adsabs/SciX_UAT_keywords huggingface dataset:
The Impulsive Acceleration of a Solar Filament Eruption Associated with a B-class Flare

The eruption of magnetic flux ropes (MFRs), often taking filaments together, leads to coronal mass ejections (CMEs). Theoretical studies propose that both the resistive magnetic reconnection and the ideal instability of an MFR system can release magnetic-free energy and accelerate CMEs (i.e., MFRs or filaments) during eruptions. Observations find that the full kinematic evolution of CMEs usually undergoes three phases: the initiation phase, impulsive acceleration phase, and propagation phase. The impulsive acceleration phase often starts and ceases simultaneously with the flare onset time and peak time, respectively. This synchronization can be explained by the positive feedback relationship between the acceleration of CMEs and flare magnetic reconnection, and suggests that the reconnection has the dominant contribution to the acceleration of CMEs. It is rare to see strong evidence that supports the dominant contribution of ideal instability to the acceleration. In this paper, we report an intriguing filament eruption that occurred on 2011 May 11. Its complete acceleration is well recorded by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory. The kinematic analysis shows that the impulsive acceleration phase starts and ceases obviously earlier than the flare onset time and peak time, respectively, which means a complete asynchronization between the impulsive acceleration phase and flare rise phase, and strongly supports that the ideal instability plays a dominant role in this impulsive acceleration. Furthermore, the accompanied flare is a B-class one, also implying that the contribution of reconnection is negligible in the energy release process.

Keywords: solar filament eruptions; solar activity; solar flares
Searching for Surviving Companion in the Young SMC Supernova Remnant 1E 0102.2-7219

1E 0102.2-7219 (hereafter E0102) is a young supernova remnant (SNR) in the Small Magellanic Cloud. It contains oxygen-rich SN ejecta, a possible neutron star (NS), and a small amount of fast-moving H-rich ejecta material. These properties are also seen in Cas A; it has thus been suggested that E0102 is also a Type IIb SNR, whose SN progenitor's hydrogen envelope was stripped off possibly via interactions with a companion star. To search for a surviving companion of E0102's SN progenitor, we have used archival Hubble Space Telescope (HST) continuum images to make photometric measurements of stars projected in the SNR to construct color-magnitude diagrams and compare the stars with those expected from surviving companions of Type IIb SNe. We have also used the Multi-Unit Spectroscopic Explorer observations taken with the Very Large Telescope to perform spectroscopic analyses of stars and search for peculiar radial velocities as diagnostics of surviving companions. We further use the HST and Gaia data to inspect proper motions of stars for complementary kinetic studies. No plausible companion candidates are found if the SN explosion site was near the NS, while the B3 V star 34a may be a plausible companion candidate if the SN explosion site is near the SN ejecta's expansion center. If the NS is real and associated with E0102, it needs a ~1000 km s-1 runaway velocity, which has been observed in other SNRs and can be acquired from an asymmetric SN explosion or a kick by the SN explosion of a massive companion.

Keywords: type ii supernovae; supernova remnants; small magellanic cloud; companion stars; magellanic clouds; massive stars
Spectral and Petrographic Properties of Inclusions in Carbonaceous Chondrites and Comparison with in Situ Images from Asteroid Ryugu

We imaged a set of carbonaceous chondrites from the CM2, CO3, CV3, and CK4 groups using the qualification model of MasCam, the camera on board the asteroid lander MASCOT, which touched down on asteroid Ryugu in 2018 October. A CI1 meteorite was also imaged but excluded from the analysis due to prominent terrestrial weathering. Following the methods used to image the rock on Ryugu, we placed a total of 14 meteorites approximately 20 cm in front of the camera to achieve a spatial resolution of about 0.2 mm per pixel and illuminated the samples with onboard light-emitting diodes of four different colors in the visible wavelength range. We mapped bright and dark inclusions within the meteorites and derived the inclusion brightness relative to the matrix in the red light, the relative spectral slope of each inclusion, the inclusion size frequency distribution and the matrix volume abundance. We find that the meteorite groups overlap within these parameters, but individual samples, as well as individual inclusions, can have deviating values. Terrestrial weathering appears to have no systematic influence on these parameters. Relating our analysis to the inclusions found in the rock on Ryugu, we find that the spectral parameters of Ryugu's inclusions fit well in the parameter space of the carbonaceous chondrites. Compared with the most common types of carbonaceous chondrites, Ryugu's rock has larger inclusions (mean diameter: 0.63 ± 0.91 mm) and a higher upper limit to the matrix abundance (92.4 vol%).

