Sazuna/UAT_keywords huggingface dataset:
A Necessary Condition for Supernova Fallback Invading Newborn Neutron-star Magnetosphere. We numerically investigate the dynamics of a supernova fallback accretion confronting with a relativistic wind from a newborn neutron star (NS). The time evolution of the accretion shock in the radial direction is basically characterized by the encounter radius of the flow renc and a dimensionless parameter $\zeta \equiv L/{\dot{M}}_{\mathrm{fb}}{c}^{2}$ , where L is the NS wind luminosity and ${\dot{M}}_{\mathrm{fb}}$ is the fallback mass accretion rate. We find that the critical condition for the fallback matter to reach near the NS surface can be simply described as $\zeta \lt {\zeta }_{\min }\equiv {{GM}}_{* }/{c}^{2}{r}_{\mathrm{enc}}$ or ${r}_{\mathrm{enc}}L/{{GM}}_{* }{\dot{M}}_{\mathrm{fb}}\lt 1$ independent of the wind Lorentz factor, where M* is the NS mass. With combining the condition for the fallback matter to bury the surface magnetic field under the NS crust, we discuss the possibility that the trifurcation of NSs into rotation-powered pulsars, central compact objects, and magnetars can be induced by supernova fallback.

Keywords: Neutron stars, Hydrodynamics
Estimating Dust Attenuation From Galactic Spectra. II. Stellar and Gas Attenuation in Star-forming and Diffuse Ionized Gas Regions in MaNGA. We investigate the dust attenuation in both stellar populations and ionized gas in kiloparsec-scale regions in nearby galaxies using integral field spectroscopy data from MaNGA MPL-9. We identify star-forming (H II) and diffuse ionized gas (DIG) regions from MaNGA data cubes. From the stacked spectrum of each region, we measure the stellar attenuation, $E{\left(B-V\right)}_{\mathrm{star}}$ , using the technique developed by Li et al., as well as the gas attenuation, $E{\left(B-V\right)}_{\mathrm{gas}}$ , from the Balmer decrement. We then examine the correlation of $E{\left(B-V\right)}_{\mathrm{star}}$ , $E{\left(B-V\right)}_{\mathrm{gas}}$ , $E{\left(B-V\right)}_{\mathrm{gas}}-E{\left(B-V\right)}_{\mathrm{star}}$ , and $E{\left(B-V\right)}_{\mathrm{star}}/E{\left(B-V\right)}_{\mathrm{gas}}$ with 16 regional/global properties, and for regions with different Hα surface brightnesses (ΣHα). We find a stronger correlation between $E{\left(B-V\right)}_{\mathrm{star}}$ and $E{\left(B-V\right)}_{\mathrm{gas}}$ in regions of higher ΣHα. The luminosity-weighted age (tL) is found to be the property that is the most strongly correlated with $E{\left(B-V\right)}_{\mathrm{star}}$ , and consequently, with $E{\left(B-V\right)}_{\mathrm{gas}}-E{\left(B-V\right)}_{\mathrm{star}}$ and $E{\left(B-V\right)}_{\mathrm{star}}/E{\left(B-V\right)}_{\mathrm{gas}}$ . At fixed ΣHα, ${\mathrm{log}}_{10}$ tL is linearly and negatively correlated with $E{\left(B-V\right)}_{\mathrm{star}}/E{\left(B-V\right)}_{\mathrm{gas}}$ at all ages. Gas-phase metallicity and ionization level are important for the attenuation in the gas. Our results indicate that the ionizing source for DIG regions is likely distributed in the outskirts of galaxies, while for H II regions, our results can be well explained by the two-component dust model of Charlot &amp; Fall.

