Sazuna/UAT_keywords huggingface dataset:
D/H Ratio in the Interiors of Rocky Protoplanets Accreting in the Solar Nebula. The deuterium/hydrogen (D/H) ratio of primordial water partitioned into a planetary interior seems to be different on Earth and Mars. Water from volcanic rocks originating from Earth's deep mantle has a low D/H ratio with high 3He/4He ratios, implying that it was inherited partially from the solar nebula. In contrast, the D/H ratio of water in the Martian meteorites considered to represent the mantle does not trend toward that of the solar nebula. These differences may be owing to differences in the types of atmospheric structures formed on protoplanets accreting in the solar nebula. Using a 1D radiative-equilibrium model, we analyze the thermal structure of a hybrid-type protoatmosphere in which the solar nebula component dominates the upper layer while a degassed component dominates the lower layer. Our analysis implies Mars-sized protoplanets maintain a hybrid-type protoatmosphere and the D/H ratio of the lower atmosphere resembles that of the building blocks. Conversely, when the mass is larger than Mars-sized, the compositional stratification is collapsed by convective mixing of the solar nebula component with the degassed component, and the D/H ratio approaches that of the solar nebula. This tendency becomes stronger when the planetary mass is larger. If water vapor is distributed through a magma ocean into the planetary interior, Mars-sized protoplanets are likely to reflect the D/H ratios of the building blocks, while larger protoplanets are likely to have acquired a solar-nebula-like D/H ratio.

Keywords: Mars, Planetary atmospheres, Earth (planet), Planetary science, Planet formation
Habitable Zones around Almost Extremely Spinning Black Holes (Black Sun Revisited). We analyzed the thermodynamics of hypothetical exoplanets at very low Keplerian circular orbits in close vicinity of rapidly spinning supermassive black holes. Such black hole exoplanets are heated by strongly blueshifted and focused flux of the incoming cosmic microwave background (CMB) and cooled by the cold part of the local sky containing the black hole shadow. This gives rise to a temperature difference, which can drive processes far from thermodynamic equilibrium in a hypothetical life form inhabiting black hole exoplanets, similar to the case of a planet heated by the radiation of the parent star and cooled by the night sky. We found that for a narrow range of radii of very low Keplerian circular orbits and for very high spin of a supermassive black hole, the temperature regime of the black hole exoplanets corresponds to the habitable zone around standard stars. The thermodynamics of black hole exoplanets therefore, in principle, does not exclude the existence of life based on known biology. The peak of the multiblackbody spectral profile of the CMB heating the exoplanet is located in the ultraviolet band, but a significant fraction of the flux comes also in the visible and infrared bands. The minimum mass of a black hole ensuring the resistance to tidal disruption of an Earth-like exoplanet orbiting in the habitable zone is estimated to 1.63 × 108 m⊙.

Keywords: Supermassive black holes, Exoplanets, Kerr black holes, Cosmic microwave background radiation, Gravitational lensing
Machine-learning Inference of the Interior Structure of Low-mass Exoplanets. We explore the application of machine-learning based on mixture density neural networks (MDNs) to the interior characterization of low-mass exoplanets up to 25 Earth masses constrained by mass, radius, and fluid Love number, k2. We create a data set of 900,000 synthetic planets, consisting of an iron-rich core, a silicate mantle, a high-pressure ice shell, and a gaseous H/He envelope, to train a MDN using planetary mass and radius as inputs to the network. For this layered structure, we show that the MDN is able to infer the distribution of possible thicknesses of each planetary layer from mass and radius of the planet. This approach obviates the time-consuming task of calculating such distributions with a dedicated set of forward models for each individual planet. While gas-rich planets may be characterized by compositional gradients rather than distinct layers, the method presented here can be easily extended to any interior structure model. The fluid Love number k2 bears constraints on the mass distribution in the planets' interiors and will be measured for an increasing number of exoplanets in the future. Adding k2 as an input to the MDN significantly decreases the degeneracy of the possible interior structures. In an open repository, we provide the trained MDN to be used through a Python Notebook.

