adsabs/SciX_UAT_keywords huggingface dataset:
On the Diversity of Jet Production Efficiency in Swift/BAT AGNs

We address the very large diversity of jet production efficiency in active galactic nuclei (AGNs) by using data on low-redshift AGNs selected from the Swift/BAT catalog and having black hole (BH) masses larger than 108.5 M⊙. Most of these AGNs accrete at intermediate rates and have bolometric luminosities dominated by mid-IR radiation. Our sample contains 14% radio-loud (RL), 6% radio-intermediate, and 80% radio-quiet (RQ) AGNs. All RL objects are found to have extended radio structures, and most of them have classical FR II morphology. Converting their radio loudness to jet production efficiency, we find that the median of this efficiency is on the order of (ɛd/0.1)%, where ${\epsilon }_{d}={L}_{\mathrm{bol}}/\dot{M}{c}^{2}$ is the radiation efficiency of the accretion disk. Without knowing the contribution of jets to the radio emission in RQ AGNs, we are only able to estimate their efficiencies using upper limits. Their median is found to be 0.002(ɛd/0.1)%. Our results suggest that some threshold conditions must be satisfied to allow the production of strong, relativistic jets in RL AGNs. We discuss several possible scenarios and argue that the production of collimated, relativistic jets must involve the Blandford-Znajek mechanism and can be activated only in those AGNs whose lifetime is longer than the time required to enter the magnetically arrested disk (MAD). Presuming that MAD is required to collimate relativistic jets, we expect that the weak nonrelativistic jets observed in some RQ AGNs are produced by accretion disks rather than by rotating BHs.

Keywords: radio active galactic nuclei; radio jets; relativistic jets; non-thermal radiation sources; agn host galaxies; galaxy accretion disks
Relationship between Total Solar Irradiance and Magnetic Flux during Solar Minima

What drives the small total solar irradiance (TSI) changes of ~50-100 parts per million (compared with >1000 ppm solar-cycle amplitudes) during a deep solar minimum, i.e., in the practical absence of detectable sunspots and long-lasting active regions? We consider the epoch 2008 June-October and investigate multiple data sets (TSI; various Mg II line-activity indices, extreme ultraviolet fluxes, and full-disk magnetograms) to show that variations in TSI closely follow changes in total magnetic flux from sources with ∣B∣ > 80 G (up to ~600 G) that persist even during extended periods with no detectable sunspots. These sources comprise the populations of (a) short-lived (<20 minutes), small-scale (predominantly a single 2″ MDI pixel), ~evenly distributed regions, and (b) on average, more extended (a few MDI pixels) and longer-lived (140-260 minutes median lifetimes) magnetic areas. We ascribe the latter to ephemeral regions, finding them clustering on ~200 Mm scales. We speculate that the short-lived MDI sources are linked to the ubiquitous magnetic bright points. Our analysis of magnetic flux variations during solar cycle 23 shows that the magnetic regions present during this deep solar minimum elevate the total magnetic flux above the total flux in just the Gaussian "cores," fitted to histogram distributions of the full-disk flux. This suggests that solar irradiance during more extended, even deeper minima, such as the Maunder Minimum, may be lower than in 2008.

Keywords: ephemeral active regions; solar magnetic bright points; solar magnetic fields; solar spectral irradiance; solar photosphere; solar activity; sunspots; quiet sun
The SUPERWIDE Catalog: A Catalog of 99,203 Wide Binaries Found in Gaia and Supplemented by the SUPERBLINK High Proper Motion Catalog

We present a catalog of 99,203 wide binary systems, initially identified as common proper motion (CPM) pairs from a subset of ∼5.2 million stars with proper motions μ > 40 mas yr-1, selected from Gaia data release 2 (DR2) and the SUPERBLINK high proper motion catalog. CPM pairs are found by searching for pairs of stars with angular separations <1° and proper motion differences Δμ < 40 mas yr-1. A Bayesian analysis is then applied in two steps. In a first pass, we use proper motion differences and angular separations to distinguish between real binaries and chance alignments. In a second pass, we use parallax data from Gaia DR2 to refine our Bayesian probability estimates. We present a table of 119,390 pairs which went through the full analysis, 99,203 of which have probabilities >95% of being real wide binaries. Of those 99,203 high-probability pairs, we estimate that only about 364 pairs are most likely to be false positives. In addition, we identify 57,506 pairs that have probabilities greater than 10% from the first pass but have high parallax errors and therefore were not vetted in the second pass. We examine the projected physical separation distribution of our highest probability pairs and note that the distribution is a simple exponential tail and shows no evidence of being bimodal. Among pairs with lower probability, wide binaries are detected at larger separations (>104-105 au), consistent with the very wide population suggested in previous studies; however, our analysis suggests that these do not represent a distinct population, but instead represent either the exponential tail of the "normal" wide binary distribution or are simply chance alignments of unrelated field stars. We examine the Hertzsprung-Russell diagram of this set of high-probability wide binaries and find evidence for 980 overluminous components among 2227 K + K wide binaries; assuming these represent unresolved subsystems, we determine that the higher-order multiplicity fraction for K + K wide systems is at least 39.6%.

