adsabs/SciX_UAT_keywords huggingface dataset:
Petrogenesis of Erg Chech 002 Achondrite and Implications for an Altered Magma Ocean

This study conducts mineralogical and chemical investigations on the oldest achondrite, Erg Chech 002 (∼4565 million yr old). This meteorite exhibits a disequilibrium igneous texture characterized by high-Mg-number (atomic Mg/(Mg + Fe2+)) orthopyroxene xenocrysts (Mg number = 60–80) embedded in an andesitic groundmass. Our research reveals that these xenocrysts were early formed crystals, loosely accumulated or scattered in the short-period magma ocean on the parent body. Subsequently, these crystals underwent agitation due to the influx of external materials. The assimilation of these materials enriched the 16O component of the magma ocean and induced a relatively reduced state. Furthermore, this process significantly cooled the magma ocean and inhibited the evaporation of alkali elements, leading to elevated concentrations of Na and K within the meteorite. Our findings suggest that the introduced materials are probably sourced from the reservoirs of CR clan meteorites, indicating extensive transport and mixing of materials within the early solar system.

Keywords: achondrites; planetesimals; planetary system evolution
Multiwavelength Observation of a Failed Eruption from a Helical Kink-unstable Prominence

Multiwavelength observations of a prominence eruption provide an opportunity to uncover the physical mechanism of the triggering and the evolution process of the eruption. In this paper, we investigate a prominence that erupted on 2012 October 14, recorded in Hα, EUV, and X-ray wavelengths. The process of the eruption gives evidence for the existence of a helical magnetic structure showing the twist converting to writhe. The estimated twist is $\sim 6\pi $ (three turns), exceeding the threshold of the kink instability. The rising plasma reached a high speed of 228 km s-1, followed by a sudden rapid acceleration of 2715 m s-2, and was synchronous with a solar flare. Co-spatial cusp-shaped structures were observed in both 131 and 94 Å images from the Atmospheric Imaging Assembly, signifying the location of the magnetic reconnection. The erupted flux rope finally underwent a deceleration with a maximum value of 391 m s-2, which is larger than the freefall acceleration on the Sun (273 m s-2), suggesting that the eruption finally failed, possibly due to an inward magnetic tension force.

Keywords: solar activity; solar flares; solar filaments; solar prominences; solar magnetic reconnection
Misaligned Circumstellar Disks and Orbital Motion of the Young Binary XZ Tau

We report our analyses of the multi-epoch (2015-2017) Atacama Large Millimeter/submillimeter Array (ALMA) archival data of the Class II binary system XZ Tau at Bands 3, 4, and 6. The millimeter dust-continuum images show compact, unresolved (r ≲ 15 au) circumstellar disks (CSDs) around the individual binary stars, XZ Tau A and B, with a projected separation of ~39 au. The 12CO (2-1) emission associated with those CSDs traces the Keplerian rotations, whose rotational axes are misaligned with each other (P.A. ~ -5° for XZ Tau A and ~130° for XZ Tau B). The similar systemic velocities of the two CSDs (VLSR ~ 6.0 km s-1) suggest that the orbital plane of the binary stars is close to the plane of the sky. From the multi-epoch ALMA data, we have also identified the relative orbital motion of the binary. Along with the previous NIR data, we found that the elliptical orbit (e = ${0.742}_{-0.034}^{+0.025}$ , $a=0\buildrel{\prime\prime}\over{.} {172}_{-0\buildrel{\prime\prime}\over{.} 003}^{+0\buildrel{\prime\prime}\over{.} 002}$ , and $\omega =-54\buildrel{\circ}\over{.} {2}_{-4\buildrel{\circ}\over{.} 7}^{+2\buildrel{\circ}\over{.} 0}$ ) is preferable to the circular orbit. Our results suggest that the two CSDs and the orbital plane of the XZ Tau system are all misaligned with each other, and possible mechanisms to produce such a configuration are discussed. Our analyses of the multi-epoch ALMA archival data demonstrate the feasibility of time-domain science with ALMA.

