adsabs/SciX_UAT_keywords huggingface dataset:
Parker Solar Probe Observations of Alfvénic Waves and Ion-cyclotron Waves in a Small-scale Flux Rope

Small-scale flux ropes (SFRs) are common in the interplanetary environment. However, previous identification procedures generally discard SFRs with medium and high Alfvénicity, which are thought to be Alfvénic waves or Alfvénic structures. This paper first identifies an SFR event with medium Alfvénicity in the inner heliosphere (at ∼0.2 au) using Parker Solar Probe measurements. We find Alfvénic waves that arise inside SFR based on high correlations between the magnetic field and velocity fluctuations. We also observe quasi-monochromatic electromagnetic waves with frequencies f that are usually larger than the local proton cyclotron frequency at the leading and trailing edges of this SFR. These waves are well explained by the outward-propagating ion-cyclotron waves, which have wave frequencies ∼0.03-0.3 Hz and wavelengths ∼60-2000 km in the plasma frame. Moreover, we show that the power spectral density of the magnetic field in SFR middle region follows the power-law distribution, where the spectral index changes from -1.5 (f ≲ 1 Hz) to -3.3 (f ≳ 1 Hz). These findings would motivate developing an automated program to identify SFRs with medium and high Alfvénicity from Alfvénic waves/structures.

Keywords: solar wind; space plasmas; plasma physics
One-dimensional Numerical Study on Ignition of the Helium Envelope in Dynamical Accretion during the Double-degenerate Merger

In order for a double-detonation model to be viable for normal type Ia supernovae, the adverse impact of helium-burning ash on early time observables has to be avoided, which requires that the helium envelope mass should be at most 0.02 M ⊙. Most of the previous studies introduced detonation by artificial hot spots, and therefore the robustness of the spontaneous helium detonation remains uncertain. In the present work, we conduct a self-consistent hydrodynamic study on the spontaneous ignition of the helium envelope in the context of the double-degenerate channel, by applying an idealized one-dimensional model and a simplified seven-isotope reaction network. We explore a wide range of the progenitor conditions and demonstrate that the chance of direct initiation of detonation is limited. Especially, the spontaneous detonation requires the primary envelope mass of ≳0.03 M ⊙. Ignition as deflagration is instead far more likely, which is feasible for the lower envelope mass down to ~0.01 M ⊙, which might lead to subsequent detonation once the deflagration-to-detonation transition (DDT) is realized. High-resolution multidimensional simulations are required to further investigate the DDT possibility, as well as accurately derive the threshold between the spontaneous detonation and deflagration ignition regimes. Another interesting finding is the effect of the composition: while mixing with the core material enhances detonation as previously suggested, it rather narrows the chance for deflagration due to the slower rate of the 12C(α,γ)16O reaction at the lower temperature ~108K, with the caveat that we presently neglect the proton-catalyzed reaction sequence of 12C(p,γ)13O(α,p)16O.

Keywords: type ia supernovae; hydrodynamical simulations
Leto Mission Concept for Green Reconnaissance of the Marius Hills Lunar Pit

Lava tubes are potentially important sites for the long-term human presence on the Moon because they provide shelter from surface hazards, including micrometeorites, radiation, extreme temperatures, and dust. The discovery of a lava tube opening or pit at Marius Hills in Oceanus Procellarum is compelling motivation for robotic and eventually human exploration missions to these sites for in situ investigations and site assessments to determine viability for habitation and utilization of lunar resources. We make the case for Marius Hills to be a high-priority landing site and present elements of lunar data analysis, instrument/payload concepts, science justification for robotic missions, and thematic geologic reconnaissance and remote sensing that should be conducted prior to any construction or emplacement of infrastructure. This is described as a "green reconnaissance" approach to lunar exploration and exploitation, which seeks to address such contamination factors as sprayed rocket exhaust and sublimating water in order to preserve science fidelity. We are developing a concept of operations called the Leto mission for a green reconnaissance approach to robotically access the Marius Hills sublunarean void.

