adsabs/SciX_UAT_keywords huggingface dataset:
The Physical Properties of Fermi-4LAC Flat Spectrum Radio Quasars

In this work, we collect quasi-simultaneous infrared, optical, X-ray and γ-ray data of 60 Fermi fourth LAT AGN catalog (4LAC) flat spectrum radio quasars (FSRQs). In the framework of the conventional one-zone leptonic model, we investigate the physical properties of Fermi-4LAC FSRQs' jets by modeling their quasi-simultaneous spectral energy distributions (SEDs). Our main results are summarized as follows. (1) There is a linear correlation between synchrotron peak frequency and curvature of the electron energy distribution. As suggested by previous works, the slope of the best linear fitting equation of this correlation is consistent with statistic acceleration that needs a fluctuation of fractional acceleration gain. (2) The γ-ray dissipation regions are located at the range from 0.1 to 10 pc away from the supermassive black hole, and located outside the broad-line region and within the dusty torus. (3) A size relation Pe (the kinetic power carried in relativistic electrons) ∼PB (Poynting flux) ≤Pr (the radiative power) <Pp (the kinetic power in cold protons) is found in our modeling. Among them, Pe ∼ PB suggests that SEDs of almost all FSRQs with parameters are close to equipartition between the magnetic field and the relativistic electrons. The Pe < Pr suggest that the most energy of the relativistic electrons are dissipated by EC radiation for FSRQs. (4) There is an anticorrelation between the peak energy of SEDs (γpeak) and the jet power (Pjet), which is consistent with the blazar sequence.

Keywords: blazars; spectral energy distribution; non-thermal radiation sources; relativistic jets
Probing Velocity Structures of Protostellar Envelopes: Infalling and Rotating Envelopes within Turbulent Dense Cores

We have observed the three low-mass protostars, IRAS 15398-3359, L1527 IRS, and TMC-1A, with the ALMA 12 m array, the ACA 7 m array, and the IRAM-30 m and APEX telescopes in the C18O J = 2-1 emission. Overall, the C18O emission shows clear velocity gradients at radii of ~100-1000 au, which likely originate from the rotation of envelopes, while velocity gradients are less clear and velocity structures are more perturbed on scales of ~1000-10,000 au. IRAS 15398-3359 and L1527 IRS show a break at radii of ~1200 and ~1700 au in the radial profile of the peak velocity, respectively. The peak velocity is proportional to r -1.38 or r -1.7 within the break radius, which can be interpreted as indicating the rotational motion of the envelope with a degree of contamination by gas motions on larger spatial scales. The peak velocity follows v peak ∝ r 0.68 or v peak ∝ r 0.46 outside the break radius, which is similar to the J/M-R relation of dense cores. TMC-1A exhibits a radial profile of the peak velocity that is not consistent with the rotational motion of the envelope nor the J/M-R relation. The origin of the relation of v peak ∝ r 0.46-r 0.68 is investigated by examining correlations of the velocity deviation (δ v) and the spatial scale (τ) in the two sources. The obtained spatial correlations, δ v ∝ τ ~0.6, are consistent with the scaling law predicted by turbulence models, which may suggest that large-scale velocity structures originate from turbulence.

Keywords: star formation; low mass stars; interstellar medium; protostars; young stellar objects; radio astronomy; millimeter astronomy
Thermal History of Asteroid Parent Bodies Is Reflected in Their Metalorganic Chemistry

Organo-magnesium compounds were shown to contribute significantly to the soluble carbon molecular complexity and diversity of meteorites, and their analysis increases our knowledge on carbon stabilization/sequestration processes in the asteroidal parent body. Here we present a new group of sulfur-magnesium-carboxylates detected using ultra-high-resolution mass spectrometry in a variety of meteorites. These novel compounds show increased abundance correlated with the thermal history of the asteroid parent bodies. By comparing the soluble organic extracts of 44 meteorites having experienced variable post-accretion history, we describe distinct organic compound patterns of sulfur-magnesium-carboxylates in relation to their long- and short-duration thermal history. It is shown that the exceptional stability of these molecules enables survival of carbon under harsh thermal extraterrestrial conditions, even in the vitrified fusion crust formed during entry into the Earth's atmosphere. Sulfur-magnesium-carboxylates augment our understanding of parent body proceedings with regard to carbon sequestration and speciation in space.

