adsabs/SciX_UAT_keywords huggingface dataset:
Imaging and Spectroscopic Observations of the Dynamic Processes in Limb Solar Flares

We investigate various dynamic processes including magnetic reconnection, chromospheric evaporation, and coronal rain draining in two limb solar flares through imaging and spectroscopic observations from the Interface Region Imaging Spectrograph (IRIS) and the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory. In the early phase of the flares, a bright and dense loop-top structure with a cusp-like shape can be seen in multiwavelength images, which is cospatial with the hard X-ray 25-50 keV emission. In particular, intermittent magnetic reconnection downflows are detected in the time-space maps of AIA 304 Å. The reconnection downflows are manifested as redshifts on one half of the loops and blueshifts on the other half in the IRIS Si IV 1393.76 Å line due to a projection effect. The Si IV profiles exhibit complex features (say, multipeak) with a relatively larger width at the loop-top region. During the impulsive phase, chromospheric evaporation is observed in both AIA images and the IRIS Fe XXI 1354.08 Å line. Upward motions can be seen from AIA 131 Å images. The Fe XXI line is significantly enhanced and shows a good Gaussian shape. In the gradual phase, warm rains are observed as downward moving plasmas in AIA 304 Å images. Both the Si IV and Fe XXI lines show a relatively symmetric shape with a larger width around the loop top. These results provide observational evidence for various dynamic processes involved in the energy release process of solar flares and are crucial to the understanding of this process.

Keywords: solar activity; solar flares; solar corona; solar transition region; solar ultraviolet emission; solar flare spectra
An X-Ray-dim "Isolated" Neutron Star in a Binary?

We report the discovery of a dark companion to 2MASS J15274848+3536572 with an orbital period of 6.14 hr. Combining the radial velocity from LAMOST observations and modeling of the multiband light curve, one obtains a mass function of ≃0.131 M ⊙, an inclination of $45\buildrel{\circ}\over{.} {20}_{-0\buildrel{\circ}\over{.} \,20}^{+0\buildrel{\circ}\over{.} \,13}$ , and a mass ratio of ${0.631}_{-0.003}^{+0.014}$ , which demonstrate the binary nature of the dark companion with a mass of 0.98 ± 0.03M ⊙ and a main-sequence K9-M0 star of 0.62 ± 0.01 M ⊙. LAMOST optical spectra at a range of orbital phases reveal extra-peaked H α emission that suggests the presence of an accretion disk. The dark companion does not seem to be a white dwarf because of the lack of any observed dwarf nova outbursts in the long-term data archive, although a magnetic white dwarf cannot be excluded. Alternatively, we propose a scenario wherein the dark companion is a neutron star, but we have not detected radio pulsations or a single pulse from the system with the FAST (Five-hundred-meter Aperture Spherical radio Telescope), which hints at a radio-quiet compact object. If the dark companion is identified as a neutron star, it will be the nearest (~118 pc) and lightest neutron star. Furthermore, kinematic analysis of the system's orbit in the galaxy may suggest its supernova event is associated with the radionuclide 60Fe signal observed from deep-sea crusts. This radio-quiet and X-ray-dim nearby neutron star may resemble an XDINS (X-ray-dim isolated neutron star) but in a binary.

Keywords: cataclysmic variable stars; neutron stars
Global Hall MHD Simulations of the Solar Wind Implantation Flux on the Lunar Surface

The solar wind can directly interact with the lunar surface and provide an important source for surface space weathering and water generation. Here we study the solar wind implantation flux on the lunar surface with global Hall MHD simulations. The shielding effects of both the Earth's magnetosphere and lunar magnetic anomalies are considered. It is found that a large-scale lunar mini-magnetosphere can be caused by the solar wind interaction with the magnetic anomalies on the lunar far side, which causes a large shielding area on the surface. In addition, the Earth's magnetosphere brings a longitudinal variation in the implantation flux, with minimum fluxes at 0° longitude. With the integrated flux over a lunation, we find that there are some local cavities on the implantation flux map, which are colocated with both the magnetic anomalies and the lunar swirls. Further studies show that there is a south-north asymmetry in the implantation flux, which can be used to explain the lower water content observed in the southern hemisphere. Our results provide a global map of the solar wind implantation flux on the lunar surface and are useful for evaluating the large-scale effect of solar wind implantation and sputtering on the space weathering and the water or gas generation of the surface.

