adsabs/SciX_UAT_keywords huggingface dataset:
Oxygen Ablation during Atmospheric Entry: Its Influence on the Isotopic Composition of Micrometeorites

Micrometeorites (MMs) offer glimpses of the diverse nature of parent bodies that accreted during the first few million years after the formation of the proto-Sun. The present work explores this by evaluating the ablation of oxygen from MMs during atmospheric entry, and the resulting effect on the oxygen isotopic composition. A Chemical ABlation MODel (CABMOD) combined with the measured oxygen isotope composition of MMs, shows that at temperatures below 2000 K a relatively small percentage (~0%-5%) of oxygen ablates; the temperature is nevertheless sufficient to induce diffusion among the different silicate phases of MMs. The large δ 18O composition found within different MM types with low oxygen ablation indicates that exchange with atmospheric oxygen is insignificant during entry. Therefore, to explain the large δ 18O values existing in heated MMs, where oxygen ablation is less than a few percent, we propose that these particles are from distinct C-type asteroids that have undergone nebular gas exchange and/or aqueously altered in their parent bodies. This is supported by the evidence from unmelted MMs that have not exchanged oxygen during atmospheric entry or undergone ablation, but have large δ 18O values. However, the oxygen isotope composition of different types of cosmic spherules does not appear to vary systematically with temperature and could be due to the heterogeneity of their precursors. This investigation overall provides insights into the oxygen ablation of the particles during atmospheric entry, oxygen isotopic alteration, and the reservoirs of the diverse extraterrestrial objects that prevailed in the early solar system.

Keywords: micrometeoroids; meteoroids
A Catalog of Habitable Zone Exoplanets

The search for habitable planets has revealed many planets that can vary greatly from an Earth analog environment. These include highly eccentric orbits, giant planets, different bulk densities, relatively active stars, and evolved stars. This work catalogs all planets found to reside in the habitable zone (HZ) and provides HZ boundaries, orbit characterization, and the potential for spectroscopic follow-up observations. Demographics of the HZ planets are compared with a full catalog of exoplanets. Extreme planets within the HZ are highlighted, and how their unique properties may affect their potential habitability is discussed. Kepler-296 f is the most eccentric ≤2 R ⊕ planet that spends 100% of its orbit in the HZ. HD 106270 b and HD 38529 c are the most massive planets (≤13 M J) that orbit within the HZ, and are ideal targets for determining the properties of potential hosts of HZ exomoons. These planets, along with the others highlighted, will serve as special edge cases to the Earth-based scenario, and observations of these targets will help test the resilience of habitability outside the standard model. The most promising observational HZ target that is known to transit is GJ 414 A b. Of the transiting, ≤2 R ⊕ HZ planets, LHS 1140 b, TRAPPIST-1 d, and K2-3 d are the most favorable. Of the nontransiting HZ planets, HD 102365 b and 55 Cnc f are the most promising, and the best nontransiting candidates that have ≤2 R ⊕ are GJ 667 C c, Wolf 1061 c, Ross 508 b, Teegarden's Star b, and Proxima Cen b.

Keywords: exoplanet astronomy; exoplanet catalogs; exoplanets; planet hosting stars; habitable planets; habitable zone; astrobiology; radial velocity; transits; observational astronomy
Giant Impacts and Debris Disk Morphology

Certain debris disks have nonaxisymmetric shapes in scattered light which are unexplained. The appearance of a disk depends on how its constituent Keplerian ellipses are arranged. The more the ellipses align apsidally, the more nonaxisymmetric the disk. Apsidal alignment is automatic for fragments released from a catastrophic collision between solid bodies. We synthesize scattered light images, and thermal emission images, of such giant impact debris. Depending on the viewing geometry, and if and how the initial apsidal alignment is perturbed, the remains of a giant impact can appear in scattered light as a one-sided or two-sided "fork," a lopsided "needle," or a set of "double wings." The last shape is difficult to reproduce in other scenarios involving gravitational forcing or gas drag, which do not align orbits as well. We compare our images with observations and offer a scorecard assessing whether the scattered light asymmetries in HD 15115, HD 32297, HD 61005, HD 111520, HD 106906, β Pic, and AU Mic are best explained by giant impacts, gravitational perturbations, or sculpting by the interstellar medium.

