adsabs/SciX_UAT_keywords huggingface dataset:
Origin of Isotopic Diversity among Carbonaceous Chondrites

Carbonaceous chondrites are some of the most primitive meteorites and derive from planetesimals that formed a few million years after the beginning of the solar system. Here, using new and previously published Cr, Ti, and Te isotopic data, we show that carbonaceous chondrites exhibit correlated isotopic variations that can be accounted for by mixing among three major constituents having distinct isotopic compositions, namely refractory inclusions, chondrules, and CI chondrite-like matrix. The abundances of refractory inclusions and chondrules are coupled and systematically decrease with increasing amount of matrix. We propose that these correlated abundance variations reflect trapping of chondrule precursors, including refractory inclusions, in a pressure maximum in the disk, which is likely related to the water ice line and the ultimate formation location of Jupiter. The variable abundance of refractory inclusions/chondrules relative to matrix is the result of their distinct aerodynamical properties resulting in differential delivery rates and their preferential incorporation into chondrite parent bodies during the streaming instability, consistent with the early formation of matrix-poor and the later accretion of matrix-rich carbonaceous chondrites. Our results suggest that chondrules formed locally from isotopically heterogeneous dust aggregates, which themselves derive from a wide area of the disk, implying that dust enrichment in a pressure trap was an important step to facilitate the accretion of carbonaceous chondrite parent bodies or, more generally, planetesimals in the outer solar system.

Keywords: carbonaceous chondrites; meteorites; chondrules; chondrites; jupiter; protoplanetary disks; planetesimals; isotopic abundances; accretion
Phase-dependent Study of Near-infrared Disk Emission Lines in LB-1

The mass, origin, and evolutionary stage of the binary system LB-1 have been intensely debated, following the claim that it hosts an ∼70M⊙ black hole, in stark contrast with the expectations for Galactic remnants. We conducted a high-resolution, phase-resolved spectroscopic study of its Paschen lines, using the Calar Alto 3.5 m telescope. We find that Paβ and Paγ (after subtraction of the stellar absorption component) are well fitted with a standard double-peaked disk profile. We measured the velocity shifts of the red and blue peaks at 28 orbital phases: the line center has an orbital motion in perfect antiphase with the secondary, and the radial velocity amplitude ranges from 8 to 13 km s-1, for different methods of profile modeling. We interpret this curve as proof that the disk traces the orbital motion of the primary, ruling out the circumbinary disk and the hierarchical triple scenarios. The phase-averaged peak-to-peak half-separation (a proxy for the projected rotational velocity of the outer part of the disk) is ∼70 km s-1, larger than the orbital velocity of the secondary and inconsistent with a circumbinary disk. From those results, we infer a primary mass 4-8 times higher than the secondary mass. Moreover, we show that the intensity ratio of the blue and red peaks has a sinusoidal behavior in phase with the secondary, which we attribute to external irradiation of the outer part of the disk. Finally, we discuss our findings in the context of competing scenarios proposed for LB-1. Further astrometric Gaia data will test between alternative solutions.

Keywords: black holes; black hole physics; stellar evolution; be stars
Planets Across Space and Time (PAST). I. Characterizing the Memberships of Galactic Components and Stellar Ages: Revisiting the Kinematic Methods and Applying to Planet Host Stars

Over 4000 exoplanets have been identified and thousands of candidates are to be confirmed. The relations between the characteristics of these planetary systems and the kinematics, Galactic components, and ages of their host stars have yet to be well explored. To address these questions, we conduct a research project, dubbed Planets Across Space and Time (PAST). To do this, one of the key steps is to accurately characterize the planet host stars. In this paper, Paper I of the PAST series, we revisit the kinematic method for classification of Galactic components and extend the applicable range of velocity ellipsoid from ∼100 pc to ∼1500 pc from the Sun in order to cover most known planet hosts. Furthermore, we revisit the age-velocity dispersion relation (AVR), which allows us to derive kinematic ages with a typical uncertainty of 10-20% for an ensemble of stars. Applying the above revised methods, we present a catalog of kinematic properties (i.e., Galactic positions, velocities, and the relative membership probabilities among the thin disk, thick disk, Hercules stream, and the halo) as well as other basic stellar parameters for 2174 host stars of 2872 planets by combining data from Gaia, LAMOST, APOGEE, RAVE, and the NASA exoplanet archive. The revised kinematic method and AVR, as well as the stellar catalog of kinematic properties and ages, lay the foundation for future studies of exoplanets in space and time in the Galactic context.

