adsabs/SciX_UAT_keywords huggingface dataset:
Evolution of Mercury's Earliest Atmosphere

MESSENGER observations suggest a magma ocean formed on proto-Mercury, during which evaporation of metals and outgassing of C- and H-bearing volatiles produced an early atmosphere. Atmospheric escape subsequently occurred by plasma heating, photoevaporation, Jeans escape, and photoionization. To quantify atmospheric loss, we combine constraints on the lifetime of surficial melt, melt composition, and atmospheric composition. Consideration of two initial Mercury sizes and four magma ocean compositions determines the atmospheric speciation at a given surface temperature. A coupled interior-atmosphere model determines the cooling rate and therefore the lifetime of surficial melt. Combining the melt lifetime and escape flux calculations provides estimates for the total mass loss from early Mercury. Loss rates by Jeans escape are negligible. Plasma heating and photoionization are limited by homopause diffusion rates of ~106 kg s-1. Loss by photoevaporation depends on the timing of Mercury formation and assumed heating efficiency and ranges from ~106.6 to ~109.6 kg s-1. The material for photoevaporation is sourced from below the homopause and is therefore energy limited rather than diffusion limited. The timescale for efficient interior-atmosphere chemical exchange is less than 10,000 yr. Therefore, escape processes only account for an equivalent loss of less than 2.3 km of crust (0.3% of Mercury's mass). Accordingly, ≤0.02% of the total mass of H2O and Na is lost. Therefore, cumulative loss cannot significantly modify Mercury's bulk mantle composition during the magma ocean stage. Mercury's high core:mantle ratio and volatile-rich surface may instead reflect chemical variations in its building blocks resulting from its solar-proximal accretion environment.

Keywords: mercury (planet); solar system terrestrial planets; planetary atmospheres; planetary science; atmospheric composition; upper atmosphere
The Role of Reconnection in the Onset of Solar Eruptions

Solar eruptive events such as coronal mass ejections and eruptive flares are frequently associated with the emergence of magnetic flux from the convection zone into the corona. We use three-dimensional magnetohydrodynamic numerical simulations to study the interaction of coronal magnetic fields with emerging flux and determine the conditions that lead to eruptive activity. A simple parameter study is performed, varying the relative angle between emerging magnetic flux and a preexisting coronal dipole field. We find that in all cases the emergence results in a sheared magnetic arcade that transitions to a twisted coronal flux rope via low-lying magnetic reconnection. This structure, however, is constrained by its own outer field and so is noneruptive in the absence of reconnection with the overlying coronal field. The amount of this overlying reconnection is determined by the relative angle between the emerged and preexisting fields. The reconnection between emerging and preexisting fields is necessary to generate sufficient expansion of the emerging structure so that flare-like reconnection below the coronal flux rope becomes strong enough to trigger its release. Our results imply that the relative angle is the key parameter in determining whether the resultant active regions exhibit eruptive behavior and is thus a potentially useful candidate for predicting eruptions in newly emerging active regions. More generally, our results demonstrate that the detailed interaction between the convection zone/photosphere and the corona must be calculated self-consistently in order to model solar eruptions accurately.

Keywords: magnetohydrodynamics; magnetohydrodynamical simulations; solar coronal mass ejections; solar prominences; solar magnetic reconnection
The Red Supergiant Binary Fraction as a Function of Metallicity in M31 and M33

Recent work measuring the binary fraction of evolved red supergiants (RSGs) in the Magellanic Clouds points to a value between 15% and 30%, with the majority of the companions being unevolved B-type stars as dictated by stellar evolution. Here I extend this research to the Local Group galaxies M31 and M33 and investigate the RSG binary fraction as a function of metallicity. Recent near-IR photometric surveys of M31 and M33 have led to the identification of a complete sample of RSGs down to a limiting $\mathrm{log}L/{L}_{\odot }\geqslant 4.2$ . To determine the binary fraction of these M31 and M33 RSGs, I used a combination of newly obtained spectroscopy to identify single RSGs and RSG+OB binaries, as well as archival UV, visible, and near-IR photometry to probabilistically classify RSGs as either single or binary based on their colors. I then adjusted the observed RSG+OB binary fraction to account for observational biases. The resulting RSG binary fraction in M33 shows a strong dependence on galactocentric distance, with the inner regions having a much higher binary fraction ( ${41.2}_{-7.3}^{+12.0} \% $ ) than the outer regions ( ${15.9}_{-1.9}^{+12.4} \% $ ). Such a trend is not seen in M31; instead, the binary fraction in lightly reddened regions remains constant at ${33.5}_{-5.0}^{+8.6} \% $ . I conclude that the changing RSG binary fraction in M33 is due to a metallicity dependence, with higher-metallicity environments having higher RSG binary fractions. This dependence most likely stems not from changes in the physical properties of RSGs due to metallicity but from changes in the parent distribution of OB binaries.