Keywords: debris disks; circumstellar disks; exoplanet dynamics; asteroids; hirayama families
WR6: A Rejuvenated Runaway Star

WR6 is considered as a runaway star because of its large separation from the Galactic mid-plane. In this note, we use Gaia DR2 data on WR6 and the systemic velocity of the nebula around this star to derive the space velocity of WR6 of ${38.1}_{-6.5}^{+9.0}\,\,\mathrm{km}\,{{\rm{s}}}^{-1}$ , confirming that this star is indeed a runaway. Possible implications of this finding are discussed.

Keywords: circumstellar matter; evolved stars; massive stars; runaway stars; wolf-rayet stars
The Behavior of Bp Si Stars in the far-UV-Paper III: HD 112413

The analysis of eleven spectra of the SiEuCr star HD 112413 recorded by the SWP camera on board the International Ultraviolet Explorer reveals variations of the far-ultraviolet spectral energy distribution over a time interval of three days and five hours. Large variations are present shortwards of 2000 Å which can be partly attributed to variations of the lines and continuum of Si II. This confirms that silicon and iron-peak elements are not distributed in a uniform manner over the surface. The FUV variations occur in antiphase with the variations of the optical brightness which probably reflects redistribution of the FUV flux toward optical wavelengths as the star rotates.

Keywords: chemically peculiar stars; bp stars
Giant Planet Engulfment by Evolved Giant Stars: Light Curves, Asteroseismology, and Survivability

About ten percent of Sun-like (1-2 M ⊙) stars will engulf a 1-10 M J planet as they expand during the red giant branch (RGB) or asymptotic giant branch (AGB) phase of their evolution. Once engulfed, these planets experience a strong drag force in the star's convective envelope and spiral inward, depositing energy and angular momentum. For these mass ratios, the inspiral takes ~10-102 yr (~102-103 orbits); the planet undergoes tidal disruption at a radius of ~1 R ⊙. We use the Modules for Experiments in Stellar Astrophysics (MESA) software instrument to track the stellar response to the energy deposition while simultaneously evolving the planetary orbit. For RGB stars, as well as AGB stars with M p ≲ 5 M J planets, the star responds quasi-statically but still brightens measurably on a timescale of years. In addition, asteroseismic indicators, such as the frequency spacing or rotational splitting, differ before and after engulfment. For AGB stars, engulfment of an M p ≳ 5 M J planet drives supersonic expansion of the envelope, causing a bright, red, dusty eruption similar to a "luminous red nova." Based on the peak luminosity, color, duration, and expected rate of these events, we suggest that engulfment events on the AGB could be a significant fraction of low-luminosity red novae in the Galaxy. We do not find conditions where the envelope is ejected prior to the planet's tidal disruption, complicating the interpretation of short-period giant planets orbiting white dwarfs as survivors of common envelope evolution.

Keywords: exoplanets; red giant stars; asymptotic giant branch stars; white dwarf stars; common envelope evolution; star-planet interactions
The Diffuse Light Envelope of Luminous Red Galaxies

We use a stacking method to study the radial light profiles of luminous red galaxies (LRGs) at redshift ∼0.62 and ∼0.25, out to a radial range of 200 kpc. We do not find noticeable evolution of the profiles at the two redshifts. The LRG profiles appear to be well approximated by a single Sérsic profile, although some excess light can be seen outside 60 kpc. We quantify the excess light by measuring the integrated flux and find that the excess is about 10%—a non-dominant but still nonnegligible component.

Keywords: galaxy evolution
Three New Late-type Stellar Companions to Very Dusty WISE Debris Disks Identified with SPHERE Imaging

Debris disk stars are good targets for high-contrast imaging searches for planetary systems, since debris disks have been shown to have a tentative correlation with giant planets. We selected 20 stars identified as debris disk hosts by the WISE mission, with particularly high levels of warm dust. We observed these with the VLT/SPHERE high-contrast imaging instrument with the goal of finding planets and imaging the disks in scattered light. Our survey reaches a median 5σ sensitivity of 10.4 MJ at 25 au and 5.9 MJ at 100 au. We identified three new stellar companions (HD 18378B, HD 19257B, and HD 133778B): two are mid-M-type stars and one is a late-K or early-M star. Three additional stars have very widely separated stellar companions (all at >2000 au) identified in the Gaia catalog. The stars hosting the three SPHERE-identified companions are all older (≳700 Myr), with one having recently left the main sequence and one a giant star. We infer that the high volumes of dust observed around these stars has been caused by a recent collision between the planets and planetesimal belts in the system, although for the most evolved star, mass loss could also be responsible for the infrared excess. Future mid-infrared spectroscopy or polarimetric imaging may allow the positions and spatial extent of these dust belts to be constrained, thereby providing evidence as to the true cause of the elevated levels of dust around these old systems. None of the disks in this survey is resolved in scattered light.