Keywords: binary stars; wide binary stars; low mass stars
"Tidal Peeling Events": Low-eccentricity Tidal Disruption of a Star by a Stellar-mass Black Hole

Close encounters between stellar-mass black holes (BHs) and stars occur frequently in dense star clusters and in the disks of active galactic nuclei. Recent studies have shown that in highly eccentric close encounters, the star can be tidally disrupted by the BH in a microtidal disruption event (microTDE), resulting in rapid mass accretion and possibly bright electromagnetic signatures. Here we consider a scenario in which the star might approach the stellar-mass BH in a gradual, nearly circular inspiral, under the influence of dynamical friction in a circum-binary gas disk or three-body interactions in a star cluster. We perform hydrodynamics simulations of this scenario using the smoothed particle hydrodynamics code PHANTOM. We find that under certain circumstances (for initial eccentricity e 0 ≳ 0.4 and penetration factor β = 1, or e 0 < 0.4 and β ≲ 0.67), the mass of the star is slowly stripped away by the BH. We call this gradual tidal disruption a "tidal-peeling event." Additionally, we discover that some low-eccentricity microTDEs (e 0 < 0.4 and β = 1) are a new form of fast luminous transients similar to parabolic microTDEs. Depending on the initial distance and eccentricity of the encounter, these low-eccentricity microTDEs might exhibit significant accretion rates and orbital evolution distinct from those of a typical (eccentric) microTDE.

Keywords: high energy astrophysics; active galactic nuclei; tidal disruption
Lethal Surface Ozone Concentrations Are Possible on Habitable Zone Exoplanets

Ozone (O3) is important for the survival of life on Earth because it shields the surface from ionizing ultraviolet radiation. However, the existence of O3 in Earth's atmosphere is not always beneficial. Resulting from anthropogenic activity, O3 exists as a biologically harmful pollutant at the surface when it forms in the presence of sunlight and other pollutants. As a strong oxidizer, O3 can be lethal to several different organisms; thus, when assessing the potential habitability of an exoplanet, a key part is determining whether toxic gases could be present at its surface. Using the Whole Atmosphere Community Climate Model version 6 (WACCM6; a three-dimensional chemistry-climate model), 12 atmospheric simulations of the terrestrial exoplanet TRAPPIST-1 e are performed with a variety of O2 concentrations and assuming two different stellar spectra proposed in the literature. Four atmospheric simulations of the exoplanet Proxima Centauri b are also included. Some scenarios for both exoplanets exhibit time-averaged surface O3 mixing ratios exceeding harmful levels of 40 ppbv, with 2120 ppbv the maximum concentration found in the cases simulated. These concentrations are toxic and can be fatal to most life on Earth. In other scenarios O3 remains under harmful limits over a significant fraction of the surface, despite there being present regions that may prove inhospitable. In the case in which O3 is detected in a terrestrial exoplanet's atmosphere, determining the surface concentration is an important step when evaluating a planet's habitability.

