Sazuna/UAT_keywords huggingface dataset:
Cosmic-Ray Drag and Damping of Compressive Turbulence. While it is well known that cosmic rays (CRs) can gain energy from turbulence via second-order Fermi acceleration, how this energy transfer affects the turbulent cascade remains largely unexplored. Here, we show that damping and steepening of the compressive turbulent power spectrum are expected once the damping time ${t}_{\mathrm{damp}}\sim \rho {v}^{2}/{\dot{E}}_{\mathrm{CR}}\propto {E}_{\mathrm{CR}}^{-1}$ becomes comparable to the turbulent cascade time. Magnetohydrodynamic simulations of stirred compressive turbulence in a gas-CR fluid with diffusive CR transport show clear imprints of CR-induced damping, saturating at ${\dot{E}}_{\mathrm{CR}}\sim \tilde{\epsilon }$ , where $\tilde{\epsilon }$ is the turbulent energy input rate. In that case, almost all of the energy in large-scale motions is absorbed by CRs and does not cascade down to grid scale. Through a Hodge-Helmholtz decomposition, we confirm that purely compressive forcing can generate significant solenoidal motions, and we find preferential CR damping of the compressive component in simulations with diffusion and streaming, rendering small-scale turbulence largely solenoidal, with implications for thermal instability and proposed resonant scattering of E ≳ 300 GeV CRs by fast modes. When CR transport is streaming dominated, CRs also damp large-scale motions, with kinetic energy reduced by up to 1 order of magnitude in realistic E CR ~ E g scenarios, but turbulence (with a reduced amplitude) still cascades down to small scales with the same power spectrum. Such large-scale damping implies that turbulent velocities obtained from the observed velocity dispersion may significantly underestimate turbulent forcing rates, i.e., $\tilde{\epsilon }\gg \rho {v}^{3}/L$ .

Keywords: Magnetohydrodynamics, Plasma astrophysics, Interstellar medium, Circumgalactic medium, Cosmic rays
3D MHD Time-dependent Charge State Ionization and Recombination Modeling of the Bastille Day Coronal Mass Ejection. Heavy ion signatures of coronal mass ejections (CMEs) indicate that rapid and strong heating takes place during the eruption and early stages of propagation. However, the nature of the heating that produces the highly ionized charge states often observed in situ is not fully constrained. An MHD simulation of the Bastille Day CME serves as a test bed to examine the origin and conditions of the formation of heavy ions evolving within the CME in connection with those observed during its passage at L1. In particular, we investigate the bimodal nature of the Fe charge state distribution, which is a quintessential heavy ion signature of CME substructure, as well as the source of the highly ionized plasma. We find that the main heating experienced by the tracked plasma structures linked to the ion signatures examined is due to field-aligned thermal conduction via shocked plasma at the CME front. Moreover, the bimodal Fe distributions can be generated through significant heating and rapid cooling of prominence material. However, although significant heating was achieved, the highest ionization stages of Fe ions observed in situ were not reproduced. In addition, the carbon and oxygen charge state distributions were not well replicated owing to anomalous heavy ion dropouts observed throughout the ejecta. Overall, the results indicate that additional ionization is needed to match observation. An important driver of ionization could come from suprathermal electrons, such as those produced via Fermi acceleration during reconnection, suggesting that the process is critical to the development and extended heating of extreme CME eruptions, like the Bastille Day CME.

Keywords: Magnetohydrodynamics, Recombination, Chemical abundances, Solar coronal mass ejections, Ionization
Effects of Barnett Magnetic Dipole-Dipole Interaction on Grain Growth and Destruction. Rapidly spinning magnetic grains can acquire large magnetic dipole moments due to the Barnett effect. Here we study the new effect of Barnett magnetic dipole-dipole interaction on grain-grain collisions and grain growth, assuming that grains are spun up by radiative torques. For the ideal situation in which grains have parallel Barnett dipole moments aligned with the ambient magnetic field, we find that the collision rate between grains having embedded iron inclusions can be significantly enhanced due to Barnett magnetic dipole-dipole interaction when grains rotate suprathermally by radiative torques. We discuss the implications of enhanced collision rate for grain growth and destruction in the circumstellar envelope of evolved stars, photodissociation regions, and protostellar environments. Our results first reveal the potential importance of the dust magnetic properties, magnetic fields, and the local radiation field for grain growth and destruction. Detailed numerical simulations of grain dynamics that take into account the variation of Barnett dipoles and grain alignment are required to quantify the exact role of Barnett dipole-dipole interaction in grain evolution.