Keywords: Interstellar dust, Stellar populations, Star forming regions, Interstellar dust extinction, Warm ionized medium, Emission nebulae, Star formation, Hot ionized medium, Interstellar extinction, Galaxy spectroscopy
Rapid Variability of Sgr A* across the Electromagnetic Spectrum. Sagittarius A* (Sgr A*) is the variable radio, near-infrared (NIR), and X-ray source associated with accretion onto the Galactic center black hole. We have analyzed a comprehensive submillimeter (including new observations simultaneous with NIR monitoring), NIR, and 2-8 keV data set. Submillimeter variations tend to lag those in the NIR by ~30 minutes. An approximate Bayesian computation fit to the X-ray first-order structure function shows significantly less power at short timescales in the X-rays than in the NIR. Less X-ray variability at short timescales, combined with the observed NIR-X-ray correlations, means the variability can be described as the result of two strictly correlated stochastic processes, the X-ray process being the low-pass-filtered version of the NIR process. The NIR-X-ray linkage suggests a simple radiative model: a compact, self-absorbed synchrotron sphere with high-frequency cutoff close to NIR frequencies plus a synchrotron self-Compton scattering component at higher frequencies. This model, with parameters fit to the submillimeter, NIR, and X-ray structure functions, reproduces the observed flux densities at all wavelengths, the statistical properties of all light curves, and the time lags between bands. The fit also gives reasonable values for physical parameters such as magnetic flux density B ≍ 13 G, source size L ≍ 2.2RS, and high-energy electron density ne ≍ 4 × 107 cm-3. An animation illustrates typical light curves, and we make public the parameter chain of our Bayesian analysis, the model implementation, and the visualization code.

Keywords: Accretion, Black hole physics, Supermassive black holes, Galactic center, High energy astrophysics, Astrophysical black holes
Role of Suprathermal Runaway Electrons Returning to the Acceleration Region in Solar Flares. During solar flares, a large flux of energetic electrons propagate from the tops of reconnecting magnetic flux tubes toward the lower atmosphere. Over the course of the electrons' transport, a co-spatial counterstreaming return current is induced, thereby balancing the current density. In response to the return-current electric field, a fraction of the ambient electrons will be accelerated into the runaway regime. However, models describing the accelerated electron beam/return-current system have not previously taken these suprathermal runaway electrons into account self-consistently. We develop a model in which an accelerated electron beam drives a steady-state, sub-Dreicer co-spatial return-current electric field, which locally balances the direct beam current and freely accelerates a fraction of background (return-current) electrons. The model is self-consistent, i.e., the electric field induced by the coevolution of the direct beam and the runaway current is considered. We find that (1) the return-current electric field can return a significant number of suprathermal electrons to the acceleration region, where they can be further accelerated to higher energies, runaway electrons can be a few tens of percent of the return-current flux returning to the nonthermal beam's acceleration region, (2) the energy gain of the suprathermal electrons can be up to 10-35 keV, (3) the heating rate in the corona can be reduced by a factor of 3 for medium range injected fluxes in comparison to models which neglect the runaway component. The results depend on the injected beam flux density, the temperature, and density of the background plasma.

Keywords: Solar flares
A High-resolution View of Fast Radio Burst Host Environments. We present Hubble Space Telescope ultraviolet and infrared observations of eight fast radio burst (FRB) host galaxies with subarcsecond localizations, including the hosts of three known repeating FRBs. We quantify their spatial distributions and locations with respect to their host galaxy light distributions, finding that they occur at moderate host-normalized offsets of 1.4re ([0.6, 2.1]re; 68% interval) and on fainter regions of their hosts in terms of IR light but overall trace the radial distribution of IR light in their galaxies. The FRBs in our tested distribution do not clearly trace the distributions of any other transient population with known progenitors and are statistically distinct from the locations of LGRBs, H-poor SLSNe, SGRBs, and Ca-rich transients. We further find that most FRBs are not in regions of elevated local star formation rates and stellar mass surface densities in comparison to the mean global values of their hosts. We also place upper limits on the IR flux at the FRB positions of mIR ≳ 24.8-27.6 AB mag, constraining both satellite and background galaxies to luminosities well below the host luminosity of FRB 121102. We find that 5/8 FRB hosts exhibit clear spiral arm features in IR light, and that the positions of all well-localized FRBs located in such hosts are consistent with their spiral arms, although not on their brightest regions. Our results do not strongly support the primary progenitor channel of FRBs being connected with either the most massive (stripped-envelope) stars or events that require kicks and long delay times (neutron star mergers).