Keywords: massive stars; red supergiant stars; binary stars; andromeda galaxy; triangulum galaxy; metallicity; ob stars
Possible Gravitational Microlensing Events in the Optical Lightcurve of Active Galaxy S5 0716+714

A well-known active galaxy of the blazar type, S5 0716+714, is characterized by a particularly high-variability duty cycle on short timescales at optical frequencies. As such, the source was subjected to numerous monitoring programs, including both ground-based as well as spaceborne telescopes. On closer inspection of the most recent accumulation of the data provided by the Transiting Exoplanet Survey Satellite, we have noticed several conspicuous events with "volcano-like" symmetric shape, all lasting for several hours, which closely resemble the achromatic events detected with the previous Whole Earth Blazar Telescope campaigns targeting the source. We propose that those peculiar features could be due to the gravitational microlensing of the innermost segments of the precessing jet in the system by a binary lens. We study the magnification pattern of the lens with the inverse-ray shooting method and the source trajectory parameters with the Python package MULENSMODEL. In this way, we were able to fit successfully all the selected events with a single lens, adjusting slightly only the source trajectory parameters for each lensing event. Based on the fit results, we postulate the presence of a massive binary lens containing an intermediate-mass black hole, possibly even a supermassive one, and a much less massive companion (by a factor of ≲0.01) located within the host galaxy of the blazar, most likely the central kiloparsec region. We discuss the major physical implications of the proposed scenario regarding the quest for the intermediate-mass and dual supermassive black holes in active galaxies.

Keywords: black holes; gravitational lensing; active galaxies; blazars; active galactic nuclei
On the Scaling Properties of Magnetic-field Fluctuations through the Inner Heliosphere

Although the interplanetary magnetic-field variability has been extensively investigated in situ using data from several space missions, newly launched missions providing high-resolution measures and approaching the Sun offer the possibility to study the multiscale variability in the innermost solar system. Here, using Parker Solar Probe measurements, we investigate the scaling properties of solar wind magnetic-field fluctuations at different heliocentric distances. The results show a clear transition at distances close to say 0.4 au. Closer to the Sun fluctuations show a f-3/2 frequency power spectra and regular scaling properties, while for distances larger than 0.4 au fluctuations show a Kolmogorov spectrum f-5/3 and are characterized by anomalous scalings. The observed statistical properties of turbulence suggest that the solar wind magnetic fluctuations, in the late stage far from the Sun, show a multifractal behavior typical of turbulence and described by intermittency, while in the early stage, when leaving the solar corona, a breakdown of these properties is observed, thus showing a statistical monofractal global self-similarity. Physically, the breakdown observed close to the Sun should be due either to a turbulence with regular statistics or to the presence of intense stochastic fluctuations able to cancel out the correlations necessary for the presence of anomalous scaling.

Keywords: solar wind; interplanetary turbulence; time series analysis; interplanetary magnetic fields
FUMES. II. Lyα Reconstructions of Young, Active M Dwarfs

The H I Lyα (1215.67 Å) emission line dominates the far-UV spectra of M dwarf stars, but strong absorption from neutral hydrogen in the interstellar medium makes observing Lyα challenging even for the closest stars. As part of the Far-Ultraviolet M-dwarf Evolution Survey, the Hubble Space Telescope has observed 10 early-to-mid M dwarfs with ages ranging from ∼24 Myr to several Gyr in order to evaluate how the incident UV radiation evolves through the lifetime of exoplanetary systems. We reconstruct the intrinsic Lyα profiles from STIS G140L and E140M spectra, and achieve reconstructed fluxes with 1σ uncertainties ranging from 5% to a factor of two for the low-resolution spectra (G140L) and 3%-20% for the high-resolution spectra (E140M). We observe broad, 500-1000 km s-1 wings of the Lyα line profile, and analyze how the line width depends on stellar properties. We find that stellar effective temperature and surface gravity are the dominant factors influencing the line width with little impact from the star's magnetic activity level, and that the surface flux density of the Lyα wings may be used to estimate the chromospheric electron density. The Lyα reconstructions on the G140L spectra are the first attempted on λ/Δλ ∼ 1000 data. We find that the reconstruction precision is not correlated with the signal-to-noise ratio of the observation—rather, it depends on the intrinsic broadness of the stellar Lyα line. Young, low-gravity stars have the broadest lines and therefore provide more information at low spectral resolution to the fit to break degeneracies among model parameters.