Keywords: exoplanets; exoplanet catalogs; stellar ages; stellar kinematics
Ultradense Gas at the Dusty Torus Scale in a Partially Obscured Quasar

We present detailed studies of the partially obscured quasar 2MASS J151653.23+190048.2 with continuous broadband spectrophotometry from near-infrared (NIR) through optical to ultraviolet (UV). The NIR and optical spectra show strong broad emission lines, while the UV spectrum is dominated by a set of rich intermediate-width emission lines (IELs). These IELs, unshifted with respect to the quasar systemic velocity measured by narrow emission lines, share a common profile of about 1900 $\mathrm{km}\,{{\rm{s}}}^{-1}$ in FWHM, in contrast to the Balmer and Paschen broad emission lines of FWHM ∼6300 $\mathrm{km}\,{{\rm{s}}}^{-1}$ observed in the optical and NIR. The intermediate width of these lines indicates that the emitting gas may come from the dusty torus region. However, the observed peculiar IEL intensity ratios, such as N V λ1240/Lyα, indicate that the emitting gas has a very high density, up to $\sim {10}^{13}\,{\mathrm{cm}}^{-3}$ . Such a high density is unusual for gas around the dusty torus region, except that we consider mechanisms such as shocks that can produce local ultradense gas. We speculate that these emission lines could originate from the shock region, possibly induced by the quasar outflow colliding with the inner wall of the dusty torus. If true, this may give us an opportunity to peep at the quasar outflows at the scale of the dusty torus that have so far been elusive due to the limited resolving powers of existing facilities.

Keywords: active galaxies; agn host galaxies; quasars
Effect of Panel Misalignment Error Distribution on the Radiation Pattern of Leighton Chajnantor Telescope's Antenna

The Leighton dish formerly at the Caltech Submillimeter Observatory will be reassembled to become the Leighton Chajnantor Telescope (LCT). It will be required to demonstrate high surface accuracy and controlled radiation patterns at high frequency, which are largely limited by surface error due to panel misalignment on the primary reflector. Not only the surface rms error but also the error distribution has effect on the radiation pattern of the antenna. Therefore, analyzing the effect of error distributions resulting from various panel misalignments on the radiation pattern of the antenna will facilitate better compensation of surface errors during the reassembly process. To acquire the radiation pattern of LCT's antenna with panel misalignments, we first propose a simulation method based on physical optics and the physical theory of diffraction, which offers precise results but is time-consuming, especially at high frequencies. Then, we propose a rapid computation method that combines the method of calculating the optical path difference (OPD), the OPD fitting method, and the aperture integration method for segmented reflectors. Experimental results demonstrate that the rapid computation method is highly efficient and accurate compared to the simulation method. In order to show the effect of error distributions due to two typical panel misalignments (i.e., piston and tip-tilt) on radiation patterns, experiments are conducted using the two proposed methods for various error distributions. These experiments indicate that for the same surface rms error, smaller panel errors at smaller normalized aperture radii are more conducive to achieving improved characteristics of the radiation patterns, such as reduced peak gain losses and lower sidelobe levels. Additionally, comparison experiments also reveal that variations in piston error have a greater impact on the radiation patterns than variations in tip-tilt error under the same surface rms error.

Keywords: radio telescopes; submillimeter astronomy; single-dish antennas; computational methods
The Nature of the IMBH Candidate CXO J133815.6+043255: High-frequency Radio Emission

The ultraluminous X-ray source CXO J133815.6+043255 is a strong candidate for a bona fide intermediate-mass black hole residing in the outskirts of NGC 5252. We present 22 GHz radio observations of this source obtained serendipitously in an ongoing high-frequency imaging survey of radio-quiet Active Galactic Nuclei (AGNs), and use this new data point to construct the broadband radio spectral energy distribution (SED). We find that the SED exhibits a spectral slope of α = -0.66 ± 0.02, consistent with a steep spectrum from optically thin synchrotron emission from an unresolved jet. We also find that the L R/L X ratio is approximately 10-3, inconsistent with radio-quiet AGN and many ULXs but consistent with low-luminosity AGN and radio-loud quasars. Together, these observations support the conclusion that CXO J133815.6+043255 is an intermediate-mass black hole producing a low-mass analog of radio jets seen in classical quasars.