Keywords: lunar science; solar wind; space plasmas; solar-planetary interactions
A Systematic Study of the Escape of LyC and Lyα Photons from Star-forming, Magnetized Turbulent Clouds

Understanding the escape of Lyman continuum (LyC) and Lyα photons from giant molecular clouds (GMCs) is crucial if we are to study the reionization of the universe and to interpret spectra of observed galaxies at high redshift. To this end, we perform high-resolution, radiation-magnetohydrodynamic simulations of GMCs with self-consistent star formation and stellar feedback. We find that a significant fraction (15%-70%) of ionizing radiation escapes from the simulated GMCs with different masses (105 and 106 M ⊙), as the clouds are dispersed within about 2-5 Myr from the onset of star formation. The fraction of LyC photons leaked is larger when the GMCs are less massive, metal poor, less turbulent, and less dense. The most efficient leakage of LyC radiation occurs when the total star formation efficiency of a GMC is about 20%. The escape of Lyα shows a trend similar to that of LyC photons, except that the fraction of Lyα photons escaping from the GMCs is larger ( ${f}_{\mathrm{Ly}\alpha }\approx {f}_{900}^{0.27}$ ) and that a GMC with strong turbulence shows larger f Lyα . The simulated GMCs show a characteristic velocity separation of Δv ≈ 120 km s-1 in the time-averaged emergent Lyα spectra, suggesting that Lyα could be useful to infer the kinematics of the interstellar and circumgalactic medium. We show that Lyα luminosities are a useful indicator of the LyC escape, provided the number of LyC photons can be deduced through stellar population modeling. Finally, we find that the correlations between the escape fractions of Lyα, ultraviolet photons at 1500 Å, and the Balmer α line are weak.

Keywords: giant molecular clouds; photoionization; reionization; lyman-alpha galaxies
The Supermassive Black Hole Masses of Reverberation-mapped Active Galactic Nuclei

Using different kinds of velocity tracers derived from the broad Hβ profile (in the mean or rms spectrum) and the corresponding virial factors f, the central supermassive black hole masses ( ${M}_{\mathrm{BH}}$ ) are calculated for a compiled sample of 120 reverberation-mapped (RM) active galactic nuclei (AGNs). For its subsample of RM AGNs with measured stellar velocity dispersion ( ${\sigma }_{* }$ ), the multivariate linear regression technique is used to calibrate the mean value f, as well as the variable FWHM-based f. It is found that, whether excluding the pseudobulges or not, the ${M}_{\mathrm{BH}}$ from the Hβ line dispersion in the mean spectrum ( ${\sigma }_{{\rm{H}}\beta ,\mathrm{mean}}$ ) has the smallest offset rms with respect to the ${M}_{\mathrm{BH}}\mbox{--}{\sigma }_{* }$ relation. For the total sample excluding SDSS-RM AGNs, with respect to ${M}_{\mathrm{BH}}$ from ${\sigma }_{* }$ or that from the Hβ line dispersion in the rms spectrum ( ${\sigma }_{{\rm{H}}\beta ,\mathrm{rms}}$ ), it is found that we can obtain ${M}_{\mathrm{BH}}$ from the ${\sigma }_{{\rm{H}}\beta ,\mathrm{mean}}$ with the smallest offset rms of 0.38 or 0.23 dex, respectively. It implies that, with respect to the Hβ FWHM, we prefer ${\sigma }_{{\rm{H}}\beta ,\mathrm{mean}}$ to calculate ${M}_{\mathrm{BH}}$ from the single-epoch spectrum. Using the FWHM-based f, we can improve the ${M}_{\mathrm{BH}}$ calculation from FWHM(Hβ) and the mean f, with a decreased offset rms from 0.52 to 0.39 dex with respect to ${M}_{\mathrm{BH}}$ from ${\sigma }_{* }$ for the subsample of 36 AGNs with ${\sigma }_{* }$ . The value of 0.39 dex is almost the same as that from ${\sigma }_{{\rm{H}}\beta ,\mathrm{mean}}$ and the mean f.

