adsabs/SciX_UAT_keywords huggingface dataset:
Influence of Thomson Electron Scattering Redistribution on Spectral Line Polarization Formed in Spherically Symmetric Extended and Expanding Atmospheres

Scattering of line photons by ambient electrons in thermal motion in the stellar atmosphere modifies the wings of both intensity and linear polarization profiles of the spectral lines. The aim of the present paper is to investigate in detail the influence of Thomson electron scattering redistribution on resonance line polarization formed in spherically symmetric extended and expanding atmospheres. A comoving frame method based on the accelerated lambda iteration technique is used to solve the concerned spherically symmetric polarized transfer equation including both the atomic and Thomson electron scattering redistribution functions. Our numerical studies highlight the importance of accounting for Thomson electron scattering redistribution in spectral line polarization problems.

Keywords: stellar atmospheres; radiative transfer; spectropolarimetry; computational methods; radiative transfer simulations
TOI-3714 b and TOI-3629 b: Two Gas Giants Transiting M Dwarfs Confirmed with the Habitable-zone Planet Finder and NEID

We confirm the planetary nature of two gas giants discovered by the Transiting Exoplanet Survey Satellite to transit M dwarfs. TOI-3714 (V = 15.24, J = 11.74) is an M2 dwarf hosting a hot Jupiter (M p = 0.70 ± 0.03 M J and R p = 1.01 ± 0.03 R J ) on an orbital period of 2.154849 ± 0.000001 days with a resolved white dwarf companion. TOI-3629 (V = 14.63, J = 11.42) is an M1 dwarf hosting a hot Jupiter (M p = 0.26 ± 0.02 M J and R p =0.74 ± 0.02 R J ) on an orbital period of ${3.936551}_{-0.000006}^{+0.000005}$ days. We characterize each transiting companion using a combination of ground-based and space-based photometry, speckle imaging, and high-precision velocimetry from the Habitable-zone Planet Finder and the NEID spectrographs. With the discovery of these two systems, there are now nine M dwarfs known to host transiting hot Jupiters. Among this population, TOI-3714 b (T eq = 750 ± 20 K and TSM = 98 ± 7) and TOI-3629 b (T eq = 690 ± 20 K and TSM = 80 ± 9) are warm gas giants amenable to additional characterization with transmission spectroscopy to probe atmospheric chemistry and, for TOI-3714, obliquity measurements to probe formation scenarios.

Keywords: exoplanet systems; extrasolar gaseous giant planets
Modifying the Free Energy in Skye

The Skye Equation of State (EOS) is built on top of automatic differentiation machinery. This makes it straightforward to modify, because all the requisite partial derivatives of the Helmholtz free energy are computed automatically via operator overloading. Here we demonstrate this advantage by implementing a new prescription for the anharmonic free energy of a crystalline one-component plasma. Apart from boilerplate and variable declarations, only 7 new lines of code were needed.

Keywords: stellar physics; stellar evolution; plasma physics; astronomy software
The SAMI Galaxy Survey: The Internal Orbital Structure and Mass Distribution of Passive Galaxies from Triaxial Orbit-superposition Schwarzschild Models

Dynamical models are crucial for uncovering the internal dynamics of galaxies; however, most of the results to date assume axisymmetry, which is not representative of a significant fraction of massive galaxies. Here, we build triaxial Schwarzschild orbit-superposition models of galaxies taken from the SAMI Galaxy Survey, in order to reconstruct their inner orbital structure and mass distribution. The sample consists of 161 passive galaxies with total stellar masses in the range 109.5-1012 M ⊙. We find that the changes in internal structures within 1R e are correlated with the total stellar mass of the individual galaxies. The majority of the galaxies in the sample (73% ± 3%) are oblate, while 19% ± 3% are mildly triaxial and 8% ± 2% have triaxial/prolate shape. Galaxies with $\mathrm{log}{M}_{\star }/{M}_{\odot }\gt 10.50$ are more likely to be non-oblate. We find a mean dark matter fraction of f DM = 0.28 ± 0.20, within 1R e. Galaxies with higher intrinsic ellipticity (flatter) are found to have more negative velocity anisotropy β r (tangential anisotropy). β r also shows an anticorrelation with the edge-on spin parameter ${\lambda }_{\mathrm{Re},\mathrm{EO}}$ , so that β r decreases with increasing ${\lambda }_{\mathrm{Re},\mathrm{EO}}$ , reflecting the contribution from disk-like orbits in flat, fast-rotating galaxies. We see evidence of an increasing fraction of hot orbits with increasing stellar mass, while warm and cold orbits show a decreasing trend. We also find that galaxies with different (V/σ - h 3) kinematic signatures have distinct combinations of orbits. These results are in agreement with a formation scenario in which slow- and fast-rotating galaxies form through two main channels.