Keywords: asteroids; meteorite composition; meteorites; carbonaceous chondrites; achondrites; astrobiology; carbon-nitrogen cycle; chemical enrichment
Air-Sea Interactions on Titan: Effect of Radiative Transfer on the Lake Evaporation and Atmospheric Circulation

Titan's northern high latitudes host many large hydrocarbon lakes. Like water lakes on Earth, Titan's lakes are constantly subject to evaporation. This process strongly affects the atmospheric methane abundance, the atmospheric temperature, the lake mixed layer temperature, and the local wind circulation. In this work we use a 2D atmospheric mesoscale model coupled to a slab lake model to investigate the effect of solar and infrared radiation on the exchange of energy and methane between Titan's lakes and atmosphere. The magnitude of solar radiation reaching the surface of Titan through its thick atmosphere is only a few watts per square meter. However, we find that this small energy input is important and is comparable in absolute magnitude to the latent and sensible heat fluxes, as suggested in a study by Rafkin & Soto (2020). The implementation of a gray radiative scheme in the model confirms the importance of radiation when studying lakes at the surface of Titan. Solar and infrared radiation change the energy balance of the system leading to an enhancement of the methane evaporation rate, an increase of the equilibrium lake temperature almost completely determined by its environment (humidity, insolation, and background wind), and a strengthening of the local sea breeze, which undergoes diurnal variations. The sea breeze efficiently transports methane vapor horizontally, from the lake to the land, and vertically due to rising motion along the sea breeze front and due to radiation-induced turbulence over the land.

Keywords: titan; natural satellite atmospheres; radiative transfer; planetary climates; planetary atmospheres
Suppressing the Thermal SZ-induced Variance in CMB-cluster Lensing Estimators

Accurate galaxy cluster mass measurements from the gravitational lensing of the cosmic microwave background temperature maps depend on mitigating potential biases from the cluster’s own thermal Sunyaev-Zel’dovich (SZ) effect signal. Quadratic lensing estimators use a pair of maps to extract the lensing signal: a large-scale gradient map and a small-scale lensing map. The SZ bias can be eliminated by using an SZ-free map in the pair, with the gradient map being favored for signal-to-noise reasons. However, while this approach eliminates the bias, the SZ power in small-scale lensing map adds extra variance that can become significant for high-mass clusters and low-noise surveys. In this work, we propose projecting out an SZ template to reduce the SZ variance. Any residual SZ signal after template fitting is uncorrelated with the SZ-free gradient map, and thus does not bias the mass measurements. For massive clusters above 4× {10}14 {M}⊙ observed by the upcoming CMB-S4 and Simons Observatory experiments, we find that the template fitting approach would increase the cluster lensing signal-to-noise by a factor of 1.4.

Keywords: sunyaev-zeldovich effect; cosmic microwave background radiation; galaxy clusters; weak gravitational lensing; observational cosmology
Photometric and Spectroscopic Studies of Superoutbursts of Three Dwarf Novae Independently Identified by the SVOM/GWAC System in 2018

We report our photometric and spectroscopic follow-up observations of the superoutbursts of three dwarf novae (DNe; GWAC 180415A, GWAC 181017A, and GWAC 181211A) identified independently by the Ground Wide-angle Cameras system, one of the ground-based instruments of the China-France SVOM mission. Based on a combination of our photometry and that taken from the American Association of Variable Star Observers, our period analysis of the superhumps enables us to determine the mass ratios to be 0.0967-0.1163, 0.1879-0.1883, and 0.0981-0.1173 for GWAC 180415A, GWAC 181017A, and GWAC 181211A, respectively. GWAC 180415A can be firmly identified as a WZ sge-type DNe due to its long duration (∼2 weeks) multiple rebrightenings with amplitudes of 3-4 mag, the early superhump associated with a double-wave modulation and the low-mass ratio. The inferred low-mass ratio and location in the \varepsilon {--}{P}orb} diagram suggest that GWAC 181211A is a WZ sge-type DNe candidate. The measured Balmer decrements suggest the Balmer line emission is produced from an optical thick region in GWAC 180415A and GWAC 181017A, and from an optically thin region in GWAC 181211A.