Keywords: m stars; interstellar absorption; stellar activity; stellar chromospheres; ultraviolet astronomy
Measuring the Chemodynamics and Ages of the M32 and M110 Dwarf Galaxies with APOGEE

We present a full-spectrum-fitting analysis of the central kinematics and chemistry of the Andromeda dwarf satellite galaxies M32 and M110. We use an Markov Chain Monte Carlo routine to fit high-resolution, near-infrared, integrated-light spectra from APOGEE with empirical simple stellar population templates constructed from individual APOGEE stellar spectra. This yields the best-fitting mean radial velocity, velocity dispersion, metallicity, α abundance, and age for each spectrum. In general, our results are consistent with literature values where available, and we explore possible reasons where offsets are measured. This study was presented in a poster at the 243rd meeting of the American Astronomical Society in 2024 January.

Keywords: dwarf galaxies
Foreshock as a Source Region of Electron-scale Magnetic Holes in the Solar Wind at 1 au

Electron-scale magnetic holes (ESMHs) can dissipate energy and transport electrons in astrophysical plasmas. They are often observed in the solar wind at 1 au, but whether they are locally generated remains unclear. Here we investigate the ESMHs in the solar wind at 1 au based on observations of the Magnetospheric Multiscale (MMS) and Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun (ARTEMIS) P1 spacecraft. There are 47 and 18 ESMH events observed by MMS1 and ARTEMIS P1, respectively, where an isolated ESMH or a train of ESMHs is regarded as an ESMH event. Our findings are as follows: (1) the occurrence rate of the ESMH events observed by MMS1 is much larger than that by ARTEMIS P1, which is located in the upstream solar wind; and (2) the proportion of the train of ESMHs in the ESMH events observed by each spacecraft is much higher in the ion foreshock than that in the undisturbed solar wind. These observations suggest that the terrestrial foreshock is an important source region of the ESMHs at 1 au, while some ESMHs come from the upstream undisturbed solar wind. The generation of these ESMHs can be explained by the electron vortex magnetic hole. Finding out the origin of the electron vortex may help to shed light on the whole chain of their generation and evolution in the foreshock.

Keywords: solar wind
The 23.01 Release of Cloudy

We announce the C23.01 update of CLOUDY. This corrects a simple coding error, present since ~1990, in one routine that required a conversion from the line-center to the mean normalization of the Lyα optical depth. This affects the destruction of H I Lyα by background opacities. Its largest effect is upon the Lyα intensity in high-ionization dusty clouds, where the predicted intensity is now up to three times stronger. Other properties that depend on Lyα destruction, such as grain infrared emission, change in response.

Keywords: astronomy software; atomic physics; active galaxies; computational methods
Complex Organic Molecules in a Very Young Hot Corino, HOPS 373SW

We present the spectra of complex organic molecules (COMs) detected in HOPS 373SW with the Atacama Large Millimeter/submillimeter Array (ALMA). HOPS 373SW, which is a component of a protostellar binary with a separation of 1500au, has been discovered as a variable protostar by the JCMT transient monitoring survey with a modest (~30%) brightness increase at submillimeter wavelengths. Our ALMA target-of-opportunity observation at ~345 GHz for HOPS 373SW revealed extremely young chemical characteristics with strong deuteration of methanol. The dust continuum opacity is very high toward the source center, obscuring line emission from within 0.″03. The other binary component, HOPS 373NE, was detected only in C17O in our observation, implying a cold and quiescent environment. We compare the COM abundances relative to CH3OH in HOPS 373SW with those of V883 Ori, which is an eruptive disk object, as well as other hot corinos, to demonstrate the chemical evolution from envelope to disk. High abundances of singly, doubly, and triply deuterated methanol (CH2DOH, CHD2OH, and CD3OH) and a low CH3CN abundance in HOPS 373SW compared to other hot corinos suggest a very early evolutionary stage of HOPS 373SW in the hot corino phase. Since the COMs detected in HOPS 373SW would have been sublimated very recently from grain surfaces, HOPS 373SW is a promising place to study the surface chemistry of COMs in the cold prestellar phase before sublimation.

