adsabs/SciX_UAT_keywords huggingface dataset:
The Role of High-frequency Transverse Oscillations in Coronal Heating

Transverse oscillations that do not show significant damping in solar coronal loops are found to be ubiquitous. Recently, the discovery of high-frequency transverse oscillations in small-scale loops has been accelerated by the Extreme Ultraviolet Imager on board Solar Orbiter. We perform a meta-analysis by considering the oscillation parameters reported in the literature. Motivated by the power law of the velocity power spectrum of propagating transverse waves detected with CoMP, we consider the distribution of energy fluxes as a function of oscillation frequencies and the distribution of the number of oscillations as a function of energy fluxes and energies. These distributions are described as a power law. We propose that the power-law slope (δ = -1.40) of energy fluxes depending on frequencies could be used for determining whether high-frequency oscillations dominate the total heating (δ < 1) or not (δ > 1). In addition, we found that the oscillation number distribution depending on energy fluxes has a power-law slope of α = 1.00, being less than 2, which means that oscillations with high energy fluxes provide the dominant contribution to the total heating. It is shown that, on average, higher energy fluxes are generated from higher-frequency oscillations. The total energy generated by transverse oscillations ranges from about 1020 to 1025 erg, corresponding to the energies for nanoflare (1024-1027 erg), picoflare (1021-1024 erg), and femtoflare (1018-1021 erg). The respective slope results imply that high-frequency oscillations could provide the dominant contribution to total coronal heating generated by decayless transverse oscillations.

Keywords: solar coronal heating; solar oscillations; solar coronal waves
A Survey of Active Galaxies at TeV Photon Energies with the HAWC Gamma-Ray Observatory

The High Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory continuously detects TeV photons and particles within its large field of view, accumulating every day a deeper exposure of two-thirds of the sky. We analyzed 1523 days of HAWC live data acquired over four and a half years, in a follow-up analysis of 138 nearby (z < 0.3) active galactic nuclei from the Third Catalog of Hard Fermi-LAT sources culminating within 40° of the zenith at Sierra Negra, the HAWC site. This search for persistent TeV emission used a maximum-likelihood analysis assuming intrinsic power-law spectra attenuated by pair production of gamma-ray photons with the extragalactic background light. HAWC clearly detects persistent emission from Mkn 421 and Mkn 501, the two brightest blazars in the TeV sky, at 65σ and 17σ level, respectively. Marginal evidence, just above the 3σ level, was found for three other known very high-energy emitters: the radio galaxy M87 and the BL Lac objects VER J0521+211 and 1ES 1215+303, the latter two at z ∼ 0.1. We find a 4.2σ evidence for collective emission from the set of 30 previously reported very high-energy sources, with Mkn 421 and Mkn 501 excluded. Upper limits are presented for the sample under the power-law assumption and in the predefined (0.5-2.0), (2.0-8.0), and (8.0-32.0) TeV energy intervals.

Keywords: active galactic nuclei; blazars; gamma-rays; gamma-ray sources; sky surveys; radio galaxies
HH 80/81: Structure and Kinematics of the Fastest Protostellar Outflow

Hubble Space Telescope (HST) images obtained in 2018 are combined with archival HST data taken in 1995 to detect changes and measure proper motions in the HH 80/81 shock complex, which is powered by the fastest known jet driven by a forming star, the massive object IRAS 18162-2048. Some persistent features close to the radio jet axis have proper motions of >1000 km s-1 away from IRAS 18162-2048. About 3-5 pc downstream from the IRAS source and beyond HH 80/81, Hα emission traces the rim of a parsec-scale bubble blown by the jet. Lower speed motions are seen in [S II] away from the jet axis; these features have a large component of motion at right angles to the jet. We identify new HH objects and H2 shocks in the counterflow opposite HH 80/81. The northeastern counterflow to HH 80/81 exhibits an extended but faint complex of 2.12 μm H2 shocks. The inner portion of the outflow is traced by dim 1.64 μm [Fe II] emission. The full extent of this outflow is at least 1500″ (~10 pc in projection at a distance of 1.4 kpc). We speculate about the conditions responsible for the production of the ultrafast jet and the absence of prominent large-scale molecular outflow lobes.

Keywords: star forming regions; star formation
A Catalog of Early-type Runaway Stars from LAMOST DR8

Runaway stars are OB-type stars ejected from their birthplace with large peculiar velocities. The leading hypothesis addressed in their formation includes the supernova ejection mechanism and the dynamic ejection scenario. Identification of runaway populations is the first step to investigating their formation and evolution. Here we present our work of searching for Galactic runaway candidate stars from the Large sky Area Multi-Object fiber Spectroscopic Telescope (LAMOST) Medium Resolution Survey Data Release 8 (DR8) database. After studying the kinematic properties for a collection of 4432 early-type stars, predominantly B-type stars, using radial velocity measurements from LAMOST DR8 and astrometric solutions made by Gaia Data Release 3, we identified 229 runaway candidate stars. They span a wide distribution in projected rotational velocities. We investigated the Galactic spatial distribution of the runaway population and noticed that most of them likely reside within the Galactic thin disk. Based upon analyzing the Doppler shifts of the candidate stars, we found two binary runaway candidates displaying velocity variations with estimated orbital periods of 40 and 61 days.

