adsabs/SciX_UAT_keywords huggingface dataset:
Fast and Wide CMEs without Observed >20 MeV Protons

Statistical studies have found a close association between large solar energetic particle (SEP) events and fast and wide coronal mass ejections (CMEs). However, not all fast and wide CMEs have an associated SEP event. From the Coordinated Data Analysis Web catalog of CMEs observed by the Solar and Heliospheric Observatory (SOHO) between 2009 January 1 and 2014 September 30, we select fast (plane-of-sky speed >1000 km s-1) and wide (plane-of-sky angular width >120°) CMEs and determine whether >20 MeV protons were detected by either SOHO or the Solar TErrestrial RElations Observatory (STEREO-A or STEREO-B). Among the 123 selected CMEs, only 11 did not produce a >20 MeV proton intensity increase at any of the three spacecraft. We use multispacecraft coronagraph observations to reevaluate the speeds and widths of the CMEs. The 11 CMEs without observed >20 MeV protons tend to be in the narrow and slow end of the distribution of the selected CMEs. We consider several factors that might play a role in the nonobservation of high-energy particles in these events, including (1) the ambiguous determination of the CME parameters, (2) the inefficiency of the particle sources to produce >20 MeV protons, (3) the lack of magnetic connection between particle sources and any spacecraft, and (4) the lack of particles accelerated and released during the parent solar eruptions. Whereas the extent of the high Mach number regions formed in front of the CME is limited, the characteristic that seems to distinguish those fast and wide CMEs that lack observed >20 MeV protons is a deficit in the release of particles during the solar eruptions.

Keywords: solar coronal mass ejections; solar coronal mass ejection shocks; solar particle emission; solar energetic particles
General Relativistic Implicit Monte Carlo Radiation-hydrodynamics

We report on a new capability added to our general relativistic radiation-magnetohydrodynamics code, Cosmos++: an implicit Monte Carlo (IMC) treatment for radiation transport. The method is based on a Fleck-type implicit discretization of the radiation-hydrodynamics equations, but generalized for both Newtonian and relativistic regimes. A multiple reference frame approach is used to geodesically transport photon packets (and solve the hydrodynamics equations) in the coordinate frame, while radiation-matter interactions are handled either in the fluid or electron frames then communicated via Lorentz boosts and orthonormal tetrad bases attached to the fluid. We describe a method for constructing estimators of radiation moments using path-weighting that generalizes to arbitrary coordinate systems in flat or curved spacetime. Absorption, emission, scattering, and relativistic Comptonization are among the matter interactions considered in this report. We discuss our formulations and numerical methods, and validate our models against a suite of radiation and coupled radiation-hydrodynamics test problems in both flat and curved spacetimes.

Keywords: hydrodynamics; astrophysical fluid dynamics; general relativity; geodesics; radiative transfer; radiative transfer equation; relativity; radiative magnetohydrodynamics
Electron Heat Flux Instabilities in the Inner Heliosphere: Radial Distribution and Implication on the Evolution of the Electron Velocity Distribution Function

This Letter investigates the electron heat flux instability using the radial models of the magnetic field and plasma parameters in the inner heliosphere. Our results show that both the electron acoustic wave and the oblique whistler wave are unstable in the regime with large relative drift speed (ΔVe) between electron beam and core populations. Landau-resonant interactions of electron acoustic waves increase the electron parallel temperature that would lead to suppressing the electron acoustic instability and amplifying the growth of oblique whistler waves. Therefore, we propose that the electron heat flux can effectively drive oblique whistler waves in an anisotropic electron velocity distribution function. This study also finds that lower-hybrid waves and oblique Alfvén waves can be triggered in the solar atmosphere, and that the former instability is much stronger than the latter. Moreover, we clarify that the excitation of lower-hybrid waves mainly results from the transit-time interaction of beaming electrons with resonant velocities v∥ ~ ω/k∥, where ω and k∥ are the wave frequency and parallel wavenumber, respectively. In addition, this study shows that the instability of quasi-parallel whistler waves can dominate the regime with medium ΔVe at the heliocentric distance nearly larger than 10 times of the solar radius.