Keywords: dwarf novae; wz sagittae stars; cataclysmic variable stars; observational astronomy; astronomical methods; automatic patrol telescopes
Astrochemical Significance of the P + SO Reaction: Spectroscopic Characterization of SPO, PSO, and SOP Isomers

The doublet and quartet potential energy surfaces for the P + SO → PO + S reaction are explored using the highly accurate explicit correlation multireference configuration interaction method, and the reaction is found to be thermodynamically favorable, with an exothermicity value of 70.5 kJ mol-1. The electronic structure, spectra, and bond dissociation energies of the intermediates involved in the reaction, such as SPO, PSO, and SOP, are calculated using high-level quantum chemistry methods. An explanation of the nondetection of the diatomic SP is proposed. At pressures relevant to astrochemistry, the reaction is overwhelmingly bimolecular, with a predicted rate coefficient of 2.1 × 10-10 (T/300)-0.23 cm3 molecule-1 s-1. The results from this study are expected to aid in the spectroscopic detection of these new species in the laboratory and the interstellar medium.

Keywords: comets; interstellar objects; interstellar molecules; interstellar medium
Optical Night Sky Brightness Measurements from the Stratosphere

This paper presents optical night sky brightness measurements from the stratosphere using CCD images taken with the Super-pressure Balloon-borne Imaging Telescope (SuperBIT). The data used for estimating the backgrounds were obtained during three commissioning flights in 2016, 2018, and 2019 at altitudes ranging from 28 to 34 km above sea level. For a valid comparison of the brightness measurements from the stratosphere with measurements from mountain-top ground-based observatories (taken at zenith on the darkest moonless night at high Galactic and high ecliptic latitudes), the stratospheric brightness levels were zodiacal light and diffuse Galactic light subtracted, and the airglow brightness was projected to zenith. The stratospheric brightness was measured around 5.5 hr, 3 hr, and 2 hr before the local sunrise time in 2016, 2018, and 2019, respectively. The B, V, R, and I brightness levels in 2016 were 2.7, 1.0, 1.1, and 0.6 mag arcsec-2 darker than the darkest ground-based measurements. The B, V, and R brightness levels in 2018 were 1.3, 1.0, and 1.3 mag arcsec-2 darker than the darkest ground-based measurements. The U and I brightness levels in 2019 were 0.1 mag arcsec-2 brighter than the darkest ground-based measurements, whereas the B and V brightness levels were 0.8 and 0.6 mag arcsec-2 darker than the darkest ground-based measurements. The lower sky brightness levels, stable photometry, and lower atmospheric absorption make stratospheric observations from a balloon-borne platform a unique tool for astronomy. We plan to continue this work in a future midlatitude long duration balloon flight with SuperBIT.

Keywords: ccd photometry; night sky brightness; sky brightness; stratosphere; high altitude balloons; optical observatories; diffuse radiation; gegenschein
On the Synthesis of the Astronomically Elusive 1-Ethynyl-3-Silacyclopropenylidene (c-SiC4H2) Molecule in Circumstellar Envelopes of Carbon-rich Asymptotic Giant Branch Stars and Its Potential Role in the Formation of the Silicon Tetracarbide Chain (SiC4)

Organosilicon molecules such as silicon carbide (SiC), silicon dicarbide (c-SiC2), silicon tricarbide (c-SiC3), and silicon tetracarbide (SiC4) represent basic molecular building blocks connected to the growth of silicon-carbide dust grains in the outflow of circumstellar envelopes of carbon-rich asymptotic giant branch (AGB) stars. Yet, the fundamental mechanisms of the formation of silicon carbides and of the early processes that initiate the coupling of silicon-carbon bonds in circumstellar envelopes have remained obscure. Here, we reveal in a crossed molecular beam experiment contemplated with ab initio electronic calculations that the astronomically elusive 1-ethynyl-3-silacyclopropenylidene molecule (c-SiC4H2, Cs, X1A') can be synthesized via a single-collision event through the barrierless reaction of the silylidyne radical (SiH) with diacetylene (C4H2). This system represents a benchmark of a previously overlooked class of reactions, in which the silicon-carbon bond coupling can be initiated by a barrierless and overall exoergic reaction between the simplest silicon-bearing radical (silylidyne) and a highly hydrogen-deficient hydrocarbon (diacetylene) in the inner circumstellar envelopes of evolved carbon-rich stars such as IRC+10216. Considering that organosilicon molecules like 1-ethynyl-3-silacyclopropenylidene might be ultimately photolyzed to bare carbon-silicon clusters like the linear silicon tetracarbide (SiC4), hydrogenated silicon-carbon clusters might represent the missing link eventually connecting simple molecular precursors such as silane (SiH4) to the population of silicon-carbide based interstellar grains ejected from carbon-rich AGB stars into the interstellar medium.