Keywords: star formation; binary stars
The Nature of LoBAL QSOs. II. HST/WFC3 Observations Reveal Host Galaxies Dominated by Mergers

Low-ionization broad absorption line QSOs (LoBALs) are suspected to be merging systems in which extreme, active galactic nucleus-driven outflows have been triggered. Whether or not LoBALs are uniquely associated with mergers, however, has yet to be established. To characterize the morphologies of LoBALs, we present the first high-resolution morphological analysis of a volume-limited sample of 22 Sloan Digital Sky Survey (SDSS)-selected LoBALs at 0.5 < z < 0.6 from Hubble Space Telescope Wide Field Camera 3 observations. Host galaxies are resolved in 86% of the systems in F125W, which is sensitive to old stellar populations, while only 18% are detected in F475W, which traces young, unobscured stellar populations. Signs of recent or ongoing tidal interaction are present in 45%-64% of the hosts, including double nuclei, tidal tails, bridges, plumes, shells, and extended debris. Ongoing interaction with a companion is apparent in 27%-41% of the LoBALs, with as much as 1/3 of the sample representing late-stage mergers at projected nuclear separations <10 kpc. Detailed surface brightness modeling indicates that 41% of the hosts are bulge dominated while only 18% are disks. We discuss trends in various properties as a function of merger stage and parametric morphology. Notably, mergers are associated with slower, dustier winds than those seen in undisturbed/unresolved hosts. Our results favor an evolutionary scenario in which quasar-level accretion during various merger stages is associated with the observed outflows in low-z LoBALs. We discuss differences between LoBALs and FeLoBALs and show that selection via the traditional balnicity index would have excluded all but one of the mergers.

Keywords: active galaxies; interacting galaxies; galaxy evolution; quasars; broad-absorption line quasar
Classification of Trajectories in a Two-planet Exosystem Using the Generalized Three-body Problem

We deploy the theory of the generalized three-body problem to describe an exosystem composed of a host star, a transiting Jupiter-sized exoplanet, and an Earth-sized exoplanet. By performing a thorough and systematic orbit classification we map a large section of the phase space and determine the final states of the Earth-sized exoplanet. In particular, we manage to classify the initial conditions of the perturber into several categories such as bounded regular or chaotic motion, collision, and escaping motion. Bounded regular motion corresponds to regions of the phase space in which the orbit of the Earth-sized planet would be stable. In our computations, we use realistic values of the involved parameters and initial conditions corresponding to real observable exosystems. Our analysis provides important information on how the mass of the host star as well as the mass of the Jupiter size affects the orbital dynamics of the Earth-sized exoplanet.

Keywords: exoplanet astronomy
Current Population Statistics Do Not Favor Photoevaporation over Core-powered Mass Loss as the Dominant Cause of the Exoplanet Radius Gap

We search for evidence of the cause of the exoplanet radius gap, I.e., the dearth of planets with radii near 1.8 R⊕. If the cause were photoevaporation, the radius gap should trend with proxies for the early-life high-energy emission of the planet-hosting stars. If, alternatively, the cause were core-powered mass loss, no such trends should exist. Critically, spurious trends between the radius gap and stellar properties arise from an underlying correlation with instellation. After accounting for this underlying correlation, we find that no trends remain between the radius gap and stellar mass or present-day stellar activity as measured by near-UV emission. We dismiss the nondetection of a radius gap trend with near-UV emission because present-day near-UV emission is unlikely to trace early-life high-energy emission, but we provide a catalog of Galaxy Evolution Explorer near-UV and far-UV emission measurements for general use. We interpret the nondetection of a radius gap trend with stellar mass by simulating photoevaporation with mass-dependent evolution of stellar high-energy emission. The simulation produces an undetectable trend between the radius gap and stellar mass under realistic sources of error. We conclude that no evidence, from this analysis or others in the literature, currently exists that clearly favors either photoevaporation or core-powered mass loss as the primary cause of the exoplanet radius gap. However, repeating this analysis once the body of well-characterized <4 R⊕ planets has roughly doubled could confirm or rule out photoevaporation.

