Sazuna/UAT_keywords huggingface dataset:
Physical Model of Dust Polarization by Radiative Torque Alignment and Disruption and Implications for Grain Internal Structures. Dust polarization depends on mechanical properties of dust as well as on local environments. To understand how dust polarization varies with different properties, we model the wavelength-dependence polarization of starlight and polarized dust emission of aligned grains by simultaneously taking into account grain alignment and rotational disruption by radiative torques (RATs). We explore a wide range of the local radiation field and grain mechanical properties characterized by tensile strength (Smax). We find that the peak wavelength shifts to shorter wavelengths as the radiation strength (U) increases due to the enhanced alignment of small grains. Grain rotational disruption by RATs tends to decrease the optical-NIR polarization but increase the UV polarization of starlight due to the conversion of large grains into smaller ones. In particular, we find that the polarization degree at 850 μm (P850) does not increase monotonically with U or grain temperature (Td), but it depends on Smax of the grains. Our model can be tested with observations toward star-forming regions or molecular clouds irradiated by a nearby star, which have higher radiation intensities than the that of the average interstellar radiation field. Finally, we compare our predictions of the P850-Td relationship with Planck data and find that the observed decrease of P850 with Td can be explained when grain disruption by RATs is accounted for, suggesting that as interstellar grains are unlikely to have a compact structure, perhaps they have a composite one. The variation of the polarization degree with U (or Td) can provide a valuable constraint on the internal structure of cosmic dust.

Keywords: Starlight polarization, Interstellar dust extinction, Interstellar medium, Interstellar radiation field
Three-dimensional Distribution Map of H I Gas and Galaxies around an Enormous Lyα Nebula and Three QSOs at z = 2.3 Revealed by the H I Tomographic Mapping Technique. We present an IGM H I tomographic map in a survey volume of $16\times 19\times 131\ {h}^{-3}\ \mathrm{comoving}\ {\mathrm{Mpc}}^{3}$ (cMpc3) centered at MAMMOTH-1 nebula and three neighboring quasars at z = 2.3. The MAMMOTH-1 nebula is an enormous Lyα nebula (ELAN), hosted by a type-II quasar dubbed MAMMOTH1-QSO, that extends over $1\ {h}^{-1}$ cMpc with no clear physical origin. Here we investigate the H I-gas distribution around MAMMOTH1-QSO with the ELAN and three neighboring type-I quasars, making the IGM H I tomographic map with a spatial resolution of 2.6 h-1 cMpc. Our H I tomographic map is reconstructed with H I Lyα forest absorption of bright background objects at z = 2.4-2.9: one eBOSS quasar and 16 Keck/LRIS galaxy spectra. We estimate the radial profile of H I overdensity for MAMMOTH1-QSO, and find that MAMMOTH1-QSO resides in a volume with fairly weak H I absorption. This suggests that MAMMOTH1-QSO may have a proximity zone where quasar illuminates and photoionizes the surrounding H I gas and suppresses H I absorption, and that the ELAN is probably a photoionized cloud embedded in the cosmic web. The H I radial profile of MAMMOTH1-QSO is very similar to those of three neighboring type-I quasars at z = 2.3, which is compatible with the AGN unification model. We compare the distributions of the H I absorption and star-forming galaxies in our survey volume, and identify a spatial offset between density peaks of star-forming galaxies and H I gas. This segregation may suggest anisotropic UV background radiation created by star-forming galaxy density fluctuations.

Keywords: Large-scale structure of the universe, Galaxy formation, Intergalactic medium
On Arrival Time Difference Between Lensed Gravitational Waves and Light. It is known that geometrical optics no longer applies to gravitational lensing if the wavelength of a propagating wave becomes comparable to or larger than the Schwarzschild radius of a lensing object. We investigate the propagation of gravitational waves in wave optics, particularly focusing on the difference between their arrival time and the arrival time of light. We argue that, contrary to the observation in the previous work, gravitational waves never arrive at an observer earlier than light when both gravitational waves and light are emitted from a same source simultaneously.