Keywords: galaxy evolution; galaxy dynamics; galaxy structure; galaxy kinematics
Stellar Radial Velocities in the Old Open Cluster M67 (NGC 2682). II. The Spectroscopic Binary Population

We present and analyze 120 spectroscopic binary and triple cluster members of the old (4 Gyr) open cluster M67 (NGC 2682). As a cornerstone of stellar astrophysics, M67 is a key cluster in the WIYN Open Cluster Study (WOCS); radial-velocity (RV) observations of M67 are ongoing and extend back over 45 yr, incorporating data from seven different telescopes, and allowing us to detect binaries with orbital periods ≲104 days. Our sample contains 1296 stars (604 cluster members) with magnitudes of 10 ≤ V ≤ 16.5 (about 1.3-0.7 M⊙), from the giants down to ∼4 mag below the main-sequence turnoff, and extends in radius to 30' (7.4 pc at a distance of 850 pc, or ∼7 core radii). This paper focuses primarily on the main-sequence binaries, but orbital solutions are also presented for red giants, yellow giants, and sub-subgiants. Out to our period detection limit and within our magnitude and spatial domain, we find a global main-sequence incompleteness-corrected binary fraction of 34% ± 3%, which rises to 70% ± 17% in the cluster center. We derive a tidal circularization period of ${P}_{\mathrm{circ}}={11.0}_{-1.0}^{+1.1}\,\mathrm{days}$ <!-- --> . We also analyze the incompleteness-corrected distributions of binary orbital elements and masses. The period distribution rises toward longer periods. The eccentricity distribution, beyond Pcirc, is consistent with a uniform distribution. The mass-ratio distribution is also consistent with a uniform distribution. Overall, these M67 binaries are closely consistent with similar binaries in the galactic field, as well as with the old (7 Gyr) open cluster NGC 188. WOCS. 83.

Keywords: spectroscopic binary stars; binary stars; radial velocity; open star clusters; star clusters; solar analogs; catalogs; observational astronomy
Monitoring the Spatio-temporal Evolution of a Reconnection X-line in Space

Inherently, magnetic reconnection—the process responsible for stellar flares and magnetospheric substorms—is very dynamic in space, owing to magnetic fluctuations and unsteady inflows. However, this process was always explained as a static picture in spacecraft measurements, neglecting the temporal evolution. This picture is not correct. Here we provide the first dynamic picture of magnetic reconnection in space, by monitoring the spatio-temporal evolution of a reconnection X-line at the magnetopause. Surprisingly, we find that the angle of a reconnection X-line can change from 44°8 to 24°9 during tens of milliseconds, which is significantly smaller than the characteristic timescale of the reconnection process (t = di/VA ∼ 410 ms). Meanwhile, the spacecraft moves from the inflow region to the outflow region (spatial evolution). This result demonstrates that the magnetic reconnection in space can develop rapidly during tens of milliseconds, and thus that the concept of dynamic reconnection should be invoked instead of a static diagram.