Keywords: exoplanets; extrasolar gaseous giant planets; debris disks; circumstellar disks; planetesimals; direct imaging; coronagraphic imaging
Ensuring Consistency between Noise and Detection in Hierarchical Bayesian Inference

Hierarchical Bayesian inference can simultaneously account for both measurement uncertainty and selection effects within astronomical catalogs. In particular, the imposed hierarchy encodes beliefs about the interdependence of the physical processes that generate the observed data. We show that several proposed approximations within the literature actually correspond to inferences that are incompatible with any physical detection process. This generically leads to biases and is associated with the assumption that detectability is independent of the observed data given the true source parameters. We show several examples of how this error can affect astrophysical inferences based on catalogs of coalescing binaries observed through gravitational waves, including misestimating the redshift evolution of the merger rate as well as incorrectly inferring that general relativity is the correct theory of gravity when it is not. In general, one cannot directly fit for the "detected distribution" and "divide out" the selection effects in post-processing. Similarly, when comparing theoretical predictions to observations, it is better to simulate detected data (including both measurement noise and selection effects) rather than comparing estimates of the detected distributions of event parameters (which include only selection effects). While the biases introduced by model misspecification from incorrect assumptions may be smaller than statistical uncertainty for moderate catalog sizes (O(100) events), they will nevertheless pose a significant barrier to precision measurements of astrophysical populations.

Keywords: gravitational waves; hierarchical models; bayesian statistics; general relativity
The Structure and Morphology of Galaxies during the Epoch of Reionization Revealed by JWST

We analyze 347 galaxies at redshift 4 < z < 9.5 using JWST observations from the Cosmic Evolution Early Release Science (CEERS) program by simultaneously fitting a two-dimensional parametric model to the seven-filter Near Infrared Camera images to measure the overall structural parameters and quantify the global properties of the galaxies in the rest-frame optical band. Particular attention is devoted to deriving robust uncertainties that include, among other factors, the influence of cosmological surface brightness dimming and resolution effects. Using the global Sérsic index (n < 1.5) and observed axial ratio (q < 0.6) as a guide, we place a conservative lower limit of ~45% on the incidence of galactic disks. Galaxies follow a relation between the rest-frame optical luminosity and effective radius in the redshift range 4 < z < 9.5, as well as separately over the intervals 4 < z < 5 and 5 ≤ z < 9.5, with a very similar slope but a marginally lower zero-point in the higher-redshift bin (R e = 0.69 ± 0.05 kpc) compared to the lower-redshift bin (R e = 0.91 ± 0.04 kpc). Within the limitations of the current sample size, we find no significant redshift evolution of n or R e at these early epochs.

Keywords: early universe; galaxy formation; galaxy evolution; high-redshift galaxies
Phase-space Properties and Chemistry of the Sagittarius Stellar Stream Down to the Extremely Metal-poor ([Fe/H] ≲ -3) Regime

In this work, we study the phase-space and chemical properties of the Sagittarius (Sgr) stream, the tidal tails produced by the ongoing destruction of the Sgr dwarf spheroidal (dSph) galaxy, focusing on its very metal-poor (VMP; [Fe/H] < -2) content. We combine spectroscopic and astrometric information from SEGUE and Gaia EDR3, respectively, with data products from a new large-scale run of the StarHorse spectrophotometric code. Our selection criteria yield ~1600 stream members, including >200 VMP stars. We find the leading arm (b > 0°) of the Sgr stream to be more metal-poor, by ~0.2 dex, than the trailing one (b < 0°). With a subsample of turnoff and subgiant stars, we estimate this substructure's stellar population to be ~1 Gyr older than the thick disk's. With the aid of an N-body model of the Sgr system, we verify that simulated particles stripped earlier (>2 Gyr ago) have present-day phase-space properties similar to lower metallicity stream stars. Conversely, those stripped more recently (<2 Gyr) are preferentially akin to metal-rich ([Fe/H] > -1) members of the stream. Such correlation between kinematics and chemistry can be explained by the existence of a dynamically hotter, less centrally concentrated, and more metal-poor population in Sgr dSph prior to its disruption, implying that this galaxy was able to develop a metallicity gradient before its accretion. Finally, we identified several carbon-enhanced metal-poor ([C/Fe] > +0.7 and [Fe/H] ≤ -1.5) stars in the Sgr stream, which might be in tension with current observations of its remaining core where such objects are not found.