Keywords: Gravitational lensing
Magnetic Energy Transfer and Distribution between Protons and Electrons for Alfvénic Waves at Kinetic Scales in Wavenumber Space. Turbulent dissipation is considered a main source of heating and acceleration in cosmic plasmas. The alternating current Joule-like term, $\langle \delta {\boldsymbol{j}}\cdot \delta {\boldsymbol{E}}\rangle $ , is used to measure the energy transfer between electromagnetic fields and particles. Because the electric field depends on the reference frame, in which frame to calculate $\langle \delta {\boldsymbol{j}}\cdot \delta {\boldsymbol{E}}\rangle $ is an important issue. We compute the scale-dependent energy transfer rate spectrum in wavevector space, and investigate the electric-field fluctuations in two reference frames: $\delta {\boldsymbol{E}}$ in the mean bulk flow frame and $\delta {\boldsymbol{E}}^{\prime} $ in the local bulk flow frame (non-inertial reference frame). Considering Alfvénic waves, we find that $\langle \delta {\boldsymbol{j}}\cdot \delta {{\boldsymbol{E}}}^{{\prime} }\rangle $ , which neglects the contribution of work done by the ion inertial force, is not consistent with the magnetic field energy damping rate (2γδB2) according to linear Maxwell-Vlasov theory, while $\langle \delta {\boldsymbol{j}}\cdot \delta {\boldsymbol{E}}\rangle $ is exactly the same as 2γδB2 in wavenumber space (k∥, k⊥), where γ is the linear damping rate. Under typical conditions of solar wind at 1 au, we find in our theoretical calculation that the field energy is mainly converted into proton kinetic energy leaving the residual minor portion for electrons. Although the electrons gain energy in the direction perpendicular to the mean magnetic field, they return a significant fraction of their kinetic energy in the parallel direction. Magnetic-field fluctuations can transfer particle energy between the parallel and perpendicular degrees of freedom. Therefore, $\langle \delta {{\boldsymbol{j}}}_{\parallel }\cdot \delta {{\boldsymbol{E}}}_{\parallel }\rangle $ and $\langle \delta {{\boldsymbol{j}}}_{\perp }\cdot \delta {{\boldsymbol{E}}}_{\perp }\rangle $ do not solely describe the energy transfer in the parallel direction and perpendicular direction, respectively.

Keywords: Interplanetary turbulence, Solar wind, Alfven waves
Coupled Thermal and Compositional Evolution of Photoevaporating Planet Envelopes. Photoevaporative mass loss sculpts the atmospheric evolution of tightly orbiting sub-Neptune-mass exoplanets. To date, models of the mass loss from warm Neptunes have assumed that the atmospheric abundances remain constant throughout the planet's evolution. However, the cumulative effects of billions of years of escape modulated by diffusive separation and preferential loss of hydrogen can lead to planetary envelopes that are enhanced in helium and metals relative to hydrogen. We have performed the first self-consistent calculations of the coupled thermal, mass-loss, and compositional evolution of hydrogen-helium envelopes surrounding sub-Neptune-mass planets. We extended the Modules for Experiments in Stellar Astrophysics stellar evolution code to model the evolving envelope abundances of photoevaporating planets. We demonstrate that H-He fractionation can lead to planetary envelopes that are significantly enriched in helium and metals compared to their initial primordial compositions. A subset of our model planets—having Rp ≲ 3.00 R⊕, initial fenv &lt; 0.5%, and irradiation flux ∼101-103 times that of Earth—obtain final helium mass fractions in excess of Y = 0.40 after several billion years of mass loss. GJ 436b, the planet that originally inspired Hu et al. to propose the formation of helium-enhanced planetary atmospheres, requires a primordial envelope that is too massive to become helium enhanced. Planets with envelope helium fractions of Y = 0.40 have radii that are between 0.5% and 10% smaller (depending on their mass, irradiation flux, and envelope mass fraction) than similar planets with solar composition (Y = 0.24) envelopes. The results of preferential loss of hydrogen may have observable consequences for the Mp - Rp relations and atmospheric spectra of sub-Neptune populations.

