Sazuna/UAT_keywords huggingface dataset:
The Impact of Inclination-dependent Attenuation on Ultraviolet Star Formation Rate Tracers. We examine and quantify how hybrid (e.g., UV+IR) star formation rate (SFR) estimators and the A FUV-β relation depend on inclination for disk-dominated galaxies using spectral energy distribution modeling that utilizes the inclination-dependent attenuation curves described in Doore et al. We perform this analysis on a sample of 133 disk-dominated galaxies from the CANDELS fields and 18 disk galaxies from the Spitzer Infrared Nearby Galaxies Survey and Key Insights on Nearby Galaxies: A Far-Infrared Survey with Herschel samples. We find that both the hybrid SFR estimators and the A FUV-β relation present clear dependencies on inclination. To quantify this dependence in the hybrid SFR estimators, we derive an inclination and a far-UV-near-IR color-dependent parametric relation for converting observed UV and IR luminosities into SFRs. For the A FUV-β relation, we introduce an inclination-dependent component that accounts for the majority of the inclination dependence with the scatter of the relation increasing with inclination. We then compare both of these inclination-dependent relations to similar inclination-independent relations found in the literature. From this comparison, we find that the UV+IR correction factor and A FUV for our hybrid and A FUV-β relations, respectively, result in a reduction in the residual scatter of our sample by approximately a factor of 2. Therefore, we demonstrate that inclination must be considered in hybrid SFR estimators and the A FUV-β relation to produce more accurate SFR estimates in disk-dominated galaxies.

Keywords: Galaxy properties, Disk galaxies, Star formation, Spectral energy distribution, Extragalactic astronomy
Tracking Movement of Long-lived Equatorial Coronal Holes from Analysis of Long-term McIntosh Archive Data. Features at the Sun's surface and atmosphere are constantly changing due to its magnetic field. The McIntosh Archive provides a long-term (45 yr) record of these features, digitized from hand-drawn synoptic maps by Patrick McIntosh. Utilizing this data, we create stack plots for coronal holes, i.e., Hovmöller-type plots of latitude bands, for all longitudes, stacked in time, allowing tracking of coronal hole movement. Using a newly developed two-step method of centroid calculation, which includes a Fourier descriptor to represent a coronal hole's boundary and calculate the centroid by the use of Green's theorem, we calculate the centroids of 31 unique, long-lived equatorial coronal holes for successive Carrington rotations during the entire solar cycle 23, and estimate their slopes (time versus longitude) as the coronal holes evolve. We compute coronal hole centroid drift speeds from these slopes, and find an eastward (prograde) pattern that is actually retrograde with respect to the local differential rotation. By discussing the plausible physical mechanisms which could cause these long-lived equatorial coronal holes to drift retrograde, we identify either classical or magnetically modified westward-propagating solar Rossby waves, with a speed of a few tens to a few hundreds of meters per second, to be the best candidate for governing the drift of deep-rooted, long-lived equatorial coronal holes. To explore plausible physics of why long-lived equatorial coronal holes appear few in number during solar minimum/early rising phase more statistics are required, which will be studied in future.

Keywords: Solar cycle, Solar coronal holes, Solar motion
The Radial Evolution of Magnetic Clouds From Helios to Ulysses. The evolution of a magnetic cloud (MC) from the inner heliosphere to the outer heliosphere has been investigated for decades. Although many studies have reported on the evolution of MCs, there is no relevant statistical study about the continuous parametric evolution of the flux rope model of the Gold-Hoyle solution for MCs from near the Sun to 5.4 au. Based on the velocity-modified uniform-twist force-free flux rope model, in this study we explore the evolution with heliodistance for some parameters from 139 MCs observed by the Helios, Wind, and Ulysses spacecraft. We find a negative/positive correlation between the central axial field strength/the radius of the cross section and the heliodistance. The angle between the axis of the MC and the Sun-spacecraft line (Θ), the expansion velocity (v  e ), and the poloidal velocity (v  p ) did not show any evident tendency to increase or decrease with the heliodistance. In addition, the number of turns of the magnetic field lines per unit length winding around the magnetic flux rope, τ, shows a weak decrease with heliodistance. Also, there is an evident negative correlation between τ and the radius of the flux rope, R. The axial magnetic flux (F  z ) and the magnetic helicity (H  m ) show a tendency to decrease within 1 au, after which they remain almost unchanged until 5.5 au. Furthermore, we do not find any evident difference in the parametric properties of MCs on and outside the ecliptic.