Keywords: plasma astrophysics; space plasmas; solar wind
SOFIA FEEDBACK Survey: Exploring the Dynamics of the Stellar Wind-Driven Shell of RCW 49

We unveil the stellar wind-driven shell of the luminous massive star-forming region of RCW 49 using SOFIA FEEDBACK observations of the [C II] 158 μm line. The complementary data set of the 12CO and 13CO J = 3 → 2 transitions is observed by the APEX telescope and probes the dense gas toward RCW 49. Using the spatial and spectral resolution provided by the SOFIA and APEX telescopes, we disentangle the shell from a complex set of individual components of gas centered around RCW 49. We find that the shell of radius ~6 pc is expanding at a velocity of 13 km s-1 toward the observer. Comparing our observed data with the ancillary data at X-ray, infrared, submillimeter, and radio wavelengths, we investigate the morphology of the region. The shell has a well-defined eastern arc, while the western side is blown open and venting plasma further into the west. Though the stellar cluster, which is ~2 Myr old, gave rise to the shell, it only gained momentum relatively recently, as we calculate the shell's expansion lifetime of ~0.27 Myr, making the Wolf-Rayet star WR 20a a likely candidate responsible for the shell's reacceleration.

Keywords: stellar feedback
The SAMI Galaxy Survey: Stellar Populations of Passive Spiral Galaxies in Different Environments

We investigate the stellar populations of passive spiral galaxies as a function of mass and environment, using integral field spectroscopy data from the Sydney-AAO Multi-object Integral field spectrograph Galaxy Survey. Our sample consists of 52 cluster passive spirals and 18 group/field passive spirals, as well as a set of S0s used as a control sample. The age and [Z/H] estimated by measuring Lick absorption line strength indices both at the center and within 1Re do not show a significant difference between the cluster and the field/group passive spirals. However, the field/group passive spirals with log(M⋆/M⊙) ≳ 10.5 show decreasing [α/Fe] along with stellar mass, which is ∼0.1 dex smaller than that of the cluster passive spirals. We also compare the stellar populations of passive spirals with S0s. In the clusters, we find that passive spirals show slightly younger age and lower [α/Fe] than the S0s over the whole mass range. In the field/group, stellar populations show a similar trend between passive spirals and S0s. In particular, [α/Fe] of the field/group S0s tend to be flattening with increasing mass above log(M⋆/M⊙) ≳ 10.5, similar to the field/group passive spirals. We relate the age and [α/Fe] of passive spirals to their mean infall time in phase space; we find a positive correlation, in agreement with the prediction of numerical simulations. We discuss the environmental processes that can explain the observed trends. The results lead us to conclude that the formation of the passive spirals and their transformation into S0s may significantly depend on their environments.

Keywords: galaxy evolution; galaxy abundances; galaxy environments; galaxy ages; extragalactic astronomy
Unusual Gas Structure in an Otherwise Normal Spiral Galaxy Hosting GRB 171205A/SN 2017iuk

We study the structure of atomic hydrogen (H I) in the host galaxy of GRB 171205A/SN 2017iuk at z = 0.037 through H I 21 cm emission line observations with the Karl G. Jansky Very Large Array. These observations reveal unusual morphology and kinematics of the H I in this otherwise apparently normal galaxy. High column density, cold H I is absent from an extended North-South region passing by the optical center of the galaxy, but instead is extended toward the South, on both sides of the galaxy. Moreover, the H I kinematics do not show a continuous change along the major axis of the galaxy as expected in a classical rotating disk. We explore several scenarios to explain the H I structure and kinematics in the galaxy: feedback from a central starburst and/or an active galactic nucleus, ram-pressure stripping, accretion, and tidal interaction from a companion galaxy. All of these options are ruled out. The most viable remaining explanation is the penetrating passage of a satellite through the disk only a few Myr ago, redistributing the H I in the GRB host without yet affecting its stellar distribution. It can also lead to the rapid formation of peculiar stars due to a violent induced shock. The location of GRB 171205A in the vicinity of the distorted area suggests that its progenitor star(s) originated in extreme conditions that share the same origin as the peculiarities in H I. This could explain the atypical location of GRB 171205A in its host galaxy.

