Sazuna/UAT_keywords huggingface dataset:
How Does Background Air Pressure Influence the Inner Edge of the Habitable Zone for Tidally Locked Planets in a 3D View?. We examine the effect of varying background N2 surface pressure (labeled as pN2) on the inner edge of the habitable zone for 1:1 tidally locked planets around M dwarfs, using the three-dimensional (3D) atmospheric general circulation model (AGCM) ExoCAM. In our experiments, the rotation period is fixed when varying the stellar flux, in order to more clearly isolate the role of pN2. We find that the stellar flux threshold for the runaway greenhouse is a non-monotonous function of pN2. This is due to the competing effects of five processes: pressure broadening, heat capacity, lapse rate, relative humidity, and clouds. These competing processes increase the complexity in predicting the location of the inner edge of the habitable zone. For a slow-rotation orbit of 60 Earth days, the critical stellar flux for the runaway greenhouse onset is 1700-1750, 1900-1950, and 1750-1800 W m-2 under 0.25, 1.0, and 4.0 bar of pN2, respectively, suggesting that the magnitude of the effect of pN2 is within ≈13%. For a rapid rotation orbit, the effect of varying pN2 on the inner edge is smaller, within a range of ≈7%. Moreover, we show that Rayleigh scattering effect as varying pN2 is unimportant for the inner edge due to the masking effect of cloud scattering and to the strong shortwave absorption by water vapor under hot climates. Future work using AGCMs having different cloud and convection schemes and cloud-resolving models having explicit cloud and convection are Required to revise this problem.

Keywords: Extrasolar rocky planets, Planetary atmospheres, Astrobiology, Habitable planets, Exoplanet atmospheres
A Magnetar Engine for Short GRBs and Kilonovae. We investigate the influence of magnetic fields on the evolution of binary neutron star (BNS) merger remnants via three-dimensional (3D) dynamical-spacetime general-relativistic magnetohydrodynamic (MHD) simulations. We evolve a post-merger remnant with an initial poloidal magnetic field, resolve the magnetoturbulence driven by shear flows, and include a microphysical finite-temperature equation of state. A neutrino leakage scheme that captures the overall energetics and lepton number exchange is also included. We find that turbulence induced by the magnetorotational instability in the hypermassive neutron star (HMNS) amplifies magnetic field to beyond magnetar strength (1015 G). The ultra-strong toroidal field is able to launch a relativistic jet from the HMNS. We also find a magnetized wind that ejects neutron-rich material with a rate of ${\dot{M}}_{\mathrm{ej}}\simeq 1\times {10}^{-1}\,{M}_{\odot }\,{{\rm{s}}}^{-1}$ . The total ejecta mass in our simulation is 5 × 10-3 M⊙. This makes the ejecta from the HMNS an important component in BNS mergers and a promising source of r-process elements that can power a kilonova. The jet from the HMNS reaches a terminal Lorentz factor of ∼5 in our highest-resolution simulation. The formation of this jet is aided by neutrino cooling preventing the accretion disk from protruding into the polar region. As neutrino pair-annihilation and radiative processes in the jet (which were not included in the simulations) will boost the Lorentz factor in the jet further, our simulations demonstrate that magnetars formed in BNS mergers are a viable engine for short gamma-ray bursts.

Keywords: Magnetohydrodynamics, Jets, High energy astrophysics, General relativity, Astrophysical fluid dynamics
The Relative Role of Bars and Galaxy Environments in AGN Triggering of SDSS Spirals. We quantify the relative role of galaxy environment and bar presence on AGN triggering in face-on spiral galaxies using a volume-limited sample with 0.02 &lt; z &lt; 0.055, Mr &lt; 19.5, and σ &gt; 70 $\,\mathrm{km}\,{{\rm{s}}}^{-1}$ selected from Sloan Digital Sky Survey (SDSS) Data Release 7. To separate their possible entangled effects, we divide the sample into bar and non-bar samples, and each sample is further divided into three environment cases of isolated galaxies, interacting galaxies with a pair, and cluster galaxies. The isolated case is used as a control sample. For these six cases, we measure AGN fractions at a fixed central star formation rate and central velocity dispersion, σ. We demonstrate that the internal process of the bar-induced gas inflow is more efficient in AGN triggering than the external mechanism of the galaxy interactions in groups and cluster outskirts. The significant effects of bar instability and galaxy environments are found in galaxies with a relatively less massive bulge. We conclude that from the perspective of AGN-galaxy coevolution, a massive black hole is one of the key drivers of spiral galaxy evolution. If it is not met, a bar instability helps the evolution, and in the absence of bars, galaxy interactions/mergers become important. In other words, in the presence of a massive central engine, the role of the two gas inflow mechanisms is reduced or almost disappears. We also find that bars in massive galaxies are very decisive in increasing AGN fractions when the host galaxies are inside clusters.