Keywords: exoplanet evolution; exoplanet catalogs; stellar activity
Effects of Heliolatitudinal Anisotropy of Solar Far-ultraviolet/Extreme-ultraviolet Emissions on Lyα Helioglow

We present a study of the influence of solar UV anisotropy on the heliospheric backscatter helioglow generated by resonant scattering of solar Lyα photons on interstellar hydrogen atoms around the Sun. Simulations based on the WawHelioGlow model suggest that the response of the helioglow pole-to-ecliptic ratio to the anisotropy is linear, but 15% of the anisotropy (polar darkening) generates 30%–40% change in the ratio in the solar minimum and 15%–20% in the solar maximum. We attribute this difference to an interplay between the solar UV anisotropy and the latitudinal structure of the solar wind in solar minima. The solar UV anisotropy also increases the helioglow intensity from the downwind direction by 5%–10%, due to the influence of the anisotropy on the ionization losses and trajectories of atoms passing by the Sun in polar regions. Consequently, midlatitude regions (in the heliographic and ecliptic coordinates) are least affected by the UV anisotropy. By comparison of the simulation results with observations of the Solar and Heliospheric Observatory/SWAN satellite instrument, we derive the day-by-day time evolution of the solar Lyα anisotropy for the north and south poles over two solar cycles from 1996 to 2022. The inferred anisotropy is ∼5%–10% in solar minima and ∼15%–25% in solar maxima, the northern anisotropy being stronger than the southern one. Our study suggests that in solar minima a highly structured solar wind is associated with relatively small solar UV anisotropy, while in solar maxima the solar wind is more isotropic but a substantial solar UV anisotropy appears.

Keywords: heliosphere; interstellar medium; solar radiation; solar wind; interplanetary physics
Physical Properties of the Host Galaxies of Ca-rich Transients

Calcium-rich (Ca-rich) transients are a new class of supernovae (SNe) that are known for their comparatively rapid evolution, modest peak luminosities, and strong nebular calcium emission lines. Currently, the progenitor systems of Ca-rich transients remain unknown. Although they exhibit spectroscopic properties not unlike core-collapse Type Ib/c SNe, nearly half are found in the outskirts of their host galaxies, which are predominantly elliptical, suggesting a closer connection to the older stellar populations of SNe Ia. In this paper, we present a compilation of publicly available multiwavelength observations of all known and/or suspected host galaxies of Ca-rich transients ranging from far-UV to IR, and use these data to characterize their stellar populations with PROSPECTOR. We estimate several galaxy parameters including integrated star formation rate, stellar mass, metallicity, and age. For nine host galaxies, the observations are sensitive enough to obtain nonparametric star formation histories, from which we recover SN rates and estimate probabilities that the Ca-rich transients in each of these host galaxies originated from a core-collapse versus Type Ia-like explosion. Our work supports the notion that the population of Ca-rich transients do not come exclusively from core-collapse explosions, and must either be only from white dwarf stars or a mixed population of white dwarf stars with other channels, potentially including massive star explosions. Additional photometry and explosion site spectroscopy of larger samples of Ca-rich host galaxies will improve these estimates and better constrain the ratio of white dwarf versus massive star progenitors of Ca-rich transients.

Keywords: supernovae; galaxies; photometry
The Strikingly Metal-rich Halo of the Sombrero Galaxy

The nature of the Sombrero galaxy (M104 = NGC 4594) has remained elusive despite many observational studies at a variety of wavelengths. Here we present Hubble Space Telescope imaging of two fields at ∼16 and 33 kpc along the minor axis to examine stellar metallicity gradients in the extended spheroid. We use this imaging, extending more than 2 mag below the tip of the red giant branch, in combination with artificial star tests to forward model observed color-magnitude diagrams, measuring metallicity distribution functions (MDFs) at different radii along the minor axis. An important and unexpected result is that the halo of the Sombrero is strikingly metal-rich: even the outer field, located at ∼17 effective radii of the bulge, has a median metallicity [Z/H] ∼ -0.15, and the fraction of stars with [Z/H] < -1.0 is negligible. This is unprecedented among massive galaxy halos studied to date, even among giant ellipticals. We find significant radial metallicity gradients, characterized by an increase in the fraction of metal-poor stars with radius and a gradient in median metallicity of ∼0.01 dex kpc-1. The density profile is well fit by power laws with slopes that exhibit a dependence on metallicity, with flatter slopes for more metal-poor stars. We discuss our results in the context of recent stellar MDF studies of other nearby galaxies and potential formation scenarios for the Sombrero galaxy.

