adsabs/SciX_UAT_keywords huggingface dataset:
Reconstruction of Plasma Structure with Anisotropic Pressure: Application to Pc5 Compressional Wave

The conventional Grad-Shafranov (GS) method is designed to reconstruct a two-dimensional magnetohydrostatic structure with isotropic pressure. In this work, we developed a new GS solver (GS-like) that includes the effect of pressure anisotropy based on reduced equations from Sonnerup et al. The new GS solver is benchmarked, and the results are compared with two other GS solvers based on the conventional GS method and that from Teh. This solver is applied to reconstruct a Pc5 compressional wave event, which has mirror-like features and includes a significant pressure anisotropy (p⊥/p∥ ~ 1.5, where p⊥ and p∥ are the thermal pressures perpendicular and parallel to the magnetic field), observed by the Magnetospheric Multiscale mission in the duskside outer magnetosphere on 2015 September 19. The recovered maps indicate that, within some model constraints, the wave in the selected time interval consists of two magnetic bottle-like structures, each with an azimuthal size of about 9000 km (wavenumber ~44) and a larger field-aligned size. The spacecraft passed through the bottles at ~1600 km southward of the bottle centers. Further multispacecraft measurements revealed that the Pc5 compressional wave propagates sunward along with the background plasma and retains the bottle-like structures, driven mainly by the ion diamagnetic currents. The reconstructed magnetic topology is similar to that described in previous empirical or theoretical antisymmetric standing wave models. This Pc5 compressional wave is possibly driven by drift-mirror-like instabilities.

Keywords: planetary magnetospheres; space plasmas
The Architecture of the V892 Tau System: The Binary and Its Circumbinary Disk

We present high-resolution millimeter continuum and CO line observations for the circumbinary disk around V892 Tau to constrain the stellar and disk properties. The total mass of the two near-equal-mass A stars is estimated to be 6.0 ± 0.2 M⊙ based on our models of the Keplerian-dominated gas disk rotation. The detection of strong ionized gas emission associated with the two stars at 8 mm, when combined with previous astrometric measurements in the near-infrared, provides an updated view of the binary orbit with a = 7.1 ± 0.1 au, e = 0.27 ± 0.1, and P = 7.7 ± 0.2 yr, which is about half of a previously reported orbital period. The binary orbital plane is proposed to be nearly coplanar to the circumbinary disk plane (with a mutual inclination of only Δ = 8 ± 4°2; another solution with Δ = 113° is less likely given the short realignment timescale). An asymmetric dust disk ring peaking at a radius of 0"2 is detected at 1.3 mm and its fainter counterparts are also detected at the longer 8 and 9.8 mm. The CO gas disk, though dominated by Keplerian rotation, presents a mild inner and outer disk misalignment. The radial extension of the disk, its asymmetric dust ring, and the presence of a disk warp could all be explained by the interaction between the eccentric binary and the circumbinary disk, which we assume were formed with nonzero mutual inclination. Some tentatively detected gas spirals in the outer disk are likely produced by interactions with the low-mass tertiary component located 4″ to the northeast. Our analyses demonstrate the promising usage of V892 Tau as an excellent benchmark system to study the details of binary-disk interactions.

Keywords: protoplanetary disks; binary stars; pre-main sequence stars
Blow-away in the Extreme Low-mass Starburst Galaxy Pox 186

Pox 186 is an exceptionally small dwarf starburst galaxy hosting a stellar mass of ∼105 M⊙. Undetected in H I (M < 106 M⊙) from deep 21 cm observations and with an [O III]/[O II] (5007/3727) ratio of 18.3 ± 0.11, Pox 186 is a promising candidate Lyman continuum emitter. It may be a possible analog of low-mass reionization-era galaxies. We present a spatially resolved kinematic study of Pox 186 and identify two distinct ionized gas components: a broad one with σ > 400 km s-1 and a narrow one with σ < 30 km s-1. We find strikingly different morphologies between the two components and direct evidence of outflows as seen in the high-velocity gas. Possible physical mechanisms driving the creation of high-velocity gas seen in [O III] are discussed, from outflow geometry to turbulent mixing between a hot (106 K) star-cluster wind and cooler (104 K) gas clouds. We find a modest mass-outflow rate of 0.022 M⊙ yr-1 with a small mass-loading factor of 0.5, consistent with other low-mass galaxies. Finally, we compare the mass-loading factor of Pox 186 with extrapolations from numerical simulations and discuss possible reasons for the apparent discrepancy between them.