Keywords: Exoplanet atmospheric composition , Exoplanet atmospheric variability, Planetary atmospheres, Exoplanet astronomy, Exoplanet evolution, Atmospheric effects, Exoplanet atmospheres
Three Lyα Emitting Galaxies within a Quasar Proximity Zone at z ∼ 5.8. Quasar proximity zones at $z\gt 5.5$ correspond to overdense and overionized environments. Galaxies found inside proximity zones can therefore display features that would otherwise be masked by absorption in the intergalactic medium. We demonstrate the utility of this quasar-galaxy synergy by reporting the discovery of the first three "proximate Lyα emitters" (LAEs) within the proximity zone of quasar J0836+0054 at z = 5.795 (Aerith A, B, and C). Aerith A, located behind the quasar with an impact parameter ${D}_{\perp }=278\pm 8$ pkpc, provides the first detection of an Lyα transverse proximity effect. We model the transmission and show that it constrains the onset of J0836's quasar phase to $0.2\mathrm{Myr}\lt t\lt 28\mathrm{Myr}$ in the past. The second object, Aerith B at a distance $D\lt 912$ pkpc from the quasar, displays a bright and broad double-peaked Lyα emission line. The peak separation implies a low ionizing ${f}_{\mathrm{esc}}\lesssim 1 \% $ . We fit the Lyα line with an outflowing shell model, finding a typical central density $\mathrm{log}\ {N}_{{\rm{H}}{\rm{I}}}/{\mathrm{cm}}^{-2}={19.3}_{-0.2}^{+0.8}$ , outflow velocity ${V}_{\mathrm{out}}={16}_{-11}^{+4}$ km s-1, and gas temperature $\mathrm{log}T/K={3.8}_{-0.7}^{+0.8}$ compared to $2\lt z\lt 3$ analog LAEs. We detect object Aerith C via an Lyα emission line at z = 5.726. This corresponds with the edge of the quasar's proximity zone ( ${\rm{\Delta }}z\lt 0.02$ ), suggesting that the proximity zone is truncated by a density fluctuation. Via the analyses conducted here, we illustrate how proximate LAEs offer unique insight into the ionizing properties of both quasars and galaxies during hydrogen reionization.

Keywords: Early universe, Galaxy formation, Quasar-galaxy pairs, Quasars, Lyman alpha forest, Spectroscopy, Reionization, Lyman-break galaxies, Galaxies
Is Betelgeuse the Outcome of a Past Merger?. We explore the possibility that the star α Orionis (Betelgeuse) is the outcome of a merger that occurred in a low-mass-ratio ( $q={{ \mathcal M }}_{2}/{{ \mathcal M }}_{1}\,=$ 0.07-0.25) binary system some time in the past hundreds of thousands of years. To that goal, we present a simple analytical model to approximate the perturbed internal structure of a post-merger object following the coalescence of a secondary in the mass range 1-4 M⊙ into the envelope of a 15-17 M⊙ primary. We then compute the long-term evolution of post-merger objects for a grid of initial conditions and make predictions about their surface properties for evolutionary stages that are consistent with the observed location of Betelgeuse in the Hertzsprung-Russell diagram. We find that if a merger occurred after the end of the primary's main-sequence phase, while it was expanding toward becoming a red supergiant star and typically with radius ∼200-300 R⊙, then its envelope is spun up to values that remain in a range consistent with Betelgeuse observations for thousands of years of evolution. We argue that the best scenario that can explain both the fast rotation of Betelgeuse and its observed large space velocity is one where a binary was dynamically ejected by its parent cluster a few million years ago and then subsequently merged. An alternative scenario in which the progenitor of Betelgeuse was spun up by accretion in a binary and released by the supernova explosion of the companion requires a finely tuned set of conditions but cannot be ruled out.

Keywords: Binary stars, Stellar mergers, Close binary stars, Stellar evolutionary models, Supergiant stars, Stellar rotation
Observation and Modeling of High-temperature Solar Active Region Emission during the High-resolution Coronal Imager Flight of 2018 May 29. Excellent coordinated observations of NOAA active region 12712 were obtained during the flight of the High-resolution Coronal Imager (Hi-C) sounding rocket on 2018 May 29. This region displayed a typical active region core structure with relatively short, high-temperature loops crossing the polarity inversion line and bright "moss" located at the footpoints of these loops. The differential emission measure (DEM) in the active region core is very sharply peaked at about 4 MK. Further, there is little evidence for impulsive heating events in the moss, even at the high spatial resolution and cadence of Hi-C. This suggests that active region core heating is occurring at a high frequency and keeping the loops close to equilibrium. To create a time-dependent simulation of the active region core, we combine nonlinear force-free extrapolations of the measured magnetic field with a heating rate that is dependent on the field strength and loop length and has a Poisson waiting time distribution. We use the approximate solutions to the hydrodynamic loop equations to simulate the full ensemble of active region core loops for a range of heating parameters. In all cases, we find that high-frequency heating provides the best match to the observed DEM. For selected field lines, we solve the full hydrodynamic loop equations, including radiative transfer in the chromosphere, to simulate transition region and chromospheric emission. We find that for heating scenarios consistent with the DEM, classical signatures of energy release, such as transition region brightenings and chromospheric evaporation, are weak, suggesting that they would be difficult to detect.

