Sazuna/UAT_keywords huggingface dataset:
Spatiotemporal Energy Partitioning in a Nonthermally Dominated Two-loop Solar Flare. Solar flares show remarkable variety in the energy partitioning between thermal and nonthermal components. Those with a prominent nonthermal component but only a modest thermal one are particularly well suited for study of the direct effect of the nonthermal electrons on plasma heating. Here, we analyze such a well-observed, impulsive single-spike nonthermal event, a solar flare SOL2013-11-05T035054, where the plasma heating can be entirely attributed to the energy losses of these impulsively accelerated electrons. Evolution of the energy budget of thermal and nonthermal components during the flare is analyzed using X-ray, microwave, and EUV observations and three-dimensional modeling. The results suggest that (I) the flare geometry is consistent with a two-loop morphology and the magnetic energy is likely released due to interaction between these two loops; (II) the released magnetic energy is converted to the nonthermal energy of accelerated electrons only, which is subsequently converted to the thermal energy of the plasma; (III) the energy is partitioned in these two flaring loops in comparable amounts; (IV) one of these flaring loops remained relatively tenuous but rather hot, while the other remained relatively cool but denser than the first. Therefore, this solar flare demonstrates an extreme efficiency of conversion of the free magnetic energy to the nonthermal energy of particle acceleration and the flow of energy into two loops from the nonthermal component to the thermal one with negligible direct heating.

Keywords: Solar flares, Solar extreme ultraviolet emission, The Sun, Solar x-ray emission, Solar radio emission
ALMA Observations of Two Massive and Dense MALT90 Clumps. We report Atacama Large Millimeter Array observations of 3 mm dust continuum emission and line emission, in HCO+, H13CO+, N2H+, and CH3CN, toward two massive and dense clumps (MDCs) in early but distinct evolutionary phases (prestellar and protostellar), made with the goal of investigating their fragmentation characteristics at angular scales of ∼1″. Toward the prestellar clump we detected 10 compact structures (cores), with radii from 1200-4500 au and masses from 1.6-20 M⊙. Half of these cores exhibit inverse P Cygni profiles in HCO+ and are subvirialized indicating that they are undergoing collapse. Toward the protostellar clump we detected a massive (119 M⊙) central core, with a strong mass infall rate, and nine less massive cores, with masses from 1.7-27 M⊙ and radii from 1000-4300 au. CH3CN rotational temperatures were derived for eight cores in the protostellar clump and three cores in the prestellar clump. Cores within the prestellar clump have smaller line widths and lower temperatures than cores within the protostellar clump. The fraction of total mass in cores to clump mass is smaller in the prestellar clump (∼6%) than in the protostellar clump (∼23%). We conclude that we are witnessing the evolution of the dense gas in globally collapsing MDCs; the prestellar clump illustrating the initial stage of fragmentation, harboring cores that are individually collapsing, and the protostellar clump reflecting a later stage in which a considerable fraction of the gas has been gravitationally focused into the central region.

Keywords: Massive stars, Star formation, Interstellar medium, Collapsing clouds
Laboratory Calibrations of Fe XII-XIV Line-intensity Ratios for Electron Density Diagnostics. We have used an electron beam ion trap to measure electron-density-diagnostic line-intensity ratios for extreme ultraviolet lines from Fe XII, XIII, and XIV at wavelengths of ≈185-205 and 255-276 Å. These ratios can be used as density diagnostics for astrophysical spectra and are especially relevant to solar physics. We found that density diagnostics using the Fe XIII 196.53/202.04 and the Fe XIV 264.79/274.21 and 270.52A/274.21 line ratios are reliable using the atomic data calculated with the Flexible Atomic Code (FAC). On the other hand, we found a large discrepancy between the FAC theory and experiment for the commonly used Fe XII (186.85 + 186.88)/195.12 line ratio. These FAC theory calculations give results similar to the data tabulated in CHIANTI, which are commonly used to analyze solar observations. Our results suggest that the discrepancies seen between solar coronal density measurements using the Fe XII (186.85 + 186.88)/195.12 and Fe XIII 196.54/202.04 line ratios are likely due to issues with the atomic calculations for Fe XII.