Keywords: dwarf irregular galaxies; galactic winds; galaxy evolution; galaxy kinematics
A Single-pulse Study of the Subpulse Drifter PSR J1631+1252 Discovered at FAST

We report on the pulse-to-pulse energy distribution and longitude-resolved modulation properties of PSR J1631+1252 discovered by the Five-hundred-meter Aperture Spherical radio Telescope. Our analysis made use of the data acquired at 1250 MHz from the follow-up timing observations that lasted over a year. PSR J1631+1252 has a rotational period of ~0.310 s, and a dispersion measure of ~32.73 pc cm-3. The energy distribution is well described by a lognormal distribution, the parameters of which do not vary with time. We show that large modulation occurs across the bridge emission of the pulse profile, with sporadic bright bursts at the leading emission region. The fluctuation spectral analysis reveals the existence of subpulse drifting in the leading component with vertical spacing between the drift bands of 3.28 ± 0.08 pulse periods between consecutive drift bands. Possible physical mechanisms for subpulse drifting are discussed.

Keywords: radio pulsars; pulsars
Neutral Hydrogen Observations of Low Surface Brightness Galaxies around M101 and NGC 5485

We present atomic hydrogen (H I) observations using the Robert C. Byrd Green Bank Telescope along the lines of sight to 27 low surface brightness (LSB) dwarf galaxy candidates discovered in optical searches around M101. We detect H I reservoirs in five targets and place stringent upper limits on the remaining 22, implying that they are gas-poor. The distances to our H I detections range from 7 to 150 Mpc, demonstrating the utility of wide-bandpass H I observations as a follow-up tool. The systemic velocities of three detections are consistent with that of the NGC 5485 group behind M101, and we suggest that our 15 nondetections with lower distance limits from the optical are associated with and have been stripped by that group. We find that the gas richness of confirmed M101 satellites are broadly consistent with those of the Milky Way satellites, as well as with those of satellites around other hosts of comparable mass, when survey completeness is taken into account. This suggests that satellite quenching and gas stripping proceed similarly around halos of similar mass, in line with theoretical expectations.

Keywords: dwarf galaxies; low surface brightness galaxies; h i line emission; galaxy evolution
The Mass-Metallicity Relation of Dwarf Galaxies at Cosmic Noon from JWST Observations

We present a study of the mass-metallicity relation (MZR) of 51 dwarf galaxies (M ⋆ ≈ 106.5-109.5 M ⊙) at z = 2-3 from the A2744 and SMACS J0723-3732 galaxy cluster fields. These dwarf galaxies are identified and confirmed by deep JWST/NIRISS imaging and slitless grism spectroscopic observations. By taking advantage of the superior performance of JWST and the gravitational lensing effect, we extend the previous MZR relation at z = 2-3 to a much lower-mass regime down by ≈2.5 orders of magnitude as compared with previous studies. We find that the MZR has a shallower slope at the low-mass end (M ⋆ < 109 M ⊙), with a slope turnover point of ≈109 M ⊙. This implies that the dominating feedback processes in dwarf galaxies may be different from that in massive galaxies. From z = 3, to z = 2, the metallicity of the dwarf galaxies is enhanced by ≈0.09 dex for a given stellar mass, consistent with the mild evolution found in galaxies with higher mass. Furthermore, we confirm the existence of a fundamental metallicity relation (FMR) between the gas-phase metallicity, stellar mass, and star formation rate in dwarf galaxies at z = 2-3. Our derived FMR, which has no significant redshift evolution, can be used as a benchmark to understand the origin of the anticorrelation between the star formation rate and metallicity of dwarf galaxies in the high-z Universe.