Keywords: Galaxy clusters, Galaxy interactions, Galaxy nuclei, Galaxy evolution, Galaxy quenching
The Origin of Inequality: Isolated Formation of a 30+10 M<SUB>⊙</SUB> Binary Black Hole Merger. The LIGO/Virgo Collaboration has reported the detection of GW190412, a black hole-black hole (BH-BH) merger with the most unequal masses to date. (Another system, with even more unequal-mass components, was recently published by LIGO/Virgo: GW190814 (m1 = 23 $\,{M}_{\odot }$ , m2 = 2.6 $\,{M}_{\odot }$ ); however, it is not known whether it is a BH-BH or BH-NS merger (Abbott et al. 2020).) They are m1 = 24.4-34.7 $\,{M}_{\odot }$ and m2 = 7.4-10.1 $\,{M}_{\odot }$ , corresponding to a mass ratio of q = 0.21-0.41 (90% probability range). Additionally, GW190412's effective spin was estimated to be χeff = 0.14-0.34, with the spin of the primary BH in the range aspin = 0.17-0.59. Based on this and prior detections, ≳10% of BH-BH mergers have q ≲ 0.4. Major BH-BH formation channels (i.e., dynamics in dense stellar systems, classical isolated binary evolution, or chemically homogeneous evolution) tend to produce BH-BH mergers with comparable masses (typically with q ≳ 0.5). Here we test whether the classical isolated binary evolution channel can produce mergers resembling GW190412. We show that our standard binary evolution scenario, with the typical assumptions on input physics that we have used in the past, produces such mergers. For this particular model of the input physics the overall BH-BH merger rate density in the local universe (z ∼ 0) is $73.5\,{\mathrm{Gpc}}^{-3}\,{\mathrm{yr}}^{-1}$ , while for systems with $q\lt 0.41$ the rate density is $6.8\,{\mathrm{Gpc}}^{-3}\,{\mathrm{yr}}^{-1}$ . The results from our standard model are consistent with the masses and spins of the black holes in GW190412, as well as with the LIGO/Virgo estimate of the fraction of unequal-mass BH-BH mergers. As GW190412 shows some weak evidence for misaligned spins, we provide distribution of the precession parameter in our models and conclude that if among the new LIGO/Virgo detections the evidence of system precession is strong and more than 10% of BH-BH mergers have large in-plane spin components (χp &gt; 0.5), then the common envelope isolated binary BH-BH formation channel can be excluded as their origin.

Keywords: Black hole physics, Black holes, High energy astrophysics, Stellar evolutionary models, Gravitational wave sources, Compact objects, Common envelope binary stars, Stellar evolution
NICER Observation of the Temporal and Spectral Evolution of Swift J1818.0-1607: A Missing Link between Magnetars and Rotation-powered Pulsars. We report on the hard X-ray burst and the first ∼100 days of NICER monitoring of the soft X-ray temporal and spectral evolution of the newly discovered magnetar Swift J1818.0-1607. The burst properties are typical of magnetars with a duration of T90 = 10 ± 4 ms and a temperature of kT = 8.4 ± 0.7 keV. The 2-8 keV pulse shows a broad, single-peak profile with a pulse fraction increasing with time from 30% to 43%. The NICER observations reveal strong timing noise with $\dot{\nu }$ varying erratically by a factor of 10, with an average long-term spin-down rate of $\dot{\nu }=(-2.48\pm 0.03)\times {10}^{-11}$ s-2, implying an equatorial surface magnetic field of 2.5 × 1014 G and a young characteristic age of ∼470 yr. We detect a large spin-up glitch at MJD 58928.56 followed by a candidate spin-down glitch at MJD 58934.81, with no accompanying flux enhancements. The persistent soft X-ray spectrum of Swift J1818.0-1607 can be modeled as an absorbed blackbody with a temperature of ∼1 keV. Its flux decayed by ∼60% while the modeled emitting area decreased by ∼30% over the NICER observing campaign. This decrease, coupled with the increase in the pulse fraction, points to a shrinking hot spot on the neutron star surface. Assuming a distance of 6.5 kpc, we measure a peak X-ray luminosity of 1.9 × 1035 erg s-1, lower than its spin-down luminosity of 7.2 × 1035 erg s-1. Its quiescent thermal luminosity is ≲1.7 × 1034 erg s-1, lower than those of canonical young magnetars. We conclude that Swift J1818.0-1607 is an important link between regular magnetars and high-magnetic-field, rotation-powered pulsars.