Keywords: active galactic nuclei; supermassive black holes; emission line galaxies; quasars; reverberation mapping
OGLE-2017-BLG-0406: Spitzer Microlens Parallax Reveals Saturn-mass Planet Orbiting M-dwarf Host in the Inner Galactic Disk

We report the discovery and analysis of the planetary microlensing event OGLE-2017-BLG-0406, which was observed both from the ground and by the Spitzer satellite in a solar orbit. At high magnification, the anomaly in the light curve was densely observed by ground-based-survey and follow-up groups, and it was found to be explained by a planetary lens with a planet/host mass ratio of $q=7.0\times {10}^{-4}$ from the light-curve modeling. The ground-only and Spitzer-"only" data each provide very strong one-dimensional (1D) constraints on the 2D microlens parallax vector ${{\boldsymbol{\pi }}}_{{\rm{E}}}$ . When combined, these yield a precise measurement of ${{\boldsymbol{\pi }}}_{{\rm{E}}}$ and of the masses of the host ${M}_{\mathrm{host}}=0.56\pm 0.07\,{M}_{\odot }$ and planet Mplanet = 0.41 ± 0.05 MJup. The system lies at a distance DL = 5.2 ± 0.5 kpc from the Sun toward the Galactic bulge, and the host is more likely to be a disk population star according to the kinematics of the lens. The projected separation of the planet from the host is ${a}_{\perp }=3.5\pm 0.3\,\mathrm{au}$ (i.e., just over twice the snow line). The Galactic-disk kinematics are established in part from a precise measurement of the source proper motion based on OGLE-IV data. By contrast, the Gaia proper-motion measurement of the source suffers from a catastrophic 10σ error.

Keywords: gravitational microlensing; gravitational microlensing exoplanet detection
Orbital Stability of Circumstellar Planets in Binary Systems

Planets that orbit only one of the stars in stellar binary systems (i.e., circumstellar) are dynamically constrained to a limited range of orbital parameters, and understanding conditions on their stability is thus of great importance in exoplanet searches. We perform ∼700 million N-body simulations to identify how stability regions depend on properties of the binary, as well as the starting planetary inclination and mean longitude relative to the binary orbit. Moreover, we provide grid interpolation maps and lookup tables for the community to use our results. Through Monte Carlo methods, we determine that planets with a semimajor axis ap ≲ 8% of the binary semimajor axis abin will likely be stable, given the known distribution of binary star parameters. This estimate varies in the Lidov-Kozai regime or for retrograde orbits to 4% or 10% of abin, respectively. Our method to quickly determine the circumstellar stability limit is important for interpreting observations of binaries using direct imaging with the James Webb Space Telescope, photometry with the Transiting Exoplanet Survey Satellite, or even astrometry with Gaia.

Keywords: orbits; habitable planets; exoplanet dynamics; exoplanets; binary stars
Thermophysical and Compositional Analyses of Dunes at Hargraves Crater, Mars

We analyze thermal emission spectra using the 2001 Mars Odyssey Thermal Emission Imaging System and the Mars Global Surveyor Thermal Emission Spectrometer to characterize grain size and mineralogical composition of dunes at Hargraves crater, Mars. Thermal inertia and bulk composition of the dunes were compared to inferred provenances from the thermal infrared response of surface constituent materials. We use a Markov Chain Monte Carlo technique to estimate the bulk amount of mineralogy contributed by each inferred provenance to the dune field composition. An average thermal inertia value of 238 ± 17 Jm-2 K-1 s-0.5 was found for the dunes, corresponding to a surface composed of an average effective grain size of ~391 ± 172 μm. This effective particle size suggests the presence of mostly medium sand-sized materials mixed with fine and coarse grain sands. The dunes are likely composed of a weakly indurated surface mixed with unconsolidated materials. Compositional analysis specifies that the dunes are composed of a mixture of feldspar, olivine, pyroxene, and relatively low bulk-silica content. Dune materials were likely derived from physical weathering, especially aeolian erosion, predominantly from the crater ejecta unit at the crater, mixed with a small amount from the crater floor and crater rim and wall lithologies-indicating that the dune materials were likely sourced locally.

Keywords: mars; solar system; solar system astronomy; solar system planets
Leptonic or Hadronic Emission: The X-Ray Radiation Mechanism of Large-scale Jet Knots in 3C 273