Keywords: galaxy abundances; interstellar medium; galaxy evolution; high-redshift galaxies
Catalog of Solar Failed Eruptions and Other Dynamic Features Registered by SDO/AIA

In this paper we present our attempt to constrain the first catalog of solar failed eruptions. We used our automatic algorithm that is able to search for dynamic features in the Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) database. We ran the algorithm on the entire SDO/AIA 171 Å data set. For the time interval from 2010 May 20 to 2019 May 20 we found 12,192 dynamic events. The dynamic events were classified in three groups. Apart from failed eruptions (1214) we obtained a large group of successful eruptions (2064) and other dynamic events (8914). The automatic algorithm enabled us to collect several observational characteristics, which are provided in files that may be downloaded from the catalog web page. In this paper we present the methodology of catalog preparation and preliminary results of the statistical analysis of observational characteristics obtained by the automatic algorithm.

Keywords: solar activity; solar active regions; solar filaments; solar prominences; solar corona; solar extreme ultraviolet emission
Red Supergiants in M31 and M33. II. The Mass-loss Rate

Mass loss is an important activity for red supergiants (RSGs) and can influence their evolution and final fate. Previous estimations of mass-loss rates (MLRs) of RSGs exhibit significant dispersion due to differences in method and the incompleteness of samples. With the improved quality and depth of surveys including the UKIRT/WFCAM observations in the near-infrared, and LGGS and PS1 in the optical, a rather complete sample of RSGs is identified in M31 and M33 according to their brightness and colors. For about 2000 objects in either galaxy from this largest ever sample, the MLR is derived by fitting the observational optical-to-mid-infrared spectral energy distribution with the DUSTY code of a 1D dust radiative transfer model. The average MLR of RSGs is found to be around 2.0 × 10-5 M⊙ yr-1 with a gas-to-dust ratio of 100, which yields a total contribution to the interstellar dust from RSGs of about 1.1 × 10-3 M⊙ yr-1 in M31 and 6.0 × 10-4 M⊙ yr-1 in M33, a non-negligible source in comparison with evolved low-mass stars. The MLRs are divided into three types by the dust species, i.e., amorphous silicate, amorphous carbon, and optically thin, and the relations between MLR and stellar parameters, infrared flux, and colors are discussed and compared with previous works for the silicate and carbon dust groups.

Keywords: red supergiant stars; stellar mass loss; circumstellar dust
Repeated Mergers, Mass-gap Black Holes, and Formation of Intermediate-mass Black Holes in Dense Massive Star Clusters

Current theoretical models predict a mass gap with a dearth of stellar black holes (BHs) between roughly 50 M ⊙ and 100 M ⊙, while above the range accessible through massive star evolution, intermediate-mass BHs (IMBHs) still remain elusive. Repeated mergers of binary BHs, detectable via gravitational-wave emission with the current LIGO/Virgo/Kagra interferometers and future detectors such as LISA or the Einstein Telescope, can form both mass-gap BHs and IMBHs. Here we explore the possibility that mass-gap BHs and IMBHs are born as a result of successive BH mergers in dense star clusters. In particular, nuclear star clusters at the centers of galaxies have deep enough potential wells to retain most of the BH merger products after they receive significant recoil kicks due to anisotropic emission of gravitational radiation. Using for the first time simulations that include full stellar evolution, we show that a massive stellar BH seed can easily grow to ~103-104 M ⊙ as a result of repeated mergers with other smaller BHs. We find that lowering the cluster metallicity leads to larger final BH masses. We also show that the growing BH spin tends to decrease in magnitude with the number of mergers so that a negative correlation exists between the final mass and spin of the resulting IMBHs. Assumptions about the birth spins of stellar BHs affect our results significantly, with low birth spins leading to the production of a larger population of massive BHs.