Keywords: the moon; lunar features; lunar science
On the Nature of Rotation in the Praesepe Cluster

Although a large number of Galactic open clusters (OCs) have been identified, the internal kinematic properties (e.g., rotation) of almost all the known OCs are still far from clear. With the high-precision astrometric data of Gaia EDR3, we have developed a methodology to unveil the rotational properties of the Praesepe cluster. Statistics of the three-dimensional residual motions of the member stars reveal the presence of Praesepe's rotation and determine its spatial rotation axis. The mean rotation velocity of the Praesepe cluster within its tidal radius is estimated to be 0.2 ± 0.05 km s-1, and the corresponding rotation axis is tilted in relation to the Galactic plane with an angle of 41° ± 12°. We also analyzed the rms rotational velocity of the member stars around the rotation axis, and found that the rotation of the member stars within the tidal radius of Praesepe probably follows Newton's classical theorems.

Keywords: open star clusters; stellar kinematics
High-energy Neutrinos from Outflows Powered by the Kicked Remnants of Binary Black Hole Mergers in Active Galactic Nucleus Accretion Disks

Merging of stellar-mass binary black holes (BBHs) could take place within the accretion disks of active galactic nuclei (AGN). The resulting BH remnant is likely to accrete the disk gas at a super-Eddington rate, launching a fast, quasi-spherical outflow (wind). Particles will be accelerated by shocks driven by the wind, subsequently interacting with the shocked disk gas or radiation field through hadronic processes and resulting in the production of high-energy neutrinos and potential electromagnetic (EM) emission. This study delves into the intricate evolution of the shock driven by a merged BH wind within an AGN disk. Subsequently, we calculated the production of neutrinos and the expected detection numbers for a single event, along with their contributions to the overall diffuse neutrino background. Our analysis, which considers various scenarios, reveals considerable neutrino production and possible detection by IceCube for nearby events. The contribution of merged BH winds on the diffuse neutrino background is minor due to the low event rate density, but it can be improved to some extent for some optimistic parameters. We also propose that there could be two neutrino/EM bursts, one originating from the premerger BBH wind and the other from the merged BH wind, with the latter typically having a delay to the gravitational wave (GW) event of around tens of days. When combined with the anticipated GWs emitted during the BBH merger, such a system emerges as a promising candidate for joint observations involving neutrinos, GWs, and EM signals.

Keywords: neutrino astronomy; high energy astrophysics; active galactic nuclei; gravitational waves; black holes
Mapping the Galactic Disk with the LAMOST and Gaia Red Clump Sample. VIII. Mapping the Kinematics of the Galactic Disk Using Mono-age and Mono-abundance Stellar Populations

We present a comprehensive study of the kinematic properties of the different Galactic disk populations, as defined by the chemical abundance ratios and stellar ages, across a large disk volume (4.5 ≤ R ≤ 15.0 kpc and ∣Z∣ ≤ 3.0 kpc), by using the LAMOST-Gaia red clump sample stars. We determine the median velocities for various spatial and population bins, finding large-scale bulk motions; for example, the wave-like behavior in radial velocity, the north-south discrepancy in azimuthal velocity and the warp signal in vertical velocity, and the amplitudes and spatial dependences of these bulk motions show significant variations for different mono-age and mono-abundance populations. The global spatial behaviors of the velocity dispersions clearly show a signal of spiral arms and a signal of the disk perturbation event within 4 Gyr, as well as disk flaring in the outer region (i.e., R ≥ 12 kpc), mostly for young or alpha-poor stellar populations. Our detailed measurements of age/[α/Fe]-velocity dispersion relations for different disk volumes indicate that young/α-poor populations are likely to originate from dynamic heating by both giant molecular clouds and spiral arms, while old/α-enhanced populations require an obvious contribution from other heating mechanisms, such as merger and accretion, or are born in the chaotic mergers of gas-rich systems and/or turbulent interstellar medium.