Keywords: Transient sources, HST photometry, Radio bursts, Galaxies, Radio transient sources
Gravitational-wave Signatures from Compact Object Binaries in the Galactic Center. Almost every galaxy has a supermassive black hole (SMBH) residing at its center, the Milky Way included. Recent studies suggest that these unique places are expected to host a high abundance of stellar and compact object binaries. These binaries form hierarchical triple systems with the SMBH and undergo the eccentric Kozai-Lidov (EKL) mechanism. Here we estimate the detectability of potential gravitational-wave emission from these compact objects within the frequency band of the Laser Interferometer Space Antenna (LISA) and Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo detectors. We generate a post-EKL population of stars at the onset of Roche limit crossing and follow their evolution to compact object binaries. As a proof of concept, we adopt two metallicities, solar metallicity (Z = 0.02) and 15% of it (Z = 0.003). We demonstrate that over the observation timescale of LISA, black hole (BH) binaries (BH-BH) and white dwarf (WD) binaries provide the most prominent GW sources via the EKL-assisted merger channel. Systems involving neutron stars (NSs) are less observable but possibly abundant through different merger channels. Our population synthesis of BH-BH with Z = 0.02 (Z = 0.003) translates to ~4 (24) events per year with LIGO within a 1 Gpc3 sphere. We also estimated the number of binaries visible in the LISA band within the inner parsec of our Galactic center (and possibly other galaxies) to be about 14-150 WD-WD, 0-2 NS-BH, 0.2-4 NS-NS, and 0.3-20 BH-BH.

Keywords: Neutron stars, Gravitational wave detectors, Binary stars, Galactic center, White dwarf stars, Compact binary stars, Gravitational waves
Gamma-Ray Thermalization and Leakage from Millisecond Magnetar Nebulae: Toward a Self-consistent Model for Superluminous Supernovae. Superluminous supernovae (SLSNe) are massive star explosions that are too luminous to be powered by traditional energy sources, such as the radioactive decay of 56Ni. Instead, they may be powered by a central engine, such as a millisecond pulsar or magnetar, whose relativistic wind inflates a nebula of high-energy particles and radiation behind the expanding supernova ejecta. We present three-dimensional Monte Carlo radiative transfer calculations of SLSNe that follow the production of high-energy emission in the nebula and its subsequent thermalization into optical radiation within the surrounding ejecta and, conversely, determine the gamma-ray emission that escapes the ejecta without thermalizing. We identify a novel mechanism by which γγ pair creation in the upstream pulsar wind regulates the mean energy of particles entering the nebula over the first several years after the explosion, rendering our results on this timescale insensitive to the (uncertain) intrinsic wind pair multiplicity. To explain the observed late-time steepening of SLSN optical light curves as being the result of gamma-ray leakage, we find that the nebular magnetization must be very low, ${\varepsilon }_{{\rm{B}}}\lesssim {10}^{-6}\mbox{--}{10}^{-4}$ . For higher ${\varepsilon }_{{\rm{B}}}$ , the more efficiently thermalized lower-energy synchrotron emission would overproduce the late-time (≳1 yr) optical radiation, inconsistent with observations. For magnetars to remain as viable contenders for powering SLSNe, we conclude that either magnetic dissipation in the wind/nebula is extremely efficient or the spin-down luminosity decays significantly faster than the canonical dipole rate ∝t-2 in a way that coincidentally mimics gamma-ray escape.

Keywords: High energy astrophysics, Core-collapse supernovae, Gamma-ray sources, Transient sources, Non-thermal radiation sources, Radiative transfer simulations, Gamma-ray transient sources, Gamma-rays
A Parametric Galactic Model toward the Galactic Bulge Based on Gaia and Microlensing Data. We developed a parametric Galactic model toward the Galactic bulge by fitting to spatial distributions of the Gaia DR2 disk velocity, VVV proper motion, BRAVA radial velocity, OGLE-III red clump star count, and OGLE-IV star count and microlens rate, optimized for use in microlensing studies. We include the asymmetric drift of Galactic disk stars and the dependence of velocity dispersion on Galactic location in the kinematic model, which has been ignored in most previous models used for microlensing studies. We show that our model predicts a microlensing parameter distribution significantly different from those typically used in previous studies. We estimate various fundamental model parameters for our Galaxy through our modeling, including the initial mass function (IMF) in the inner Galaxy. Combined constraints from star counts and the microlensing event timescale distribution from the OGLE-IV survey, in addition to a prior on the bulge stellar mass, enable us to successfully measure IMF slopes using a broken power-law form over a broad mass range, ${\alpha }_{\mathrm{bd}}={0.22}_{-0.55}^{+0.20}$ for M &lt; 0.08 M⊙, ${\alpha }_{\mathrm{ms}}={1.16}_{-0.15}^{+0.08}$ for 0.08 M⊙ ≤ M &lt; Mbr, and ${\alpha }_{\mathrm{hm}}={2.32}_{-0.10}^{+0.14}$ for M ≥ Mbr, as well as a break mass at ${M}_{\mathrm{br}}={0.90}_{-0.14}^{+0.05}\,{M}_{\odot }$ . This is significantly different from the Kroupa IMF for local stars, but similar to the Zoccali IMF measured from a bulge luminosity function. We also estimate the dark matter mass fraction in the bulge region of 28% ± 7% which could be larger than a previous estimate. Because our model is purely parametric, it can be universally applied using the parameters provided in this paper. (A tool for microlensing simulation using our Galactic model has been published, Koshimoto &amp; Ranc 2021, and can be downloaded at https://github.com/nkoshimoto/genulens.)

