adsabs/SciX_UAT_keywords huggingface dataset:
Potential for Liquid Water Biochemistry Deep under the Surfaces of the Moon, Mars, and beyond

We investigate the prospects for the past or current existence of habitable conditions deep underneath the surfaces of the Moon and Mars, as well as generic bound and free-floating extrasolar rocky objects. We construct a simple model that takes into account the thermal limits of life as well as the size, surface temperature, and relative radionuclide abundance of a given object and yields the spatial extent of the subsurface habitable region. We also investigate the constraint imposed by pressure on habitability, and show that it is unlikely to rule out the prospects for life altogether. We estimate the maximum biomass that might be sustainable in deep subsurface environments as a function of the aforementioned parameters from an energetic perspective. We find that it might be a few percent that of Earth's subsurface biosphere, and three orders of magnitude smaller than Earth's global biomass, under ideal circumstances. We conclude with a brief exposition of the prevalence of rocky objects with deep biospheres and methods for detecting signatures of biological activity through forthcoming missions to visit the Moon and Mars.

Keywords: mars; the moon; free floating planets; astrobiology; biosignatures; exoplanets; planetary interior
The Behavior of Bp HgMn Stars in the Far UV-Paper 28: HD 110073

The analysis of three spectra of the B8 Mn star HD 110073 recorded by the SWP camera on board the International Ultraviolet Explorer does not reveal any variations of the far ultraviolet spectral energy distribution shortwards of 1800 Å in spectra collected over 8 yr with identical exposure times. The Ga II line at 1414.40 Å is a prominent feature in the mean FUV spectrum of this star. The modeling of the optical line of Ga II at 6334.07 Å yields an overabundance of 1600 times the solar abundance, much lower than previous determinations. The projected rotational velocity ${v}_{{\rm{e}}}\sin \,i$ is close to 15 km s-1. The silicon abundance derived from the Si II line at 6347.10 Å is solar.

Keywords: chemically peculiar stars; mercury-manganese stars
The Effect of the Approach to Gas Disk Gravitational Instability on the Rapid Formation of Gas Giant Planets. II. Quadrupled Spatial Resolution

Observations support the hypothesis that gas disk gravitational instability might explain the formation of massive or wide-orbit gas giant exoplanets. The situation with regard to Jupiter-mass exoplanets orbiting within ∼20 au is more uncertain. Theoretical models yield divergent assessments often attributed to the numerical handling of the gas thermodynamics. Boss used the β cooling approximation to calculate three-dimensional hydrodynamical models of the evolution of disks with initial masses of 0.091 M⊙ extending from 4 to 20 au around 1 M⊙ protostars. The models considered a wide range (1-100) of β cooling parameters and started from an initial minimum Toomre stability parameter of Qi = 2.7 (gravitationally stable). The disks cooled down from initial outer disk temperatures of 180 K to as low as 40 K as a result of the β cooling, leading to fragmentation into dense clumps, which were then replaced by virtual protoplanets (VPs) and evolved for up to ∼500 yr. The present models test the viability of replacing dense clumps with VPs by quadrupling the spatial resolution of the grid once dense clumps form, sidestepping in most cases VP insertion. After at least ∼200 yr of evolution, the new results compare favorably with those of Boss: similar numbers of VPs and dense clumps form by the same time for the two approaches. The results imply that VP insertion can greatly speed disk instability calculations without sacrificing accuracy.

Keywords: hydrodynamical simulations; gravitational instability; exoplanet formation; protoplanetary disks
RC100: Rotation Curves of 100 Massive Star-forming Galaxies at z = 0.6-2.5 Reveal Little Dark Matter on Galactic Scales