Keywords: stellar streams; dwarf galaxies; cemp stars; galactic archaeology; milky way stellar halo; stellar kinematics
Millimeter and Submillimeter Spectroscopy of the Deuterated Molecular Ion SD+

Seven rotational and fine-structure transitions of the deuterated molecular ion SD+ in the X 3Σ‑ ground electronic state have been measured in the 271–863 GHz region in the laboratory. This ion has been produced by direct-current glow discharge using a mixture of D2S and argon in a free space cell in a temperature range of ‑140°C to ‑160°C. The rotational, centrifugal distortion, spin–spin interaction, and hyperfine constants have been determined; the standard deviation of the residuals in the fitting is 109 kHz. The set of obtained spectroscopic parameters provides a list of accurate submillimeter rest frequencies of SD+ for astronomical detection. We have investigated lines of SD+ toward the quasar PKS 1830-211 using the Atacama Large Millimeter/submillimeter Array archive, as the z = 0.89 molecular absorber exists in front of this quasar. A data set covering the 297 GHz region includes the N J = 23–12 transition at 561 GHz due to redshift, providing an upper limit of the column density N tot = 3 × 1012 cm‑2 for SD+.

Keywords: laboratory astrophysics; molecular physics; submillimeter astronomy; rotational spectroscopy; molecular clouds
A Generalist, Automated ALFALFA Baryonic Tully-Fisher Relation

The baryonic Tully-Fisher relation (BTFR) has applications in galaxy evolution as a test bed for the galaxy-halo connection and in observational cosmology as a redshift-independent secondary distance indicator. This analysis leverages the 31,000+ galaxy Arecibo Legacy Fast ALFA (Arecibo L-band Feed Array) Survey (ALFALFA) sample-which provides redshifts, velocity widths, and H I content for a large number of gas-bearing galaxies in the local universe-to fit and test an extensive local universe BTFR. The fiducial relation is fit using a 3000-galaxy subsample of ALFALFA, and is shown to be consistent with the full sample. This BTFR is designed to be as inclusive of ALFALFA and comparable samples as possible. Velocity widths measured via an automated method and M b proxies extracted from survey data can be uniformly and efficiently measured for other samples, giving this analysis broad applicability. We also investigate the role of sample demographics in determining the best-fit relation. We find that the best-fit relations are changed significantly by changes to the sample mass range and to second order by changes to mass sampling, gas fraction, different stellar mass and velocity width measurements. We use a subset of ALFALFA with demographics that reflect the full sample to measure a robust BTFR slope of 3.30 ± 0.06. We apply this relation and estimate source distances, finding general agreement with flow-model distances as well as average distance uncertainties of ~0.17 dex for the full ALFALFA sample. We demonstrate the utility of these distance estimates by applying them to a sample of sources in the Virgo vicinity, recovering signatures of infall consistent with previous work.

Keywords: galactic and extragalactic astronomy; galaxy distances; h i line emission; galaxy dynamics; spiral galaxies
Persistent Radio Emission from Synchrotron Heating by a Repeating Fast Radio Burst Source in a Nebula

The first repeating fast radio burst (FRB), FRB 121102, was found to be associated with a spatially coincident, persistent nonthermal radio source, but the origin of the persistent emission remains unknown. In this paper, we propose that the persistent emission is produced via a synchrotron-heating process by multiple bursts of FRB 121102 in a self-absorbed synchrotron nebula. With a population of bursts of the repeating FRB absorbed by the synchrotron nebula, the energy distribution of electrons in the nebula will change significantly. As a result, the spectrum of the nebula will show a hump steadily. For the persistent emission of FRB 121102, the total energy of bursts injecting into the nebula is required to be about 3.3 × 1049 erg, the burst injection age is over 6.7 × 104 yr, the nebula size is ∼0.02 pc, and the electron number is about 3.2 × 1055. We predict that as more bursts inject, the brightness of the nebula would be brighter than the current observation, and meanwhile, the peak frequency would become higher. Due to the synchrotron absorption of the nebula, some low-frequency bursts would be absorbed, which may explain why most bursts were detected above ∼1 GHz.