Keywords: Interstellar dust, Dust physics, Dust destruction, Galaxy environments, Dust formation, Astrophysical dust processes
Effects of Heat Conduction on Blocking off the Super-Eddington Growth of Black Holes at High Redshift. We investigate the effect of conductive heating of the gas surrounding a geometrically thick accretion disk on the growth of a black hole (BH) at high redshift. If a BH is accreting the surrounding gas at a super-Eddington rate, the X-ray radiation from the vicinity of the BH would be highly anisotropic due to the self-shielding of a geometrically thick accretion disk, and then the radiative feedback on the surrounding medium would be suppressed in the equatorial region, within which super-Eddington accretion can continue. However, if this region is sufficiently heated via thermal conduction from the adjacent region that is not shielded and heated by the X-ray irradiation, the surrounding gas becomes isotropically hot, and the Bondi accretion rate would be suppressed and become sub-Eddington. We evaluate the condition under which such isotropic heating is realized and derive new criteria required for super-Eddington accretion.

Keywords: Accretion, Supermassive black holes, Bondi accretion, Quasars
Magnetohydrodynamic Mode Conversion in the Solar Corona: Insights from Fresnel-like Models of Waves at Sharp Interfaces. The solar atmosphere is known to contain many different types of wave-like oscillation. Waves and other fluctuations (e.g., turbulent eddies) are believed to be responsible for at least some of the energy transport and dissipation that heats the corona and accelerates the solar wind. Thus, it is important to understand the behavior of magnetohydrodynamic (MHD) waves as they propagate and evolve in different regions of the Sun's atmosphere. In this paper, we investigate how MHD waves can affect the overall plasma state when they reflect and refract at sharp, planar interfaces in density. First, we correct an error in a foundational paper (Stein) that affects the calculation of wave energy-flux conservation. Second, we apply this model to reflection-driven MHD turbulence in the solar wind, where the presence of density fluctuations can enhance the generation of inward-propagating Alfvén waves. This model reproduces the time-averaged Elsässer imbalance fraction (i.e., the ratio of inward to outward Alfvénic power) from several published numerical simulations. Lastly, we model how the complex magnetic field threading the transition region (TR) between the chromosphere and corona helps convert a fraction of upward-propagating Alfvén waves into fast-mode and slow-mode MHD waves. These magnetosonic waves dissipate in a narrow region around the TR and produce a sharp peak in the heating rate. This newly found source of heating sometimes exceeds the expected heating rate from Alfvénic turbulence by an order of magnitude. It may explain why some earlier models seemed to require an additional ad hoc heat source at this location.

Keywords: Magnetohydrodynamics, Interplanetary turbulence, Solar coronal heating, Solar wind, Alfven waves, Solar corona
Gaia17bpp: A Giant Star with the Deepest and Longest Known Dimming Event. We report the serendipitous discovery of Gaia17bpp/2MASS J19372316+1759029, a binary star with a deep single large-amplitude dimming event of ~4.5 mag that lasted over 6.5 yr. Using the optical-to-IR spectral energy distribution (SED), we constrain the primary star to be a cool giant M0III star with effective temperature T eff = 3850 K and radius R = 58 R ☉. Based on the SED fitting, we obtained a bimodal posterior distribution of primary stellar masses with a stronger preference for a 1.5 M ☉ mass star. Within the last 66 yr of photometric coverage, no other significant dimming events of this depth and duration were identified in the optical light curves. Using a Gaussian process, we fit a generalized Gaussian distribution to the optical and IR light curves and conclude that the dimming event exhibits moderate asymmetries from optical to IR. At the minimum of the dimming event, the Wide-field Infrared Survey Explorer color (W1-W2) differed by ~0.2 mag relative to the primary star color outside the dimming event. The ingress and egress colors show a shallow reddening profile. We suggest that the main culprit of the dimming event is likely due to the presence of a large, optically thick disk transiting the primary giant star. By fitting a monochromatic transit model of an oblate disk transiting a star, we found good agreement with a slow-moving (0.005 km s-1) disk with a ~1.4 au radius. We propose that Gaia17bpp belongs to a rare binary star population similar to the ϵ Aurigae system, which consists of a secondary star enshrouded by an optically thick debris disk.