Keywords: solar magnetic reconnection; dynamical evolution; space plasmas; plasma physics; solar wind
Galaxy Clustering in the Mira-Titan Universe. I. Emulators for the Redshift Space Galaxy Correlation Function and Galaxy-Galaxy Lensing

We construct accurate emulators for the projected and redshift space galaxy correlation functions and excess surface density as measured by galaxy-galaxy lensing, based on halo occupation distribution modeling. Using the complete Mira-Titan suite of 111 N-body simulations, our emulators vary over eight cosmological parameters and include the effects of neutrino mass and dynamical dark energy. We demonstrate that our emulators are sufficiently accurate for the analysis of the Baryon Oscillation Spectroscopic Survey DR12 CMASS galaxy sample over the range 0.5 ≤ r ≤ 50 h -1 Mpc. Furthermore, we show that our emulators are capable of recovering unbiased cosmological constraints from realistic mock catalogs over the same range. Our mock catalog tests show the efficacy of combining small-scale galaxy-galaxy lensing with redshift space clustering and that we can constrain the growth rate and σ 8 to 7% and 4.5%, respectively, for a CMASS-like sample using only the measurements covered by our emulator. With the inclusion of a cosmic microwave background prior on H 0, this reduces to a 2% measurement of the growth rate.

Keywords: cosmology; large-scale structure of the universe
The ALMA Survey of 70 μm Dark High-mass Clumps in Early Stages (ASHES). II. Molecular Outflows in the Extreme Early Stages of Protocluster Formation

We present a study of outflows at extremely early stages of high-mass star formation obtained from the ALMA Survey of 70 μm dark High-mass clumps in Early Stages (ASHES). Twelve massive 3.6-70 μm dark prestellar clump candidates were observed with the Atacama Large Millimeter/submillimeter Array (ALMA) in Band 6. Forty-three outflows are identified toward 41 out of 301 dense cores using the CO and SiO emission lines, yielding a detection rate of 14%. We discover six episodic molecular outflows associated with low- to high-mass cores, indicating that episodic outflows (and therefore episodic accretion) begin at extremely early stages of protostellar evolution for a range of core masses. The time span between consecutive ejection events is much smaller than those found in more evolved stages, which indicates that the ejection episodicity timescale is likely not constant over time. The estimated outflow dynamical timescale appears to increase with core masses, which likely indicates that more massive cores have longer accretion timescales than less massive cores. The lower accretion rates in these 70 μm dark objects compared to the more evolved protostars indicate that the accretion rates increase with time. The total outflow energy rate is smaller than the turbulent energy dissipation rate, which suggests that outflow-induced turbulence cannot sustain the internal clump turbulence at the current epoch. We often detect thermal SiO emission within these 70 μm dark clumps that is unrelated to CO outflows. This SiO emission could be produced by collisions, intersection flows, undetected protostars, or other motions.

Keywords: infrared dark clouds; star formation; massive stars; protostars; interstellar medium; stellar winds; interstellar line emission; stellar jets; protoclusters
TESS Extended Mission 10 Minute Cadence Retains Nyquist Aliases

During its two-year prime mission, the Transiting Exoplanet Survey Satellite (TESS) is obtaining full-frame images with a regular 30-minute cadence in a sequence of 26 sectors that cover a combined 85% of the sky. While its primary science case is to discover new exoplanets transiting nearby stars, TESS data are superb for studying many types of stellar variability, with the number of publications using TESS data for other areas of astrophysics keeping pace with exoplanet papers. Following the conclusion of its prime mission in July 2020, TESS will revisit the sky in an extended mission that records full-frame images at a faster ten-minute cadence. In this note, I demonstrate that choosing a large submultiple of the original exposure times for the new cadence limits the synergy between prime and extended TESS mission data since both sampling rates produce many of the same Nyquist aliases. Adjusting the extended mission exposure time by as little as one second would largely resolve Nyquist ambiguities in the combined TESS data set.

Keywords: astrostatistics strategies; astronomical techniques; time series analysis; variable stars
Grain Formation around the AGB Star L2 Puppis Based On ALMA Observations

While models of grain formation in the outflows of carbon-rich stars have been relatively successful, models of outflows from oxygen-rich, asymptotic giant branch stars have been less fortunate. Under current modeling, it is difficult to produce sufficient amounts of silicate grains with high enough opacity to form a dust-driven wind from these stars. To investigate the cause of this difference, this work is a comparison between typical outflow model results and a model using input from Atacama Large Millimeter/submillimeter Array observations of L2 Puppis. The temperatures from these observations are much lower than would typically be used in the standard outflow model. In addition, the observed gas densities are much higher than predicted from typical outflow models. Both of these differences make the formation of silicate grains much more favorable than predicted in current outflow models. We then explore the effects of other possible nonideal conditions including the efficiency of cluster growth prior to nucleation, the efficiency of grain growth following nucleation and the variation of grain coupling to stellar radiation during grain growth. Finally, we calculate the potential enhancement in grain production based on possible increased refractory abundances resulting from the vaporization of millimeter-scale and larger particles left over from the presence of a former planetary system.