Keywords: exoplanets; habitable planets; exoplanet atmospheres; exoplanet atmospheric composition
Evaluating the Reliability of a Simple Method to Map the Magnetic Field Azimuth in the Solar Chromosphere

The Zeeman effect is of limited utility for probing the magnetism of the quiet solar chromosphere. The Hanle effect in some spectral lines is sensitive to such magnetism, but the interpretation of the scattering polarization signals requires taking into account that the chromospheric plasma is highly inhomogeneous and dynamic (i.e., that the magnetic field is not the only cause of symmetry breaking). Here we investigate the reliability of a well-known formula for mapping the azimuth of chromospheric magnetic fields directly from the scattering polarization observed in the Ca II 8542 Å line, which is typically in the saturation regime of the Hanle effect. To this end, we use the Stokes profiles of the Ca II 8542 Å line computed with the PORTA radiative transfer code in a three-dimensional (3D) model of the solar chromosphere, degrading them to mimic spectropolarimetric observations for a range of telescope apertures and noise levels. The simulated observations are used to obtain the magnetic field azimuth at each point of the field of view, which we compare with the actual values within the 3D model. We show that, apart from intrinsic ambiguities, the method provides solid results. Their accuracy depends more on the noise level than on the telescope diameter. Large-aperture solar telescopes, like DKIST and EST, are needed to achieve the required polarimetric sensitivity using reasonable exposure times.

Keywords: solar chromosphere; polarimetry; astronomy data analysis; solar magnetic fields; radiative transfer
Measuring Galaxy Abundance and Clustering at High Redshift from Incomplete Spectroscopic Data: Tests on Mock Catalogs

The number density and correlation function of galaxies are two key quantities to characterize the distribution of the observed galaxy population. High-z spectroscopic surveys, which usually involve complex target selection and are incomplete in redshift sampling, present both opportunities and challenges to measure these quantities reliably in the high-z Universe. Using realistic mock catalogs, we show that target selection and redshift incompleteness can lead to significantly biased results, especially due to the flux-limit selection criteria. We develop a new method to correct the flux-limit effect, using information provided by the parent photometric data from which the spectroscopic sample is constructed. Our tests using realistic mock samples show that the method is able to reproduce the true stellar mass function and correlation function reliably. Mock catalogs are constructed for the existing zCOSMOS and VIPERS surveys, as well as for the forthcoming Prime Focus Spectrograph (PFS) galaxy evolution survey. The same set of mock samples are used to quantify the total variance expected for different sample sizes. We find that the total variance decreases very slowly when the survey area reaches about 4 deg2 for the abundance and about 8 deg2 for the clustering, indicating that the cosmic variance is no longer the dominant source of error for PFS-like surveys. We also quantify the improvements expected in the PFS-like galaxy survey relative to zCOSMOS and VIPERS surveys.

Keywords: galaxy abundances; two-point correlation function; redshift surveys; high-redshift galaxies
The Cosmic Ultraviolet Baryon Survey (CUBS). VII. On the Warm-hot Circumgalactic Medium Probed by O VI and Ne VIII at 0.4 ≲ z ≲ 0.7

This paper presents a newly established sample of 103 unique galaxies or galaxy groups at 0.4 ≲ z ≲ 0.7 from the Cosmic Ultraviolet Baryon Survey (CUBS) for studying the warm-hot circumgalactic medium (CGM) probed by both O VI and Ne VIII absorption. The galaxies and associated neighbors are identified at <1 physical Mpc from the sightlines toward 15 CUBS QSOs at z QSO ≳ 0.8. A total of 30 galaxies or galaxy groups exhibit associated O VI λ λ 1031, 1037 doublet absorption within a line-of-sight velocity interval of ±250 km s‑1, while the rest show no trace of O VI to a detection limit of . Meanwhile, only five galaxies or galaxy groups exhibit the Ne VIII λ λ 770, 780 doublet absorption, down to a limiting column density of . These O VI- and Ne VIII-bearing halos reside in different galaxy environments with stellar masses ranging from to ≈11.5. The warm-hot CGM around galaxies of different stellar masses and star formation rates exhibits different spatial profiles and kinematics. In particular, star-forming galaxies with show a significant concentration of metal-enriched warm-hot CGM within the virial radius, while massive quiescent galaxies exhibit flatter radial profiles of both column densities and covering fractions. In addition, the velocity dispersion of O VI absorption is broad with σ υ > 40 km s‑1 for galaxies of within the virial radius, suggesting a more dynamic warm-hot halo around these galaxies. Finally, the warm-hot CGM probed by O VI and Ne VIII is suggested to be the dominant phase in sub-L* galaxies with based on their high ionization fractions in the CGM.