Keywords: Stellar occultation, Binary stars, Peculiar variable stars
Proton Synchrotron Origin of the Very-high-energy Emission of GRB 190114C. We consider here a proton-synchrotron model to explain the MAGIC observation of GRB 190114C afterglow in the energy band of 0.2-1 TeV, while the X-ray spectra are explained by electron-synchrotron emission. Given the uncertainty of the particle acceleration process, we consider several variations of the model, and show that they all match the data very well. We find that the values of the uncertain model parameters are reasonable: isotropic explosion energy ~1054.5 erg, ambient density ~10-100 cm-3, and the fraction of electrons/protons accelerated to a high-energy power law is of a few percent. All these values are directly derived from the observed teraelectronvolt and X-ray fluxes. The model also requires that protons be accelerated to observed energies as high as a few 1020 eV. Further, assuming that the jet break takes place after 106 s gives the beaming-corrected energy of the burst to be ≈1053 erg, which is one to two orders of magnitude higher than usually inferred, because of the small fraction of electrons accelerated. Our modeling is consistent with both late time data at all bands, from optical to X-rays, and with numerical models of particle acceleration. Our results thus demonstrate the relevance of proton-synchrotron emission to the high-energy observations of gamma-ray bursts during their afterglow phase.

Keywords: Gamma-ray bursts, Interstellar synchrotron emission
The Iron Yield of Core-collapse Supernovae. We present a systematic analysis of 191 stripped-envelope supernovae (SE SNe), aimed at computing their 56Ni masses from the luminosity in their radioactive tails ( ${M}_{\mathrm{Ni}}^{\mathrm{tail}}$ ) and/or in their maximum light, and the mean 56Ni and iron yields of SE SNe and core-collapse SNe. Our sample consists of SNe IIb, Ib, and Ic from the literature and from the Zwicky Transient Facility Bright Transient Survey. To calculate luminosities from optical photometry, we compute bolometric corrections using 49 SE SNe with optical and near-IR photometry, and develop corrections to account for the unobserved UV and IR flux. We find that the equation of Khatami &amp; Kasen for radioactive 56Ni-powered transients with a single free parameter does not fit the observed peak time-luminosity relation of SE SNe. Instead, we find a correlation between ${M}_{\mathrm{Ni}}^{\mathrm{tail}}$ , peak time, peak luminosity, and decline rate, which allows for measuring individual 56Ni masses to a precision of 14%. Applying this method to the whole sample, we find, for SNe IIb, Ib, and Ic, mean 56Ni masses of 0.066 ± 0.006, 0.082 ± 0.009, and 0.132 ± 0.011 M ☉, respectively. After accounting for their relative rates, for SE SNe as a whole, we compute mean 56Ni and iron yields of 0.090 ± 0.005 and 0.097 ± 0.007 M ☉, respectively. Combining these results with the recent Type II SN mean 56Ni mass derived by Rodríguez et al., core-collapse SNe, as a whole, have mean 56Ni and iron yields of 0.055 ± 0.006 and 0.058 ± 0.007 M ☉, respectively. We also find that radioactive 56Ni-powered models typically underestimate the peak luminosity of SE SNe by 60%-70%, suggesting the presence of an additional power source contributing to the luminosity at peak.