Keywords: stellar abundances; stellar kinematics; stellar populations; milky way formation; milky way evolution; milky way disk; milky way dynamics
Born in a Pair (?): Pisces II and Pegasus III

We have used B, V time-series photometry collected with the Large Binocular Telescope to undertake the first study of variable stars in the Milky Way ultra-faint dwarf (UFD) satellites Pisces II and Pegasus III. In Pisces II we have identified an RRab star, one confirmed and a candidate SX Phoenicis star, and a variable with uncertain classification. In Pegasus III we confirmed the variability of two sources: an RRab star and a variable with uncertain classification, similar to the case found in Pisces II. Using the intensity-averaged apparent magnitude of the bona fide RRab star in each galaxy, we estimate distance moduli of (m - M)0 = 21.22 ± 0.14 mag (d = 175 ± 11 kpc) and 21.21 ± 0.23 mag (d = 174 ± 18 kpc) for Pisces II and Pegasus III, respectively. Tests performed to disentangle the actual nature of variables with an uncertain classification led us to conclude that they most likely are bright, long-period, and very metal-poor RRab members of their respective hosts. This may indicate that Pisces II and Pegasus III contain a dominant old stellar population (t > 12 Gyr) with metallicity ⟨[Fe/H]⟩ - 1.8 dex along with, possibly, a minor, more metal-poor component, as supported by the V, B - V color-magnitude diagrams of the two UFDs and their spectroscopically confirmed members. The metallicity spread that we derived from our data sample is ≳0.4 dex in both systems. Lastly, we built isodensity contour maps that do not reveal any irregular shape, thus making the existence of a physical connection between these UFDs unlikely. * Based on data collected with the Large Binocular Cameras at the Large Binocular Telescope, PI: G. Clementini.

Keywords: dwarf galaxies; galaxy distances; variable stars
The Pair-instability Mass Gap for Black Holes

Stellar evolution theory predicts a "gap" in the black hole birth function caused by the pair instability. Many presupernova stars that have a core mass below some limiting value, Mlow, after all pulsational activity is finished, collapse to black holes, while more massive ones, up to some limiting value, Mhigh, explode, promptly and completely, as pair-instability supernovae. Previous work has suggested Mlow ≈ 50 M⊙ and Mhigh ≈ 130 M⊙. These calculations have been challenged by recent LIGO observations that show many black holes merging with individual masses Mlow ≳ 65 M⊙. Here we explore four factors affecting the theoretical estimates for the boundaries of this mass gap: nuclear reaction rates, evolution in detached binaries, rotation, and hyper-Eddington accretion after black hole birth. Current uncertainties in reaction rates by themselves allow Mlow to rise to 64 M⊙ and Mhigh as large as 161 M⊙. Rapid rotation could further increase Mlow to ∼70 M⊙, depending on the treatment of magnetic torques. Evolution in detached binaries and super-Eddington accretion can, with great uncertainty, increase Mlow still further. Dimensionless Kerr parameters close to unity are allowed for the more massive black holes produced in close binaries, though they are generally smaller.

Keywords: stellar mass black holes; core-collapse supernovae; hypernovae; gravitational wave astronomy
Exploring the Shallow Subsurface of Mars with the Ma_MISS Spectrometer on the ExoMars Rover Rosalind Franklin

An essential part of the Exomars 2022 payload is the Mars Multispectral Imager for Subsurface Studies (Ma_MISS) experiment hosted by the drill system. Ma_MISS is a visible and near-infrared (0.4-2.3 μm) miniaturized spectrometer with an optical head inside the drill tip capable of observing the drill borehole with a spatial resolution of 120 μm. Here we report on how the Ma_MISS hyperspectral information provides in situ investigation of the subsurface at very fine resolution, prior to the collection of the samples that will be manipulated and crushed for further analysis by the analytical laboratory on the rover. Ma_MISS is the instrument that will closely investigate the subsurface mineralogical characteristics in its original geologic context at depths never reached before in Mars exploration. Ma_MISS recognizes all the major spectral features of the clays, basaltic, and minor phases expected at the ExoMars landing site, Oxia Planum. The high spatial resolution on the borehole wall is such that single grains of about 100 μm can be distinguishable in the assemblage of minerals observed by Ma_MISS. The spatial distribution of the mineralogies within the borehole walls is associated with the rocks and the processes that put these materials in place and possibly altered them with time, characterizing the habitats found in the stratigraphic record, indicating which ones are the most suitable to have held or to be holding nowadays traces of life.