Keywords: Solar coronal mass ejections, Heliosphere
Quasi-periodic Oscillations of the X-Ray Burst from the Magnetar SGR J1935-2154 and Associated with the Fast Radio Burst FRB 200428. The origin(s) and mechanism(s) of fast radio bursts (FRBs), which are short radio pulses from cosmological distances, have remained a major puzzle since their discovery. We report a strong quasi-periodic oscillation (QPO) of ~40 Hz in the X-ray burst from the magnetar SGR J1935+2154 and associated with FRB 200428, significantly detected with the Hard X-ray Modulation Telescope (Insight-HXMT) and also hinted at by the Konus-Wind data. QPOs from magnetar bursts have only been rarely detected; our 3.4σ (p-value is 2.9e-4) detection of the QPO reported here reveals the strongest QPO signal observed from magnetars (except in some very rare giant flares), making this X-ray burst unique among magnetar bursts. The two X-ray spikes coinciding with the two FRB pulses are also among the peaks of the QPO. Our results suggest that at least some FRBs are related to strong oscillation processes of neutron stars. We also show that we may overestimate the significance of the QPO signal and underestimate the errors of QPO parameters if QPO exists only in a fraction of the time series of an X-ray burst that we use to calculate the Leahy-normalized periodogram.

Keywords: Soft gamma-ray repeaters, Time domain astronomy, Magnetars, Astronomical methods, X-ray bursts
Implications of a Temperature-dependent Initial Mass Function. I. Photometric Template Fitting. A universal stellar initial mass function (IMF) should not be expected from theoretical models of star formation, but little conclusive observational evidence for a variable IMF has been uncovered. In this paper, a parameterization of the IMF is introduced into photometric template fitting of the COSMOS2015 catalog. The resulting best-fit templates suggest systematic variations in the IMF, with most galaxies exhibiting top-heavier stellar populations than in the Milky Way. At fixed redshift, only a small range of IMFs are found, with the typical IMF becoming progressively top-heavier with increasing redshift. Additionally, subpopulations of ULIRGs, quiescent and star-forming galaxies are compared with predictions of stellar population feedback and show clear qualitative similarities to the evolution of dust temperatures.

Keywords: Stellar mass functions, Initial mass function, Galaxy evolution
Implications of a Temperature-dependent Initial Mass Function. II. An Updated View of the Star-forming Main Sequence. The stellar initial mass function (IMF) is predicted to depend upon the temperature of gas in star-forming molecular clouds. The introduction of an additional parameter, T IMF, into photometric template fitting, allows galaxies to be fit with a range of IMFs. Three surprising new features appear: (1) most star-forming galaxies are best fit with a bottom-lighter IMF than the Milky Way; (2) most star-forming galaxies at fixed redshift are fit with a very similar IMF; and (3) the most-massive star-forming galaxies at fixed redshift instead exhibit a less bottom-light IMF, similar to that measured in quiescent galaxies. Additionally, since stellar masses and star formation rates both depend on the IMF, these results slightly modify the resulting relationship, while yielding similar qualitative characteristics to previous studies.