Keywords: gamma-ray bursts; type ic supernovae; interstellar medium; galaxy dynamics; galaxy kinematics; h i line emission; galaxy interactions
Early Warnings of Binary Neutron Star Coalescence Using the SPIIR Search

Gravitational waves from binary neutron star mergers can be used as alerts to enable prompt follow-up observations. In particular, capturing prompt electromagnetic and astroparticle emissions from the moment of a binary merger presents unique constraints on the timescale and sky localization for online gravitational-wave detection. Here we present the expected performance of the SPIIR online detection pipeline that is designed for this purpose in the upcoming international LIGO-Virgo's 4th Science Run (O4). Using simulated Gaussian data for the two LIGO observatories with expected O4 sensitivity, we demonstrate that there is a nonnegligible opportunity to deliver premerger warnings at least 10 s before the final plunge. These alerts are expected to be issued at a nominal rate of one binary neutron star coalescence per year and localized within a median searched area of 300 deg2. We envision such detection to be extremely useful for follow-up observatories with a large field of view such as the Murchison Widefield Array radio facility in Western Australia.

Keywords: gravitational wave astronomy; compact binary stars; gravitational wave sources; neutron stars
Near-infrared and Optical Observations of Type Ic SN 2020oi and Broad-lined Type Ic SN 2020bvc: Carbon Monoxide, Dust, and High-velocity Supernova Ejecta

We present near-IR (NIR) and optical observations of the Type Ic supernova (SN Ic) SN 2020oi in the galaxy M100 and the broad-lined SN Ic SN 2020bvc in UGC 9379, using Gemini, Las Cumbres Observatory, Southern Astrophysical Telescope, and other ground-based telescopes. The NIR spectrum of SN 2020oi at day 63 since the explosion shows strong CO emissions and a rising K-band continuum, which is the first unambiguous dust detection from an SN Ic. Non-LTE CO modeling shows that CO is still optically thick and that the lower limit to the CO mass is 10-3 M⊙. The dust temperature is 810 K, and the dust mass is ∼10-5 M⊙. We explore the possibilities that the dust is freshly formed in the ejecta, heated dust in the preexisting circumstellar medium, and an infrared echo. The light curves of SN 2020oi are consistent with a STELLA model with canonical explosion energy, 0.07 M⊙ Ni mass, and 0.7 M⊙ ejecta mass. A model of high explosion energy of 1052 erg, 0.4 M⊙ Ni mass, and 6.5 M⊙ ejecta mass with the circumstellar matter reproduces the double-peaked light curves of SN 2020bvc. We observe temporal changes of absorption features of the IR Ca II triplet, S I at 1.043 μm, and Fe II at 5169 Å. The blueshifted lines indicate high velocities, up to 60,000 km s-1 for SN 2020bvc and 20,000 km s-1 for SN 2020oi, and the expansion velocity rapidly declines before the optical maximum. We present modeled spectral signatures and diagnostics of CO and SiO molecular bands between 1.4 and 10 μm.

Keywords: core-collapse supernovae; type ic supernovae; carbonaceous grains; cosmochemistry; interstellar molecules; molecular spectroscopy; high resolution spectroscopy; line intensities; silicate grains; interstellar dust; explosive nucleosynthesis; nucleosynthesis
On the Formation of the W-shaped O II Lines in Spectra of Type I Superluminous Supernovae

H-poor Type I superluminous supernovae (SLSNe I) are characterized by O II lines around 4000–4500 Å in pre-/near-maximum spectra, the so-called W-shaped O II lines. As these lines are from relatively high excitation levels, they have been considered a sign of nonthermal processes, which may provide a hint of the power sources of SLSNe I. However, the conditions for these lines to appear have not been well understood. In this work, we systematically calculate synthetic spectra to reproduce the observed spectra of eight SLSNe I, parameterizing departure coefficients from the nebular approximation in the supernova ejecta (expressed as b neb). We find that most of the observed spectra can be well reproduced with b neb ≲ 10, which means that no strong departure is necessary for the formation of the W-shaped O II lines. We also show that the appearance of the W-shaped O II lines is sensitive to temperature; only spectra with temperatures in the range of T ∼ 14,000–16,000 K can produce the W-shaped O II lines without large departures. Based on this, we constrain the nonthermal ionization rate near the photosphere. Our results suggest that spectral features of SLSNe I can give independent constraints on the power source through the nonthermal ionization rates.