Keywords: black holes; intermediate-mass black holes; active galactic nuclei
The Presolar Grain Database. I. Silicon Carbide

The Presolar Grain Database (PGD) contains the vast majority of isotope data (published and unpublished) on presolar grains and was first released as a collection of spreadsheets in 2009. It has been a helpful tool used by many researchers in cosmochemistry and astrophysics. However, over the years, accumulated errors compromised major parts of the PGD. Here, we provide a fresh start, with the PGD for silicon carbide (SiC) grains rebuilt from the ground up. We also provide updated rules for SiC grain type classification to unify previous efforts, taking into account newly discovered grain types. We also define a new grain type D, which includes some grains previously classified as ungrouped. Future work will focus on rebuilding the PGD for other kinds of presolar grains: graphite, oxides, silicates, and rarer phases.

Keywords: nucleosynthesis; stellar nucleosynthesis; circumstellar grains; circumstellar matter; carbonaceous grains; circumstellar dust; meteorites; isotopic abundances
X-Ray Superflares from Pre-main-sequence Stars: Flare Energetics and Frequency

Solar-type stars exhibit their highest levels of magnetic activity during their early convective pre-main-sequence (PMS) phase of evolution. The most powerful PMS flares, superflares and megaflares, have peak X-ray luminosities of $\mathrm{log}({L}_{{\rm{X}}})=30.5\mbox{-}34.0$ erg s-1 and total energies $\mathrm{log}({E}_{{\rm{X}}})=34\mbox{-}38$ erg. Among >24,000 X-ray-selected young (t ≲ 5 Myr) members of 40 nearby star-forming regions from our earlier Chandra MYStIX and SFiNCs surveys, we identify and analyze a well-defined sample of 1086 X-ray superflares and megaflares, the largest sample ever studied. Most are considerably more powerful than optical/X-ray superflares detected on main-sequence stars. This study presents energy estimates of these X-ray flares and the properties of their host stars. These events are produced by young stars of all masses over evolutionary stages ranging from protostars to diskless stars, with the occurrence rate positively correlated with stellar mass. Flare properties are indistinguishable for disk-bearing and diskless stars indicating star-disk magnetic fields are not involved. A slope of α ≃ 2 in the flare energy distributions ${dN}/{{dE}}_{{\rm{X}}}\propto {E}_{{\rm{X}}}^{-\alpha}$ is consistent with that of optical/X-ray flaring from older stars and the Sun. Megaflares ($\mathrm{log}({E}_{{\rm{X}}})\gt 36.2$ erg) from solar-mass stars have an occurrence rate of ${1.7}_{-0.6}^{+1.0}$ flares/star/year and contribute at least 10%-20% to the total PMS X-ray energetics. These explosive events may have important astrophysical effects on protoplanetary disk photoevaporation, ionization of disk gas, production of spallogenic radionuclides in disk solids, and hydrodynamic escape of young planetary atmospheres. Our following paper details plasma and magnetic loop modeling of the >50 brightest X-ray megaflares.

Keywords: planetary atmospheres; pre-main sequence stars; protostars; protoplanetary disks; stellar x-ray flares; x-ray stars
Fluid Mixing during Phase Separation in Crystallizing White Dwarfs

Accurate models of cooling white dwarfs must treat the energy released as their cores crystallize. This phase transition slows the cooling by releasing latent heat and also gravitational energy, which results from phase separation: liquid C is released from the solid C/O core, driving an outward carbon flux. The Gaia color–magnitude diagram provides striking confirmation of this theory by revealing a mass-dependent overdensity of white dwarfs, indicating slowed cooling at the expected location. However, the observed overdensity is enhanced relative to the models. Additionally, it is associated with increased magnetism, suggesting a link between crystallization and magnetic field generation. Recent works aimed at explaining an enhanced cooling delay and magnetic field generation employ a uniform mixing prescription that assumes large-scale turbulent motions; we show here that these calculations are not self-consistent. We also show that thermohaline mixing is most likely efficient enough to provide the required chemical redistribution during C/O phase separation, and that the resulting velocities and mixing lengths are much smaller than previous estimates. These reduced fluid motions cannot generate measurable magnetic fields, suggesting any link with crystallization needs to invoke a separate mechanism. Finally, this mixing alters the chemical profiles, which in turn affects the frequencies of the pulsation modes.