Keywords: astrochemistry; interstellar dust; laboratory astrophysics; circumstellar envelopes
Detection of Molecular H2O on Nominally Anhydrous Asteroids

We used the FORCAST instrument on SOFIA to obtain mid-infrared spectra (4.9–13.7 μm) of four S-type asteroids: (7) Iris, (11) Parthenope, (18) Melpomene, and (20) Massalia. Three of these four silicate-rich asteroids (Iris, Melpomene, and Massalia) were observed to have 3 μm features indicative of hydration by McAdam et al. We report a detection of a 6 μm feature that is unambiguously attributed to molecular water on two asteroids, Iris and Massalia, with peak heights of 4.532% ± 0.011% and 4.476% ± 0.012%, respectively. We estimate the abundance of molecular water based on these peak heights to be 454 ± 202 μg g‑1 and 448 ± 209 μg g‑1, consistent with values found on the sunlit Moon by SOFIA+FORCAST.

Keywords: asteroids; infrared spectroscopy; surface composition
Precovery Observations Confirm the Capture Time of Asteroid 2020 CD3 as Earth's Minimoon

Asteroid 2020 CD3 was discovered on 2020 February 15 by the Catalina Sky Survey while it was temporarily captured in a geocentric orbit before escaping Earth's Hill sphere on 2020 March 7. We searched archival images and found precoveries of 2020 CD3 from the Dark Energy Camera and Catalina Sky survey. The Dark Energy Camera images yielded three observations on 2019 January 17, while the Catalina Sky Survey images yielded four observations on 2019 January 24 from the Mt. Lemmon telescope and four observations on 2018 May 9 from the Mt. Bigelow telescope. These precovery observations allowed us to refine the orbit of 2020 CD3 and determine that it was captured in a geocentric orbit on 2017 September 15 after a close approach to the Moon at a distance of 11,974 ± 10 km. We analyzed the trajectory of 2020 CD3 to look for potential Earth impacts within the next 100 years and find a ≳1% probability of an impact between 2061 and 2120 depending on nongravitational force model assumptions. The small size of 2020 CD3, about 1 to 2 m, makes any potential impact harmless.

Keywords: near-earth objects; asteroids
Effective Collision Strengths and Radiative Parameters for Lines in the Sc II Spectrum

This work reports large-scale calculations of electron excitation effective collision strengths and transition rates for a wide range of Sc II spectral lines for astrophysical analysis and modeling. The present results are important for reliable abundance determinations in various astrophysical objects, including metal-poor stars, H II regions, and gaseous nebulae. Accurate descriptions of the target wave functions and adequate accounts of the various interactions between the target levels are of primary importance for calculations of collision and radiative parameters. The target wave functions have been determined by a combination of the multiconfiguration Hartree-Fock and B-spline box-based close-coupling methods, together with the nonorthogonal orbitals technique. The calculations of the collision strengths have been performed using the B-spline Breit-Pauli R-matrix method. The close-coupling expansion includes 145 fine-structure levels of Sc II belonging to the terms of the 3p 63d 2, 3p 63d4l (l = 0-3), 3p 63d5l (l = 0-3), 3p 63d6s, 3p 64s 2, 3p 64s4l (l = 0-3), 3p 64s5l (l = 0-1), and 3p 64p 2 configurations. The effective collision strengths are reported as a function of electron temperature in the range from 103 to 105 K. The collision and radiative rates are reported for all of the possible transitions between the 145 fine-structure levels. Striking discrepancies exist with the previous R-matrix calculations of the effective collision strengths for the majority of the transitions, indicating possible systematic errors in these calculations. Thus, there is a need for accurate calculations to reduce the uncertainties in the atomic data. The likely uncertainties in our effective collision strengths and radiative parameters have been assessed by means of comparisons with other collision calculations and available experimental radiative parameters.