Keywords: meteorites; carbonaceous chondrites; asteroids; asteroid surfaces; spectroscopy; planetary science; landers
Effects of Earth's Oblateness on Black Hole Imaging through Earth–Space and Space–Space Very Long Baseline Interferometry

Earth-based very long baseline interferometry (VLBI) has made rapid advances in imaging black holes. However, due to the limitations imposed on terrestrial VLBI by the Earth's finite size and turbulent atmosphere, it is imperative to have a space-based component in future VLBI missions. This paper investigates the effect of the Earth's oblateness, also known as the J 2 effect, on orbiters in Earth–space and space–space VLBI. The paper provides an extensive discussion on how the J 2 effect can directly impact orbit selection for black hole observations and how, through informed choices of orbital parameters, the effect can be used to a mission's advantage, a fact that has not been addressed in previous space VLBI investigations. We provide a comprehensive study of how the orbital parameters of several current space VLBI proposals will vary specifically due to the J 2 effect. For black hole accretion flow targets of interest, we demonstrate how the J 2 effect leads to a modest increase in shorter-baseline coverage, filling gaps in the (u, v) plane. Subsequently, we construct a simple analytical formalism that allows isolation of the impact of the J 2 effect on the (u, v) plane without requiring computationally intensive orbit propagation simulations. By directly constructing (u, v) coverage using J 2-affected and J 2-invariant equations of motion, we obtain distinct coverage patterns for M87* and Sgr A* that show extremely dense coverage on short baselines as well as long-term orbital stability on longer baselines.

Keywords: astrophysical black holes; artificial satellites; very long baseline interferometry; space observatories
Small Magellanic Cloud Field Stars Meddling in Star Cluster Age Estimates

I revisited the age of the Small Magellanic Cloud (SMC) cluster HW 42, whose previous estimates differ in more than 6 Gyr, thus challenging the most updated knowledge of the SMC star formation history. I performed an analysis of number stellar density profiles at different brightness levels; carried out a field star decontamination of the cluster color-magnitude diagram; and estimated the cluster fundamental parameters from the minimization of likelihood functions and their uncertainties from standard bootstrap methods. I conclude that HW 42 is a ${6.2}_{-1.3}^{+1.6}$ Gyr old ([Fe/H] = -0.89 ${}_{-0.11}^{+0.10}$ dex) SMC cluster projected on to a SMC composite star field population which shows variations in magnitude, color, and stellar density of Main Sequence stars. The present outcome solves the conundrum of the previous age discrepancies and moves HW 42 to a region in the SMC age-metallicity relationship populated by star clusters.

Keywords: astronomical techniques; small magellanic cloud; star clusters
Cross Correlation of Pencil-beam Galaxy Surveys and Line-intensity Maps: An Application of the James Webb Space Telescope

Line-intensity mapping (IM) experiments seek to perform statistical measurements of large-scale structure with spectral lines such as 21 cm, CO, and Lyα. A challenge in these observations is to ensure that astrophysical foregrounds, such as galactic synchrotron emission in 21 cm measurements, are properly removed. One method that has the potential to reduce foreground contamination is to cross correlate with a galaxy survey that overlaps with the IM volume. However, telescopes sensitive to high-redshift galaxies typically have small field of views compared to IM surveys. Thus, a galaxy survey for cross correlation would necessarily consist of pencil beams that sparsely fill the IM volume. In this paper, we develop the formalism to forecast the sensitivity of cross correlations between IM experiments and pencil-beam galaxy surveys. We find that a random distribution of pencil beams leads to very similar overall sensitivity as a lattice spaced across the IM survey and derive a simple formula for random configurations that agrees with the Fisher matrix formalism. We explore examples of combining high-redshift James Webb Space Telescope (JWST) observations with both an SPHEREx-like Lyα IM survey and a 21 cm experiment based on the Hydrogen Epoch of Reionization Array (HERA). We find that the JWST-SPHEREx case is promising, leading to a total signal-to-noise ratio of ~5 after 100 total hours of JWST (at z = 7). We find that HERA is not well-suited for this approach owing to its drift-scan strategy, but that a similar experiment that can integrate down on one field could be.