Keywords: mars
Collision Chains among the Terrestrial Planets. II. An Asymmetry between Earth and Venus

During the late stage of terrestrial planet formation, hit-and-run collisions are about as common as accretionary mergers, for expected velocities and angles of giant impacts. Average hit-and-runs leave two major remnants plus debris: the target and impactor, somewhat modified through erosion, escaping at lower relative velocity. Here we continue our study of the dynamical effects of such collisions. We compare the dynamical fates of intact runners that start from hit-and-runs with proto-Venus at 0.7 au and proto-Earth at 1.0 au. We follow the orbital evolutions of the runners, including the other terrestrial planets, Jupiter, and Saturn, in an N-body code. We find that the accretion of these runners can take ≳10 Myr (depending on the egress velocity of the first collision) and can involve successive collisions with the original target planet or with other planets. We treat successive collisions that the runner experiences using surrogate models from machine learning, as in previous work, and evolve subsequent hit-and-runs in a similar fashion. We identify asymmetries in the capture, loss, and interchange of runners in the growth of Venus and Earth. Hit-and-run is a more probable outcome at proto-Venus, being smaller and faster orbiting than proto-Earth. But Venus acts as a sink, eventually accreting most of its runners, assuming typical events, whereas proto-Earth loses about half, many of those continuing to Venus. This leads to a disparity in the style of late-stage accretion that could have led to significant differences in geology, composition, and satellite formation at Earth and Venus.

Keywords: solar system terrestrial planets; solar system formation
Fast Outflowing Warm Absorbers in Narrow-line Seyfert 1 Galaxy PG 1001+054 Revealed by HST/COS Spectra

Narrow-line Seyfert 1 (NLS1) galaxies are an important type of active galactic nucleus (AGN), generally expected to be accreting at a high Eddington rate. The properties of their outflows and importance of AGN feedback remain intriguing. We report on the discovery of fast outflowing warm absorbers (WAs) in the NLS1 PG 1001+054 with velocities in the range of ~7000-9000 km s-1. They are identified with blueshifted Lyα, N V, and Si IV lines in the high-resolution ultraviolet (UV) spectra taken with the Cosmic Origins Spectrograph on board the Hubble Space Telescope. We perform photoionization modeling using XSTAR with three WAs. The derived physical properties are typical of WAs in terms of ionization and column density, whereas the outflow velocities are significantly higher. The estimated location of these WAs ranges from 1 to 73 parsecs away from the AGN. Together with previous detection of high ionization absorbers in the X-ray for PG 1001+054, we suggest that fast outflowing UV absorbers are probably part of a multiphase outflow. Such a structure is likely produced by the outflow launched from the AGN at an accretion disk scale, which shocks the ambient interstellar medium (ISM), producing stratified absorbers. Assuming contribution from the three WAs at tens of parsecs, the estimated ratio between the kinetic power of the outflow and AGN Eddington luminosity could reach 1.7%, raising the possibility of sufficient influence on the host galaxy when compared to some theoretical models for efficient AGN feedback.

Keywords: seyfert galaxies; warm ionized medium; broad-absorption line quasar; ultraviolet sources
Young Star Clusters Dominate the Production of Detached Black Hole–Star Binaries

The recent discovery of two detached black hole–star (BH–star) binaries from Gaia's third data release has sparked interest in understanding the formation mechanisms of these systems. We investigate the formation of these systems by dynamical processes in young star clusters (SCs) and via isolated binary (IB) evolution, using a combination of direct N-body and population synthesis simulations. We find that dynamical formation in SCs is nearly 50 times more efficient per unit of star formation at producing BH–star binaries than IB evolution. We expand this analysis to the full Milky Way (MW) using a FIRE-2 hydrodynamical simulation of an MW-mass galaxy. Even assuming that only 10% of star formation goes into SCs, we find that approximately four out of every five BH–star systems are formed dynamically, and that the MW contains a total of ∼2 × 105 BH–star systems. Many of these dynamically formed systems have longer orbital periods, greater eccentricities, and greater black hole masses than their isolated counterparts. For binaries older than 100 Myr, we show that any detectable system with e ≳ 0.5 or M BH ≳ 10 M ⊙ can only be formed through dynamical processes. Our MW model predicts between 64 and 215 such detections from the complete DR4 Gaia catalog, with the majority of systems being dynamically formed in massive and metal-rich SCs. Finally, we compare our populations to the recently discovered Gaia BH1 and Gaia BH2, and conclude that the dynamical scenario is the most favorable formation pathway for both systems.

