adsabs/SciX_UAT_keywords huggingface dataset:
A Pre-main-sequence γ Dor-δ Sct Hybrid with Extremely Slow Internal Rotation in a Short-period Eclipsing Binary KIC 9850387 Revealed by Asteroseismology

A complete understanding of the formation process of close binaries relies on the reliable determination of their masses and ages, as well as the interior structure of pre-main-sequence (PMS) binaries. PMS eclipsing binaries containing stellar oscillations are therefore benchmarks since the binarity makes it possible to measure the masses and radii independently with great accuracy, while stellar oscillations represent a unique method of probing stellar interiors. Here we report the discovery of KIC 9850387, a short-period PMS eclipsing binary exhibiting hybrid γ Dor-δ Sct pulsations that is also the inner binary of a probable hierarchical triple system. From the light-curve and radial-velocity modeling we determine the masses and radii of the component stars, which suggest the probable PMS nature of the system. Based on four years of Kepler data, the intrinsic oscillations of the star are analyzed. The pulsation spectrum shows 17 low-frequency peaks spaced at exactly equidistant periods that are identified as dipole gravity modes. The practically constant period spacing indicates an extremely slow near-core rotation of the pulsator with a period deduced to be longer than 1 yr. This enables us to fit the pulsation frequencies precisely with non-rotating models. The stellar parameters yielded by asteroseismology modeling are in consistent with the dynamic ones given by the binary model. The results indicate that the pulsator is a young PMS star with an age between 6.4 and 7.1 Myr. KIC 9850387 is therefore the first PMS eclipsing binary identified by asteroseismology.

Keywords: eclipsing binary stars; pre-main sequence stars; stellar oscillations; stellar rotation; stellar interiors
The Alignment of Satellite Systems with Cosmic Filaments in the SDSS DR12

Galaxies, as well as their satellites, are known to form within the cosmic web, the large, multi-scale distribution of matter in the universe. It is known that the surrounding large-scale structure (LSS) can impact and influence the formation of galaxies, e.g., the spin and shape of halos or galaxies are correlated with the LSS and the correlation depends on halo mass or galaxy morphology. In this work, we use group and filament catalogs constructed from the SDSS DR12 to investigate the correlation between satellite systems and the large-scale filaments they are located in. We find that the distribution of satellites is significantly correlated with filaments, namely the major axis of the satellite systems are preferentially aligned with the spine of the closest filament. Stronger alignment signals are found for the cases where the system is far from the filament spine, while systems close to the filament spine show significantly weaker alignment. Our results suggest that satellites are accreted along filaments, which agrees with previous works. The case where the system is far from the filament spine may help us to understand how the filament forms as well as the peculiar satellite distribution in the local universe.

Keywords: astrostatistics; observational astronomy; galaxy evolution; galaxies; large-scale structure of the universe
Citizen Science Discovery of a Recurrently Active Jupiter-Family Comet: (551023) 2012 UQ192

We have discovered evidence of cometary activity originating from (551023) 2012 UQ192 (alternately designated 2019 SN40), which we dynamically classify as a Jupiter Family Comet (JFC). JFCs have eccentric Jupiter-crossing orbits and originate in the Kuiper Belt. Analysis of these objects can provide vital information about minor planets in the outer solar system, such as the distribution of volatiles within the solar system. Activity on 2012 UQ192 was first recognized by volunteers on our NASA Partner Citizen Science project Active Asteroids. Through our own examination of archival image data, we found a total of ~30 images presenting strong evidence of activity near perihelion during two separate orbits. 2012 UQ192 is notable as we found it to be recurrently active. When 2012 UQ192 approaches its perihelion passage in 2027 September, we predict it will reactivate and will be a prime subject for follow-up observations.