A comprehensively theoretical analysis of the broadband spectral energy distributions (SEDs) of large-scale jet knots in 3C 273 is presented to reveal their X-ray radiation mechanism. We show that these SEDs cannot be explained with a single-electron population model when the Doppler boosting effect is either considered or not. By adding a more energetic electron (the leptonic model) or proton (the hadronic model) population, the SEDs of all knots are well represented. In the leptonic model, the electron population that contributes the X-ray emission is more energetic than the one responsible for the radio-optical emission by almost two orders of magnitude; the derived equipartition magnetic field strengths (Beq) are ∼0.1 mG. In the hadronic model, protons with energy ∼20 PeV are required to interpret the observed X-rays; the Beq values are several mG, larger than those in the leptonic model. Based on the fact that no resolved substructures are observed in these knots and the fast cooling time of the high-energy electrons does not easily explain the observed X-ray morphologies, we argue that the two distinct electron populations accelerated in these knots are unreasonable and their X-ray emission is attributed to the proton synchrotron radiation accelerated in these knots. In cases where these knots have relativistic motion toward the observer, the super-Eddington issue of the hadronic model can be avoided. Multiwavelength polarimetry and γ-ray observations with high resolution may be helpful to discriminate these models.

Keywords: galaxy jets; active galactic nuclei; non-thermal radiation sources; x-ray active galactic nuclei
Two-point Correlation Function Studies for the Milky Way: Discovery of Spatial Clustering from Disk Excitations and Substructure

We introduce a two-particle correlation function (2PCF) for the Milky Way, constructed to probe spatial correlations in the orthogonal directions of the stellar disk in the Galactic cylindrical coordinates of R, ϕ, and z. We use this new tool to probe the structure and dynamics of the Galaxy using the carefully selected set of solar neighborhood stars (d ≲ 3 kpc) from Gaia Data Release 2 that we previously employed for studies of axial symmetry breaking in stellar number counts. We make additional, extensive tests, comparing to reference numerical simulations, to ensure our control over possibly confounding systematic effects. Supposing either axial or north-south symmetry, we divide this data set into two nominally symmetric sectors and construct the 2PCF, in the manner of the Landy-Szalay estimator, from the Gaia data. In so doing, working well away from the midplane region in which the spiral arms appear, we have discovered distinct symmetry-breaking patterns in the 2PCF in its orthogonal directions, thus establishing the existence of correlations in stellar number counts alone at subkiloparsec length scales for the very first time. In particular, we observe extensive wavelike structures of amplitude greatly in excess of what we would estimate if the system were in a steady state. We study the variations in these patterns across the Galactic disk, and with increasing ∣z∣, and we show how our results complement other observations of non-steady-state effects near the Sun, such as vertical asymmetries in stellar number counts and the Gaia snail.

Keywords: milky way galaxy; galaxy structure
Coronal Seismology Using Damping of Propagating Kink Waves

We consider the use of propagating kink waves, such as those observed by the Coronal Multi-channel Polarimeter, as a diagnostic technique. The transverse structuring of the plasma may be inferred by the frequency-dependent wave damping, which is attributed to resonant absorption. We include the effect of reflection of waves at the loop footpoints, which leads to the asymmetry parameter, describing the ratio of driven wave power at the footpoints becoming weakly constrained. The classical model of resonant absorption based on an exponential damping profile significantly overestimates the damping rate in coronal loops with low density contrast ratios. The use of the exponential profile in an analysis of observations therefore leads to underestimates for the density contrast ratio and associated parameters such as the heating rate following phase mixing.

Keywords: magnetohydrodynamics; solar coronal seismology; solar corona; solar coronal waves; bayesian statistics; markov chain monte carlo
Traveling Planetary-scale Waves Cause Cloud Variability on Tidally Locked Aquaplanets

Cloud cover at the planetary limb of water-rich Earth-like planets is likely to weaken chemical signatures in transmission spectra, impeding attempts to characterize these atmospheres. However, based on observations of Earth and Solar System worlds, exoplanets with atmospheres should have both short-term weather and long-term climate variability, implying that cloud cover may be less during some observing periods. We identify and describe a mechanism driving periodic clear sky events at the terminators in simulations of tidally locked Earth-like planets. A feedback between dayside cloud-radiative effects, incoming stellar radiation and heating, and the dynamical state of the atmosphere, especially the zonal wavenumber 1 Rossby wave identified in past work on tidally locked planets, leads to oscillations in Rossby wave phase speeds and in the position of Rossby gyres, and this results in advection of clouds to or away from the planet's eastern terminator. We study this oscillation in simulations of Proxima Centauri b, TRAPPIST-1e, and rapidly rotating versions of these worlds located at the inner edge of their stars' habitable zones. We simulate time series of the transit depths of the 1.4 μm water feature and 2.7 μm carbon dioxide feature. The impact of atmospheric variability on the transmission spectra is sensitive to the structure of the dayside cloud cover and the location of the Rossby gyres, but none of our simulations have variability significant enough to be detectable with current methods.