Keywords: supernovae
Magnetic Structure of an Erupting Filament

The full 3D vector magnetic field of a solar filament prior to eruption is presented. The filament was observed with the Facility Infrared Spectropolarimeter at the Dunn Solar Telescope in the chromospheric He I line at 10830 Å on 2017 May 29 and 30. We inverted the spectropolarimetric observations with the Hanle and Zeeman Light code to obtain the chromospheric magnetic field. A bimodal distribution of field strength was found in or near the filament. The average field strength was 24 Gauss, but prior to the eruption we find the 90th percentile of field strength was 435 Gauss for the observations on May 29. The field inclination was about 67° from the solar vertical. The field azimuth made an angle of about 47°-65° to the spine axis. The results suggest an inverse configuration indicative of a flux rope topology. He I intensity threads were found to be coaligned with the magnetic field direction. The filament had a sinistral configuration as expected for the southern hemisphere. The filament was stable on 2017 May 29 and started to rise during two observations on May 30, before erupting and causing a minor coronal mass ejection. There was no obvious change of the magnetic topology during the eruption process. Such information on the magnetic topology of erupting filaments could improve the prediction of the geoeffectiveness of solar storms.

Keywords: quiet solar chromosphere; solar filaments; solar filament eruptions; solar magnetic fields
LISA Gravitational Wave Sources in a Time-varying Galactic Stochastic Background

A unique challenge for data analysis with the Laser Interferometer Space Antenna (LISA) is that the noise backgrounds from instrumental noise and astrophysical sources will change significantly over both the year and the entire mission. Variations in the noise levels will be on timescales comparable to, or shorter than, the time most signals spend in the detector's sensitive band. The variation in the amplitude of the galactic stochastic GW background from galactic binaries as the antenna pattern rotates relative to the galactic center is a particularly significant component of the noise variation. LISA's sensitivity to different source classes will therefore vary as a function of sky location and time. The variation will impact both overall signal-to-noise and the efficiency of alerts to EM observers to search for multimessenger counterparts.

Keywords: gravitational waves; gravitational wave astronomy; compact binary stars; supermassive black holes
Sensitivity of Simulations of Double-detonation Type Ia Supernovae to Integration Methodology

We study the coupling of hydrodynamics and reactions in simulations of the double-detonation model for Type Ia supernovae. When assessing the convergence of simulations, the focus is usually on spatial resolution; however, the method of coupling the physics together as well as the tolerances used in integrating a reaction network also play an important role. In this paper, we explore how the choices made in both coupling and integrating the reaction portion of a simulation (operator/Strang splitting versus the simplified spectral deferred corrections method we introduced previously) influences the accuracy, efficiency, and nucleosynthesis of simulations of double detonations. We find no need to limit reaction rates or reduce the simulation time step to the reaction timescale. The entire simulation methodology used here is GPU-accelerated and made freely available as part of the Castro simulation code.

Keywords: explosive nucleosynthesis; algorithms; hydrodynamical simulations; computational astronomy; astronomical simulations; nuclear fusion; nuclear astrophysics
On the Variation in the Volumetric Evolution of CMEs from the Inner to Outer Corona

Some of the major challenges faced in understanding the early evolution of coronal mass ejections (CMEs) are due to the limited observations in the inner corona (<3 R ⊙) and the plane-of-sky measurements. In this work, we have thus extended the application of the Graduated Cylindrical Shell (GCS) model to inner coronal observations from the ground-based coronagraph K-Cor of the Mauna Loa Solar Observatory, along with the pairs of observations from COR-1 on board the Solar Terrestrial Relations Observatory. We study the rapid initial acceleration and width expansion phases of five CMEs in white light at the lower heights. We also study the evolution of the modeled volumes of these CMEs in the inner corona and report, for the first time, a power-law dependence of CME volume with distance from the Sun. We further find that the volumes of the ellipsoidal leading front and the conical legs follow different power laws, thus indicating differential volume expansion throughout a CME. The study also reveals two distinct power laws for the total volume evolution of CMEs in the inner and outer corona, thus suggesting different expansion mechanisms at these different heights. Besides aiding our current understanding of CME evolution, these results will also provide better constraints to CME initiation and propagation models. Also, given the loss of the STEREO-B (and hence COR-1B data) from 2016, the modified GCS model presented here will still enable stereoscopy in the inner corona for the 3D study of CMEs in white light.