Keywords: astrophysical black holes; black holes; intermediate-mass black holes; stellar mass black holes; gravitational waves; gravitational wave sources; gravitational wave detectors; gravitational wave astronomy; star clusters
Single-pulse Modeling and the Bi-drifting Subpulses of Radio Pulsar B1839-04

We study the bi-drifting pulsar B1839-04, where the observed subpulse drift direction in the two leading pulse components is opposite from that in the two trailing components. Such diametrically opposed apparent motions challenge our understanding of an underlying structure. We find that for the geometry spanned by the observer and the pulsar magnetic and rotation axes, the observed bi-drifting in B1839-04 can be reproduced assuming a nondipolar configuration of the surface magnetic field. Acceptable solutions are found to either have relatively weak (∼1012 G) or strong (∼1014 G) surface magnetic fields. Our single-pulse modeling shows that a global electric potential variation at the polar cap that leads to a solid-body-like rotation of spark forming regions is favorable in reproducing the observed drift characteristics. This variation of the potential additionally ensures that the variability is identical in all pulse components resulting in the observed phase locking of subpulses. Thorough and more general studies of pulsar geometry show that a low ratio of impact factor to opening angle (β/ρ) increases the likelihood of bi-drifting to be observed. We thus conclude that bi-drifting is visible when our line of sight crosses close to the magnetic pole.

Keywords: pulsars
Challenges in Identifying Artificial Objects in the Near-Earth Object Population: Spectral Characterization of 2020 SO

Since the dawn of the Space Age, hundreds of payloads have been launched into heliocentric space. As near-Earth object (NEO) surveys search deeper for small asteroids, more artificial objects in heliocentric orbits are being discovered. We now face a challenge to identify the true nature of these objects and avoid contaminating the NEO catalog. Here, we present the methods used to characterize one such object. 2020 SO was discovered by the Pan-STARRS1 survey on 2020 September 17. Originally classified as a NEO, the object's artificial nature became evident due to its low velocity relative to Earth and solar radiation pressure affecting its orbit about the Sun. Based on a backward propagation of its orbit, 2020 SO is thought to be a Centaur rocket body (R/B) from the launch of the Surveyor 2 mission to the Moon. We characterized 2020 SO using a range of ground-based optical and near-infrared telescopes to constrain its true nature. We find that its reflectance spectrum is consistent with that of other Centaur R/B launched during a similar time frame, and we identify 1.4, 1.7, and 2.3 μm absorption bands consistent with polyvinyl fluoride used on the aft bulkhead radiation shield exterior of Centaur-D R/B at the time.

Keywords: artificial satellites; near-earth objects; infrared spectroscopy; asteroids
Formation Channels of Diffuse Lights in Groups and Clusters over Time

We explore the formation of the intragroup light and intracluster light, representing diffuse lights within groups and clusters, from the point that z = 1.5. For this, we perform multiresolution cosmological N-body simulations using the "galaxy replacement technique" and identify the progenitors in which the diffuse light stars existed when they fell into the groups or clusters. Our findings reveal that typical progenitors contributing to diffuse lights enter the host halo with massive galaxies containing a stellar mass of , regardless of the mass or dynamical state of the host halos at z = 0. In cases where the host halos are dynamically unrelaxed or more massive, diffuse lights from massive progenitors with are more prominent, with over half of them already preprocessed before entering the host halo. Additionally, we find that the main formation mechanism of diffuse lights is the stripping process of satellites, and a substantial fraction (40%–45%) of diffuse light stars are linked to the merger tree of the brightest cluster galaxy. Remarkably, all trends persist for groups and clusters at higher redshifts. The fraction of diffuse lights in the host halos with a similar mass decreases as the redshift increases, but they are already substantial at z = 1.5 (∼10%). However, it is crucial to acknowledge that detection limits related to the observable radius and faint-end surface brightness may obscure numerous diffuse light stars and even alter the main formation channel of diffuse lights.