Keywords: exoplanets; exoplanet atmospheric dynamics; exoplanet atmospheres; exoplanet atmospheric variability
Slow Solar Wind Connection Science during Solar Orbiter's First Close Perihelion Passage

The Slow Solar Wind Connection Solar Orbiter Observing Plan (Slow Wind SOOP) was developed to utilize the extensive suite of remote-sensing and in situ instruments on board the ESA/NASA Solar Orbiter mission to answer significant outstanding questions regarding the origin and formation of the slow solar wind. The Slow Wind SOOP was designed to link remote-sensing and in situ measurements of slow wind originating at open-closed magnetic field boundaries. The SOOP ran just prior to Solar Orbiter's first close perihelion passage during two remote-sensing windows (RSW1 and RSW2) between 2022 March 3-6 and 2022 March 17-22, while Solar Orbiter was at respective heliocentric distances of 0.55-0.51 and 0.38-0.34 au from the Sun. Coordinated observation campaigns were also conducted by Hinode and IRIS. The magnetic connectivity tool was used, along with low-latency in situ data and full-disk remote-sensing observations, to guide the target pointing of Solar Orbiter. Solar Orbiter targeted an active region complex during RSW1, the boundary of a coronal hole, and the periphery of a decayed active region during RSW2. Postobservation analysis using the magnetic connectivity tool, along with in situ measurements from MAG and SWA/PAS, showed that slow solar wind originating from two out of three of the target regions arrived at the spacecraft with velocities between ~210 and 600 km s-1. The Slow Wind SOOP, despite presenting many challenges, was very successful, providing a blueprint for planning future observation campaigns that rely on the magnetic connectivity of Solar Orbiter.

Keywords: solar physics; slow solar wind; solar wind; solar active regions
Early Ultraviolet Observations of Type IIn Supernovae Constrain the Asphericity of Their Circumstellar Material

We present a survey of the early evolution of 12 Type IIn supernovae (SNe IIn) at ultraviolet and visible light wavelengths. We use this survey to constrain the geometry of the circumstellar material (CSM) surrounding SN IIn explosions, which may shed light on their progenitor diversity. In order to distinguish between aspherical and spherical CSM, we estimate the blackbody radius temporal evolution of the SNe IIn of our sample, following the method introduced by Soumagnac et al. We find that higher-luminosity objects tend to show evidence for aspherical CSM. Depending on whether this correlation is due to physical reasons or to some selection bias, we derive a lower limit between 35% and 66% for the fraction of SNe IIn showing evidence for aspherical CSM. This result suggests that asphericity of the CSM surrounding SNe IIn is common—consistent with data from resolved images of stars undergoing considerable mass loss. It should be taken into account for more realistic modeling of these events.

Keywords: supernovae
Photospheric Velocity Gradients and Ejecta Masses of Hydrogen-poor Superluminous Supernovae: Proxies for Distinguishing between Fast and Slow Events

We present a study of 28 Type I superluminous supernovae (SLSNe) in the context of the ejecta mass and photospheric velocity. We combine photometry and spectroscopy to infer ejecta masses via the formalism of radiation diffusion equations. We present an improved method to determine the photospheric velocity by combining spectrum modeling and cross-correlation techniques. We find that Type I SLSNe can be divided into two groups according to their pre-maximum spectra. Members of the first group have a W-shaped absorption trough in their pre-maximum spectrum, usually identified as due to O II. This feature is absent in the spectra of supernovae in the second group, whose spectra are similar to that of SN 2015bn. We confirm that the pre- or near-maximum photospheric velocities correlate with the velocity gradients: faster evolving SLSNe have larger photospheric velocities around maximum. We classify the studied SLSNe into the Fast or the Slow evolving group according to their estimated photospheric velocities, and find that all those objects that resemble SN 2015bn belong to the Slow evolving class, while SLSNe showing the W-like absorption are represented in both Fast and Slow evolving groups. We estimate the ejecta masses of all objects in our sample, and obtain values in the range 2.9 (±0.8)-208 (±61) M⊙, with a mean of 43 (±12) M⊙. We conclude that Slow evolving SLSNe tend to have higher ejecta masses compared to the Fast SLSNe. Our ejecta mass calculations suggests that SLSNe are caused by energetic explosions of very massive stars, irrespective of the powering mechanism of the light curve.

Keywords: supernovae; ejecta; radiative transfer