Keywords: star formation; astrochemistry
Classifying Blazar Candidates from the 3FGL Unassociated Catalog into BL Lacertae Objects and Flat Spectrum Radio Quasars Using Swift and WISE Data

We utilize machine-learning methods to distinguish BL Lacertae (BL Lac) objects from flat spectrum radio quasars (FSRQs) within a sample of likely X-ray blazar counterparts to Fermi 3FGL unassociated gamma-ray sources. From our previous work, we have extracted 84 sources that were classified as ≥99% likely to be blazars. We then utilize Swift-XRT, Fermi, and The Wide-field Infrared Survey Explorer (WISE) data together to distinguish the specific type of blazar, FSRQs, or BL Lac objects. Various X-ray and gamma-ray parameters can be used to differentiate between these subclasses. These are also known to occupy different parameter space on the WISE color-color diagram. Using all these data together would provide more robust results for the classified sources. We utilized a random forest classifier to calculate the probability for each blazar to be associated with a BL Lac object or an FSRQ. Based on Pbll, which is the probability for each source to be a BL Lac object, we placed our sources into five different categories based on this value as follows: Pbll ≥ 99%: highly likely BL Lac object, Pbll ≥ 90%: likely BL Lac object, Pbll ≤ 1%: highly likely FSRQ, Pbll ≤ 10%: likely FSRQ, and 90% < Pbll < 10%: ambiguous. Our results categorize the 84 blazar candidates as 50 likely BL Lac objects and the other 34 as being ambiguous. A small subset of these sources have been listed as associated sources in the most recent Fermi catalog, 4FGL, and in these cases our results are in agreement on the classification.

Keywords: blazars; high energy astrophysics; bl lacertae objects
TOI-954 b and K2-329 b: Short-period Saturn-mass Planets that Test whether Irradiation Leads to Inflation

We report the discovery of two short-period Saturn-mass planets, one transiting the G subgiant TOI-954 (TIC 44792534, V = 10.343, T = 9.78) observed in TESS sectors 4 and 5 and one transiting the G dwarf K2-329 (EPIC 246193072, V = 12.70, K = 10.67) observed in K2 campaigns 12 and 19. We confirm and characterize these two planets with a variety of ground-based archival and follow-up observations, including photometry, reconnaissance spectroscopy, precise radial velocity, and high-resolution imaging. Combining all available data, we find that TOI-954 b has a radius of ${0.852}_{-0.062}^{+0.053}\,{R}_{{\rm{J}}}$ and a mass of ${0.174}_{-0.017}^{+0.018}$ MJ and is in a 3.68 day orbit, while K2-329 b has a radius of ${0.774}_{-0.024}^{+0.026}\,{R}_{{\rm{J}}}$ and a mass of ${0.260}_{-0.022}^{+0.020}$ MJ and is in a 12.46 day orbit. As TOI-954 b is 30 times more irradiated than K2-329 b but more or less the same size, these two planets provide an opportunity to test whether irradiation leads to inflation of Saturn-mass planets and contribute to future comparative studies that explore Saturn-mass planets at contrasting points in their lifetimes.

Keywords: exoplanet systems; photometry; transit photometry; spectroscopy; high resolution spectroscopy; g stars; g dwarf stars; g subgiant stars; hot jupiters
Elemental Abundances of Kepler Objects of Interest in APOGEE DR17

The elemental abundances of planet host stars can shed light on the conditions of planet forming environments. We test if individual abundances of 130 known/candidate planet hosts in APOGEE are statistically different from those of a reference doppelgänger sample. The reference set comprises objects selected with the same T eff, $\mathrm{log}g$ , [Fe/H], and [Mg/H] as each Kepler Object of Interest (KOI). We predict twelve individual abundances (X = C, N, O, Na, Al, Si, Ca, Ti, V, Cr, Mn, Ni) for the KOIs and their doppelgängers using a local linear model of these four parameters, training on ASPCAP abundance measurements for a sample of field stars with high-fidelity (signal-to-noise ratio > 200) APOGEE observations. We compare element prediction residuals (model-measurement) for the two samples and find them to be indistinguishable, given a high-quality sample selection. We report median intrinsic dispersions of ~0.038 dex and ~0.041 dex, for the KOI and doppelgänger samples, respectively, for these elements. We conclude that the individual abundances at fixed T eff, $\mathrm{log}g$ , [Fe/H], and [Mg/H] are unremarkable for known planet hosts. Our results establish an upper limit on the abundance precision required to uncover any chemical signatures of planet formation in planet host stars.