We analyze Hα or CO rotation curves extending out to several galaxy effective radii for 100 massive, large, star-forming disk galaxies (SFGs) across the peak of cosmic galaxy star formation (z ~ 0.6-2.5), more than doubling the previous sample presented by Genzel et al. and Price et al. The observations were taken with SINFONI and KMOS integral-field spectrographs at the ESO-Very Large Telescope, LUCI-LBT, NOEMA-IRAM, and Atacama Large Millimeter/submillimeter Array. We fit the major-axis kinematics with beam-convolved, forward models of turbulent rotating disks with bulges embedded in dark matter (DM) halos, including the effects of pressure support. The fraction of dark to total matter within the disk effective radius (R e ~ 5 kpc), f DM(R e) = V 2 DM(R e)/V 2 circ(R e) decreases with redshift: at z ~ 1 (z ~ 2) the median DM fraction is 0.38 ± 0.23 (0.27 ± 0.18), and a third (half) of all galaxies are maximal disks with f DM(R e) < 0.28. DM fractions correlate inversely with the baryonic surface density, and the low DM fractions can be explained with a flattened, or cored, inner DM density distribution. At z ~ 2, there is ≈40% less DM mass on average within R e compared to expected values based on cosmological stellar-mass-halo-mass relations. The DM deficit is more evident at high star formation rate surface densities (≳2.5 M ⊙ yr-1 kpc2) and galaxies with massive bulges (≥1010 M ⊙). A combination of stellar or active galactic nucleus feedback, and/or heating due to dynamical friction, may drive the DM from cuspy into cored mass distributions, pointing to an efficient buildup of massive bulges and central black holes at z ~ 2 SFGs.

Keywords: galaxy evolution; galaxy kinematics; galaxy rotation curves; galaxy dark matter halos; galaxy structure; galaxy dynamics
The Perkins INfrared Exosatellite Survey (PINES). II. Transit Candidates and Implications for Planet Occurrence around L and T Dwarfs

We describe a new transit-detection algorithm designed to detect single-transit events in discontinuous Perkins INfrared Exosatellite Survey (PINES) observations of L and T dwarfs. We use this algorithm to search for transits in 131 PINES light curves and identify two transit candidates: 2MASS J18212815+1414010 (2MASS J1821+1414) and 2MASS J08350622+1953050 (2MASS J0835+1953). We disfavor 2MASS J1821+1414 as a genuine transit candidate due to the known variability properties of the source. We cannot rule out the planetary nature of 2MASS J0835+1953's candidate event and perform follow-up observations in an attempt to recover a second transit. A repeat event has yet to be observed, but these observations suggest that target variability is an unlikely cause of the candidate transit. We perform a Markov Chain Monte Carlo simulation of the light curve and estimate a planet radius ranging from ${4.2}_{-1.6}^{+3.5}{R}_{\oplus }$ to ${5.8}_{-2.1}^{+4.8}{R}_{\oplus }$ , depending on the host's age. Finally, we perform an injection and recovery simulation on our light-curve sample. We inject planets into our data using measured M-dwarf planet occurrence rates and attempt to recover them using our transit-search algorithm. Our detection rates suggest that, assuming M-dwarf planet occurrence rates, we should have roughly a 1% chance of detecting a candidate that could cause the transit depth we observe for 2MASS J0835+1953. If 2MASS J0835+1953 b is confirmed, it would suggest an enhancement in the occurrence of short-period planets around L and T dwarfs in comparison to M dwarfs, which would challenge predictions from planet formation models.

Keywords: surveys; brown dwarfs; l dwarfs; t dwarfs; transit photometry; exoplanet astronomy; infrared photometry
Evidence for a Supergalactic Structure of Magnetic Deflection Multiplets of Ultra-high-energy Cosmic Rays

Evidence for a large-scale supergalactic cosmic-ray multiplet (arrival directions correlated with energy) structure is reported for ultra-high-energy cosmic-ray (UHECR) energies above 1019 eV using 7 years of data from the Telescope Array (TA) surface detector and updated to 10 years. Previous energy-position correlation studies have made assumptions regarding magnetic field shapes and strength, and UHECR composition. Here the assumption tested is that, because the supergalactic plane is a fit to the average matter density of the local large-scale structure, UHECR sources and intervening extragalactic magnetic fields are correlated with this plane. This supergalactic deflection hypothesis is tested by the entire field-of-view (FOV) behavior of the strength of intermediate-scale energy-angle correlations. These multiplets are measured in spherical cap section bins (wedges) of the FOV to account for coherent and random magnetic fields. The structure found is consistent with supergalactic deflection, the previously published energy spectrum anisotropy results of the TA (the Hotspot and Coldspot), and toy-model simulations of a supergalactic magnetic sheet. The seven year data posttrial significance of this supergalactic structure of multiplets appearing by chance, on an isotropic sky, is found by Monte Carlo simulation to be 4.2σ. The 10 years of data posttrial significance is 4.1σ. Furthermore, the starburst galaxy M82 is shown to be a possible source of the TA Hotspot, and an estimate of the supergalactic magnetic field using UHECR measurements is presented.