Keywords: Atomic physics, Laboratory astrophysics, Atomic spectroscopy, Solar corona, Spectroscopy
Angular Correlation Function Estimators Accounting for Contamination from Probabilistic Distance Measurements. With the advent of surveys containing millions to billions of galaxies, it is imperative to develop analysis techniques that utilize the available statistical power. In galaxy clustering, even small sample contamination arising from distance uncertainties can lead to large artifacts, which the standard estimator for two-point correlation functions does not account for. We first introduce a formalism, termed decontamination, that corrects for sample contamination by utilizing the observed cross-correlations in the contaminated samples; this corrects any correlation function estimator for contamination. Using this formalism, we present a new estimator that uses the standard estimator to measure correlation functions in the contaminated samples but then corrects for contamination. We also introduce a weighted estimator that assigns each galaxy a weight in each redshift bin based on its probability of being in that bin. We demonstrate that these estimators effectively recover the true correlation functions and their covariance matrices. Our estimators can correct for sample contamination caused by misclassification between object types as well as photometric redshifts; they should be particularly helpful for studies of galaxy evolution and baryonic acoustic oscillations, where forward modeling the clustering signal using the contaminated redshift distribution is undesirable.

Keywords: Cosmology, Two-point correlation function, Large-scale structure of the universe
Hydrodynamic Escape of Water Vapor Atmospheres near Very Active Stars. When exposed to the high-energy X-ray and ultraviolet radiation of a very active star, water vapor in the upper atmospheres of planets can be photodissociated and rapidly lost to space. In this paper, I study the chemical, thermal, and hydrodynamic processes in the upper atmospheres of terrestrial planets, concentrating on water-vapor-dominated atmospheres orbiting in the habitable zones of active stars. I consider different stellar activity levels and find very high levels of atmospheric escape in all cases, with the outflowing gas being dominated by atomic hydrogen and oxygen in both their neutral and ion forms. In the lower activity cases, I find that the accumulation of O2 and increases in the D/H ratios in the atmospheres due to mass fractionation are possible, but in the higher activity cases, no mass fractionation takes place. Connecting these results to stellar activity evolution tracks for solar-mass stars, I show that huge amounts of water vapor can be lost, and both the losses and the amount of O2 that can be accumulated in the atmosphere depend sensitively on the star's initial rotation rate. For an Earth-mass planet in the habitable zone of a low-mass M dwarf, my results suggest that the accumulation of atmospheric O2 is unlikely unless water loss can take place after the star's most active phase.

Keywords: Upper atmosphere, Water vapor, Planetary atmospheres, Stellar activity, Exoplanet atmospheres
Large-scale Dynamics of Winds Originating from Black Hole Accretion Flows. I. Hydrodynamics. Winds from black hole accretion flows are ubiquitous. Previous works mainly focus on the launching of wind on the accretion flow scale. It still remains unclear how far the winds can propagate outward and what their large-scale dynamics is. As the first paper of this series, we study the large-scale dynamics of thermal wind beyond accretion scales via analytical and numerical methods. Boundary conditions, which are crucial to our problem, are analyzed and presented based on small-scale simulations combined with observations of winds. Both black hole and galaxy potential are taken into account. For winds originating from hot accretion flows, we find that the wind can reach large scales. The radial profiles of velocity, density, and temperature can be approximated by ${V}_{r}\approx {V}_{r0},\rho \approx {\rho }_{0}{(r/{r}_{0})}^{-2}$ and $T\approx {T}_{0}{(r/{r}_{0})}^{-2(\gamma -1)}$ , where Vr0, ρ0, and T0 are the velocity, density, and temperature of winds at the boundary ${r}_{0}(\equiv {10}^{3}{r}_{g})$ , and γ is the polytropic index. During the outward propagation, the enthalpy and rotational energy compensate for the increase of gravitational potential. For thin disks, we find that because the Bernoulli parameter is smaller, winds cannot propagate as far as the hot winds, but stop at a certain radius where the Bernoulli parameter is equal to the potential energy. Before the winds stop, the profiles of dynamical quantities can also be approximated by the above relations. In this case, the rotational energy alone compensates for the increase in potential energy.