Keywords: Neutron stars, Magnetars, X-ray stars, Pulsars
Spectral Variability of the Blazar 3C 279 in the Optical to X-Ray Band during 2009-2018. We report on the spectral variability of the blazar 3C 279 in the optical to X-ray band between MJD 55100 and 58400 during which long-term radio variability was observed. We construct light curves and band spectra in each of the optical (2 × 1014-1.5 × 1015 Hz) and X-ray (0.3-10 keV) bands, measure the spectral parameters (flux F and spectral index α), and investigate the correlation between F and α within and across the bands. We find that the correlation of the optical properties dramatically change after ∼MJD 55500 and the light curves show more frequent activity after ∼MJD 57700. We therefore divide the time interval into three "states" based on the correlation properties and source activity in the light curves, and analyze each of the three states separately. We find various correlations between the spectral parameters in the states and an intriguing 65 day delay of the optical emission with respect to the X-ray one in state 2 (MJD 55500-57700). We attempt to explain these findings using a one-zone synchro-Compton emission scenario.

Keywords: Blazars, Active galactic nuclei, Spectral energy distribution, High energy astrophysics
The Relative Emission from Chromospheres and Coronae: Dependence on Spectral Type and Age. Extreme-ultraviolet and X-ray emission from stellar coronae drives mass loss from exoplanet atmospheres, and ultraviolet emission from stellar chromospheres drives photochemistry in exoplanet atmospheres. Comparisons of the spectral energy distributions of host stars are, therefore, essential for understanding the evolution and habitability of exoplanets. The large number of stars observed with the MUSCLES, Mega-MUSCLES, and other recent Hubble Space Telescope observing programs has provided for the first time a large sample (79 stars) of reconstructed Lyα fluxes that we compare with X-ray fluxes to identify significant patterns in the relative emission from these two atmospheric regions as a function of stellar age and effective temperature. We find that as stars age on the main sequence, the emissions from their chromospheres and coronae follow a pattern in response to the amount of magnetic heating in these atmospheric layers. A single trend-line slope describes the pattern of X-ray versus Lyα emission for G and K dwarfs, but the different trend lines for M dwarf stars show that the Lyα fluxes of M stars are significantly smaller than those of warmer stars with the same X-ray flux. The X-ray and Lyα luminosities divided by the stellar bolometric luminosities show different patterns depending on stellar age. The L(Lyα)/L(bol) ratios increase smoothly to cooler stars of all ages, but the L(X)/L(bol) ratios show different trends. For older stars, the increase in coronal emission with decreasing ${T}_{\mathrm{eff}}$ is much steeper than that of chromospheric emission. We suggest a fundamental link between atmospheric properties and trend lines relating coronal and chromospheric heating, * Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Mikulski Archive for Space Telescopes (MAST) at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS AR-09525.01A. These observations are associated with program Nos. 12475, 12596, 13650, 14640, and 15071.