Keywords: astrophysical black holes; black holes; stellar mass black holes; open star clusters; star clusters; young star clusters; gaia; binary stars
On the True Fractions of Repeating and Nonrepeating Fast Radio Burst Sources

Observationally, fast radio bursts (FRBs) can be divided into repeating and apparently nonrepeating (one-off) ones. It is unclear whether all FRBs repeat and whether there are genuine nonrepeating FRBs. We attempt to address these questions using Monte Carlo simulations. We define a parameter Tc at which the accumulated number of nonrepeating sources becomes comparable to the total number of repeating sources, which is a good proxy to denote the intrinsic repeater fraction among FRBs. Assuming that both types of sources exist and their burst energies follow power-law distributions, we investigate how the observed repeater fraction evolves with time for different parameters. If the lifetime of repeaters is sufficiently long that the evolutionary effect can be neglected within the observational time span, unless Tc → ∞ (i.e., there is no genuine nonrepeating FRB source), the observed repeater fraction should increase with time first, reach a peak, and then decline. The peak time Tp and peak fraction Fr,obs,p depend on Tc and other repeating rate parameters. With the current data, we pose a lower limit Tc > 0.1 day for reasonable parameter values. We predict that future continuous monitoring of FRBs with CHIME or similar wide-field radio telescopes would obtain an Fr,obs less than 0.04. The detection of a smaller peak value Fr,obs,p < 0.04 in the near future would disfavor the ansatz that "all FRB sources repeat."

Keywords: radio transient sources
A Data-driven, Physics-based Transport Model of Solar Energetic Particles Accelerated by Coronal Mass Ejection Shocks Propagating through the Solar Coronal and Heliospheric Magnetic Fields

In an effort to develop computational tools for predicting radiation hazards from solar energetic particles (SEPs), we have created a data-driven physics-based particle transport model to calculate the injection, acceleration, and propagation of SEPs from coronal mass ejection (CME) shocks traversing through the solar corona and interplanetary magnetic fields. The model runs on an input of corona and heliospheric plasma and magnetic field configuration from a magnetohydrodynamic model driven by solar photospheric magnetic field measurements superposed with observed CME shocks determined from coronagraph images. SEP source particles are injected at the shock using the result of diffusive shock acceleration formulation from a characteristic obliquity-dependent injection from a heated solar wind thermal tail population. With several advanced computation techniques involving stochastic simulation and integration, the model obtains the particle intensity at any location in interplanetary space through the rigorous solution to the time-dependent 5D focus transport equation in the phase space that includes perpendicular diffusion. We apply the model to the 2011 November 3 CME event. The calculation results reproduce multispacecraft SEP observations at Earth and STEREO-B reasonably well without normalization of particle flux. The observations at STEREO-A can be reproduced by rescaling particle energy or modified energy dependence of particle diffusion coefficients. This circumsolar SEP event seen by spacecraft at Earth, STEREO-A, and STEREO-B at widely separated longitudes can be explained by diffusive shock acceleration by a single CME shock with a moderate speed.

Keywords: solar energetic particles; solar coronal mass ejection shocks; space weather
Cross-loop Propagation of a Quasiperiodic Extreme-ultraviolet Wave Train Triggered by Successive Stretching of Magnetic Field Structures during a Solar Eruption

Solar extreme-ultraviolet (EUV) waves generally refer to large-scale disturbances propagating outward from sites of solar eruptions in EUV imaging observations. Using the recent observations from the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory, we report a quasiperiodic wave train propagating outward at an average speed of ~308 km s-1. At least five wave fronts can be clearly identified with the period being ~120 s. These wave fronts originate from the coronal loop expansion, which propagates with an apparent speed of ~95 km s-1, about 3 times slower than the wave train. In the absence of a strong lateral expansion, these observational results might be explained by the theoretical model of Chen et al., which predicted that EUV waves may have two components: a faster component that is a fast-mode magnetoacoustic wave or shock wave and a slower apparent front formed as a result of successive stretching of closed magnetic field lines. In this scenario, the wave train and the successive loop expansion we observed likely correspond to the fast and slow components in the model, respectively.

Keywords: solar coronal mass ejections; solar flares; solar oscillations; solar coronal waves