Keywords: Supermassive black holes, Black holes, High energy astrophysics, Hydrodynamics, Active galactic nuclei, Interdisciplinary astronomy, Astrophysical fluid dynamics, Astrophysical black holes
Large-scale Dynamics of Winds Originating from Black Hole Accretion Flows. II. Magnetohydrodynamics. The great difference in dynamical range between small-scale accretion disk simulations and large-scale or cosmological simulations creates difficulties in tracking the disk wind kinematics. In the first paper of this series, we studied the dynamics of hydrodynamic winds from the outer edge of the accretion disk toward galactic scales. In this paper, we further incorporate magnetic fields by employing a one-dimensional magnetohydrodynamic model, with fiducial boundary conditions set for hot accretion flows. The wind solution is achieved through requiring gas to pass smoothly through the slow, Alfvén, and fast magnetosonic points. Beyond the fast magnetosonic point, physical quantities are found to show power-law dependences with cylindrical radius R, I.e., $\rho \propto {R}^{-2},{V}_{{\rm{p}}}\propto \mathrm{const}.,{V}_{\phi }\propto {R}^{-1},{B}_{\phi }\propto {R}^{-1},$ and $\beta \propto {\rho }^{\gamma -1}$ . The magnetization of wind is dominant in determining the wind properties. The wind is accelerated to greater terminal velocities with stronger magnetizations. The fiducial parameters result in a terminal velocity of about 0.016c. The dependence of the wind physical quantities on temperature, field line angular velocity, and adiabatic index is also discussed.

Keywords: Supermassive black holes, Magnetohydrodynamics, Black holes, High energy astrophysics, Active galactic nuclei, Astrophysical fluid dynamics, Astrophysical black holes
Tracking Downflows from the Chromosphere to the Photosphere in a Solar Arch Filament System. We study the dynamics of plasma along the legs of an arch filament system (AFS) from the chromosphere to the photosphere, observed with high-cadence spectroscopic data from two ground-based solar telescopes: the GREGOR telescope (Tenerife) using the GREGOR Infrared Spectrograph in the He I 10830 Å range and the Swedish Solar Telescope (La Palma) using the CRisp Imaging Spectro-Polarimeter to observe the Ca II 8542 Å and Fe I 6173 Å spectral lines. The temporal evolution of the draining of the plasma was followed along the legs of a single arch filament from the chromosphere to the photosphere. The average Doppler velocities inferred at the upper chromosphere from the He I 10830 Å triplet reach velocities up to 20-24 km s-1, and in the lower chromosphere and upper photosphere the Doppler velocities reach up to 11 km s-1 and 1.5 km s-1 in the case of the Ca II 8542 Å and Si I 10827 Å spectral lines, respectively. The evolution of the Doppler velocities at different layers of the solar atmosphere (chromosphere and upper photosphere) shows that they follow the same line-of-sight (LOS) velocity pattern, which confirms the observational evidence that the plasma drains toward the photosphere as proposed in models of AFSs. The Doppler velocity maps inferred from the lower photospheric Ca I 10839 Å or Fe I 6173 Å spectral lines do not show the same LOS velocity pattern. Thus, there is no evidence that the plasma reaches the lower photosphere. The observations and the nonlinear force-free field (NLFFF) extrapolations demonstrate that the magnetic field loops of the AFS rise with time. We found flow asymmetries at different footpoints of the AFS. The NLFFF values of the magnetic field strength help us to explain these flow asymmetries.

Keywords: Observational astronomy, High resolution spectroscopy, Solar photosphere, Astronomy data analysis, Solar chromosphere
Neutrino Production Associated with Late Bumps in Gamma-Ray Bursts and Potential Contribution to Diffuse Flux at IceCube. IceCube has detected many TeV-PeV neutrinos, but their astrophysical origins remain largely unknown. Motivated by the observed late-time X-ray/optical bumps in some gamma-ray bursts (GRBs), we examine the correlation between IceCube neutrinos and GRBs allowing delayed neutrinos ∼days after the prompt gamma-rays. Although we have not found any definitive correlation, up to ∼10% of the events observed so far at IceCube may have been neutrinos produced by the late-time GRB activities at ∼1 day. Assuming a connection between some IceCube events and the late GRB bumps, we show in a model-independent way that GRB sites capable of producing late ∼PeV neutrinos should be nonrelativistic or mildly relativistic. We estimate the diffuse neutrino flux from such sources and find that they can possibly account for a few IceCube events. Future observations of high-energy neutrinos and late-time GRB afterglows can further test the above proposed connection.