Keywords: Type Ic supernovae, Core-collapse supernovae, Type II supernovae, Type Ib supernovae, Supernovae
Nozzle Shocks, Disk Tearing, and Streamers Drive Rapid Accretion in 3D GRMHD Simulations of Warped Thin Disks. The angular momentum of gas feeding a black hole (BH) may be misaligned with respect to the BH spin, resulting in a tilted accretion disk. Rotation of the BH drags the surrounding spacetime, manifesting as Lense-Thirring torques that lead to disk precession and warping. We study these processes by simulating a thin (H/r = 0.02), highly tilted ( ${ \mathcal T }=65^\circ $ ) accretion disk around a rapidly rotating (a = 0.9375) BH at extremely high resolutions, which we performed using the general-relativistic magnetohydrodynamic code H-AMR. The disk becomes significantly warped and continuously tears into two individually precessing subdisks. We find that mass accretion rates far exceed the standard α-viscosity expectations. We identify two novel dissipation mechanisms specific to warped disks that are the main drivers of accretion, distinct from the local turbulent stresses that are usually thought to drive accretion. In particular, we identify extreme scale height oscillations that occur twice an orbit throughout our disk. When the scale height compresses, "nozzle" shocks form, dissipating orbital energy and driving accretion. Separate from this phenomenon, there is also extreme dissipation at the location of the tear. This leads to the formation of low-angular momentum "streamers" that rain down onto the inner subdisk, shocking it. The addition of low-angular momentum gas to the inner subdisk causes it to rapidly accrete, even when it is transiently aligned with the BH spin and thus unwarped. These mechanisms, if general, significantly modify the standard accretion paradigm. Additionally, they may drive structural changes on much shorter timescales than expected in α-disks, potentially explaining some of the extreme variability observed in active galactic nuclei.

Keywords: Accretion, Magnetohydrodynamics, Black holes, General relativity, Astronomical simulations
Modeling of Transverse Oscillations Driven by p-modes in Short Coronal Loops. Recent observations have revealed two types of decayless transverse oscillations in short coronal loops: one with short periods scaling with loop lengths, and the other with longer periods that exhibit a peak at around 5 minutes in the period distribution. To understand such a difference in period, we work in the framework of ideal MHD and model a short coronal loop embedded in an atmosphere with density stratification from the chromosphere to the corona. An inclined p-mode-like driver with a period of 5 minutes is launched at one loop footpoint. It is discovered that two types of decayless transverse oscillations can be excited in the loop. We interpret the 5 minutes periodicity as being directly driven by the footpoint driver, while the others, with periods of several tens of seconds, are regarded as kink eigenmodes of different harmonics. Therefore, our simulation shows that both types of decayless oscillations found in observations can be excited by p-modes in one short coronal loop. This study extends our understanding of ubiquitous decayless transverse oscillations in the corona. Furthermore, it suggests that p-modes could be an important energy source for coronal heating by driving decayless transverse oscillations.

Keywords: Solar atmosphere, Magnetohydrodynamics, Solar coronal loops, Solar coronal waves, Solar oscillations, Magnetohydrodynamical simulations
ESCARGOT: Mapping Vertical Phase Spiral Characteristics Throughout the Real and Simulated Milky Way. The recent discovery of a spiral pattern in the vertical kinematic structure in the solar neighborhood provides a prime opportunity to study nonequilibrium dynamics in the Milky Way from local stellar kinematics. Furthermore, results from simulations indicate that even in a limited volume, differences in stellar orbital histories allow us to trace variations in the initial perturbation across large regions of the disk. We present ESCARGOT, a novel algorithm for studying these variations in both simulated and observed data sets. ESCARGOT automatically extracts key quantities from the structure of a given phase spiral, including the time since perturbation and the perturbation mode. We test ESCARGOT on simulated data and show that it is capable of accurately recovering information about the time since the perturbation occurred as well as subtle differences in phase spiral morphology due to stellar locations in the disk at the time of perturbation. We apply ESCARGOT to kinematic data from data release 3 of the Gaia mission in bins of guiding radius. We show that similar structural differences in morphology occur in the Gaia phase spirals as a function of stellar orbital history. These results indicate that the phase spirals are the product of a complex dynamical response in the disk with large-scale coupling between different regions of phase space.

Keywords: Solar neighborhood, Galaxy disks, Milky Way disk, Galaxy kinematics, Galaxy evolution
Stars, Gas, and Star Formation of Distant Post-starburst Galaxies. We present a comprehensive multiwavelength study of five post-starburst galaxies with M * &gt; 1011 M ☉ at z ~ 0.7, examining their stars, gas, and current and past star formation activities. Using optical images from the Subaru Telescope and Hubble Space Telescope, we observe a high incidence of companion galaxies and low surface brightness tidal features, indicating that quenching is closely related to interactions between galaxies. From optical spectra provided by the LEGA-C survey, we model the stellar continuum to derive the star formation histories and show the stellar masses of progenitors ranging from 2 × 109 M ☉ to 1011 M ☉, undergoing a burst of star formation several hundred million years prior to observation, with a decay timescale of ~100 Myr. Our Atacama Large Millimeter/submillimeter Array observations detect CO(2-1) emission in four galaxies, with the molecular gas spreading over up to &gt;1″, or ~10 kpc, with a mass of up to ~2 × 1010 M ☉. However, star-forming regions are unresolved by either the slit spectra or 3 GHz continuum observed by the Very Large Array. Comparisons between the star formation rates (SFRs) and gas masses, and the sizes of CO emission and star-forming regions suggest a low star-forming efficiency. We show that the SFRs derived from IR and radio luminosities with commonly used calibrations tend to overestimate the true values because of the prodigious amount of radiation from old stars and the contribution from active galactic nuclei (AGNs), as the optical spectra reveal weak AGN-driven outflows.