Keywords: Planetary theory, Exoplanets, Neural networks, Computational methods, Exoplanet structure, Planetary interior
Dense Cores, Filaments, and Outflows in the S255IR Region of High-mass Star Formation. We investigate at a high angular resolution the spatial and kinematic structure of the S255IR high-mass star-forming region, which demonstrated recently the first disk-mediated accretion burst in the massive young stellar object. The observations were performed with the Atacama Large Millimeter/submillimeter Array (ALMA) in Band 7 at an angular resolution of ∼ 0"1, which corresponds to ∼180 au. The 0.9 mm continuum, C34S(7-6) and CCH N = 4 - 3 data show a presence of very narrow (∼1000 au), very dense (n ∼ 107 cm-3), and warm filamentary structures in this area. At least some of them represent apparently dense walls around the high velocity molecular outflow with a wide opening angle from the S255IR-SMA1 core, which is associated with the NIRS3 YSO. This wide-angle outflow surrounds a narrow jet. At the ends of the molecular outflow there are shocks, traced in the SiO(8-7) emission. The SiO abundance there is enhanced by at least 3 orders of magnitude. The CO(3-2) and SiO(8-7) data show a collimated and extended high velocity outflow from another dense core in this area, SMA2. The outflow is bent and consists of a chain of knots, which may indicate periodic ejections possibly arising from a binary system consisting of low- or intermediate-mass protostars. The C34S emission shows evidence of rotation of the parent core. Finally, we detected two new low-mass compact cores in this area (designated as SMM1 and SMM2), which may represent prestellar objects.

Keywords: Interstellar molecules, Stellar jets, Massive stars, Stellar winds, Star formation
The Luminosity Function of Red Supergiants in M31. The mass-loss rates of red supergiant stars (RSGs) are poorly constrained by direct measurements, and yet the subsequent evolution of these stars depends critically on how much mass is lost during the RSG phase. In 2012 the Geneva evolutionary group updated their mass-loss prescription for RSGs with the result that a 20 M⊙ star now loses 10 times more mass during the RSG phase than in the older models. Thus, higher-mass RSGs evolve back through a second yellow supergiant phase rather than exploding as Type II-P supernovae, in accord with recent observations (the so-called "RSG Problem"). Still, even much larger mass-loss rates during the RSG phase cannot be ruled out by direct measurements of their current dust-production rates, as such mass loss is episodic. Here, we test the models by deriving a luminosity function for RSGs in the nearby spiral galaxy, M31, which is sensitive to the total mass loss during the RSG phase. We carefully separate RSGs from asymptotic giant branch stars in the color-magnitude diagram following the recent method exploited by Yang and collaborators in their Small Magellanic Cloud studies. Comparing our resulting luminosity function with that predicted by the evolutionary models shows that the new prescription for RSG mass loss does an excellent job of matching the observations, and we can readily rule out significantly larger values.

Keywords: Luminosity function, Red supergiant stars, Massive stars, Stellar mass loss, Andromeda Galaxy
Eating Planets for Lunch and Dinner: Signatures of Planet Consumption by Evolving Stars. Exoplanets have been observed around stars at all stages of stellar evolution, in many cases orbiting in configurations that will eventually lead to the planets being engulfed or consumed by their host stars, such as hot Jupiters or ultrashort period planets. Furthermore, objects such as polluted white dwarfs provide strong evidence that the consumption of planets by stars is a common phenomenon. This consumption causes several significant changes in the stellar properties, such as changes to the stellar spin, luminosity, chemical composition, or mass-loss processes. Here, we explore this wide variety of effects for a comprehensive range of stellar and planetary masses and stages of stellar evolution, from the main sequence over red giants to white dwarfs. We determine that planet consumption can cause transient luminosity features that last on the order of centuries to millennia, and that the post-consumption stellar spins can often reach breakup speeds. Furthermore, stellar mass loss can be caused by this spin-up, as well as through surface grazing interactions, leading to to the formation of unusual planetary nebula shapes or collimated stellar gas ejections. Our results highlight several observable stellar features by which the presence or previous existence of a planet around a given star can be deduced. This will provide future observational campaigns with the tools to better constrain exoplanet demographics, as well as planetary formation and evolution histories.