Keywords: Neutrino astronomy, Gamma-ray bursts, High energy astrophysics
Serial Flaring in an Active Region: Exploring Why Only One Flare Is Eruptive. Over a four hour period between 2014 June 12-13 a series of three flares were observed within AR 12087. This sequence of flares started with a non-eruptive M-class flare, followed by a non-eruptive C-class flare, and finally ended with a second C-class flare that had an associated filament eruption. In this paper we combine spectroscopic analysis of Interface Region Imaging Spectrometer observations of the Si IV line during the three flares along with a series of nonlinear force-free field (NLFFF) extrapolations in order to investigate the conditions that lead the final flare to be eruptive. From this analysis it is found to be unlikely that the eruption was triggered by either kink instability or by tether-cutting reconnection, allowing the flux rope to rise into a region where it would be susceptible to the torus instability. The NLFFF modeling does, however, suggest that the overlying magnetic field has a fan-spine topology, raising the possibility that breakout reconnection occurring during the first two flares weakened the overlying field, allowing the flux rope to erupt in the subsequent third flare.

Keywords: Solar active region magnetic fields, Solar flares, Solar active region filaments, Solar flare spectra, Solar physics, Solar active regions, Solar activity
Dissecting the Phase Space Snail Shell. The ongoing vertical phase-mixing, manifesting itself as a snail shell in the $Z-{V}_{Z}$ phase space, has been discovered with Gaia DR2 data. To better understand the origin and properties of the phase-mixing process, we study the vertical phase-mixing signatures in arches (including the classical "moving groups") of the ${V}_{R}-{V}_{\phi }$ phase space near the solar circle. Interestingly, the phase space snail shell exists only in the arches with $| {V}_{\phi }-{V}_{\mathrm{LSR}}| \,\lesssim 30$ km s-1, I.e., stars on dynamically "colder" orbits. The snail shell becomes much weaker and eventually disappears for increasingly larger radial action (JR), quantifying the "hotness" of orbits. Thus, one should pay closer attention to the colder orbits in future phase-mixing studies. We also confirm that the Hercules stream has two branches (at fast and slow Vφ), which may not be explained by a single mechanism, since only the fast branch shows the prominent snail shell feature. The hotter orbits may have phase-wrapped away already due to the much larger dynamical range in radial variation to facilitate faster phase-mixing. To explain the lack of a well-defined snail shell in the hotter orbits, the disk should have been perturbed at least 500 Myr ago. Our results offer more support to the recent satellite-disk encounter scenario than the internal bar-buckling perturbation scenario as the origin of the phase space mixing. The origin of the more prominent snail shell in the Vφ color-coded phase space is also discussed.

Keywords: Galaxy disks, Milky Way disk, Galaxy structure, Milky Way dynamics
The Large-scale Behavior in the Disk of δ Scorpii from 2000 to 2018. We model the circumstellar disk of δ Sco using the three-dimensional Monte Carlo radiative transfer code HDUST in order to quantify the large-scale changes in the disk through the years 2000-2018, and to see if these changes can be attributed to the secondary star affecting the disk throughout its orbit. We determine our best-fitting models through matching simulated observations to actual Hα spectroscopy and V-band photometric observations. Our modeling results confirm previous findings that the disk of δ Sco was forming early in the century. We also find a period of disk dissipation when the companion is at apastron, as well as a significant growth of the disk between 2009 and 2011, prior to the periastron of 2011. Due to the steady-state nature of the disk after 2011, it is difficult to say whether the variations seen are due to the effect of the close passage of the binary companion.