Keywords: extragalactic magnetic fields; ultra-high-energy cosmic radiation; cosmic rays; high energy astrophysics; astrophysical magnetism; cosmic ray astronomy; cosmic ray sources
Comparing Approximate Bayesian Computation with the Poisson-Likelihood Method for Exoplanet Occurrence Rates

We present Kepler exoplanet occurrence rates inferred with approximate Bayesian computation (ABC). By using the same planet catalog, stellar sample, and characterization of completeness and reliability as Bryson et al. (2020), we are able to provide the first direct comparison of results from ABC to those derived with the popular Poisson-likelihood method. For planets with orbital periods between 50 and 400 days and radii between 0.75 and 2.5 R⊕, we find an integrated occurrence rate ${F}_{0}={0.596}_{-0.099}^{+0.092}$ planets per GK dwarf star. After correcting for reliability against astrophysical false positives and false alarms, we find ${F}_{0}={0.421}_{-0.072}^{+0.086}$ . Our findings agree within 1σ of Bryson et al. (2020), indicating that the results are robust and not method-dependent.

Keywords: exoplanet astronomy; exoplanet catalogs; exoplanet detection methods; transit photometry; astrostatistics; bayesian statistics; astrostatistics strategies
OGLE-2018-BLG-0677Lb: A Super-Earth Near the Galactic Bulge

We report the analysis of the microlensing event OGLE-2018-BLG-0677. A small feature in the light curve of the event leads to the discovery that the lens is a star-planet system. Although there are two degenerate solutions that could not be distinguished for this event, both lead to a similar planet-host mass ratio. We perform a Bayesian analysis based on a Galactic model to obtain the properties of the system and find that the planet corresponds to a super-Earth/sub-Neptune with a mass of ${M}_{\mathrm{planet}}={3.96}_{-2.66}^{+5.88}{M}_{\oplus }$ . The host star has a mass of ${M}_{\mathrm{host}}={0.12}_{-0.08}^{+0.14}\,{M}_{\odot }$ . The projected separation for the inner and outer solutions are ${0.63}_{-0.17}^{+0.20}$ au and ${0.72}_{-0.19}^{+0.23}$ au respectively. At ${\rm{\Delta }}{\chi }^{2}={\chi }^{2}(1{\rm{L}}1{\rm{S}})-{\chi }^{2}(2{\rm{L}}1{\rm{S}})=46$ , this is by far the lowest Δχ2 for any securely detected microlensing planet to date, a feature that is closely connected to the fact that it is detected primarily via a "dip" rather than a "bump."

Keywords: gravitational microlensing exoplanet detection; astrostatistics strategies; super earths; exoplanets
Giant Outer Transiting Exoplanet Mass (GOT 'EM) Survey. II. Discovery of a Failed Hot Jupiter on a 2.7 Yr, Highly Eccentric Orbit

Radial velocity (RV) surveys have discovered giant exoplanets on au-scale orbits with a broad distribution of eccentricities. Those with the most eccentric orbits are valuable laboratories for testing theories of high-eccentricity migration. However, few such exoplanets transit their host stars, thus removing the ability to apply constraints on formation from their bulk internal compositions. We report the discovery of Kepler-1704 b, a transiting 4.15 MJ giant planet on a 988.88 day orbit with an extreme eccentricity of ${0.921}_{-0.015}^{+0.010}$ . Our decade-long RV baseline from the Keck I telescope allows us to measure the orbit and bulk heavy-element composition of Kepler-1704 b and place limits on the existence of undiscovered companions. A failed hot Jupiter, Kepler-1704 b was likely excited to high eccentricity by scattering events that possibly began during its gas accretion phase. Its final periastron distance was too large to allow for tidal circularization, so now it orbits its host from distances spanning 0.16-3.9 au. The maximum difference in planetary equilibrium temperature resulting from this elongated orbit is over 700 K. A simulation of the thermal phase curve of Kepler-1704 b during periastron passage demonstrates that it is a remarkable target for atmospheric characterization from the James Webb Space Telescope, which could potentially also measure the planet's rotational period as the hot spot from periastron rotates in and out of view. Continued characterization of the Kepler-1704 system promises to refine theories explaining the formation of hot Jupiters and cool giant planets like those in the solar system. * Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