Keywords: solar coronal mass ejections
Reconstruction of Coronal Magnetic Fields Using a Poloidal-Toroidal Representation

A new method for reconstruction of coronal magnetic fields as force-free fields (FFFs) is presented. Our method employs poloidal and toroidal functions to describe divergence-free magnetic fields. This magnetic field representation naturally enables us to implement the boundary conditions at the photospheric boundary, i.e., the normal magnetic field and the normal current density there, in a straightforward manner. At the upper boundary of the corona, a source surface condition can be employed, which accommodates magnetic flux imbalance at the bottom boundary. Although our iteration algorithm is inspired by extant variational methods, it is nonvariational and requires far fewer iteration steps than most others. The computational code based on our new method is tested against the analytical FFF solutions by Titov & Démoulin. It is found to excel in reproducing a tightly wound flux rope, a bald patch, and quasi-separatrix layers with a hyperbolic flux tube.

Keywords: solar magnetic fields; solar corona; computational methods
Disentangling the Dominant Drivers of Gravity Wave Variability in the Martian Thermosphere

In this study, we extracted the amplitudes of the gravity waves (GWs) from the neutral densities measured in situ by the neutral gas and ion mass spectrometer aboard the Mars Atmosphere and Volatile Evolution mission. The spatial and temporal variabilities of the GWs show that solar activity (the F10.7 cm solar flux corrected for a heliocentric distance of 1.66 au), solar insolation, and the lower atmospheric dust are the dominant drivers of the GW variability in the thermosphere. We developed a methodology in which a linear regression analysis has been used to disentangle the complex variabilities of the GWs. The three dominant drivers could account for most of the variability in the GW amplitudes. Variability caused by the sources of GWs and the effects of winds and the global circulation in the mesosphere and lower thermosphere are the other factors that could not be addressed. The results of the present study show that for every 100 sfu increase in the solar activity, the GW amplitudes in the thermosphere decrease by ~9%. Solar insolation drives the diurnal, seasonal, and latitudinal variations of ~9%, ~4%, and ~6%, respectively. Using the historical data of the dust opacity and solar activity, we estimated the GW amplitudes of the Martian thermosphere from MY 24 to MY 35. The GW amplitudes were significantly reduced during the maximum of solar cycle 23 and were highest in the solar minimum. The global dust storms of MY 25, 28, and 34 lead to significant enhancements in the GW amplitudes.

Keywords: mars; thermosphere; planetary atmospheres; upper atmosphere
Low-activity Main-belt Comet 133P/Elst-Pizarro: New Constraints on Its Albedo, Temperature, and Active Mechanism from a Thermophysical Perspective

133P/Elst-Pizarro is the first recognized main-belt comet, but we still know little about its nucleus. First we use mid-infrared data of Spitzer MIPS, Spitzer IRS, and the Wide-field Infrared Survey Explorer to estimate its effective diameter, ${D}_{\mathrm{eff}}={3.9}_{-0.3}^{+0.4}$ km, geometric albedo, ${p}_{{\rm{v}}}=0.074\pm 0.013$ , and mean Bond albedo ${A}_{\mathrm{eff},{\rm{B}}}=0.024\pm 0.004$ . The albedo is used to compute 133P's temperature distribution, which shows significant seasonal variation, especially polar regions, ranging from ∼40 to ∼200 K. Based on current activity observations, the maximum water gas production rate is estimated to be $\sim 1.4\times {10}^{23}\,{{\rm{s}}}^{-1}$ , being far weaker than $\sim {10}^{26}\,{{\rm{s}}}^{-1}$ of JFC 67P at a similar heliocentric distance of ∼2.7 au, indicating a thick dust mantle on the surface to lower down the gas production rate. The diameter of the sublimation area may be <∼200 m according to our model prediction. We thus propose that 133P's activity is more likely to be caused by sublimation of a regional near-surface ice patch rather than a homogeneous buried ice layer. Such a small near-surface ice patch might be exposed by one impact event, before which 133P may be an extinct comet (or ice-rich asteroid) with an ice layer buried below ∼40 m depth. The proposed ice patch may be located somewhere within latitude -50 ∼ 50° by comparing theoretical variation of sublimation temperature to the constraints from observations. The timescale to form such a thick dust mantle is estimated to be >100 Myr, indicating that 133P may be more likely to be a relatively old planetesimals or a member of an old family than a recently formed fragment of some young family.

Keywords: comets; asteroid belt; small solar system bodies