Keywords: asteroids; comet tails; comet dynamics; short period comets; astronomy data analysis
Characteristics of Interplanetary Discontinuities in the Inner Heliosphere Revealed by Parker Solar Probe

We present a statistical analysis for the characteristics and spatial evolution of the interplanetary discontinuities (IDs) in the solar wind, from 0.13-0.9 au, by using the Parker Solar Probe measurements on Orbits 4 and 5. We collected 3948 IDs, including 2511 rotational discontinuities (RDs) and 557 tangential discontinuities (TDs), with the remnant unidentified. The statistical results show that (1) the ID occurrence rate decreases from 200 events per day at 0.13 au to 1 event per day at 0.9 au, following a spatial scaling of r-2.00, (2) the RD to TD ratio decreases quickly with the heliocentric distance, from 8 at r < 0.3 au to 1 at r > 0.4 au, (3) the magnetic field tends to rotate across the IDs, 45° for TDs and 30° for RDs, in the pristine solar wind within 0.3 au, (4) a special subgroup of RDs exists within 0.3 au, characterized by small field rotation angles and parallel or antiparallel propagations to the background magnetic fields, (5) the TD thicknesses normalized by local ion inertial lengths (di) show no clear spatial scaling and generally range from 5-35 di and the normalized RD thicknesses follow an r-1.09 spatial scaling, and (6) the outward (antisunward) propagating RDs predominate in all RDs, with the propagation speeds in the plasma rest frame proportional to r-1.03. This work could improve our understanding of the ID characteristics and evolution and shed light on the study of the turbulent environment in the pristine solar wind.

Keywords: interplanetary discontinuities; solar wind; interplanetary magnetic fields; magnetohydrodynamics
Rotationally Constrained Convection in the Sun: Applicable to Planetary Atmospheres?

Rotational suppression of convection can occur on length scales which are larger than a critical length. Featherstone & Hindman suggest that this can account for a second preferred length-scale in solar convection on supergranule scales. Here, I explore if rotational suppression of convection also occurs in the atmospheres of Earth and Venus.

Keywords: solar convective zone
Implications of a Temperature-dependent Initial Mass Function. II. An Updated View of the Star-forming Main Sequence

The stellar initial mass function (IMF) is predicted to depend upon the temperature of gas in star-forming molecular clouds. The introduction of an additional parameter, T IMF, into photometric template fitting, allows galaxies to be fit with a range of IMFs. Three surprising new features appear: (1) most star-forming galaxies are best fit with a bottom-lighter IMF than the Milky Way; (2) most star-forming galaxies at fixed redshift are fit with a very similar IMF; and (3) the most-massive star-forming galaxies at fixed redshift instead exhibit a less bottom-light IMF, similar to that measured in quiescent galaxies. Additionally, since stellar masses and star formation rates both depend on the IMF, these results slightly modify the resulting relationship, while yielding similar qualitative characteristics to previous studies.

Keywords: star formation; star forming regions; initial mass function; galaxy quenching; galaxy evolution
Nonthermal Motions and Atmospheric Heating of Cool Stars

The magnetic processes associated with the nonthermal broadening of optically thin emission lines appear to carry enough energy to heat the corona and accelerate the solar wind. We investigate whether nonthermal motions in cool stars exhibit the same behavior as on the Sun by analyzing archival stellar spectra taken by the Hubble Space Telescope, and full-disk Solar spectra taken by the Interface Region Imaging Spectrograph. We determined the nonthermal velocities by measuring the excess broadening in optically thin emission lines formed in the stellar atmosphere; the chromosphere, the transition region, and the corona. Assuming the nonthermal broadening is caused by the presence of Alfvén waves, we also determined the associated wave energy densities. Our results show that with a nonthermal velocity of ~23 km s-1 the Sun-as-a-star results are in very good agreement with values obtained from spatially resolved solar observations. The nonthermal broadening in our sample shows a correlation to stellar rotation, with the strength of the nonthermal velocity decreasing with decreasing rotation rate. Finally, the nonthermal velocity in cool Sun-like stars varies with atmospheric height or temperature of the emission lines, and peaks at transition region temperatures. This points toward a solar-like Alfvén wave-driven heating in stellar atmospheres. However, the peak is at a lower temperature in some cool stars suggesting that other magnetic processes such as flaring events could also dominate.