Keywords: Solar corona
A New Estimate for the Orientation of Underlying Heliospheric Magnetic Field Associated with Alfvénic Fluctuations. In the solar wind Alfvénic fluctuations are coupled fluctuations in the transverse components of plasma velocity, ${\boldsymbol{V}}$, and magnetic field, ${\boldsymbol{B}}$, in which $\left|{\boldsymbol{B}}\right|$ remains nearly constant. Consequently, the fluctuations in the component of ${\boldsymbol{V}}$ and ${\boldsymbol{B}}$ along the direction of the underlying magnetic field, ${{\boldsymbol{B}}}_{0}$, are always one-sided relative to base values rather than mean values. This paper proposes a new method for estimating ${{\boldsymbol{B}}}_{0}$ and verifies it using simulation data. The new approach is to find a consistent minimum variance direction of magnetic field for two different data subsets divided by a threshold angle from the original data set. Simulation results show that (1) the direction of ${{\boldsymbol{B}}}_{0}$ predicted by the new method is generally more accurate than the average magnetic field, ${{\boldsymbol{b}}}_{\mathrm{av}}$, and that (2) ${{\boldsymbol{b}}}_{\mathrm{av}}$ does not correspond to ${{\boldsymbol{B}}}_{0}$ when the averages of the transverse field fluctuations are nonzero. Two events of one-sided Alfvénic fluctuations in the solar wind observed at 0.36 and 1 au, where a small but significant mean appears in the transverse field fluctuation, are demonstrated for the new method. Results show that the new estimate is more radial than ${{\boldsymbol{b}}}_{\mathrm{av}}$ and also different from that predicted by Parker's model of the heliospheric magnetic field (HMF). This new technique will be useful for comparing solar wind observations with the global HMF model and for determining the fluctuation k-vector, which is presumably directed along ${{\boldsymbol{B}}}_{0}$ .

Keywords: Alfven waves, Solar wind, Interplanetary magnetic fields
Influence of Coronal Holes on CME Deflections: Numerical Study. The understanding of the causes that produce the deflection of coronal mass ejections (CMEs) is essential for the space weather forecast. We study the effects on CME trajectories produced by the different properties of a coronal hole (CH), close to the ejection area. We perform ideal magnetohydrodynamics simulations emulating the early rising of the CME in the presence of a CH. We find that, the stronger the magnetic field and the wider the CH area, the larger the CME deflection. The deflection reduces as the CH moves away from the ejection region. To quantify the deflection we propose a dimensionless parameter that depends on the CH properties. We show that a minimum magnetic energy region, responsible for the deflection, is associated with the presence of the CH near the CME. We establish a relationship between the CH properties, the location of the minimum magnetic region, and the CME deflection.

Keywords: Magnetohydrodynamics, Space weather, Solar physics, Solar coronal mass ejections, Solar magnetic fields, Solar coronal holes, Magnetohydrodynamical simulations
A Machine Learning-based Source Property Inference for Compact Binary Mergers. The detection of the binary neutron star merger, GW170817, was the first success story of multi-messenger observations of compact binary mergers. The inferred merger rate, along with the increased sensitivity of the ground-based gravitational-wave (GW) network in the present LIGO/Virgo, and future LIGO/Virgo/KAGRA observing runs, strongly hints at detections of binaries that could potentially have an electromagnetic (EM) counterpart. A rapid assessment of properties that could lead to a counterpart is essential to aid time-sensitive follow-up operations, especially robotic telescopes. At minimum, the possibility of counterparts requires a neutron star (NS). Also, the tidal disruption physics is important to determine the remnant matter post-merger, the dynamics of which could result in the counterparts. The main challenge, however, is that the binary system parameters, such as masses and spins estimated from the real-time, GW template-based searches, are often dominated by statistical and systematic errors. Here, we present an approach that uses supervised machine learning to mitigate such selection effects to report the possibility of counterparts based on the presence of an NS component, and the presence of remnant matter post-merger in real time.