Keywords: Ultraviolet sources, Stellar chromospheres, Exoplanet atmospheres, Exoplanet evolution, Stellar coronae, X-ray stars
Disk Illumination and Jet Variability of the Herbig Ae Star HD 163296 Using Multi-epoch HST/STIS Optical, Near-IR, and Radio Imagery and Spectroscopy. We present two new epochs of Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph coronagraphic imaging, along with multi-epoch optical, near-IR, and radio monitoring, of the HD 163296 system. We find that ansae features identified in earlier-epoch HST imagery are a fourth ring that resides at a semimajor axis distance of 3"25 (330 au). We determine that the scale height of the dust is 64 au at a radial distance of 330 au. We observe surface brightness variations in the fourth ring on &lt;3 month timescales, including large-scale, azimuthally asymmetric changes. This variability resembles earlier studies of the innermost disk ring (0"66, 67 au), suggesting a common origin. We find no evidence for the ejection of new HH knots predicted to occur in 2018. Moreover, our nondetection of older HH knots indicates that the knots could be experiencing less shock heating. We also detect one clear dipper event in our optical light curve from 2018. Using the timescale and spatial extent of the disk illumination changes we observe, we estimate that the source of this shadowing resides within 0.5 au from the star, must extend at least 0.08 au above the midplane of the disk, and has an azimuthal extent of 0.26 au. We estimate that the source of the dipper event reaches a scale height of 0.37 au above the midplane at 0.41 au and has an azimuthal extent of 0.3 au. We suggest that these similarities could indicate that the same (or similar) mechanisms are responsible for producing both dippers and variable ring illumination in the system.

Keywords: Stellar jets, Coronagraphic imaging, Protoplanetary disks, Stellar accretion, Near infrared astronomy
Magnetospheric Multiscale Observations of Foreshock Transients at Their Very Early Stage. Foreshock transients are ion kinetic structures in the ion foreshock. Due to their dynamic pressure perturbations, they can disturb the bow shock and magnetosphere-ionosphere system. They can also accelerate particles contributing to shock acceleration. However, it is still unclear how exactly they form. Recent particle-in-cell simulations point out the important role of the electric field and Hall current in the formation process. To further examine this, we use data from the Magnetospheric Multiscale (MMS) mission to apply case studies on two small (1000-2000 km) foreshock transient events that just started to form. In event 1 where MMS was in a tetrahedral formation, we show that the current density configuration, which determined the magnetic field profile, was mainly driven by Hall currents generated by demagnetized foreshock ions. The resulting time variation of the magnetic field induced an electric field that drove cold plasma moving outward with magnetic field lines. In event 2 where MMS was in a string-of-pearls formation, we analyze the evolution of field and plasma parameters. We show that the magnetic flux and mass flux were transported outward from the core, resulting in the steepening of the boundary. The steepened boundary, which trapped more foreshock ions and caused stronger demagnetization of foreshock ions, nonlinearly further enhanced the Hall current. Based on our observations, we propose a physical formation process wherein the positive feedback of foreshock ions on the varying magnetic field caused by the foreshock ion Hall current enables an "instability" and the growth of the structure.

Keywords: Shocks, Planetary bow shocks
SN 2018fif: The Explosion of a Large Red Supergiant Discovered in Its Infancy by the Zwicky Transient Facility. High-cadence transient surveys are able to capture supernovae closer to their first light than ever before. Applying analytical models to such early emission, we can constrain the progenitor stars' properties. In this paper, we present observations of SN 2018fif (ZTF 18abokyfk). The supernova was discovered close to first light and monitored by the Zwicky Transient Facility (ZTF) and the Neil Gehrels Swift Observatory. Early spectroscopic observations suggest that the progenitor of SN 2018fif was surrounded by relatively small amounts of circumstellar material compared to all previous cases. This particularity, coupled with the high-cadence multiple-band coverage, makes it a good candidate to investigate using shock-cooling models. We employ the SOPRANOS code, an implementation of the model by Sapir &amp; Waxman and its extension to early times by Morag et al. Compared with previous implementations, SOPRANOS has the advantage of including a careful account of the limited temporal validity domain of the shock-cooling model as well as allowing usage of the entirety of the early UV data. We find that the progenitor of SN 2018fif was a large red supergiant with a radius of $R={744.0}_{-128.0}^{+183.0}\,{R}_{\odot }$ and an ejected mass of ${M}_{\mathrm{ej}}={9.3}_{-5.8}^{+0.4}\,{M}_{\odot }$ . Our model also gives information on the explosion epoch, the progenitor's inner structure, the shock velocity, and the extinction. The distribution of radii is double-peaked, with smaller radii corresponding to lower values of the extinction, earlier recombination times, and a better match to the early UV data. If these correlations persist in future objects, denser spectroscopic monitoring constraining the time of recombination, as well as accurate UV observations (e.g., with ULTRASAT), will help break the extinction/radius degeneracy and independently determine both.