Keywords: exoplanet migration; exoplanet formation; transit photometry; extrasolar gaseous planets; radial velocity
Signatures of Recent Cosmic-Ray Acceleration in the High-latitude Gamma-Ray Sky

Cosmic-ray (CR) sources temporarily enhance the relativistic particle density in their vicinity over the background distribution accumulated from the Galaxy-wide past injection activity and propagation. If individual sources are close enough to the solar system, their localized enhancements may present as features in the measured spectra of the CRs and in the associated secondary electromagnetic emissions. Large-scale loop-like structures visible in the radio sky are possible signatures of such nearby CR sources. If so, these loops may also have counterparts in the high-latitude γ-ray sky. Using ~10 yr of data from the Fermi Large Area Telescope, applying Bayesian analysis including Gaussian Processes, we search for extended enhanced emission associated with putative nearby CR sources in the energy range from 1 GeV to 1 TeV for the sky region ∣b∣ > 30°. We carefully control the systematic uncertainty due to imperfect knowledge of the interstellar gas distribution. Radio Loop IV is identified for the first time as a γ-ray emitter, and we also find significant emission from Loop I. Strong evidence is found for asymmetric features about the Galactic l = 0° meridian that may be associated with parts of the so-called "Fermi Bubbles," and some evidence is also found for γ-ray emission from other radio loops. Implications for the CRs producing the features and possible locations of the sources of the emissions are discussed.

Keywords: cosmic ray sources; galactic cosmic rays; interstellar medium; gamma-ray astronomy; high-energy cosmic radiation; galaxy structure
Study of the Observation Sensitivity of Gamma-Ray Bursts for the HADAR Project

The High Altitude Detection of Astronomical Radiation (HADAR) is a novel wide-field Cherenkov Telescope. It is designed for gamma-ray astronomy in the energy range of 10 GeV to 100 TeV, with gamma-ray bursts (GRBs) being one of its primary research focuses. To assess its complementary capabilities, this study first presents the Crab sensitivity of HADAR. Then, to compare the sensitivity of GRBs, the observation time for all experiments is standardized to 100 s. To clearly demonstrate HADAR's advantages, we estimate its observational results with a 221009A-like GRB. The study found that HADAR is capable of more comprehensively recording the bending and absorption of self-Compton radiation, which is expected to fill observational gaps in space- and ground-based experiments. We anticipate that this facility will ensure a large statistical GRB sample and advance our understanding of GRBs.

Keywords: gamma-ray bursts; cosmic rays; gamma-ray telescopes
Equilibrium Eccentricity of Accreting Binaries

Using high-resolution hydrodynamics simulations, we show that equal-mass binaries accreting from a circumbinary disk evolve toward an orbital eccentricity of e ≃ 0.45, unless they are initialized on a nearly circular orbit with e ≲ 0.08, in which case they further circularize. The implied bi-modal eccentricity distribution resembles that seen in post-AGB stellar binaries. Large accretion spikes around periapse impart a tell-tale, quasiperiodic, bursty signature on the light curves of eccentric binaries. We predict that intermediate-mass and massive black hole binaries at z ≲ 10 entering the LISA band will have measurable eccentricities in the range of e ≃ 10-3 - 10-2, if they have experienced a gas-driven phase. On the other hand, GW190521 would have entered the LIGO/Virgo band with undetectable eccentricity ∼10-6 if it had been driven into the gravitational-wave regime by a gas disk.

Keywords: eccentricity; binary stars; astrophysical black holes; gravitational wave sources; hydrodynamical simulations
Multimode δ Sct stars from the Zwicky Transient Facility Survey

We obtain the largest catalog of multimode δ Sct stars in the northern sky to date using the Zwicky Transient Facility (ZTF) Data Release 20. The catalog includes 2254 objects, of which 2181 are new to our study. Among these multimode δ Sct stars, 2142 objects are double-mode δ Sct, while 109 objects are triple-mode δ Sct and three are quadruple-mode δ Sct. By analyzing the light curves in the r and g bands of the ZTF, we determine the basic parameters of multimode δ Sct stars, including the periods and amplitudes. Periods are checked by comparison with the Optical Gravitational Lensing Experiment catalog of double-mode δ Sct stars. On the Petersen diagram, multimode δ Sct stars form six sequences. We find that in Galactic coordinates, the periods of 1O/F double-mode δ Sct stars at high latitudes are shorter than those of 1O/F double-mode δ Sct stars in the disk, due to metallicity variations. In the future, our catalog can be used to establish the period–luminosity relation and the period–metallicity relation of double-mode δ Sct stars, and to study the Galactic structure.