Keywords: cosmology; reionization; high-redshift galaxies
Gaussbock: Fast Parallel-iterative Cosmological Parameter Estimation with Bayesian Nonparametrics

We present and apply Gaussbock, a new embarrassingly parallel iterative algorithm for cosmological parameter estimation designed for an era of cheap parallel-computing resources. Gaussbock uses Bayesian nonparametrics and truncated importance sampling to accurately draw samples from posterior distributions with an orders-of-magnitude speed-up in wall time over alternative methods. Contemporary problems in this area often suffer from both increased computational costs due to high-dimensional parameter spaces and consequent excessive time requirements, as well as the need to fine-tune proposal distributions or sampling parameters. Gaussbock is designed specifically with these issues in mind. We explore and validate the performance and convergence of the algorithm on a fast approximation to the Dark Energy Survey Year 1 (DES Y1) posterior, finding reasonable scaling behavior with the number of parameters. We then test on the full DES Y1 posterior using large-scale supercomputing facilities and recover reasonable agreement with previous chains, although the algorithm can underestimate the tails of poorly constrained parameters. Additionally, we discuss and demonstrate how Gaussbock recovers complex posterior shapes very well at lower dimensions, but faces challenges to perform well on such distributions in higher dimensions. In addition, we provide the community with a user-friendly software tool for accelerated cosmological parameter estimation based on the methodology described in this paper.

Keywords: cosmological parameters; astrostatistics; astronomy data analysis
High-resolution Spectroscopic Study of Dwarf Stars in the Northern Sky: Lithium, Carbon, and Oxygen Abundances

Abundances of lithium, carbon, and oxygen have been derived using spectral synthesis for a sample of 249 bright F, G, and K Northern Hemisphere dwarf stars from the high-resolution spectra acquired with the VUES spectrograph at the Molėtai Astronomical Observatory of Vilnius University. The sample stars have metallicities, effective temperatures, and ages between (-0.7 $\div$ 0.4) dex, (5000 $\div$ 6900) K, (1 $\div$ 12) Gyr, accordingly. We confirm a so far unexplained lithium abundance decrease at supersolar metallicities—A(Li) in our sample stars, which drop by 0.7 dex in the [Fe/H] range from +0.10 to +0.55 dex. Furthermore, we identified stars with similar ages, atmospheric parameters, and rotational velocities, but with significantly different lithium abundances, which suggests that additional specific evolutionary factors should be taken into account while interpreting the stellar lithium content. Nine stars with predominantly supersolar metallicities, i.e., about 12% among 78 stars with C and O abundances determined, have the C/O number ratios larger than 0.65, thus may form carbon-rich rocky planets. Ten planet-hosting stars, available in our sample, do not show a discernible difference from the stars with no planets detected regarding their lithium content.

Keywords: chemical abundances; dwarf stars; solar neighborhood; high resolution spectroscopy
A Catalog of Compact Blue Strongly Lensed Sources in the Footprint of Ground-based Surveys

We present a catalog of Compact Blue Strongly Lensed Sources in the footprint of ground-based surveys. We visually inspected the high-quality strong lensing candidates from the Kilo Degree Survey, the Hyper Suprime-Cam Subaru Strategic Program and the Dark Energy Survey. We have collected 63 multiple-imaged systems that are similar to the lensed post-blue nuggets found in Napolitano et al. and fully characterized in Li et al. Data, including gri cutouts, are made publicly available (https://cosviewer.com/en/special-objects#bluenuggets).

Keywords: gravitational lensing; catalogs
OGLE-2007-BLG-224L: A Direct Test of Terrestrial Parallax

We present limits on the lens flux of OGLE-2007-BLG-224 based on MagAO imaging taken seven years after the microlensing event. At the time of the observations, the lens should have been separated from the microlensing source by 292 mas. However, no new sources are detected with MagAO. We place an upper limit on the lens flux of H > 20.57. This measurement supports the conclusion of Gould et al. that the lens in this event should be a brown dwarf. This is the first test of a prediction based on the terrestrial microlens parallax effect and the first AO confirmation of a substellar/dark microlens.