Keywords: Observational astronomy, Astronomy data modeling, Ultraviolet transient sources, Type II supernovae, Transient sources, Supernovae
Modeling Quasar UV/Optical Variability with the Corona-heated Accretion-disk Reprocessing (CHAR) Model. The rest-frame UV/optical variability of the quasars in the Sloan Digital Sky Survey Stripe 82 is used to test the Corona-Heated Accretion-disk Reprocessing (CHAR) model of Sun et al. We adopt our CHAR model and the observed black hole masses (MBH) and luminosities (L) to generate mock light curves that share the same measurement noise and sampling as the real observations. Without any fine-tuning, our CHAR model can satisfactorily reproduce the observed ensemble structure functions for different MBH, L, and rest-frame wavelengths. Our analyses reveal that a luminosity-dependent bolometric correction is disfavored over the constant bolometric correction for UV/optical luminosities. Our work demonstrates the possibility of extracting quasar properties (e.g., the bolometric correction or the dimensionless viscosity parameter) by comparing the physical CHAR model with quasar light curves.

Keywords: Accretion, Supermassive black holes, Active galactic nuclei, Quasars
High-resolution Chromospheric Observations of a Solar Minifilament: Formation and Destabilization. Using Hα line core and off-band imaging data from the New Vacuum Solar Telescope in China, we present a high-resolution observation on the entire life cycle of a solar minifilament from its birth to its final eruption. We find that the minifilament originates from a series of cascade-like reconfigurations of chromospheric fine structures. During which, owing to strong photospheric shearing and converging flows near its polarity inversion line, basic short chromospheric fibrils first slowly coalesce to elongated dark threads, and then further create a longer filament channel in a "head-to-tail" linkage scenario. In this course, obvious magnetic flux cancelation simultaneously proceeds below it, and further facilitates its destabilization. In its onset phase, clear clues indicate that the minifilament first starts to rise without brightening signals; instead, after a slow-to-fast acceleration, obvious runaway reconnection soon takes over its final jet-like eruption. Besides, off-band observations further reveal that the formed minifilament has a possible flux-rope configuration, and chromospheric upflows that detected in its early forming phase persistently supplies cool plasma into its channel. This observation is consistent with earlier observations and supports the view that both miniature and large-scale filaments may share analogous formation and destabilization mechanisms.

Keywords: Solar activity, Solar filaments, Solar magnetic fields
The Central 300 pc of the Galaxy Probed by Infrared Spectra of H<SUB>3</SUB><SUP>+</SUP> and CO. II. Expansion and Morphology of the Warm Diffuse Gas. Velocity profiles of a line of ${{\rm{H}}}_{3}^{+}$ at 3.7 μm produced in warm diffuse gas have been observed toward 18 stars in the Central Molecular Zone (CMZ) of the Galaxy. Their longitude-velocity diagram indicates that the gas is radially expanding within the CMZ at speeds up to a maximum of ∼150 km s-1. The current momentum and energy in the gas are ∼5 × 108 M☉ km s-1 and ∼5 × 1053 erg. The motion is similar to that of the Expanding Molecular Ring discovered in 1972 by Kaifu et al. and by Scoville. We propose that the expanding gas seen in ${{\rm{H}}}_{3}^{+}$ is part of the same phenomenon, despite differences in estimates of density, morphology, and degree of rotation. The outward motion suggests that one or more ejection events occurred near the center of the CMZ (0.5-1) × 106 yr ago, which may be related to creation of the recently observed microwave bubble. These observations revive the circular face-on view of the CMZ proposed in 1972, which fell out of favor after 1991 when Binney et al. proposed that a face-on view of the CMZ would show it to have an elliptical shape, with high eccentricity. While that model may apply on kiloparsec scales, we argue that it is incorrect to apply it to the much smaller CMZ. We discuss the fate of the expanding gas, which appears to be eventual infall into the center, leading to episodes of star formation and violent events associated with accretion onto Sgr A*.

Keywords: Interstellar molecules, Galactic center, High energy astrophysics, Interstellar line absorption, Astrochemistry, Interstellar clouds, Cosmic rays