Keywords: Tidal interaction, Stellar rotation, Stellar evolution
Initial Results from a Systematic Search for Changing-look Active Galactic Nuclei Selected via Mid-infrared Variability. Changing-look active galactic nuclei (CL AGNs) can yield considerable insight into accretion physics as well as the co-evolution of black holes and their host galaxies. A large sample of these CL AGNs is essential to achieve the latter goal. We propose an effective method to select CL candidates from spectroscopic quasar catalogs using the mid-infrared (MIR) variability information derived from ALLWISE/NEOWISE data releases. Our primary selection criteria include both a large amplitude flux variation and a transition of MIR color from an AGN to a normal galaxy. A pilot spectroscopic follow-up of seven candidates among about 300 candidates selected from Sloan Digital Sky Survey low-redshift (z &lt; 0.5) AGN sample results in three new turn-off CL AGNs and three ambiguous objects for suffering low spectral quality. We expect to obtain hundreds of CL AGNs once full spectroscopic follow-up of the sample is carried out.

Keywords: Active galaxies, Infrared galaxies, Galaxy nuclei
Debris Disks in Multiplanet Systems: Are Our Inferences Compromised by Unseen Planets?. Resolved debris disk features (e.g., warps, offsets, edges and gaps, azimuthal asymmetries, radially thickened rings, scale heights) contain valuable information about the underlying planetary systems, such as the posited planet's mass, semimajor axis, and other orbital parameters. Most existing models assume a single planet is sculpting the disk feature, but recent observations of mature planetary systems (e.g., by radial velocity surveys or Kepler) have revealed that many planets reside in multiplanet systems. Here we investigate if/how planet properties inferred from single-planet models are compromised when multiple planets reside in the system. For each disk feature, we build a two-planet model that includes a planet b with fixed parameters and a planet c with a full range of possible parameters. We investigate these two-planet systems and summarize the configurations for which assuming a single planet (I.e., planet b) leads to significantly flawed inferences of that planet's properties. We find that although disk features are usually primarily dominated by a single planet, when using single-planet models, we are at risk of misinterpreting planet properties by orders of magnitude in extreme cases. Specifically, we are at high risk of misinterpreting planet properties from disk warps; at moderate risk from disk edges and gaps, radially thickened rings, and scale height features; and at low risk from host star-disk center offsets and azimuthal asymmetries. We summarize situations where we can infer the need to use a multiplanet model instead of a single-planet one from disk morphology dissimilarities.

Keywords: Circumstellar matter, Debris disks
Detection of Missing Baryons in Galaxy Groups with Kinetic Sunyaev-Zel'dovich Effect. We present the detection of the kinetic Sunyaev-Zel'dovich effect (kSZE) signals from groups of galaxies as a function of halo mass down to $\mathrm{log}({M}_{500}/{M}_{\odot })\sim 12.3$ using the Planck cosmic microwave background maps and stacking about 40,000 galaxy systems with known positions, halo masses, and peculiar velocities. The signals from groups of different mass are constrained simultaneously to take care of the projection effects of nearby halos. The total kSZE flux within halos estimated implies that the gas fraction in halos is about the universal baryon fraction, even in low-mass halos, indicating that the "missing baryons" are found. Various tests performed show that our results are robust against systematic effects, such as contamination by infrared/radio sources and background variations, beam size effects, and contributions from halo exteriors. Combined with the thermal Sunyaev-Zel'dovich effect, our results indicate that the "missing baryons" associated with galaxy groups are contained in warm-hot media with temperatures between 105 and 106 K.

Keywords: Galaxy clusters, Galaxy dark matter halos, Galaxy formation, Galaxy environments, Galaxy evolution, Galaxy groups, Circumgalactic medium, Extragalactic astronomy
The ELM Survey. VIII. Ninety-eight Double White Dwarf Binaries. We present the final sample of 98 detached double white dwarf (WD) binaries found in the Extremely Low Mass (ELM) Survey, a spectroscopic survey targeting &lt;0.3 M☉ He-core WDs completed in the Sloan Digital Sky Survey footprint. Over the course of the survey we observed ancillary low-mass WD candidates like GD 278, which we show is a P = 0.19 day double WD binary, as well as candidates that turn out to be field blue straggler/subdwarf A-type stars with luminosities too high to be WDs given their Gaia parallaxes. Here, we define a clean sample of ELM WDs that is complete within our target selection and magnitude range 15 &lt; g0 &lt; 20 mag. The measurements are consistent with 100% of ELM WDs being 0.0089 &lt; P &lt; 1.5 day double WD binaries, 35% of which belong to the Galactic halo. We infer that these are mostly He+CO WD binaries given the measurement constraints. The merger rate of the observed He+CO WD binaries exceeds the formation rate of stable mass-transfer AM CVn binaries by a factor of 25, and so the majority of He+CO WD binaries must experience unstable mass transfer and merge. The systems with the shortest periods, such as J0651+2844, are signature LISA verification binaries that can be studied with gravitational waves and light.