Keywords: microlensing parallax; high-resolution microlensing event imaging; gravitational microlensing; brown dwarfs
Properties of the Turbulence and Topology in a Turbulent Magnetic Reconnection

Magnetic reconnection is a crucial process responsible for energy conversion and particle acceleration in space, astrophysical, and laboratory plasmas. Turbulence and magnetic reconnection can be mutually driven, but the underlying nature of energy dissipation, intrinsic turbulence waves, and magnetic field topologies in turbulent magnetic reconnection is still poorly understood. Here, using advanced multi-spacecraft mission and innovative methods, we provide a few new perspectives to investigate the properties of the turbulence and topology in a turbulent magnetic reconnection in the magnetotail. Our results reveal that in turbulent magnetic reconnection: (1) cyclotron resonance, an important mechanism of energy dissipation, is more effective in the core region of the reconnection than in the outflow regions; (2) energy is deposited in the form of kinetic Alfvén waves (KAWs) and fast/slow waves, with KAWs corresponding to low-frequency (ion cyclotron scale) and fast/slow waves corresponding to high-frequency (low-hybrid scale); and (3) the number of spiral nulls (O-lines) were about 3.6 times more than radial ones (X-lines), and three-dimensional structures were about 8 times more prevalent than two-dimensional ones. These findings should help us better unravel the dynamics of turbulent magnetic reconnection.

Keywords: spectral index; interplanetary turbulence; space plasmas
Divergence in Mass Ratio Distributions between Low-mass and High-mass Coalescing Binary Black Holes

Coalescing binary black hole (BBH) systems are likely formed via several channels, and it is challenging to understand their formation/evolutionary processes. Some features in the mass function of the primary components (m 1), such as the distinct Gaussian-like peak located at ~34 M ⊙, have been previously found. In this work, we investigate the possible dependence of the mass ratio (q = m 2/m 1) distribution on the primary mass. We find a Bayesian odds ratio of 18.1 in favor of divergence in the mass ratio distributions between the low- and high-mass ranges over an invariable mass ratio distribution. BBHs with m 1 ≳ 29 M ⊙ have a stronger preference of being symmetric compared to those with m 1 ≲ 29 M ⊙ at a 97.6% credible level. Additionally, we find mild evidence that BBHs with m 1 located in the Gaussian-like peak have a mass ratio distribution different from that of other BBHs. Our findings may favor some formation channels, such as chemically homogeneous evolution and dynamical assembly in globular clusters/nuclear star clusters, which are more likely to provide symmetric BBHs in the high-mass range.

Keywords: gravitational wave astronomy; high energy astrophysics
The Appearance of Vortices in Protoplanetary Disks in Near-infrared Scattered Light

Azimuthally asymmetric structures have been discovered in millimeter continuum emission from many protoplanetary disks. One hypothesis is that they are vortices produced by the Rossby wave instability, for example at the edges of planet-opened gaps or dead zones. Confirming the vortex nature of these structures will have profound implications to planet formation. One way to test the hypothesis is to compare the observed morphology of vortex candidates in near-infrared scattered light with theoretical expectations. To this end, we synthesize the appearance of vortices in H-band polarized light by combining hydrodynamic and radiative transfer simulations of the Rossby wave instability at a dead-zone edge. In a disk at 140 pc, at the peak in its evolution a vortex at 65 au may appear as a radially narrow arc 50%-70% brighter compared with an axisymmetric disk model. The contrast depends on the inclination of the disk and the position angle of the vortex only weakly. Such contrast levels are well detectable in imaging observations of bright disks using instruments such as the Very Large Telescope/SPHERE, Subaru/SCExAO, and Gemini/GPI. A vortex also casts a shadow in the outer disk, which may aid its identification. Finally, at modest-to-high inclinations (e.g., 60°) a vortex may mimic a one-armed spiral. In the HD 34282 disk, such a one-armed spiral with a shadowed region on the outside has been found in scattered light. This feature roughly coincides with an azimuthal asymmetry in millimeter continuum emission, signifying the presence of a vortex.