Keywords: surveys; circumgalactic medium; quasar absorption line spectroscopy; galaxy evolution
Quantitative Criteria for Defining Planets

The current International Astronomical Union (IAU) definition of "planet" is problematic because it is vague and excludes exoplanets. Here, we describe aspects of quantitative planetary taxonomy and examine the results of unsupervised clustering of solar system bodies to guide the development of possible classification frameworks. Two unsurprising conclusions emerged from the clustering analysis: (1) satellites are distinct from planets and (2) dynamical dominance is a natural organizing principle for planetary taxonomy. To generalize an existing dynamical dominance criterion, we adopt a universal clearing timescale applicable to all central bodies (brown dwarfs, stars, and stellar remnants). Then, we propose two quantitative, unified frameworks to define both planets and exoplanets. The first framework is aligned with both the IAU definition of planet in the solar system and the IAU working definition of an exoplanet. The second framework is a simpler mass-based framework that avoids some of the difficulties ingrained in current IAU recommendations.

Keywords: solar system planets; exoplanets; natural satellites (solar system); orbits; planetary dynamics; classification; classification systems; clustering; dwarf planets; accretion
High-resolution [O I] Line Spectral Mapping of TW Hya Consistent with X-Ray-driven Photoevaporation

Theoretical models indicate that photoevaporative and magnetothermal winds play a crucial role in the evolution and dispersal of protoplanetary disks and affect the formation of planetary systems. However, it is still unclear what wind-driving mechanism is dominant or if both are at work, perhaps at different stages of disk evolution. Recent spatially resolved observations by Fang et al. of the [O I] 6300 Å spectral line, a common disk wind tracer in TW Hya, revealed that about 80% of the emission is confined to the inner few astronomical units of the disk. In this work, we show that state-of-the-art X-ray-driven photoevaporation models can reproduce the compact emission and the line profile of the [O I] 6300 Å line. Furthermore, we show that the models also simultaneously reproduce the observed line luminosities and detailed spectral profiles of both the [O I] 6300 Å and the [Ne II] 12.8 μm lines. While MHD wind models can also reproduce the compact radial emission of the [O I] 6300 Å line, they fail to match the observed spectral profile of the [O I] 6300 Å line and underestimate the luminosity of the [Ne II] 12.8 μm line by a factor of 3. We conclude that, while we cannot exclude the presence of an MHD wind component, the bulk of the wind structure of TW Hya is predominantly shaped by a photoevaporative flow.

Keywords: protoplanetary disks; computational astronomy; classical t tauri stars
Hotter than Expected: Hubble Space Telescope (HST)/WFC3 Phase-resolved Spectroscopy of a Rare Irradiated Brown Dwarf with Strong Internal Heat Flux

With infrared flux contrasts larger than typically seen in hot Jupiter, tidally locked white dwarf-brown dwarf binaries offer a superior opportunity to investigate atmospheric processes in irradiated atmospheres. NLTT5306 is such a system, with a M BD = 52 ± 3 M Jup brown dwarf, orbiting a T eff = 7756 ± 35 K white dwarf with an ultra-short period of ~102 minutes. We present Hubble Space Telescope/Wide Field Camera 3 spectroscopic phase curves of NLTT5306, consisting of 47 spectra from 1.1 to 1.7 μm with an average signal-to-noise ratio ~ 65 per wavelength. We extracted the phase-resolved spectra of the brown dwarf NLTT5306B, finding a small <100 K day-night temperature difference (~5% of the average day-side temperature). Our best-fit model phase curves revealed a complex wavelength-dependence on amplitudes and relative phase offsets, suggesting longitudinal-vertical atmospheric structure. The night-side spectrum was well fit by a cloudy, nonirradiated atmospheric model while the day side was best matched by a cloudy, weakly irradiated model. Additionally, we created a simple radiative energy redistribution model of the atmosphere and found evidence for efficient day-to-night heat redistribution and a moderately high Bond albedo. We also discovered an internal heat flux much higher than expected given the published system age, leading to an age reassessment that resulted in NLTT5306B most likely being much younger. We find that NLTT5306B is the only known significantly irradiated brown dwarf where the global temperature structure is not dominated by external irradiation, but rather its own internal heat. Our study provides an essential insight into the drivers of global circulation and day-to-night heat transport as a function of irradiation, rotation rate, and internal heat.