Keywords: radio bursts; radio continuum emission; extragalactic radio sources
Charge Injection Device Extreme Contrast Imaging of the Sirius Field

The intrinsic nature of many astronomical objects, such as binary systems, exoplanets, circumstellar disks, and quasar host galaxies, introduces challenging requirements on observational instrumentation and techniques. In each case, we encounter situations where the light from bright sources completely outshines the surrounding faint targets. As a result, we are yet to fully understand the processes governing star and galaxy formation and evolution, and there are ongoing attempts to search for habitable worlds around other stars. To explore all features of such astronomical objects, we must perform observations at the maximum possible contrast ratios. Here, we demonstrate the extreme contrast ratio imaging capabilities of the latest generation of commercially available charge injection devices, the SpectraCAM XDR, using Sirius field observations from a world-class observing site. Based on wavelet-based image analysis and precise photometric calibration, we report a direct contrast ratio of 1 part in 100 million.

Keywords: astronomical instrumentation; astronomical techniques; astronomy data analysis
TOI-6883.01: A Single-transit Planet Candidate Detected from TESS

A new candidate exoplanet, proposed in ExoFOP by authors, it was promoted from TIC 393818343 to TOI-6883.01 at coordinates R.A.(J2000)20:41:10.01 decl.(J2000) + 3:38:17.87 in the Delphinus constellation and its distance is (93.73 ± 0.35) pc from Earth. The target star is a Sun-type having G0 class according to Skiff spectral classification and it has photometric magnitude V(Johnson) = 9.5 mag. We analyzed the transit light curve using Transit Exoplanet Survey Satellite's ExoMAST tool, and evaluated the Lightcurve Analysis Tool for Transiting Exoplanets-report by excluding false positives, studying the background, satellite and centroid motion, and analyzing the pixels in sector 55 to define the source goodness. The candidate exoplanet transit has a duration of TD = 3.957 hr, Depth = 0.1196% and mid-transit time occurs at TBJD = 2811.24. Only one event was observed, so the orbital period cannot be evaluated.

Keywords: exoplanets; transit photometry; light curves; exoplanet astronomy
ESPRESSO Observations of Gaia BH1: High-precision Orbital Constraints and no Evidence for an Inner Binary

We present high-precision radial velocity observations of Gaia BH1, the nearest known black hole (BH). The system contains a solar-type G star orbiting a massive dark companion, which could be either a single BH or an inner BH + BH binary. A BH + BH binary is expected in some models where Gaia BH1 formed as a hierarchical triple, which is attractive because they avoid many of the difficulties associated with forming the system through isolated binary evolution. Our observations test the inner binary scenario. We have measured 115 precise RVs of the G star, including 40 from ESPRESSO with a precision of 3–5 m s‑1, and 75 from other instruments with a typical precision of 30–100 m s‑1. Our observations span 2.33 orbits of the G star and are concentrated near a periastron passage, when perturbations due to an inner binary would be largest. The RVs are well-fit by a Keplerian two-body orbit and show no convincing evidence of an inner binary. Using REBOUND simulations of hierarchical triples with a range of inner periods, mass ratios, eccentricities, and orientations, we show that plausible inner binaries with periods P inner ≳ 1.5 days would have produced larger deviations from a Keplerian orbit than observed. Binaries with P inner ≲ 1.5 days are consistent with the data, but these would merge within a Hubble time and would thus imply fine-tuning. We present updated parameters of Gaia BH1's orbit. The RVs yield a spectroscopic mass function $f\left({M}_{\mathrm{BH}}\right)=3.9358\pm 0.0002\,{M}_{\odot }$ —about 7000σ above the ∼2.5 M ⊙ maximum neutron star mass. Including the inclination constraint from Gaia astrometry, this implies a BH mass of M BH = 9.27 ± 0.10 M ⊙.

Keywords: multiple stars; black holes