Keywords: atomic physics; laboratory astrophysics
Monotonicity of the Cores of Massive Stars

Massive stars are linked to diverse astronomical processes and objects including star formation, supernovae and their remnants, cosmic rays, interstellar media, and galaxy evolution. Understanding their properties is of primary importance for modern astronomy, and finding simple rules that characterize them is especially useful. However, theoretical simulations have not yet realized such relations, instead finding that the late evolutionary phases are significantly affected by a complicated interplay between nuclear reactions, chemical mixing, and neutrino radiation, leading to nonmonotonic initial-mass dependencies of the iron core mass and the compactness parameter. We conduct a set of stellar evolution simulations, in which evolutions of He star models are followed until their central densities uniformly reach 1010 g cm-3, and analyze their final structures as well as their evolutionary properties, including the lifetime, surface radius change, and presumable fates after core collapse. Based on the homogeneous data set, we have found that monotonicity is inherent in the cores of massive stars. We show that not only the density, entropy, and chemical distributions, but also their lifetimes and explosion properties such as the proto-neutron-star mass and the explosion energy can be simultaneously ordered into a monotonic sequence. This monotonicity can be regarded as an empirical principle that characterizes the cores of massive stars.

Keywords: stellar evolution; core-collapse supernovae
The SAMI Galaxy Survey: Kinematics of Stars and Gas in Brightest Group Galaxies—The Role of Group Dynamics

We study the stellar and gas kinematics of the brightest group galaxies (BGGs) in dynamically relaxed and unrelaxed galaxy groups for a sample of 154 galaxies in the SAMI galaxy survey. We characterize the dynamical state of the groups using the luminosity gap between the two most luminous galaxies and the BGG offset from the luminosity centroid of the group. We find that the misalignment between the rotation axis of gas and stellar components is more frequent in the BGGs in unrelaxed groups, although with quite low statistical significance. Meanwhile, galaxies whose stellar dynamics would be classified as "regular rotators" based on their kinemetry are more common in relaxed groups. We confirm that this dependency on group dynamical state remains valid at fixed stellar mass and Sérsic index. The observed trend could potentially originate from a differing BGG accretion history in virialized and evolving groups. Among the halo relaxation probes, the group BGG offset appears to play a stronger role than the luminosity gap on the stellar kinematic differences of the BGGs. However, both the group BGG offset and luminosity gap appear to roughly equally drive the misalignment between the gas and stellar component of the BGGs in one direction. This study offers the first evidence that the dynamical state of galaxy groups may influence the BGG's stellar and gas kinematics, and we call for further studies using a larger sample with higher signal-to-noise.

Keywords: galaxy kinematics; galaxy rotation; galaxy evolution; galaxy groups; galaxy mergers; galaxy dynamics
GTC Follow-up Observations of Very Metal-poor Star Candidates from DESI

The observations from the Dark Energy Spectroscopic Instrument (DESI) will significantly increase the numbers of known extremely metal-poor stars by a factor of ~10, improving the sample statistics to study the early chemical evolution of the Milky Way and the nature of the first stars. In this paper we report follow-up observations with high signal-to-noise ratio of nine metal-poor stars identified during the DESI commissioning with the Optical System for Imaging and Low-Resolution Integrated Spectroscopy (OSIRIS) instrument on the 10.4 m Gran Telescopio Canarias. The analysis of the data using a well-vetted methodology confirms the quality of the DESI spectra and the performance of the pipelines developed for the data reduction and analysis of DESI data.

Keywords: spectroscopy; field stars; milky way formation
TOI-5205b: A Short-period Jovian Planet Transiting a Mid-M Dwarf

We present the discovery of TOI-5205b, a transiting Jovian planet orbiting a solar metallicity M4V star, which was discovered using Transiting Exoplanet Survey Satellite photometry and then confirmed using a combination of precise radial velocities, ground-based photometry, spectra, and speckle imaging. TOI-5205b has one of the highest mass ratios for M-dwarf planets, with a mass ratio of almost 0.3%, as it orbits a host star that is just 0.392 ± 0.015 M ⊙. Its planetary radius is 1.03 ± 0.03 R J, while the mass is 1.08 ± 0.06 M J. Additionally, the large size of the planet orbiting a small star results in a transit depth of ~7%, making it one of the deepest transits of a confirmed exoplanet orbiting a main-sequence star. The large transit depth makes TOI-5205b a compelling target to probe its atmospheric properties, as a means of tracing the potential formation pathways. While there have been radial-velocity-only discoveries of giant planets around mid-M dwarfs, this is the first transiting Jupiter with a mass measurement discovered around such a low-mass host star. The high mass of TOI-5205b stretches conventional theories of planet formation and disk scaling relations that cannot easily recreate the conditions required to form such planets.

Keywords: radial velocity; m dwarf stars; extrasolar gaseous giant planets; transits