Keywords: white dwarf stars; stellar magnetic fields; stellar interiors; stellar oscillations; stellar physics; stellar convective zones
The DECam Local Volume Exploration Survey: Overview and First Data Release

The DECam Local Volume Exploration survey (DELVE) is a 126-night survey program on the 4 m Blanco Telescope at the Cerro Tololo Inter-American Observatory in Chile. DELVE seeks to understand the characteristics of faint satellite galaxies and other resolved stellar substructures over a range of environments in the Local Volume. DELVE will combine new DECam observations with archival DECam data to cover ~15,000 deg2 of high Galactic latitude (∣b∣ > 10°) southern sky to a 5σ depth of g, r, i, z ~ 23.5 mag. In addition, DELVE will cover a region of ~2200 deg2 around the Magellanic Clouds to a depth of g, r, i ~ 24.5 mag and an area of ~135 deg2 around four Magellanic analogs to a depth of g, i ~ 25.5 mag. Here, we present an overview of the DELVE program and progress to date. We also summarize the first DELVE public data release (DELVE DR1), which provides point-source and automatic aperture photometry for ~520 million astronomical sources covering ~5000 deg2 of the southern sky to a 5σ point-source depth of g = 24.3 mag, r = 23.9 mag, i = 23.3 mag, and z = 22.8 mag. DELVE DR1 is publicly available via the NOIRLab Astro Data Lab science platform.

Keywords: surveys; catalogs; local group; magellanic clouds; dwarf galaxies
Recent Outbursts of the High-mass X-Ray Binary CI Camelopardalis

CI Camelopardalis (CI Cam) is a High Mass X-Ray Binary (HMXB) that was discovered by the All Sky Monitor on board the Rossi X-Ray Timing Explorer when it underwent an outburst in 1998. CI Cam, also known as XTE J0421+560, peaked first in X-rays followed by optical and radio wavelengths (2.25, 8.3, 15 GHz). Several soft X-ray flares were observed after the initial flare. The optical flux was observed to quickly return to quiescent levels, while the radio flare was of much longer duration. The outburst was also detected by the X-ray satellite BeppoSax and the Burst and Transient Source Experiment on board the Compton Gamma Ray Observatory. The optical counterpart, CI Cam, is a B0-2 blue supergiant Be star and, assuming a compact object as an accretion companion (black hole, neutron star, white dwarf), the system can be designated an HMXB. Additionally, there is a pulsating third companion with periods of 0.41521 and 0.26647 days. While the initial outburst occurred in 1998, there is photometric evidence that there have been several later outbursts of similar magnitude to the original 1998 event. This paper will discuss these later outburst events as well as the identified pulsation modes.

Keywords: high mass x-ray binary stars
A Near-half-century Simulation of the Solar Corona

We present an overview of results from a magnetofrictional model of the entire solar corona over a period of 47 yr. The simulation self-consistently reproduces decades of solar phenomena, varying in duration between rapid eruptions and the long-term solar cycles, from an input of observed active regions emerging at the photosphere. We have developed a geometric approach to use magnetic helicity to identify and localize the frequent eruptions that occur in the simulation. This method allows us to match our results to extreme-ultraviolet observations of transient events. We have analyzed the evolving magnetic topology by computing the squashing factor and segmenting the corona into discrete magnetic domains bounded by the Separatrix-Web. The simulations show a more dynamic structure to the Separatrix-Web than is predicted by potential field models, which may explain solar wind observations.