Keywords: protoplanetary disks; radiative transfer; hydrodynamical simulations; exoplanets; antumbra
Physical Conditions of Gas Components in Debris Disks of 49 Ceti and HD 21997

Characterization of the gas component in debris disks is of fundamental importance for understanding their origin. To address this goal, we have conducted non-LTE (local thermodynamic equilibrium) analyses of the rotational spectral lines of CO including those of rare isotopologues (13CO and C18O) that have been observed toward the gaseous debris disks of 49 Ceti and HD 21997 with the Atacama Large Millimeter/submillimeter Array (ALMA) and the Atacama Compact Array (ACA). The analyses have been carried out for a wide range of H2 density, and the observed line intensities are found to be reproduced as long as the H2 density is higher than 103 cm-3. The CO column density and the gas temperature are evaluated to be (1.8-5.9) × 1017 cm-2 and 8-11 K for 49 Ceti and (2.6-15) × 1017 cm-2 and 8-12 K for HD 21997, respectively, where the H2 collision is assumed for the rotational excitation of CO. The results do not change significantly even if electron collision is considered. Thus, CO molecules can be excited under environments containing no H2 or a small number of H2 molecules, even where collisions with CO, C, O, and C+ would make an important contribution to the CO excitation in addition to H2. Meanwhile, our result does not rule out the case of abundant H2 molecules. The low gas temperature observed in the debris disks is discussed in terms of inefficient heating by interstellar and stellar UV radiation.

Keywords: observational astronomy; circumstellar gas; debris disks; submillimeter astronomy; astrochemistry
Ready, Set, Launch: Time Interval between a Binary Neutron Star Merger and Short Gamma-Ray Burst Jet Formation

The joint detection of GW170817/GRB 170817 confirmed the long-standing theory that binary neutron star mergers produce short gamma-ray burst (sGRB) jets that can successfully break out of the surrounding ejecta. At the same time, the association with a kilonova provided unprecedented information regarding the physical properties (such as masses and velocities) of the different ejecta constituents. Combining this knowledge with the observed luminosities and durations of cosmological sGRBs detected by the Burst Alert Telescope onboard the Neil Gehrels Swift Observatory, we revisit the breakout conditions of sGRB jets. Assuming self-collimation of sGRB jets does not play a critical role, we find that the time interval between the binary merger and the launch of a typical sGRB jet is $\lesssim 0.1\,{\rm{s}}$ . We also show that for a fraction of at least $\sim 30 \% $ of sGRBs, the usually adopted assumption of static ejecta is inconsistent with observations, even if the polar ejecta mass is an order of magnitude smaller than that in GRB 170817. Our results disfavor magnetar central engines for powering cosmological sGRBs, limit the amount of energy deposited in the cocoon prior to breakout, and suggest that the observed delay of ∼1.7 s in GW170817/GRB 170817 between the gravitational wave and gamma-ray signals is likely dominated by the propagation time of the jet to the gamma-ray production site.

Keywords: gamma-ray bursts; relativistic jets; neutron stars; gravitational wave sources; astrophysical black holes
An Angular Diameter Measurement of β UMa via Stellar Intensity Interferometry with the VERITAS Observatory

We use the Very Energetic Radiation Imaging telescope Array System (VERITAS) imaging air Cherenkov telescope array to obtain the first measured angular diameter of β UMa at visual wavelengths using stellar intensity interferometry (SII) and independently constrain the limb-darkened angular diameter. The age of the Ursa Major moving group has been assessed from the ages of its members, including nuclear member Merak (β UMa), an A1-type subgiant, by comparing effective temperature and luminosity constraints to model stellar evolution tracks. Previous interferometric limb-darkened angular-diameter measurements of β UMa in the near-infrared (Center for High Angular Resolution Astronomy (CHARA) Array, 1.149 ± 0.014 mas) and mid-infrared (Keck Nuller, 1.08 ± 0.07 mas), together with the measured parallax and bolometric flux, have constrained the effective temperature. This paper presents current VERITAS-SII observation and analysis procedures to derive squared visibilities from correlation functions. We fit the resulting squared visibilities to find a limb-darkened angular diameter of 1.07 ± 0.04 (stat) ± 0.05 (sys) mas, using synthetic visibilities from a stellar atmosphere model that provides a good match to the spectrum of β UMa in the optical wave band. The VERITAS-SII limb-darkened angular diameter yields an effective temperature of 9700 ± 200 ± 200 K, consistent with ultraviolet spectrophotometry, and an age of 390 ± 29 ± 32 Myr, using MESA Isochrones and Stellar Tracks. This age is consistent with 408 ± 6 Myr from the CHARA Array angular diameter.

Keywords: long baseline interferometry; fundamental parameters of stars; astronomy data modeling