Keywords: stellar atmospheres; stellar winds
Laboratory Data on the EUV/Soft-X-Ray Flux Problem of Fe XVIII and Fe XIX

Observations by the spacecraft Extreme Ultraviolet Explorer (EUVE), Far Ultraviolet Spectroscopic Explorer (FUSE), Chandra, and XMM-Newton of Capella (α Aurigae) have encountered problems with the relative intensities of the Fe XVIII and Fe XIX line emission in the soft-X-ray (XUV) and extreme-ultraviolet spectral ranges versus various model predictions based on theoretical atomic data. The reason may either lie in astrophysical phenomena, e.g., at emission or because of absorption by the interstellar medium, in the theoretical atomic data, in one or more spectrometer calibrations, or in the spectral modeling. By measurements using an electron beam ion trap we provide laboratory data obtained under conditions that are reasonably close to stellar emission regions. The laboratory data on Fe XVIII and Fe XIX show line ratios that are rather similar to the observations of Capella. The measurements, therefore, rule out astrophysical phenomena and calibration errors and point to issues with the modeling of the observed Capella emission.

Keywords: atomic data benchmarking; atomic spectroscopy; line intensities
Mutual Neutralization in Li++H-/D- and Na++H-/D- Collisions: Implications of Experimental Results for Non-LTE Modeling of Stellar Spectra

Advances in merged-beams instruments have allowed experimental studies of the mutual neutralization (MN) processes in collisions of both Li+ and Na+ ions with D- at energies below 1 eV. These experimental results place constraints on theoretical predictions of MN processes of Li+ and Na+ with H-, important for non-LTE modeling of Li and Na spectra in late-type stars. We compare experimental results with calculations for methods typically used to calculate MN processes, namely the full quantum (FQ) approach, and asymptotic model approaches based on the linear combination of atomic orbitals (LCAO) and semiempirical (SE) methods for deriving couplings. It is found that FQ calculations compare best overall with the experiments, followed by the LCAO, and the SE approaches. The experimental results together with the theoretical calculations, allow us to investigate the effects on modeled spectra and derived abundances and their uncertainties arising from uncertainties in the MN rates. Numerical experiments in a large grid of 1D model atmospheres, and a smaller set of 3D models, indicate that neglect of MN can lead to abundance errors of up to 0.1 dex (26%) for Li at low metallicity, and 0.2 dex (58%) for Na at high metallicity, while the uncertainties in the relevant MN rates as constrained by experiments correspond to uncertainties in abundances of much less than 0.01 dex (2%). This agreement for simple atoms gives confidence in the FQ, LCAO, and SE model approaches to be able to predict MN with the accuracy required for non-LTE modeling in stellar atmospheres.

Keywords: stellar abundances; laboratory astrophysics; stellar atmospheres; reaction rates
S-type Stars: LaO Line List for the B2Σ+-X2Σ+ Band System

LaO bands are a characteristic feature in the spectrum of cool S-type stars. La is made primarily by the s-process during the asymptotic giant branch phase of stellar evolution. The B2Σ+-X2Σ+ and A2Π-X2Σ+ band systems can be used to determine the La abundances in cool S stars. The bands of the B2Σ+-X2Σ+ with $v^{\prime} $ and $v^{\prime\prime} \leqslant 5$ have been rotationally analyzed from an emission spectrum from a carbon furnace. Line strengths are calculated using an ab initio transition dipole function, corrected using experimental lifetimes. We provide a line list for the B2Σ+-X2Σ+ band system that can be used to determine La abundances.

Keywords: spectral line lists; laboratory astrophysics
Dark Energy Survey Year 3 Results: Photometric Data Set for Cosmology

We describe the Dark Energy Survey (DES) photometric data set assembled from the first three years of science operations to support DES Year 3 cosmologic analyses, and provide usage notes aimed at the broad astrophysics community. Y3 GOLD improves on previous releases from DES, Y1 GOLD, and Data Release 1 (DES DR1), presenting an expanded and curated data set that incorporates algorithmic developments in image detrending and processing, photometric calibration, and object classification. Y3 GOLD comprises nearly 5000 deg2 of grizY imaging in the south Galactic cap, including nearly 390 million objects, with depth reaching a signal-to-noise ratio ∼10 for extended objects up to iAB ∼ 23.0, and top-of-the-atmosphere photometric uniformity <3 mmag. Compared to DR1, photometric residuals with respect to Gaia are reduced by 50%, and per-object chromatic corrections are introduced. Y3 GOLD augments DES DR1 with simultaneous fits to multi-epoch photometry for more robust galactic color measurements and corresponding photometric redshift estimates. Y3 GOLD features improved morphological star-galaxy classification with efficiency >98% and purity >99% for galaxies with 19 < iAB < 22.5. Additionally, it includes per-object quality information, and accompanying maps of the footprint coverage, masked regions, imaging depth, survey conditions, and astrophysical foregrounds that are used to select the cosmologic analysis samples.