Keywords: asymptotic giant branch stars; circumstellar dust; circumstellar envelopes
Constraints on the Explosion Timescale of Core-collapse Supernovae Based on Systematic Analysis of Light Curves

The explosion mechanism of core-collapse supernovae is not fully understood yet. In this work, we give constraints on the explosion timescale based on 56Ni synthesized by supernova explosions. First, we systematically analyze multiband light curves of 82 stripped-envelope supernovae (SESNe) to obtain bolometric light curves, which is among the largest samples of the bolometric light curves of SESNe derived from the multiband spectral energy distribution. We measure the decline timescale and the peak luminosity of the light curves and estimate the ejecta mass (M ej) and 56Ni mass (M Ni) to connect the observed properties with the explosion physics. We then carry out one-dimensional hydrodynamics and nucleosynthesis calculations, varying the progenitor mass and the explosion timescale. From the calculations, we show that the maximum 56Ni mass that 56Ni-powered SNe can reach is expressed as M Ni ≲ 0.2 M ej. Comparing the results from the observations and the calculations, we show that the explosion timescale shorter than 0.3 s explains the synthesized 56Ni mass of the majority of the SESNe.

Keywords: core-collapse supernovae; supernovae; type ib supernovae; type ic supernovae
Turbulence and Waves in the Sub-Alfvénic Solar Wind Observed by the Parker Solar Probe during Encounter 10

During its 10th orbit around the Sun, the Parker Solar Probe sampled two intervals where the local Alfvén speed exceeded the solar wind speed, lasting more than 10 hours in total. In this paper, we analyze the turbulence and wave properties during these periods. The turbulence is observed to be Alfvénic and unbalanced, dominated by outward-propagating modes. The power spectrum of the outward-propagating Elsässer z + mode steepens at high frequencies while that of the inward-propagating z - mode flattens. The observed Elsässer spectra can be explained by the nearly incompressible (NI) MHD turbulence model with both 2D and Alfvénic components. The modeling results show that the z + spectra are dominated by the NI/slab component, and the 2D component mainly affects the z - spectra at low frequencies. An MHD wave decomposition based on an isothermal closure suggests that outward-propagating Alfvén and fast magnetosonic wave modes are prevalent in the two sub-Alfvénic intervals, while the slow magnetosonic modes dominate the super-Alfvénic interval in between. The slow modes occur where the wavevector is nearly perpendicular to the local mean magnetic field, corresponding to nonpropagating pressure-balanced structures. The alternating forward and backward slow modes may also be features of magnetic reconnection in the near-Sun heliospheric current sheet.

Keywords: solar coronal waves; interplanetary turbulence; solar wind
Evidence for a Cyclotron Absorption Line and Spectral Transition in EXO 2030+375 during the 2021 Giant Outburst

Based on Insight-HXMT observations of EXO 2030+375 during its 2021 giant outburst, we report the analysis of pulse variations and the broadband X-ray spectrum, and find the presence of a potential cyclotron resonant scattering feature (CRSF) with the fundamental line at ∼47 keV from both average spectra and phase-resolved spectroscopy. During the outburst, the source reached an X-ray luminosity of ∼1038 erg s‑1 from 2 to 105 keV at a distance of 7.1 kpc. The X-ray pulsar at the spin period of 41.27 ± 0.61 s exhibits complex timing and spectral variations with both energy and luminosity during the outburst. The shapes of the pulse profiles show the single main peak above ∼20 keV, while appearing to exhibit multipeak patterns in low-energy bands, and the transition of the 10–20 keV pulse profiles from multipeak to single peak is observed at ∼0.8 × 1038 erg s‑1, which suggests the evolution from the subcritical luminosity (pencil-beam dominated) to the supercritical luminosity (fan-beam dominated) regime. A dip structure before the energy of the CRSFs is found in the pulse fraction–energy relation of EXO 2030+375 near the peak luminosity. A detailed analysis of spectral parameters showed that the power-law photon index exhibits three distinct trends as luminosity increases, and these spectral changes also signify a spectral transition from subcritical to supercritical regimes. The critical luminosity infers a magnetic field of ∼(4.8‑6.0) × 1012 G, which supports the presence of the cyclotron line at ∼47 keV. A Comptonization model applied for the broad X-ray spectra during the outburst also suggests the surface magnetic field ranging from ∼(5‑9) × 1012 G.