Keywords: Initial mass function, Star forming regions, Star formation, Galaxy evolution, Galaxy quenching
Testing High-energy Emission Models for Blazars with X-Ray Polarimetry. Both leptonic and hadronic emission processes may contribute to blazar jet emission; which dominates in blazars' high-energy emission component remains an open question. Some intermediate synchrotron peaked blazars transition from their low- to high-energy emission components in the X-ray band making them excellent laboratories to probe both components simultaneously, and good targets for the newly launched Imaging X-ray Polarimetry Explorer (IXPE). We characterize the spectral energy distributions for three such blazars, CGRaBS J0211+1051, TXS 0506+056, and S5 0716+714, predicting their X-ray polarization behavior by fitting a multizone polarized leptonic jet model. We find that a significant detection of electron synchrotron dominated polarization is possible with a 300 ks observation for S5 0716+714 and CGRaBS J0211+1051 in their flaring states, while even 500 ks observations are unlikely to measure synchrotron self-Compton (SSC) polarization. Importantly, nonleptonic emission processes like proton synchrotron are marginally detectable for our brightest intermediate synchrotron peaked blazar (ISP), S5 0716+714, during a flaring state. Improved IXPE data reduction methods or next-generation telescopes like eXTP are needed to confidently measure SSC polarization.

Keywords: BL Lacertae objects, Relativistic jets, Galaxy jets, X-ray telescopes, X-ray active galactic nuclei, Polarimeters, Polarimetry
Solar Flare Heating with Turbulent Suppression of Thermal Conduction. During solar flares, plasma is typically heated to very high temperatures, and the resulting redistribution of energy via thermal conduction is a primary mechanism transporting energy throughout the flaring solar atmosphere. The thermal flux is usually modeled using Spitzer's theory, which is based on local Coulomb collisions between the electrons carrying the thermal flux and those in the background. However, often during flares, temperature gradients become sufficiently steep that the collisional mean free path exceeds the temperature-gradient scale size, so that thermal conduction becomes inherently nonlocal. Further, turbulent angular scattering, which is detectable in nonthermal widths of atomic emission lines, can also act to increase the collision frequency and thus suppress the heat flux. Recent work by Emslie &amp; Bian extended Spitzer's theory of thermal conduction to account for both nonlocality and turbulent suppression. We have implemented their theoretical expression for the heat flux (which is a convolution of the Spitzer flux with a kernel function) into the RADYN flare-modeling code and performed a parameter study to understand how the resulting changes in thermal conduction affect the flare dynamics and hence the radiation produced. We find that models with reduced heat fluxes predict slower bulk flows, less intense line emission, and longer cooling times. By comparing the features of atomic emission lines predicted by the models with Doppler velocities and nonthermal line widths deduced from a particular flare observation, we find that models with suppression factors between 0.3 and 0.5 relative to the Spitzer value best reproduce the observed Doppler velocities across emission lines forming over a wide range of temperatures. Interestingly, the model that best matches the observed nonthermal line widths has a kappa-type velocity distribution function.

Keywords: Hydrodynamical simulations, Solar flares, Solar ultraviolet emission, Solar corona, Radiative transfer simulations, Solar chromosphere
Lithium Detection in Red Supergiant Stars of the Perseus Complex. We present the first systematic study of lithium abundance in a chemically homogeneous sample of 27 red supergiants (RSGs) in the young Perseus complex. For these stars, accurate stellar parameters and detailed chemical abundances of iron and iron peak, CNO, alpha, light, and neutron capture elements have already been obtained by means of high-resolution optical and near-infrared spectroscopy. The observed RSGs have half-solar metallicity, 10-30 Myr ages, bolometric luminosities in the 104-105 L ⊙ range, and likely mass progenitors in the 9-14 M ⊙ range. We detected the optical Li I doublet in eight out of the 27 observed K- and M-type RSGs, finding relatively low A(Li) &lt; 1.0 dex abundances, while for the remaining 19 RSGs upper limits of A(Li) &lt; -0.2 dex have been set. Warmer and less luminous (i.e., likely less massive) as well as less mixed (i.e., with lower [C/N] and 12C/13C depletion) RSGs with Li detection show somewhat higher Li abundances. In order to explain the Li detection in ~30% of the observed RSGs, we speculate that some stochasticity should be at work, in a scenario where the Li was not completely destroyed in the convective atmospheres and/or a secondary production took place during the post-main-sequence evolution.