Keywords: exoplanet astronomy; exoplanet formation; high resolution spectroscopy; stellar abundances
GRB 201104A: A "Repetitive" Short Gamma-Ray Burst?

Gamma-ray bursts (GRBs) are divided into short gamma-ray bursts (SGRBs) and long gamma-ray bursts (LGRBs) based on the bimodal distribution of their durations. LGRBs and SGRBs are typically characterized by different statistical characteristics. Nevertheless, there are some samples that challenge such a framework, such as GRB 060614, a long-duration burst with short-burst characteristics. Furthermore, GRBs are generally considered to be an event with no periodic or repetitive behavior, since the progenitors usually undergo destructive events, such as massive explosions or binary compact star mergers. In this work, we investigated Fermi data for possible quasiperiodic oscillations and repetitive behaviors of GRBs using timing analysis methods and report a special event GRB 201104A, which is a long-duration burst with the characteristics of an SGRB, and it exhibits a "repetitive" behavior. We propose that such a situation may arise from lensed SGRBs and attempt to verify it by Bayesian inference. In addition, we extend the spectral analysis to Bayesian inference. In spite of the existence of at least two distinct time periods with a nearly identical spectrum, there is no strong evidence that they result from a lensing GRB. Taking the gravitational-lensing scenario out of consideration, a long burst would resemble a short burst in its repetitive behavior, which presents a challenge for the current classification scheme.

Keywords: gamma-ray bursts; gravitational lensing
High-resolution Mid-infrared Spectroscopy of GV Tau N: Surface Accretion and Detection of NH3 in a Young Protoplanetary Disk

Physical processes that redistribute or remove angular momentum from protoplanetary disks can drive mass accretion onto the star and affect the outcome of planet formation. Despite ubiquitous evidence that protoplanetary disks are engaged in accretion, the process(es) responsible remain unclear. Here we present evidence for redshifted molecular absorption in the spectrum of a Class I source that indicates rapid inflow at the disk surface. High-resolution mid-infrared spectroscopy of GV Tau N reveals a rich absorption spectrum of individual lines of C2H2, HCN, NH3, and H2O. From the properties of the molecular absorption, we can infer that it carries a significant accretion rate ${\dot{M}}_{\mathrm{abs}}$ ∼ 10-8-10-7 M⊙ yr-1, comparable to the stellar accretion rates of active T Tauri stars. Thus, we may be observing disk accretion in action. The results may provide observational evidence for supersonic "surface accretion flows," which have been found in MHD simulations of magnetized disks. The observed spectra also represent the first detection of NH3 in the planet formation region of a protoplanetary disk. With NH3 only comparable in abundance to HCN, it cannot be a major missing reservoir of nitrogen. If, as expected, the dominant nitrogen reservoir in inner disks is instead N2, its high volatility would make it difficult to incorporate into forming planets, which may help to explain the low nitrogen content of the bulk Earth.

Keywords: t tauri stars; protoplanetary disks; stellar accretion disks; circumstellar disks; planet formation; interstellar molecules
Anthropogenic Coal Ash as a Contaminant in a Micro-meteoritic Underwater Search

Chemical composition for spherules recovered from the search area of CNEOS 2014-01-08 in the Pacific Ocean has been recently released. A three-order of magnitude difference from CI-chondrites has been identified for elements beryllium, lanthanum and uranium in five samples. The lack of consensus regarding atmospheric survival and precision of path estimates motivate an examination of possible contaminants. Contents of nickel, beryllium, lanthanum and uranium are examined in the context of a known anthropogenic source of contamination, and found to be consistent with coal ash as suggested from a publicly available coal chemical composition database (COALQUAL). The meteoritic origin is disfavored.

Keywords: meteorite composition; micrometeorites; interdisciplinary astronomy