Keywords: Galaxy stellar content, Galaxy kinematics, Galaxy evolution, Interstellar medium, Active galactic nuclei, Star formation, Galaxy quenching, Post-starburst galaxies
Triplet Pairing in Neutron Matter. The presence of superfluidity in neutron star interiors can affect the cooling of neutron stars in intricate ways, enhancing certain mechanisms and suppressing others. Model calculations employing realistic nuclear potentials in Bardeen-Cooper-Schrieffer theory generally suggest the development of a 3P2-3F2 pairing gap, and therefore the presence of superfluidity in dense neutron star matter. Improved models that go beyond conventional mean-field calculations by including polarization effects suggest a suppression of the triplet gap. We have evaluated the pairing interaction by summing the "parquet" Feynman diagrams, which include both ladder and ring diagrams systematically, plus a set of important nonparquet diagrams, making this the most comprehensive diagram-based approach presently available. Our results suggest a radical suppression of the 3P2-3F2 triplet pairing gap and an enhancement of 3P0 pairing.

Keywords: Nuclear physics
Estimating Ejecta Mass Ratios in Kepler's Supernova Remnant: Global X-Ray Spectral Analysis Including Suzaku Systematics and Emitting Volume Uncertainties. The exact origins of many Type Ia supernovae-progenitor scenarios and explosive mechanisms-remain uncertain. In this work, we analyze the global Suzaku X-ray spectrum of Kepler's supernova remnant (SNR) in order to constrain the mass ratios of various ejecta species synthesized during explosion. Critically, we account for the Suzaku telescope effective-area calibration uncertainties of 5%-20% by generating 100 mock effective-area curves and using Markov Chain Monte Carlo-based spectral fitting to produce 100 sets of best-fit parameter values. Additionally, we characterize the uncertainties from assumptions made about the emitting volumes of each model plasma component and find that these uncertainties can be the dominant source of error. We then compare our calculated mass ratios to previous observational studies of Kepler's SNR and to the predictions of Type Ia simulations. Our mass ratio estimates require a 90% attenuated 12C+16O reaction rate and are potentially consistent with both near- and sub-M Ch progenitors, but are inconsistent with the dynamically stable double-detonation origin scenario and only marginally consistent with the dynamically unstable dynamically driven double-degenerate double-detonation (D6) scenario.

Keywords: X-ray astronomy, Ejecta, High energy astrophysics, Astronomy data analysis, X-ray telescopes, Supernova remnants, Calibration, Spectroscopy, Markov chain Monte Carlo
Modeling the Spectral Energy Distribution of the Active Galactic Nucleus inside NGC 4395. We study the broadband spectral energy distribution (SED) of the prototypical low-mass active galactic nucleus (AGN) in NGC 4395. We jointly model the optical through mid-IR SED with a combination of galaxy and AGN light, and find that on arcsecond scales the AGN dominates at most wavelengths. However, there is still some ambiguity about emission from the galaxy, owing partially to the strong short-term variability of the black hole. We investigate the use of smooth- and clumpy-torus models in order to disentangle the nuclear IR emission, as well as exploring the use of poloidal wind emission to account for the blue spectral slope observed in the near-IR. Even when simultaneously fitting the full optical-IR spectral range, we find that degeneracies still remain in the best-fit models. We conclude that high-spatial-resolution and wider-wavelength coverage with the JWST is needed to understand the mid-IR emission in this complex, highly variable object, which is the best nearby example to provide a blueprint to finding other low-mass AGNs via their mid-IR emission in the future.

Keywords: Intermediate-mass black holes, Active galactic nuclei, Spectral energy distribution