Keywords: periodic variable stars; pulsating variable stars; delta scuti variable stars; stellar oscillations; distance indicators; astronomy databases
Explosion Mechanism of Core-collapse Supernovae: Role of the Si/Si-O Interface

We present a simple criterion to predict the explodability of massive stars based on the density and entropy profiles before collapse. If a pronounced density jump is present near the Si/Si-O interface, the star will likely explode. We develop a quantitative criterion by using ~1300 1D simulations where ν-driven turbulence is included via time-dependent mixing-length theory. This criterion correctly identifies the outcome of the supernova more than 90% of the time. We also find no difference in how this criterion performs on two different sets of progenitors, evolved using two different stellar evolution codes: FRANEC and KEPLER. The explodability as a function of mass of the two sets of progenitors is very different, showing: (i) that uncertainties in the stellar evolution prescriptions influence the predictions of supernova explosions; (ii) the most important properties of the pre-collapse progenitor that influence the explodability are its density and entropy profiles. We highlight the importance that ν-driven turbulence plays in the explosion by comparing our results to previous works.

Keywords: supernova dynamics; core-collapse supernovae; supernovae; supernova neutrinos; gravitational collapse; massive stars
Implications of Flat Optically Thick Microwave Spectra in Solar Flares for Source Size and Morphology

The study aims to examine the spectral dynamics of the low-frequency, optically thick gyrosynchrotron microwave emission in solar flares to determine the characteristics of the emitting source. We present the high-resolution spectra of a set of microwave bursts observed by the Expanded Owens Valley Solar Array (EOVSA) during its commissioning phase in the 2.5-18 GHz frequency range with 1 second time resolution. Out of the 12 events analyzed in this study, nine bursts exhibit a direct decrease with time in the optically thick spectral index αl, an indicator of source morphology. Particularly, five bursts display a "flat" spectrum (αl ≤ 1.0) compared to that expected for a homogeneous/uniform source (αl ≈ 2.9). These flat spectra at low frequencies (<10 GHz) can be defined as the emission from a spatially inhomogeneous source with a large area and/or with multiple emission components. In a subset of six events with partial cross-correlation data, both the events with flat spectra show a source size of ~120″ at 2.6-3 GHz. Modeling based on inhomogeneity supports the conclusion that multiple discrete sources can only reproduce a flat spectrum. We report that these flat spectra appear predominantly in the decay phase and typically grow flatter over the duration in most of the bursts, which indicates an increasing inhomogeneity and complexity of the emitting volume as the flare progresses. This large volume of flare emission filled with the trapped energetic particles is often invisible in other wavelengths, like hard X-rays, presumably due to the collisionless conditions in these regions of low ambient density and magnetic field strength.

Keywords: solar flare spectra; solar flares; solar radio flares; solar radio emission; non-thermal radiation sources; solar coronal radio emission; active solar corona
Initiation and Early Kinematic Evolution of Solar Eruptions

We investigate the initiation and early evolution of 12 solar eruptions, including six active-region hot channel and six quiescent filament eruptions, which were well observed by the Solar Dynamics Observatory, as well as by the Solar Terrestrial Relations Observatory for the latter. The sample includes one failed eruption and 11 coronal mass ejections, with velocities ranging from 493 to 2140 km s-1. A detailed analysis of the eruption kinematics yields the following main results. (1) The early evolution of all events consists of a slow-rise phase followed by a main-acceleration phase, the height-time profiles of which differ markedly and can be best fit, respectively, by a linear and an exponential function. This indicates that different physical processes dominate in these phases, which is at variance with models that involve a single process. (2) The kinematic evolution of the eruptions tends to be synchronized with the flare light curve in both phases. The synchronization is often but not always close. A delayed onset of the impulsive flare phase is found in the majority of the filament eruptions (five out of six). This delay and its trend to be larger for slower eruptions favor ideal MHD instability models. (3) The average decay index at the onset heights of the main acceleration is close to the threshold of the torus instability for both groups of events (although, it is based on a tentative coronal field model for the hot channels), suggesting that this instability initiates and possibly drives the main acceleration.

Keywords: solar coronal mass ejections; stellar coronal mass ejections; solar storm