Keywords: Stellar abundances, Red supergiant stars, Spectroscopy
Reionization with SIMBA: How Much Does Astrophysics Matter in Modeling Cosmic Reionization?. Traditional large-scale models of reionization usually employ simple deterministic relations between halo mass and luminosity to predict how reionization proceeds. We here examine the impact on modeling reionization of using more detailed models for the ionizing sources as identified within the 100 h -1 Mpc cosmological hydrodynamic simulation SIMBA, coupled with postprocessed radiative transfer. Comparing with simple (one-to-one) models, the main difference with using SIMBA sources is the scatter in the relation between dark matter halos and star formation, and hence ionizing emissivity. We find that, at the power spectrum level, the ionization morphology remains mostly unchanged, regardless of the variability in the number of sources or escape fraction. In particular, the power spectrum shape remains unaffected and its amplitude changes slightly by less than 5%-10%, throughout reionization, depending on the scale and neutral fraction. Our results show that simplified models of ionizing sources remain viable to efficiently model the structure of reionization on cosmological scales, although the precise progress of reionization requires accounting for the scatter induced by astrophysical effects.

Keywords: Radiative transfer simulations, Reionization, Galaxy evolution
Slow Magnetoacoustic Oscillations in Stellar Coronal Loops. Slow magnetoacoustic oscillations in stellar coronal loops with gravitational stratification are analyzed with a numerical solution of the boundary value problem for eigenvalues and eigenfunctions. In this study, we only focus on the resonant periods. The effects of the gravitational stratification, star mass, loop temperature, and loop length on the properties of slow magnetoacoustic oscillations are investigated. It is shown that the discrepancy between stratified and nonstratified loops is higher in density perturbations than in velocity perturbations. When the star has a larger mass, higher coronal temperature, and longer loop, the density perturbations in the stratified loop are significantly different from the harmonic functions. The periods in the stratified loop are slightly longer than in the nonstratified loop. The periods calculated in our model (14-644 minutes) are consistent with the periods of stellar quasi-periodic pulsations observed in both soft X-rays (2-70 minutes) and white lights (8-390 minutes).

Keywords: Magnetohydrodynamics, Solar coronal loops, Stellar flares, Stellar coronal loops, Solar oscillations, Stellar oscillations
Determining the Age for the Red Giants KIC 9145955 and KIC 9970396 by Gravity-dominated Mixed Modes. Determining the ages and helium core sizes of red giants is a challenging problem. To estimate the age and helium core size precisely requires a good understanding of the internal structure of the red giant. The properties of the g-dominated mixed modes of red giants are closely related to their inner radiative cores, especially the central helium core. Thus, the g-dominated mixed modes are useful indicators for probing the properties of the helium core and constraining the age of red giants. In our previous work, we have estimated the helium core sizes of the red giants KIC 9145955 and KIC 9970396 by asteroseismic models. In this work, we take a further step to calibrate the ages and core overshooting parameters for these two red giants. We find that the ages of these two stars are 4.61 ± 0.23 and 6.13 ± 0.19 Gyr, respectively. From a comparative study, we find that, for a single red giant, the age estimated by the asteroseismology of g-dominated mixed modes is likely to be more precise than that estimated by the combination of the asteroseismic (Δν and ΔP obs) and spectroscopic (T eff and [Fe/H]) observations. In addition, we estimate the core overshooting parameters of these two stars. We find that the overshooting parameter f ov of KIC 9145955 and KIC 9970396 was probably overestimated in previous works.

Keywords: Stellar oscillations, Asteroseismology, Stellar ages, Red giant stars
Termination Shocks and the Extended X-Ray Emission in Mrk 78. Subarcsecond imaging of the X-ray emission in the type 2 active galactic nucleus (AGN) Mrk 78 with Chandra shows complex structure with spectral variations on scales from ~200 pc to ~2 kpc. Overall the X-ray emission is aligned E-W with the radio (3.6 cm) and narrow emission line region as mapped in [O III], with a marked E-W asymmetry. The eastern X-ray emission is mostly in a compact knot coincident with the location where the radio source is deflected, while the western X-ray emission forms a loop or shell ~2 kpc from the nucleus with radius ~0.7 kpc. There is suggestive evidence of shocks in both the eastern knot and the western arc. Both these positions coincide with large changes in the velocities of the [O III] outflow. We discuss possible reasons why the X-ray shocks on the western side occur ~1 kpc farther out than on the eastern side. We estimate that the thermal energy injected by the shocks into the interstellar medium corresponds to 0.05%-0.6% of the AGN bolometric luminosity.