Keywords: solar physics; solar corona; solar prominences; solar coronal mass ejections; solar cycle
The Impact of the Free-floating Planet Mass Function on the Event Rate for Accurate Microlensing Parallax Determination: Application to Euclid and Roman Parallax Observation

A microlensing event is mainly used to search for free-floating planets (FFPs). To estimate the FFP mass and distance via the microlensing effect, a microlensing parallax is one of the key parameters. A short duration of FFP microlensing makes it difficult to yield a parallax by the observer's motion at a recognizable level, so the FFP microlensing parallax is expected on the simultaneous observation by multiple telescopes. Here, we approach the FFP detection by considering a variation in the FFP mass functions and the event rate of accurately measured microlensing parallaxes. We used our FFP microlensing simulator assuming a parallax observation between upcoming space-based missions (Euclid and Roman) with full kinematics. As a result, we confirmed that the event rate of accurately measured microlensing parallaxes (i.e., within a factor of 2 uncertainty) does not simply follow the number of FFPs at a given mass but the ratio of the FFP population per star. This is because the population ratio determines the optical depth for a given mass and potential sources. In addition, we found that the probability of the event that can estimate the FFP mass and distance within a factor of 2 is not so high: ∼40% of Earth-mass, ∼16% of Neptune-mass, and ∼4% of Jupiter-mass FFP events under our criteria. The probability can be improved by some technical approach such as using high cadence and observation in parallax of more than two observers.

Keywords: exoplanet astronomy
The Selection Function of Gaia DR3 RR Lyrae

The Third Data Release (DR3) of the Gaia mission almost doubled the number of RR Lyrae (RRL) stars release in its Specific Object Studies (SOS) catalog, in comparison with DR2. Here I provide empirically inferred 2D and 3D completeness maps for the Gaia DR3 SOS RRL catalog along with maps for the combined Gaia SOS+PS1+ASAS-SN-II catalog. The latter currently has the best performance with an improvement of 9% relative to Gaia DR3 alone and close to 20% relative to Gaia DR2 for the VC+SOS RRL, while significantly smoothing out the effect of the Gaia scanning law.

Keywords: rr lyrae variable stars; astronomy databases
Fast Radio Bursts from Activity of Neutron Stars Newborn in BNS Mergers: Offset, Birth Rate, and Observational Properties

Young neutron stars (NSs) born in core-collapse explosions are promising candidates for the central engines of fast radio bursts (FRBs), since the first localized repeating burst FRB 121102 occurs in a star-forming dwarf galaxy similar to the host galaxies of superluminous supernovae and long gamma-ray bursts. However, FRB 180924 and FRB 190523 are localized to massive galaxies with low rates of star formation, compared with the host of FRB 121102. The offsets between the bursts and host centers are about 4 and 29 kpc for FRB 180924 and FRB 190523, respectively. These host properties are similar to those of short gamma-ray bursts (GRBs), which are produced by binary neutron star (BNS) or NS-black hole mergers. Therefore, the NSs powering FRBs may be formed in BNS mergers. In this paper, we study BNS merger rates and merger times, and predict the most likely merger locations for different types of host galaxies using the population synthesis method. We find that the BNS merger channel is consistent with the recently reported offsets of FRB 180924 and FRB 190523. The offset distribution of short GRBs is well reproduced by population synthesis using a galaxy model similar to that of GRB hosts. The event rate of FRBs (including non-repeating and repeating), is larger than those of BNS mergers and short GRBs, and requires a large fraction of observed FRBs emitting several bursts. Using curvature radiation by bunches in NS magnetospheres, we also predict the observational properties of FRBs from BNS mergers, including the dispersion measure and rotation measure. At late times (t ≥ 1 yr), the contribution to dispersion measure and rotation measure from BNS merger ejecta can be neglected.

Keywords: radio bursts; gamma-ray bursts; magnetars; binary stars; gravitational waves
Kilonova Parameter Estimation with LSST at Vera C. Rubin Observatory

The upcoming Vera Rubin Observatory's Legacy Survey of Space and Time (LSST) opens a new opportunity to rapidly survey the southern sky at optical wavelengths (i.e., ugrizy bands). In this study, we aim to test the possibility of using LSST observations to constrain the mass and velocity of different kilonova (KN) ejecta components from the observation of a combined set of light curves from afterglows of γ-ray bursts and KNe. We used a sample of simulated light curves from the aforementioned events as they would have been seen during the LSST survey to study how the choice of observing strategies impacts the parameter estimation. We found that the design of observing strategy that is the best compromise between light-curve coverage, observed filters, and reliability of the fit involves a high number of visits with long-gap pairs of about 4 hr every two nights in the same or different filters. The features of the observing strategy will allow us to recognize the different stages of the evolution of the light curve and gather observations in at least three filters.

Keywords: compact objects; surveys; gravitational wave sources; astrophysical explosive burning; nuclear astrophysics; optical identification; optical astronomy