Keywords: Binary stars, Circumstellar disks, Photometry, Spectroscopy, Be stars, Stellar spectral lines
Confirmation of the Stellar Binary Microlensing Event, Macho 97-BLG-28. The high-magnification microlensing event MACHO-97-BLG-28 was previously determined to be a binary system composed of either two M dwarfs or an M dwarf and a brown dwarf. We present a revised light-curve model using additional data from the Mt. Stromlo 74″ telescope, model estimates of stellar limb darkening, and fitting of the blend separately for each telescope and passband. We find a lensing system with a larger mass ratio, q = 0.28 ± 0.01, and smaller projected separation, s = 0.61 ± 0.01, than those presented in the original study. We revise the estimate of the lens-source relative proper motion to μrel = 2.8 ± 0.5 mas yr-1, which indicates that 16.07 yr after the event maximum the lens and source should have separated by 46 ± 8 mas. We revise the radius of the source star using more recent reddening maps and angular diameter-color relations to R* = (10.3 ± 1.9) R⊙. K- and J-band adaptive optics images of the field taken at this epoch using the NIRC2 imager on the Keck telescope show that the source and lens are still blended, consistent with our light-curve model. With no statistically significant excess flux detection we constrain the mass, ${M}_{L}={0.24}_{-0.12}^{+0.28}\,{M}_{\odot }$ , and distance, DL = 7.0 ± 1.0 kpc, of the lensing system. This supports the interpretation of this event as a stellar binary in the Galactic bulge. This lens mass gives a companion mass of $M={0.07}_{-0.04}^{+0.08}\,{M}_{\odot }$ , close to the boundary between being a star and a brown dwarf.

Keywords: Gravitational microlensing, Proper motions, Exoplanets
Detecting Magnetic Fields in Exoplanets with Spectropolarimetry of the Helium Line at 1083 nm. The magnetic fields of the solar system's planets provide valuable insights into their interiors and can have dramatic consequences for the evolution of their atmospheres and interaction with the solar wind. However, we have little direct knowledge of magnetic fields in exoplanets. Here we present a method for detecting magnetic fields in the atmospheres of close-in exoplanets based on spectropolarimetric transit observations at the wavelength of the helium line at 1083 nm. This methodology has been successfully applied for exploring magnetic fields in solar coronal filaments. Strong absorption signatures (transit depths on the order of a few percent) in the 1083 nm line have recently been observed for several close-in exoplanets. We show that in the conditions in these escaping atmospheres, metastable helium atoms should be optically pumped by the starlight and, for field strengths more than a few × 10-4 G, should align with the magnetic field. This results in linearly polarized absorption at 1083 nm that traces the field direction (the Hanle effect), which we explore by both analytic computation and the Hazel numerical code. The linear polarization √{{Q}^{2}+{U}^{2}}/I ranges from ∼10-3 in optimistic cases down to a few × 10-5 for particularly unfavorable cases, with very weak dependence on field strength. The line-of-sight component of the field results in a slight circular polarization (the Zeeman effect), also reaching V/I∼ few × {10}^{-5}({B}_{\parallel }/10 G). We discuss the detectability of these signals with current (SPIRou) and future (Extremely Large Telescope) high-resolution infrared spectropolarimeters, and we briefly comment on possible sources of astrophysical contamination.

Keywords: Spectropolarimetry, Magnetic fields, Exoplanet atmospheres
The Effect of Cosmic Rays on Cometary Nuclei. I. Dose Deposition. Comets are small bodies thought to contain the most pristine material in the solar system. However, since their formation ≈4.5 Gy ago, they have been altered by different processes. While not exposed to much electromagnetic radiation, they experience intense particle radiation. Galactic cosmic rays and solar energetic particles have a broad spectrum of energies and interact with the cometary surface and subsurface; they are the main source of space weathering for a comet in the Kuiper Belt or in the Oort Cloud, and also affect the ice prior to the comet agglomeration. While low-energy particles interact only with the cometary surface, the most energetic ones deposit a significant amount of energy down to tens of meters. This interaction can modify the isotopic ratios in cometary ices and create secondary compounds through radiolysis, such as O2 and H2O2 (Paper II). In this paper, we model the energy deposition of energetic particles as a function of depth using a Geant4 application modified to account for the isotope creation process. We quantify the energy deposited in cometary nucleus by galactic cosmic rays and solar energetic particles. The consequences of the energy deposition on the isotopic and chemical composition of cometary ices and their implication on the interpretation of cometary observations, notably of 67P/Churyumov Gerasimenko by the ESA Rosetta spacecraft, will be discussed in Paper II.

Keywords: Solar energetic particles, Galactic cosmic rays, Comets, Pre-biotic astrochemistry, Cosmic rays