Keywords: Initial mass function, Galactic bulge, Milky Way disk, Gravitational microlensing, Milky Way Galaxy
Molecular Gas in a Gravitationally Lensed Galaxy Group at z = 2.9. Most molecular gas studies of z &gt; 2.5 galaxies are of intrinsically bright objects, despite the galaxy population being primarily normal galaxies with less extreme star formation rates. Observations of normal galaxies at high redshift provide a more representative view of galaxy evolution and star formation, but such observations are challenging to obtain. In this work, we present Atacama Large Millimeter/submillimeter Array 12CO(J = 3 → 2) observations of a submillimeter selected galaxy group at z = 2.9, resulting in spectroscopic confirmation of seven images from four member galaxies. These galaxies are strongly lensed by the MS 0451.6-0305 foreground cluster at z = 0.55, allowing us to probe the molecular gas content on levels of 109-1010 M☉. Four detected galaxies have molecular gas masses of (0.2-13.1) × 1010 M☉, and the nondetected galaxies have inferred molecular gas masses of &lt;8.0 × 1010 M☉. We compare these new data to a compilation of 546 galaxies up to z = 5.3, and find that depletion times decrease with increasing redshift. We then compare the depletion times of galaxies in overdense environments to the field-scaling relation from the literature, and find that the depletion time evolution is steeper for galaxies in overdense environments than for those in the field. More molecular gas measurements of normal galaxies in overdense environments at higher redshifts (z &gt; 2.5) are needed to verify the environmental dependence of star formation and gas depletion.

Keywords: High-redshift galaxy clusters, Strong gravitational lensing, Star formation, Galaxy evolution, High-redshift galaxies
A Study of the Photometric and Spectroscopic Variations of the Prototypical FU Orionis-type Star V1057 Cyg. Among the low-mass pre-main sequence stars, a small group called FU Orionis-type objects (FUors) are notable for undergoing powerful accretion outbursts. V1057 Cyg, a classical example of an FUor, went into outburst around 1969-1970, after which it faded rapidly, making it the fastest-fading FUor known. Around 1995, a more rapid increase in fading occurred. Since that time, strong photometric modulations have been present. We present nearly 10 yr of source monitoring at Piszkéstető Observatory, complemented with optical/NIR photometry and spectroscopy from the Nordic Optical Telescope, Bohyunsan Optical Astronomy Observatory, Transiting Exoplanet Survey Satellite, and Stratospheric Observatory for Infrared Astronomy. Our light curves show continuation of significant quasi-periodic variability in brightness over the past decade. Our spectroscopic observations show strong wind features, shell features, and forbidden emission lines. All of these spectral lines vary with time. We also report the first detection of [S II], [N II], and [O III] lines in the star.

Keywords: Multi-color photometry, FU Orionis stars, Light curves, Young stellar objects, Spectroscopy, Circumstellar disks, Photometry
Magnetic Twists of Solar Filaments. Solar filaments are cold and dense materials situated in magnetic dips, which show distinct radiation characteristics compared to the surrounding coronal plasma. They are associated with coronal sheared and twisted magnetic field lines. However, the exact magnetic configuration supporting a filament material is not easy to ascertain because of the absence of routine observations of the magnetic field inside filaments. Since many filaments lie above weak-field regions, it is nearly impossible to extrapolate their coronal magnetic structures by applying the traditional methods to noisy photospheric magnetograms, in particular the horizontal components. In this paper, we construct magnetic structures for some filaments with the regularized Biot-Savart laws and calculate their magnetic twists. Moreover, we make a parameter survey for the flux ropes of the Titov-Démoulin-modified model to explore the factors affecting the twist of a force-free magnetic flux rope. It is found that the twist of a force-free flux rope, $| \overline{{T}_{{\rm{w}}}}| $ , is proportional to its ratio of axial length to minor radius, L/a, and is basically independent of the overlying background magnetic field strength. Thus, we infer that long quiescent filaments are likely to be supported by more twisted flux ropes than short active-region filaments, which is consistent with observations.