Keywords: White dwarf stars, Compact binary stars, Galaxy stellar content
Young Stars near Cometary Globule CG 30 in the Tumultuous Gum Nebula. We have conducted a high-dispersion (R ∼ 34,000) optical spectroscopic study of 10 young stars near the cometary globule CG 30 in the Gum Nebula, a diffuse H II region home to at least 32 cometary globules. All 10 spectroscopically observed stars at the nebula's northern edge are of low mass (spectral types M4.5-K5), have broad Hα emission, and show spectral veiling. Eight of the 10 are classical T Tauri stars. We spectroscopically measure the photospheric properties of CG 30 IRS 4 inside CG 30. Though embedded, CG 30 IRS 4 is T Tauri-like, with relatively slow projected rotation and moderate veiling. Undepleted Li absorptions, strong Hα emissions, and positions well above the main sequence on an H-R diagram suggest that the 10 stars are ≲1 Myr old. Using our measurements, previous spectroscopy, and previous photometry of 11 other young stars in the area, we determine stellar, kinematic, and accretion properties of a total of 21 young stars. Shared radial velocities, proper motions, distances, and ages suggest that 14 of the young stars (including CG 30 IRS 4) are kinematically related to CG 30. From Gaia DR2 distances to six of these stars, we derive a distance of 358.1 ± 2.2 pc to the cometary globule complex CG 30/31/38. The CG 30 association has an accretor fraction of 29% ± 14%, low for quiescent clusters of similar age but consistent with other irradiated clusters. The Gum Nebula's moderate radiation environment ( ${G}_{0}={6.6}_{-2.7}^{+3.2}$ at CG 30) may be strong enough to shorten disk lifetimes.

Keywords: Accretion, Stellar properties, Fundamental parameters of stars, Star forming regions, Young star clusters, Cometary globules, Pre-main sequence stars, Protoplanetary disks, Low mass stars, Pre-main sequence, Stellar accretion disks, Stellar accretion
Evidence for a Dichotomy in the Interior Structures of Jupiter and Saturn from Helium Phase Separation. We examine the comparative thermal evolution of Jupiter and Saturn, applying recent theoretical results for helium's immiscibility in fluid metallic hydrogen. The redistribution of helium in their interiors proceeds very differently for the two planets. We confirm that, based on Jupiter's atmospheric helium depletion as observed in situ by the Galileo entry probe, Jupiter's interior helium has differentiated modestly, and we present models reconciling Jupiter's helium depletion, radius, and heat flow at the solar age. Jupiter's recently revised Bond albedo implies a higher intrinsic flux for the planet, accommodating more luminosity from helium differentiation, such that mildly superadiabatic interiors can satisfy all constraints. The same phase diagram applied to the less massive Saturn predicts dramatic helium differentiation, to the degree that Saturn inevitably forms a helium-rich shell or core, an outcome previously proposed by Stevenson &amp; Salpeter and others. The luminosity from Saturn's helium differentiation is sufficient to extend its cooling time to the solar age, even for adiabatic interiors. This model predicts Saturn's atmospheric helium to be depleted to Y &amp;equals; 0.07 ± 0.01, corresponding to a He/H2 mixing ratio 0.036 ± 0.006. We also show that neon differentiation may have contributed to both planets' luminosity in the past. These results demonstrate that Jupiter and Saturn's thermal evolution can be explained self-consistently with a single physical model, and emphasize that nontrivial helium distributions should be considered in future models for Saturn's internal structure and dynamo.