Keywords: galaxy stellar halos; galaxy spheroids; metallicity; star formation; galaxy stellar content
A Recently Quenched Isolated Dwarf Galaxy Outside of the Local Group Environment

We report the serendipitous identification of a low-mass (M* ∼ 2 × 106 M⊙), isolated, likely quenched dwarf galaxy in the "foreground" of the COSMOS-CANDELS field. From deep Hubble Space Telescope (HST) imaging we infer a surface brightness fluctuation distance for COSMOS-dw1 of DSBF = 22 ± 3 Mpc, which is consistent with its radial velocity of cz = 1222 ± 64 km s-1 via Keck/LRIS. At this distance, the galaxy is 1.4 Mpc in projection from its nearest massive neighbor. We do not detect significant Hα emission (EW(Hα)= - 0.4 ± 0.5 Å), suggesting that COSMOS-dw1 is likely quenched. Very little is currently known about isolated quenched galaxies in this mass regime. Such galaxies are thought to be rare, as there is no obvious mechanism to permanently stop star formation in them; to date there are only four examples of well-studied quenched field dwarfs, only two of which appear to have quenched in isolation. COSMOS-dw1 is the first example outside of the immediate vicinity of the Local Group. COSMOS-dw1 has a relatively weak Dn4000 break and the HST data show a clump of blue stars indicating that star formation ceased only recently. We speculate that COSMOS-dw1 was quenched due to internal feedback, which was able to temporarily suspend star formation. In this scenario the expectation is that quenched isolated galaxies with masses M* = 106-107 M⊙ generally have luminosity-weighted ages ≲1 Gyr.

Keywords: dwarf galaxies; galaxy quenching; quenched galaxies; galaxy evolution
The Airborne Infrared Spectrometer: Development, Characterization, and the 2017 August 21 Eclipse Observation

On 2017 August 21, the Airborne Infrared Spectrometer (AIR-Spec) observed the total solar eclipse at an altitude of 14 km from aboard the NSF/NCAR Gulfstream V research aircraft. The instrument successfully observed the five coronal emission lines that it was designed to measure: Si X 1.431 μm, S XI 1.921 μm, Fe IX 2.853 μm, Mg VIII 3.028 μm, and Si IX 3.935 μm. Characterizing these magnetically sensitive emission lines is an important first step in designing future instruments to monitor the coronal magnetic field, which drives space weather events, as well as coronal heating, structure, and dynamics. The AIR-Spec instrument includes an image stabilization system, feed telescope, grating spectrometer, and slit-jaw imager. This paper details the instrument design, optical alignment method, image processing, and data calibration approach. The eclipse observations are described and the available data are summarized.

Keywords: solar coronal lines; solar instruments; total eclipses; spectrometers; solar e corona
MIR Spectra and Analysis of Jovian Trojan Asteroids

Jovian Trojan asteroids make up a large group of primitive bodies that populate Jupiter's L4 and L5 Lagrange points. The Trojans' dynamics and composition carry insight into the formation mechanisms that shaped our solar system. Mid-infrared (MIR; 5-35 μm) spectra of Trojans exhibit puzzling silicate emission features, like spectra of optically thin comet comae, which may be interpreted as "fluffy" regoliths. By understanding the physical properties of the regolith (e.g., particle size and regolith porosity), more accurate compositional interpretations can be made. Here we show 14 Spitzer Space Telescope MIR spectra of Trojans and their compositional makeup. Through parameterization of spectral features and comparison to laboratory and remote-sensing spectra, the results show that the Trojans have highly porous regoliths of fine-particulate crystalline (forsterite, enstatite, and possibly a small amount of fayalite and diopside) and amorphous silicates. These results are consistent with a primordial Kuiper Belt origin.

Keywords: asteroids; small solar system bodies; trojan asteroids; asteroid surfaces; spectral energy distribution; infrared spectroscopy; spectroscopy
Deep Chandra Observations of NGC 5728: Morphology and Spectral Properties of the Extended X-Ray Emission