Keywords: Markarian galaxies, Active galaxies, Seyfert galaxies, Active galactic nuclei, X-ray active galactic nuclei
The Effects of Disk-induced Apsidal Precession on Planets Captured into Mean Motion Resonance. The process of migration into resonance capture has been well studied for planetary systems where the gravitational potential is generated exclusively by the star and planets. However, massive protoplanetary disks add a significant perturbation to these models. In this paper we consider two limiting cases of disk-induced precession on migrating planets and find that small amounts of precession significantly affect the equilibrium reached by migrating planets. We investigate these effects with a combination of semianalytic models of the resonance and numerical integrations. We also consider the case of the disk's dispersal, which can excite significant libration amplitude and can cause ejection from resonance for large enough precession rates. Both of these effects have implications for interpreting the known exoplanet population and may prove to be important considerations as the population of well-characterized exoplanet systems continues to grow.

Keywords: Exoplanet dynamics, Protoplanetary disks
Magnetar XTE J1810-197: Spectro-temporal Evolution of Average Radio Emission. We present the long-term spectro-temporal evolution of the average radio emission properties of the magnetar XTE J1810-197 (PSR J1809-1943), following its most recent outburst in late 2018. We report the results from a 2.5 yr monitoring campaign with the upgraded Giant Metrewave Radio Telescope, carried out over the frequency range of 300-1450 MHz. Our observations show intriguing time variability in the average profile width, flux density, spectral index, and broadband spectral shape. While the average profile width appears to gradually decrease at later epochs, the flux density shows multiple episodes of radio rebrightening over the course of our monitoring. Our systematic monitoring observations reveal that the radio spectrum has steepened over time, resulting in evolution from a magnetar-like spectrum to a more pulsar-like spectrum. A more detailed analysis reveals that the radio spectrum has a turnover, and that this turnover shifts toward lower frequencies with time. We present the details of our analysis leading to these results, and discuss our findings in the context of magnetar radio emission mechanisms, as well as potential manifestations of the intervening medium. We also briefly discuss whether an evolving spectral turnover could be a ubiquitous property of radio magnetars.

Keywords: Neutron stars, Rotation powered pulsars, Pulsars, Soft gamma-ray repeaters, Radio bursts, Interstellar absorption, Non-thermal radiation sources, Interstellar medium, Radio transient sources, Magnetars, Radio pulsars
Milliarcsecond X-Ray Astrometry to Resolve Inner Regions of AGN at z &gt; 1 Using Gravitational Lensing. We report the localization of the X-ray emission from two strongly lensed AGN, CLASS B0712+472 (z = 1.34) and CLASS B1608+656 (z = 1.394). We obtain milliarcsecond X-ray astrometry by developing a novel method that combines parametric lens modeling with a Bayesian analysis. We spatially locate the X-ray sources in CLASS B0712+472 and CLASS B1608+656 within 11 mas and 9 mas from the radio source, respectively. For CLASS B0712+472, we find that the X-ray emission is cospatial with the radio and optical emission. On the other hand, for CLASS B1608+656, the X-ray emission is cospatial with radio but displaced with respect to the optical emission at the 1σ level, which positions this source as an offset AGN candidate. This high astrometric precision improves on the limitations of existing X-ray instruments by two orders of magnitude. The demonstrated method opens a path to search for offset and binary AGN at z &gt; 1, and to directly test supermassive black hole formation models in a redshift range that has been mostly underconstrained to date.

Keywords: Black hole physics, Supermassive black holes, Strong gravitational lensing, Active galaxies, Active galactic nuclei, Astrometry, X-ray quasars