Keywords: surveys; catalogs; observational cosmology
Photoionization from the Ground and Excited Vibrational States of {{H}}_{2}(+) and Its Deuterated Isotopologues

Photoionization cross sections and rate coefficients have been calculated for all bound vibrational levels of the 1sσ g state of ${{\rm{H}}}_{2}^{+}$ , HD+, and ${{\rm{D}}}_{2}^{+}$ . The Born-Oppenheimer approximation is employed in our calculation of vibrationally resolved photoionization cross sections. Vibrationally resolved and local thermal equilibrium photoionization rate coefficients are presented for photon temperatures less than 50,000 K and are found to be several orders of magnitude larger than previous results in the literature. Analytic fits for the vibrationally resolved and local thermal equilibrium photoionization rate coefficients are provided. Near-threshold oscillations in the vibrationally resolved photoionization are observed. A benchmark set of photoionization cross sections are presented. Fixed-nuclei photoionization cross sections are calculated using two-center true continuum wave functions and are verified by comparison with previous calculations and are found to be in excellent agreement in all cases. Data files for our set of benchmark cross sections, rate coefficients, and fitting parameters for ${{\rm{H}}}_{2}^{+}$ , HD+, and ${{\rm{D}}}_{2}^{+}$ are available on Zenodo under an open-source Creative Commons Attribution license at doi:10.5281/zenodo.8304061.

Keywords: photoionization; reaction rates; molecular physics
The Instrument of the Imaging X-Ray Polarimetry Explorer

While X-ray spectroscopy, timing, and imaging have improved much since 1962 when the first astronomical nonsolar source was discovered, especially wi the launch of the Newton/X-ray Multi-Mirror Mission, Rossi/X-ray Timing Explorer, and Chandra/Advanced X-ray Astrophysics Facility, the progress of X-ray polarimetry has been meager. This is in part due to the lack of sensitive polarization detectors, which in turn is a result of the fate of approved missions and because celestial X-ray sources appear less polarized than expected. Only one positive measurement has been available until now: the Orbiting Solar Observatory measured the polarization of the Crab Nebula in the 1970s. The advent of microelectronics techniques has allowed for designing a detector based on the photoelectric effect of gas in an energy range where the optics are efficient at focusing in X-rays. Here we describe the instrument, which is the major contribution of the Italian collaboration to the Small Explorer mission called IXPE, the Imaging X-ray Polarimetry Explorer, which will launch in late 2021. The instrument is composed of three detector units based on this technique and a detector service unit. Three mirror modules provided by Marshall Space Flight Center focus X-rays onto the detectors. We show the technological choices, their scientific motivation, and results from the calibration of the instrument. IXPE will perform imaging, timing, and energy-resolved polarimetry in the 2-8 keV energy band opening this window of X-ray astronomy to tens of celestial sources of almost all classes.

Keywords: x-ray astronomy; x-ray detectors; polarimetry
Light-curve Structure and Hα Line Formation in the Tidal Disruption Event AT 2019azh