Recent deep Chandra observations of nearby Compton-thick (CT) active galactic nuclei (AGNs) have produced surprising results, uncovering extended emission not only in soft X-rays but also in hard emission (>3 keV), challenging the long-held belief that the characteristic hard X-ray continuum and fluorescent Fe K lines are associated with the torus in the standard picture of AGNs. In this work, we present an analysis of our deep (~261 ks) X-ray Chandra ACIS-S observations of NGC 5728, a nearby (z = 0.00932) CT AGN. We find that the diffuse emission is more extended at lower energies, in the bicone direction out to ~2 kpc radially, but also significantly extended in the direction of the cross-cone, out to ~1.4 kpc. Our results suggest that the ratio of detected photons in the cross-cone to the bicone region is ~16%, below 3 keV, decreasing to 5% for energies 3-6 keV. The nuclear spectrum suggests a low-photoionization phase mixed with a more ionized gas component, while the bicone and cross-cone spectra are dominated by a mix of photoionization and shocked gas emission. A mixture of thermal and photoionization models used to fit the spectra indicates the presence of complex gas interactions, consistent with previous observations of other CT AGNs (e.g., ESO 428-G014).

Keywords: agn host galaxies; x-ray active galactic nuclei
High-energy Neutrino Emission Associated with GWs from Binary Black Hole Mergers in AGN Accretion Disks

The search for multimessenger signals of binary black hole (BBH) mergers is crucial to understanding the merger process of BBH and the relative astrophysical environment. Considering BBH mergers occurring in the active galactic nuclei (AGN) accretion disks, we focus on the accompanying high-energy neutrino production from the interaction between the jet launched by the postmerger remnant BH and disk materials. Particles can be accelerated by the shocks generated from the jet-disk interaction and subsequently interact with the disk gas and radiations to produce high-energy neutrinos through hadronic processes. We demonstrate that the identification of the high-energy neutrino signal from BBH merger in AGN disks is feasible. In addition, the joint BBH gravitational wave (GW) and neutrino detection rate is derived, which can be used to constrain the BBH merger rate and the accretion rate of the remnant BH based on the future associated detections of GWs and neutrinos. To date, an upper limit of BBH merger rate density in AGN disks of R 0 ≲ 3 Gpc-3 yr-1 is derived for the fiducial parameter values based on the current null association of GWs and neutrinos.

Keywords: neutrino astronomy; high energy astrophysics; active galactic nuclei; gravitational waves; black holes
Transition Region from Turbulent to Dead Zone in Protoplanetary Disks: Local Shearing Box Simulations

The dynamical evolution of protoplanetary disks is of key interest for building a comprehensive theory of planet formation and to explain the observational properties of these objects. Using the magnetohydrodynamics code Athena++, with an isothermal shearing box setup, we study the boundary between the active and dead zone, where the accretion rate changes and mass can accumulate. We quantify how the turbulence level is affected by the presence of a non-uniform Ohmic resistivity in the radial x direction that leads to a region of inhibited turbulence (or dead zone). Comparing the turbulent activity to that of ideal simulations, the turbulence-inhibited area shows density fluctuations and magnetic activity at its boundaries, driven by energy injection from the active (ideal) zone boundaries. We find magnetic dissipation to be significantly stronger in the ideal regions, and the turbulence penetration through the boundary of the dead zone is determined by the value of the resistivity itself, through the Ohmic dissipation process, though the thickness of the transition does not play a significant role in changing the dissipation. We investigate the 1D spectra along the shearing direction: magnetic spectra appear flat at large scales both in ideal as well as resistive simulations, though a Kolmogorov scaling over more than one decade persists in the dead zone, suggesting the turbulent cascade is determined by the hydrodynamics of the system: magnetorotational instability dynamo action is inhibited where sufficiently high resistivity is present.

Keywords: star formation; stellar accretion disks; planet formation
The Behavior of Bp He-weak Stars in the Far UV-Paper VI: HD 21699

The analysis of spectra of the B8 He-weak Si star HD 21699 recorded by the SWP camera on board the International Ultraviolet Explorer in 1987 reveals large amplitude variations of the far-ultraviolet spectral energy distribution over a time interval of about four days in 1987 October. In contrast, the level of the mid-UV flux did not vary between phases of FUV flux maximum and minimum which suggests that changes of the silicon continuous and line opacity play an important role in the variations. The lines of C IV doublet near 1550 Å are stronger and have an extended blue wing at phase of far-UV maximum. The optical brightness recorded by the Fine Error Sensor on board IUE is probably anticorrelated with the FUV flux, reflecting the redistribution of the FUV flux toward longer wavelengths.

Keywords: chemically peculiar stars; helium-weak stars