergiant star, we have carried out the first general relativistic simulations of the accretion flow onto a nonrotating black hole moving supersonically in a medium with regular but different density gradients. The simulations reveal that the supersonic motion always rapidly reaches a stationary state and produces a shock cone in the downstream part of the flow. In the absence of density gradients we recover the phenomenology already observed in the well-known Bondi-Hoyle-Lyttleton accretion problem, with super-Eddington mass accretion rate and a shock cone whose axis is stably aligned with the direction of motion. However, as the density gradient is made stronger, the accretion rate also increases and the shock cone is progressively and stably dragged toward the direction of motion. With sufficiently large gradients, the shock-cone axis can become orthogonal to the direction, or even move in the upstream region of the flow in the case of the largest density gradient. Together with the phenomenological aspects of the accretion flow, we have also quantified the rates of accretion of mass and momentum onto the black hole. Simple analytic expressions have been found for the rates of accretion of mass, momentum, drag force, and bremsstrahlung luminosity, all of which have been employed in the astrophysical modeling of the secular evolution of a binary system experiencing a common-envelope evolution. We have also compared our results with those of previous studies in Newtonian gravity, finding similar phenomenology and rates for motion in a uniform medium. However, differences develop for nonzero density gradients, with the general relativistic rates increasing almost exponentially with the density gradients, while the opposite is true for the Newtonian rates. Finally, the evidence that mass accretion rates well above the Eddington limit can be achieved in the presence of nonuniform media increases the chances of observing this process also in binary systems of stellar-mass black holes.

Keywords: Black hole physics, Bondi accretion, Common envelope evolution
Modeling Observable Differences in Flare Loop Evolution due to Reconnection Location and Current Sheet Structure. Flare reconnection is expected to occur at some point within a large-scale coronal current sheet. The structure of the magnetic field outside this sheet is almost certain to affect the flare, especially its energy release. Different models for reconnection have invoked different structures for the current sheet's magnetic field and different locations for the reconnection electric field within it. Models invoking Petschek-type reconnection often use a uniform field. Others invoke a field bounded by two Y-points with a field strength maximum between them and propose this maximum as the site of the reconnection electric field. Still other models, such as the collapsing trap model, require that the field strength peak at or near the edge of the current sheet and propose that reconnection occurs above this peak. At present there is no agreement as to where reconnection might occur within a global current sheet. We study the post-reconnection dynamics under all these scenarios, seeking potentially observable differences between them. We find that reconnection occurring above the point of strongest field leads to the highest density and the highest emission measure of the hottest material. This scenario offers a possible explanation of superhot coronal sources seen in some flares.

Keywords: Solar flares, Solar magnetic reconnection
A Systematic Study of Galactic Outflows via Fluorescence Emission: Implications for Their Size and Structure. Galactic outflows play a major role in the evolution of galaxies, but the underlying physical processes are poorly understood. This is mainly because we have little information about the outflow structure, especially on large scales. In this paper, we probe the structure of galactic outflows in low-z starbursts using a combination of ultraviolet spectroscopy and imaging of the fluorescence emission lines (associated with transitions to excited fine-structure levels) and spectroscopy of the corresponding strongly blueshifted resonance absorption lines. We find that, in the majority of cases, the observed fluorescence emission lines are much weaker and narrower than the absorption lines, originating in the star-forming interstellar medium and/or the slowest-moving part of the inner outflow. In a minority of cases, the outflowing absorbing material does make a significant contribution to the fluorescence emission. These latter systems are characterized by both strong Lyα emission lines and weak low-ionization absorption lines (both known to be empirical signs of Lyman-continuum leakage). We argue that the observed weakness of emission from the outflow seen in the majority of cases is due to the missing emission arising on scales larger than those encompassed by the aperture of the Cosmic Origins Spectrograph on board the Hubble Space Telescope. This implies shallow radial density profiles in these outflows, and suggests that most of the observed absorbing material must be created/injected at radii much larger than that of the starburst. This has important implications both for our understanding of the physics of galactic outflows and for our estimation of their principal properties.

Keywords: Starburst galaxies, Galaxy formation, Galaxy winds, Interstellar medium, Circumgalactic medium, Extragalactic astronomy
Strong Lensing Model of SPT-CL J0356-5337, a Major Merger Candidate at Redshift 1.0359. We present an analysis of the mass distribution inferred from strong lensing by SPT-CL J0356-5337, a cluster of galaxies at redshift $z=1.0359$ revealed in the follow-up of the SPT-SZ clusters. The cluster has an Einstein radius of ${\theta }_{{\rm{E}}}\simeq $ 14″ for a source at z = 3 and a mass within 500 kpc of ${M}_{500\mathrm{kpc}}=4.0\pm 0.8\times {10}^{14}\,$ ${M}_{\odot }$ . Our spectroscopic identification of three multiply imaged systems ( $z=2.363$ , $z=2.364$ , and $z=3.048$), combined with HSTF606W-band imaging allows us to build a strong lensing model for this cluster with an rms of $\leqslant 0\buildrel{\prime\prime}\over{.} 3$ . Our modeling reveals a two-component mass distribution in the cluster. One mass component is dominated by the brightest cluster Galaxy and the other component, separated by ∼170 kpc, contains a group of eight red elliptical galaxies confined in a ∼9″ (∼70 kpc) diameter circle. We estimate the mass ratio between the two components to be between 1:1.25 and 1:1.58. In addition, spectroscopic data reveal that these two near-equal mass cores have only a small velocity difference of ∼300 km s-1 between the two components. This small radial velocity difference suggests that most of the relative velocity takes place in the plane of the sky, and implies that SPT-CL J0356-5337 is a major merger with a small impact parameter seen face-on. We also assess the relative contributions of Galaxy-scale halos to the overall mass of the core of the cluster and find that within 800 kpc from the brightest cluster Galaxy about 27% of the total mass can be attributed to visible and dark matter associated with galaxies, whereas only 73% of the total mass in the core comes from cluster-scale dark matter halos.

Keywords: Galaxy clusters, Strong gravitational lensing, Dark matter distribution, Gravitational lensing