AT 2019azh is a H+He tidal disruption event (TDE) with one of the most extensive ultraviolet and optical data sets available to date. We present our photometric and spectroscopic observations of this event starting several weeks before and out to approximately 2 yr after the g-band's peak brightness and combine them with public photometric data. This extensive data set robustly reveals a change in the light-curve slope and a possible bump in the rising light curve of a TDE for the first time, which may indicate more than one dominant emission mechanism contributing to the pre-peak light curve. Indeed, we find that the MOSFiT-derived parameters of AT 2019azh, which assume reprocessed accretion as the sole source of emission, are not entirely self-consistent. We further confirm the relation seen in previous TDEs whereby the redder emission peaks later than the bluer emission. The post-peak bolometric light curve of AT 2019azh is better described by an exponential decline than by the canonical t ‑5/3 (and in fact any) power-law decline. We find a possible mid-infrared excess around the peak optical luminosity, but cannot determine its origin. In addition, we provide the earliest measurements of the Hα emission-line evolution and find no significant time delay between the peak of the V-band light curve and that of the Hα luminosity. These results can be used to constrain future models of TDE line formation and emission mechanisms in general. More pre-peak 1–2 days cadence observations of TDEs are required to determine whether the characteristics observed here are common among TDEs. More importantly, detailed emission models are needed to fully exploit such observations for understanding the emission physics of TDEs.

Keywords: accretion; tidal disruption; supermassive black holes; ultraviolet transient sources
HD 145263: Spectral Observations of Silica Debris Disk Formation via Extreme Space Weathering?

We report here time-domain infrared spectroscopy and optical photometry of the HD 145263 silica-rich circumstellar-disk system taken from 2003 through 2014. We find an F4V host star surrounded by a stable, massive 1022-1023 kg (MMoon to MMars) dust disk. No disk gas was detected, and the primary star was seen rotating with a rapid ∼1.75 day period. After resolving a problem with previously reported observations, we find the silica, Mg-olivine, and Fe-pyroxene mineralogy of the dust disk to be stable throughout and very unusual compared to the ferromagnesian silicates typically found in primordial and debris disks. By comparison with mid-infrared spectral features of primitive solar system dust, we explore the possibility that HD 145263's circumstellar dust mineralogy occurred with preferential destruction of Fe-bearing olivines, metal sulfides, and water ice in an initially comet-like mineral mix and their replacement by Fe-bearing pyroxenes, amorphous pyroxene, and silica. We reject models based on vaporizing optical stellar megaflares, aqueous alteration, or giant hypervelocity impacts as unable to produce the observed mineralogy. Scenarios involving unusually high Si abundances are at odds with the normal stellar absorption near-infrared feature strengths for Mg, Fe, and Si. Models involving intense space weathering of a thin surface patina via moderate (T < 1300 K) heating and energetic ion sputtering due to a stellar super-flare from the F4V primary are consistent with the observations. The space-weathered patina should be reddened, contain copious amounts of nanophase Fe, and should be transient on timescales of decades unless replenished.

Keywords: planetary system formation; time domain astronomy; stellar astronomy; spectroscopy; circumstellar matter; stellar classification
Bridging the Gap: Categorizing Gravitational-wave Events at the Transition between Neutron Stars and Black Holes

We search for features in the mass distribution of detected compact binary coalescences which signify the transition between neutron stars (NSs) and black holes (BHs). We analyze all gravitational-wave (GW) detections by the LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration (LVK) made through the end of the first half of the third observing run, and find clear evidence for two different populations of compact objects based solely on GW data. We confidently (99.3%) find a steepening relative to a single power law describing NSs and low-mass BHs below ${2.4}_{-0.5}^{+0.5}{M}_{\odot }$ , which is consistent with many predictions for the maximum NS mass. We find suggestions of the purported lower mass gap between the most massive NSs and the least massive BHs, but are unable to conclusively resolve it with current data. If it exists, we find the lower mass gap's edges to lie at ${2.2}_{-0.5}^{+0.7}{M}_{\odot }$ and ${6.0}_{-1.4}^{+2.4}{M}_{\odot }$ . We reexamine events that have been deemed "exceptional" by the LVK collaborations in the context of these features. We analyze GW190814 self-consistently in the context of the full population of compact binaries, finding support for its secondary to be either a NS or a lower mass gap object, consistent with previous claims. Our models are the first to accommodate this event, which is an outlier with respect to the binary BH population. We find that GW200105 and GW200115 probe the edges of, and may have components within, the lower mass gap. As future data improve global population models, the classification of these events will also improve.

Keywords: gravitational wave astronomy; gravitational waves; gravitational wave sources; neutron stars; compact objects; nuclear astrophysics; astrophysical black holes; black holes; ligo