Keywords: brown dwarfs; exoplanet atmospheres; white dwarf stars; hot jupiters
Difference of Intermittency between Electric Field and Magnetic Field Fluctuations from Ion Scale Down to Sub-electron Scale in the Magnetosheath Turbulence

We use the measurements from the Magnetospheric MultiScale spacecraft to study the intermittency of the magnetic field (B-field) and electric field (E-field) fluctuations from ion scales (around 1 Hz in the spacecraft frame) to sub-electron scales (about 1000Hz) in the magnetosheath. For the first time, this study shows remarkable differences of intermittent properties between these two fields: (1) The multiorder structure functions of E-field trace fluctuations are more flattened as compared to those of B-field trace fluctuations. (2) The flatness of E-field fluctuations increases monotonically with decreasing scales and eventually exceeds 100 at 1000 Hz, whereas the flatness of B-field fluctuations does not rise so high (less than 100) and tends to fall off at frequencies larger than 1000 Hz. (3) It is revealed that ζ(p) monotonically and quasi-linearly increases with increasing p for B-field fluctuations even at sub-electron scales. However, ζ(p) for E-field is concave, turning over at around p = 2 from increasing to decreasing trends. We quantitatively analyze and find that, with decreasing scales (defined as τ), the variance of $\mathrm{ln}\sigma $ (defined as λ2), where σ is the local standard deviation, increases much more slowly than the most probable $\mathrm{ln}\sigma $ (defined as μ) decreases (I.e., $\left|\tfrac{d{\lambda }^{2}}{d\mathrm{ln}\tau }\right|\ll \left|\tfrac{d\mu }{d\mathrm{ln}\tau }\right|$ ) for the B-field case, while the changing rate of the two quantities are of the same order $(-\tfrac{d{\lambda }^{2}}{d\mathrm{ln}\tau }\approx \tfrac{1}{3}\tfrac{d\mu }{d\mathrm{ln}\tau })$ for the E-field case. These results indicate the distinct intermittency nature between magnetic and electric fields and impose a constraint on theoretical turbulence models.

Keywords: interplanetary turbulence; planetary bow shocks
State-to-state Rate Constants for the H + LiH(v0 = 0, j0 = 0) Reaction: An Accurate Nonadiabatic Dynamical Study

The state-to-state rate constants for hydrogen abstraction, nonadiabatic hydrogen abstraction, and exchange channels of the H + LiH reaction have been studied in the temperature range from 10 to 5000 K by using the nonadiabatic time-dependent wave packet method. The total and vibrational state-resolved rate constants of the H + LiH (v0 = 0, j0 = 0) → Li(22S) + H2 reaction are calculated and compared with previous adiabatic values. The results indicated that adiabatic values always overestimate the rate constant due to the nonadiabatic effect not being considered. In addition, the ratio of adiabatic vibrational state-resolved rate constants versus that of nonadiabatic ones is calculated for the hydrogen abstraction channel. This reflects that the nonadiabatic effect is mainly focused on the low-lying vibrational states. Moreover, the rovibrational state-resolved rate constants show that the largest population of product is located at (v' = 2, j' = 11), (v' = 0, j' = 5), and (v' = 0, j' = 6) for the hydrogen abstraction, nonadiabatic hydrogen abstraction and exchange channels, respectively. The total and vibrational state-resolved rate constants of the Li(22P) → Li(22S) quenching process are also calculated in the temperature range up to 5000 K. The results show that when the temperature is lower than 200 K, the quenching efficiency increases rapidly, but with the further increase of temperature, the quenching efficiency hardly changes.

Keywords: early universe; recombination (cosmology); theoretical models; galaxies
Testing the Kerr Black Hole Hypothesis with GX 339-4 by a Combined Analysis of Its Thermal Spectrum and Reflection Features

We analyze simultaneous observations with NuSTAR and Swift of the black hole binary GX 339-4 in which we clearly detect both a strong thermal component and prominent relativistic reflection features. We employ nkbb and relxill_nk, which are the state of the art of, respectively, the thermal and reflection models to test the Kerr black hole hypothesis. We obtain unprecedented precise measurements of the Johannsen deformation parameter α13: ${\alpha }_{13}=-{0.012}_{-0.039}^{+0.011}$ (lamppost coronal geometry) and ${\alpha }_{13}=-{0.010}_{-0.018}^{+0.024}$ (broken power-law emissivity profile) at a 90% confidence level, where the Kerr metric corresponds to α13 = 0. We investigate the systematic uncertainties by fitting the data with different models.

Keywords: kerr metric; astrophysical black holes; stellar mass black holes; x-ray astronomy