Keywords: magnetic fields; x-ray binary stars; high mass x-ray binary stars
Multiplicity Boost of Transit Signal Classifiers: Validation of 69 New Exoplanets using the Multiplicity Boost of ExoMiner

Most existing exoplanets are discovered using validation techniques rather than being confirmed by complementary observations. These techniques generate a score that is typically the probability of the transit signal being an exoplanet (y(x) = exoplanet) given some information related to that signal (represented by x). Except for the validation technique in Rowe et al. (2014), which uses multiplicity information to generate these probability scores, the existing validation techniques ignore the multiplicity boost information. In this work, we introduce a framework with the following premise: given an existing transit-signal vetter (classifier), improve its performance using multiplicity information. We apply this framework to several existing classifiers, which include vespa, Robovetter, AstroNet, ExoNet, GPC and RFC, and ExoMiner, to support our claim that this framework is able to improve the performance of a given classifier. We then use the proposed multiplicity boost framework for ExoMiner V1.2, which addresses some of the shortcomings of the original ExoMiner classifier, and validate 69 new exoplanets for systems with multiple Kepler Objects of Interests from the Kepler catalog.

Keywords: exoplanet astronomy; exoplanet catalogs; exoplanets; exoplanet detection methods; exoplanet systems; convolutional neural networks; neural networks
High-resolution Spectral Line Indices Useful for the Analysis of Stellar Populations

The well-known age-metallicity-attenuation degeneracy does not permit unique and good estimates of basic parameters of stars and stellar populations. The effects of dust can be avoided using spectral line indices, but current methods have not been able to break the age-metallicity degeneracy. Here we show that using at least two new spectral line indices defined and measured on high-resolution (R = 6000) spectra of a signal-to-noise ratio (S/N) ≥ 10, one gets unambiguous estimates of the age and metallicity of intermediate to old stellar populations. Spectroscopic data retrieved with new astronomical facilities, e.g., X-shooter, MEGARA, and MOSAIC, can be employed to infer the physical parameters of the emitting source by means of spectral line index and index-index diagram analysis.

Keywords: astronomy data analysis
COMAP Early Science. VI. A First Look at the COMAP Galactic Plane Survey

We present early results from the CO Mapping Array Project (COMAP) Galactic Plane Survey conducted between 2019 June and 2021 April, spanning 20° < ℓ < 40° in Galactic longitude and ∣b∣ < 1.°5 in Galactic latitude with an angular resolution of 4.'5. We present initial results from the first part of the survey, including the diffuse emission and spectral energy distributions of H II regions and supernova remnants (SNRs). Using low- and high-frequency surveys to constrain free-free and thermal dust emission contributions, we find evidence of excess flux density at 30 GHz in six regions, which we interpret as anomalous microwave emission. Furthermore we model ultracompact H II contributions using data from the 5 GHz CORNISH catalog and reject these as the cause of the 30 GHz excess. Six known SNRs are detected at 30 GHz, and we measure spectral indices consistent with the literature or show evidence of steepening. The flux density of the SNR W44 at 30 GHz is consistent with a power-law extrapolation from lower frequencies with no indication of spectral steepening in contrast with recent results from the Sardinia Radio Telescope. We also extract five hydrogen radio recombination lines (RRLs) to map the warm ionized gas, which can be used to estimate electron temperatures or to constrain continuum free-free emission. The full COMAP Galactic Plane Survey, to be released in 2023/2024, will span ℓ ~ 20°-220° and will be the first large-scale radio continuum and RRL survey at 30 GHz with 4.'5 resolution.

Keywords: surveys; h ii regions; supernova remnants; interstellar medium; milky way galaxy; radio continuum emission