Keywords: Neutron stars, Black holes, Compact objects
Discovery of Delayed Spin-up Behavior Following Two Large Glitches in the Crab Pulsar, and the Statistics of Such Processes. Glitches correspond to sudden jumps of rotation frequency (ν) and its derivative ( $\dot{\nu }$ ) of pulsars, the origin of which remains not well understood yet, partly because the jump processes of most glitches are not well time-resolved. There are three large glitches of the Crab pulsar, detected in 1989, 1996, and 2017, which were found to have delayed spin-up processes before the normal recovery processes. Here we report two additional glitches of this pulsar that occurred in 2004 and 2011 for which we discovered delayed spin-up processes, and present refined parameters of the largest glitch, which occurred in 2017. The initial rising time of the glitch is determined as &lt;0.48 hr. The two glitches that occurred in 2004 and 2011 had delayed spin-up time scales (τ1) of 1.7 ± 0.8 days and 1.6 ± 0.4 days, respectively. We also carried out a statistical study of these five glitches with observed spin-up processes. We find that the Δν versus $| {\rm{\Delta }}\dot{\nu }| $ relation of these five glitches is similar to those with no detected delayed spin-up process, indicating that they are similar to the others in nature except that they have larger amplitudes. For these five glitches, the amplitudes of the delayed spin-up process ( $| {\rm{\Delta }}{\nu }_{{\rm{d}}1}| $ ) and recovery process (Δνd2), their time scales (τ1, τ2), and permanent changes in spin frequency (Δνp) and total frequency step (Δνg) have positive correlations. From these correlations, we suggest that the delayed spin-up processes are common for all glitches, but are too short and thus difficult to be detected for most glitches.

Keywords: Neutron stars, Nuclear astrophysics, Neutron star cores, Rotation powered pulsars
The Birth Function for Black Holes and Neutron Stars in Close Binaries. The mass function for black holes and neutron stars at birth is explored for mass-losing helium stars. These should resemble, more closely than similar studies of single hydrogen-rich stars, the results of evolution in close binary systems. The effects of varying the mass-loss rate and metallicity are calculated using a simple semi-analytic approach to stellar evolution that is tuned to reproduce detailed numerical calculations. Though the total fraction of black holes made in stellar collapse events varies considerably with metallicity, mass-loss rate, and mass cutoff, from 5% to 30%, the shapes of their birth functions are very similar for all reasonable variations in these quantities. Median neutron star masses are in the range 1.32-1.37 ${M}_{\odot }$ regardless of metallicity. The median black hole mass for solar metallicity is typically 8-9 ${M}_{\odot }$ if only initial helium cores below 40 ${M}_{\odot }$ (ZAMS mass less than 80 ${M}_{\odot }$ ) are counted, and 9-13 ${M}_{\odot }$, in most cases, if helium cores with initial masses up to 150 ${M}_{\odot }$ (ZAMS mass less than 300 ${M}_{\odot }$ ) contribute. As long as the mass-loss rate as a function of mass exhibits no strong nonlinearities, the black hole birth function from 15 to 35 ${M}_{\odot }$ has a slope that depends mostly on the initial mass function for main-sequence stars. These findings imply the possibility of constraining the initial mass function and the properties of mass loss in close binaries using ongoing measurements of gravitational-wave radiation. The expected rotation rates of the black holes are briefly discussed.

Keywords: Neutron stars, Core-collapse supernovae, Close binary stars, Massive stars, Stellar evolutionary models, Stellar mass black holes, Stellar mass loss
Improving Coronal Magnetic Field Models Using Image Optimization. We have reported previously on our development and testing of a new method for using coronal images to improve coronal magnetic field models. In this technique, which we call image-optimization, coronal magnetic field models are extrapolated from synoptic photospheric magnetograms. The resulting models are then compared to morphological constraints derived from images of the solar corona, and the photospheric magnetograms are perturbed iteratively via an optimization algorithm to achieve optimal agreement with the image-based constraints. Here we present results from the first application of this technique using Mauna Loa Solar Observatory K-Coronagraph images and Global Oscillation Network Group synoptic magnetograms to create optimized models for two time periods, 2014 November 16-29 and 2016 May 16-29. We find that for both time periods the optimization algorithm converges well and results in better agreement between the model and the images, relatively small changes to the synoptic magnetogram, and an overall increase in the amount of open magnetic flux.

Keywords: Solar magnetic fields, Solar corona