Keywords: galaxy clusters; galaxy formation; galaxy evolution; computational methods
On the Hydrosphere Stability of TESS Targets: Applications to 700 d, 256 b, and 203 b

A main determinant of the habitability of exoplanets is the presence of stable liquid surface water. In an era of abundant possible targets, the potential to find a habitable world remains a driving force in prioritization. We present here a data-forward method to investigate the likelihood of a stable hydrosphere on the timescales of the formation of life, 1 Gyr, and beyond. As our primary application, we use this method to examine the potential hydrospheres of TESS objects of interest 700 d, 256 b (LHS 1140 b), and 203 b. We first present our selection criteria, which are based on an implementation of the Earth Similarity Index, as well as the results of an initial investigation into the desiccation of the targets, which reveals that TOI 203 b is almost certainly desiccated based on TESS observations. We then describe the characterization of the remaining targets and their host stars from 2MASS, Gaia, and TESS data and the derivation of sampled probability distributions for their parameters. Following this, we describe our process of simulating the desiccation of the targets' hydrospheres using the Virtual Planet Simulator, VPlanet, with inputs directly linked to the previously derived probability distributions. We find that 50.86% of the likely cases for TOI 700 d are desiccated, and no modeled cases for TOI 256 b are without water. In addition, we calculate the remaining water inventory for the targets, the percentage of cases that are continuing to lose water, and the rate at which these cases are losing water.

Keywords: exoplanet astronomy; exoplanet evolution; habitable planets; transit photometry
Schwarzschild and Ledoux are Equivalent on Evolutionary Timescales

Stellar evolution models calculate convective boundaries using either the Schwarzschild or Ledoux criterion, but confusion remains regarding which criterion to use. Here we present a 3D hydrodynamical simulation of a convection zone and adjacent radiative zone, including both thermal and compositional buoyancy forces. As expected, regions that are unstable according to the Ledoux criterion are convective. Initially, the radiative zone adjacent to the convection zone is Schwarzschild unstable but Ledoux stable due to a composition gradient. Over many convective overturn timescales, the convection zone grows via entrainment. The convection zone saturates at the size originally predicted by the Schwarzschild criterion, although in this final state the Schwarzschild and Ledoux criteria agree. Therefore, the Schwarzschild criterion should be used to determine the size of stellar convection zones, except possibly during short-lived evolutionary stages in which entrainment persists.

Keywords: stellar convective zones; stellar physics; stellar evolutionary models
Physics of Pair Producing Gaps in Black Hole Magnetospheres. II. General Relativity

This is the second paper in a series where we examine the physics of pair producing gaps in low-luminosity accreting supermassive black hole systems. In this paper, we carry out time-dependent self-consistent fully general relativistic 1D particle-in-cell simulations of the gap, including full inverse Compton scattering and photon tracking. Similar to the previous paper, we find a highly time-dependent solution where a macroscopic vacuum gap can open quasiperiodically, producing bursts of ${e}^{\pm }$ pairs and high energy radiation. We present the light curve, particle spectrum, and photon spectrum from this process. Using an empirical scaling relation, we rescale the parameters to the inferred values at the base of the jet in M87, and find that the observed TeV flares could potentially be explained by this model under certain parameter assumptions.

Keywords: black hole physics; high energy astrophysics; plasma astrophysics; non-thermal radiation sources
Exoplanet Volatile Carbon Content as a Natural Pathway for Haze Formation

We explore terrestrial planet formation with a focus on the supply of solid-state organics as the main source of volatile carbon. For the water-poor Earth, the water ice line, or ice sublimation front, within the planet-forming disk has long been a key focal point. We posit that the soot line, the location where solid-state organics are irreversibly destroyed, is also a key location within the disk. The soot line is closer to the host star than the water snow line and overlaps with the location of the majority of detected exoplanets. In this work, we explore the ultimate atmospheric composition of a body that receives a major portion of its materials from the zone between the soot line and water ice line. We model a silicate-rich world with 0.1% and 1% carbon by mass with variable water content. We show that as a result of geochemical equilibrium, the mantle of these planets would be rich in reduced carbon but have relatively low water (hydrogen) content. Outgassing would naturally yield the ingredients for haze production when exposed to stellar UV photons in the upper atmosphere. Obscuring atmospheric hazes appear common in the exoplanetary inventory based on the presence of often featureless transmission spectra. Such hazes may be powered by the high volatile content of the underlying silicate-dominated mantle. Although this type of planet has no solar system counterpart, it should be common in the galaxy with potential impact on habitability.

Keywords: exoplanet formation