Keywords: Planetary structure, Saturn, Planetary interior, Jupiter
Reality or Mirage? Observational Test and Implications for the Claimed Extremely Magnified Quasar at z = 6.3. In the last two decades, approximately 200 quasars have been discovered at $z\gt 6$ , hosting active supermassive black holes with masses ${M}_{\bullet }\gtrsim {10}^{9}\,{M}_{\odot }$ . While these sources reflect only the tip of the iceberg of the black hole mass distribution, their detection challenges standard growth models. The most massive $z\gt 6$ black hole that was inferred thus far (J0100+2802, ${M}_{\bullet }\approx 1.2\times {10}^{10}\,{M}_{\odot }$ ) was recently claimed to be lensed, with a magnification factor $\mu =450$ . Here, we perform a consistency check of this claim, finding that the detection of such a source requires a bright-end slope $\beta \geqslant 3.7$ for the intrinsic quasar luminosity function (LF), ${\rm{\Phi }}(L)\propto {L}^{-\beta }$ . Commonly used values of $\beta \sim 2.8$ are rejected at $\gt 3\sigma $ . If the claim is confirmed, it is very unlikely that all the remaining 51 sources in the Sloan Digital Sky Survey sample are not magnified. Furthermore, it suffices that $\gtrsim 25 \% $ of the remaining sources are lensed for the intrinsic LF to differ significantly (I.e., $\gt 3\sigma $ ) from the observed one. The presence of additional extremely magnified sources in the sample would lower the requirement to $\sim 4 \% $ . Our results urge the community to perform more extended multiwavelength searches targeting $z\gt 6$ lensed quasars, also among known samples. This effort could vitally contribute to solving the open problem of the growth of the brightest $z\sim 7$ quasars.

Keywords: Luminosity function, Supermassive black holes, Early universe, Quasars, Strong gravitational lensing, Active galaxies, Reionization
Chandra Observations of High-energy X-Ray Sources Discovered by INTEGRAL. The International Gamma-Ray Astrophysics Laboratory (INTEGRAL) satellite has detected in excess of 1000 sources in the ∼20-100 keV band during its surveys of the sky over the past 17 years. We obtained 5 ks observations of 15 unclassified INTEGRAL Gamma-Ray (IGR) sources with the Chandra X-ray Observatory in order to localize them, to identify optical/IR counterparts, to measure their soft X-ray spectra, and to classify them. For 10 of the IGR sources, we detect Chandra sources that are likely (or in some cases certain) to be the counterparts. IGR J18007-4146 and IGR J15038-6021 both have Gaia parallax distances, placing them at ${2.5}_{-0.4}^{+0.5}$ and ${1.1}_{-0.4}^{+1.5}$ kpc, respectively. We tentatively classify both of them as intermediate polar-type cataclysmic variables. Also, IGR J17508-3219 is likely to be a Galactic source, but it is unclear if it is a Dwarf Nova or another type of transient. For IGR J17118-3155, we provide a Chandra localization, but it is unclear if the source is Galactic or extragalactic. Based on either near-IR/IR colors or the presence of extended near-IR emission, we classify four sources as active galactic nuclei (AGNs; IGR J16181-5407, IGR J16246-4556, IGR J17096-2527, and IGR J19294+1327), and IGR J20310+3835 and IGR J15541-5613 are AGN candidates. In addition, we identified an AGN in the INTEGRAL error circle of IGR J16120-3543 that is a possible counterpart.

Keywords: High mass x-ray binary stars, Galaxy stellar content, Active galactic nuclei, X-ray sources, Cataclysmic variable stars
An Apparently Eccentric Orbit of the Exoplanet WASP-12 b as a Radial Velocity Signature of Planetary-induced Tides in the Host Star. Massive exoplanets on extremely tight orbits, such as WASP-12 b, induce equilibrium tides in their host stars. Following the orbital motion of the planet, the tidal fluid flow in the star can be detected with the radial velocity method. Its signature manifests as the second harmonics of the orbital frequency that mimics a nonzero orbital eccentricity. Using the new radial velocity measurements acquired with the HARPS-N spectrograph at the Telescopio Nazionale Galileo and combining them with the literature data, we show that the apparent eccentricity of WASP-12 b's orbit is nonzero at a 5.8σ level, and the longitude of periastron of this apparently eccentric orbit is close to 270°. This orbital configuration is compatible with a model composed of a circular orbit and a signature of tides raised in the host star. The radial velocity amplitude of those tides was found to be consistent with the equilibrium tide approximation. The tidal deformation is predicted to produce a flux modulation with an amplitude of 80 ppm that could be detected using space-borne facilities.

Keywords: Radial velocity, Exoplanet tides, Hot Jupiters