Keywords: Solar magnetic fields, Solar filaments, Solar corona, Solar prominences
Impact of Magnetorotational Instability on Grain Growth in Protoplanetary Disks. II. Increased Grain Collisional Velocities. Turbulence is the dominant source of collisional velocities for grains with a wide range of sizes in protoplanetary disks. So far, only Kolmogorov turbulence has been considered for calculating grain collisional velocities, despite the evidence that turbulence in protoplanetary disks may be non-Kolmogorov. In this work, we present calculations of grain collisional velocities for arbitrary turbulence models characterized by power-law spectra and determined by three dimensionless parameters: the slope of the kinetic energy spectrum, the slope of the autocorrelation time, and the Reynolds number. The implications of our results are illustrated by numerical simulations of the grain size evolution for different turbulence models. We find that for the modeled cases of the Iroshnikov-Kraichnan turbulence and the turbulence induced by the magnetorotational instabilities, collisional velocities of small grains are much larger than those for the standard Kolmogorov turbulence. This leads to faster grain coagulation in the outer regions of protoplanetary disks, resulting in rapid increase of dust opacity in millimeter wavelength and possibly promoting planet formation in very young disks.

Keywords: Interstellar dust, Protoplanetary disks
Generic Models for Disk-resolved and Disk-integrated Phase-dependent Linear Polarization of Light Reflected from Exoplanets. Similar to the case of solar system planets, reflected starlight from exoplanets is expected to be polarized due to atmospheric scattering, and the net disk-integrated polarization should be nonzero owing to the asymmetrical illumination of the planetary disk. The computation of the disk-integrated reflected flux and its state of polarization involves techniques for the calculation of the local reflection matrices, as well as the numerical recipes for integration over the planetary disks. In this paper, we present a novel approach to calculate the azimuth-dependent reflected intensity vectors at each location on the planetary disk divided into grids. We achieve this by solving the vector radiative transfer equations that describe linear polarization. Our calculations incorporate self-consistent atmospheric models of exoplanets over a wide range of equilibrium temperature, surface gravity, atmospheric composition, and cloud structure. A comparison of the flux and the amount of polarization calculated by considering both single and multiple scattering exhibits the effect of depolarization due to multiple scattering of light depending on the scattering albedo of the atmosphere. We have benchmarked our basic calculations against some of the existing models. We have also presented our models for the hot Jupiter HD 189733 b, indicating the level of precision required by future observations to detect the polarization of this planet in the optical and near-infrared wavelength region. The generic nature and the accuracy offered by our models make them an effective tool for modeling future observations of the polarized light reflected from exoplanets.

Keywords: Exoplanet atmospheric composition , Hot Jupiters, Exoplanets, Polarimetry, Exoplanet atmospheres
The Infrared Echo of SN2010jl and Its Implications for Shock Breakout Characteristics. SN 2010jl is a Type IIn core-collapse supernova whose radiative output is powered by the interaction of the supernova (SN) shock wave with its surrounding dense circumstellar medium (CSM). After day ~60, its light curve developed a near-infrared (NIR) excess emission from dust. This excess could be a thermal IR echo from preexisting CSM dust, or emission from newly formed dust either in the cooling post-shock region of the CSM, or in the cooling SN ejecta. Recent analysis has shown that dust formation in the CSM can commence only after day ~380, and has also ruled out newly formed ejecta dust as the source of the NIR emission. The early (&lt;380 days) NIR emission can therefore only be attributed to an IR echo. The H-K color temperature of the echo is about 1250 K. The best-fitting model requires the presence of about 1.6 × 10-4 M⊙ of amorphous carbon dust at a distance of 2.2 × 1016 cm from the explosion. The CSM-powered luminosity is preceded by an intense burst of hard radiation generated by the breakout of the SN shock through the stellar surface. The peak burst luminosity seen by the CSM dust is significantly reduced by Thomson scattering in the CSM, but still has the potential of evaporating the dust needed to produce the echo. We show that the survival of the echo-producing dust provides important constraints on the intensity, effective temperature, and duration of the burst.

Keywords: Core-collapse supernovae, Light curves, Circumstellar shells, Circumstellar grains, Shocks, Circumstellar dust