Keywords: early-type stars; runaway stars; catalogs; surveys
The Magnetic Field in the Colliding Filaments G202.3+2.5

We observe the magnetic field morphology toward a nearby star-forming filamentary cloud, G202.3+2.5, using James Clerk Maxwell Telescope/POL-2 850 μm thermal dust polarization observations with an angular resolution of 14.″4 (∼0.053 pc). The average magnetic field orientation is found to be perpendicular to the filaments, while showing different behaviors in the four subregions, suggesting various effects from the filaments' collision in these subregions. With the kinematics obtained by the ${{{\rm{N}}}_{2}{\rm{H}}}^{+}$ observation by IRAM, we estimate the plane-of-sky magnetic field strength by two methods, the classical Davis–Chandrasekhar–Fermi (DCF) method and the angular dispersion function (ADF) method, giving B pos,dcf and B pos,adf of ∼90 and ∼53 μG. We study the relative importance between the gravity (G), magnetic field (B), and turbulence (T) in the four subregions, and find G > T > B, G ≥ T > B, G ∼ T > B, and T > G > B in the north tail, west trunk, south root, and east wing, respectively. In addition, we investigate the projection effects on the DCF and ADF methods, based on a similar simulation case, and find the 3D magnetic field strength may be underestimated by a factor of ∼3 if applying the widely used statistical B pos-to-B 3D factor when using the DCF or ADF methods, which may further underestimate/overestimate the related parameters.

Keywords: magnetic fields; star formation
Discovery of the Closest Saturnian Irregular Moon, S/2019 S 1, and Implications for the Direct/Retrograde Satellite Ratio

We present a tracked orbit for a recently discovered 25th magnitude irregular moon of Saturn, using Canada-France-Hawaii Telescope imaging. Our 2 yr of observational arc on the moon leads to an orbit with a semimajor axis of 11.2 million kilometers and an inclination of 44 deg. This makes it one of the smallest Saturnian irregular moon orbits known and puts the moon in the Inuit group. This moon is also a magnitude brighter than the faintest known Saturnian irregulars. We show that the moon's small semimajor axis results in it spending most of the time lost in the glare of the often-nearby planet, thus explaining how it escaped detection in previous surveys. We postulate that the disparity in the known inventory with more retrograde than direct irregular moons is partly due to the selection bias against finding the direct moons (whose groupings have smaller semimajor axis).

Keywords: irregular satellites; saturnian satellites; natural satellites (solar system); saturn
Strong Variability in AzV 493, an Extreme Oe-type Star in the SMC

We present 18 yr of OGLE photometry together with spectra obtained over 12 yr revealing that the early Oe star AzV 493 shows strong photometric (ΔI < 1.2 mag) and spectroscopic variability with a dominant, 14.6 yr pattern and ~40 day oscillations. We estimate the stellar parameters T eff = 42,000 K, $\mathrm{log}L/{L}_{\odot }=5.83\pm 0.15$ , M/M ⊙ = 50 ± 9, and v sin i = 370 ± 40 km s-1. Direct spectroscopic evidence shows episodes of both gas ejection and infall. There is no X-ray detection, and it is likely a runaway star. The star AzV 493 may have an unseen companion on a highly eccentric (e > 0.93) orbit. We propose that close interaction at periastron excites ejection of the decretion disk, whose variable emission-line spectrum suggests separate inner and outer components, with an optically thick outer component obscuring both the stellar photosphere and the emission-line spectrum of the inner disk at early phases in the photometric cycle. It is plausible that AzV 493's mass and rotation have been enhanced by binary interaction followed by the core-collapse supernova explosion of the companion, which now could be either a black hole or a neutron star. This system in the Small Magellanic Cloud can potentially shed light on OBe decretion disk formation and evolution, massive binary evolution, and compact binary progenitors.

Keywords: early-type stars; oe stars; be stars; circumstellar disks; interacting binary stars; compact objects; runaway stars
Detections of Simultaneous Brightening of γ-Ray and Optical Emissions of a Distant Blazar GB 1508+5714 at Redshift 4.3

GB 1508+5714 is a high-redshift blazar (z = 4.3), and a spectrally soft γ-ray source has been detected in its direction. By analyzing 11.4 yr Fermi Large Area Telescope data, significant long-term variability of the γ-ray source is confirmed. More importantly, a γ-ray emission flare appeared in an epoch of several tens of days in 2018, when the flux was about four times the value from the global fit. Meanwhile, optical flares were displayed in both the r and i bands from the Zwicky Transient Facility light curves. Detections of the simultaneous γ-ray and optical brightening provide decisive evidence to pin down the association between the γ-ray source and GB 1508+5714, which makes it the first identified γ-ray blazar beyond redshift 4. A broadband spectral energy distribution in the high flux state is constructed, and the origin of the multiwavelength brightening is also briefly discussed. Upcoming wide-deep-fast optical telescopes together with the γ-ray sky surveyors will shed light on the role that the active galactic nucleus jets play in the early cosmic time.

Keywords: galaxy jets; quasars; gamma-ray sources; non-thermal radiation sources; high-redshift galaxies
Repeating Fast Radio Bursts Reveal Memory from Minutes to an Hour

Fast radio bursts (FRBs) are brief, luminous pulses with unknown physical origin. The repetition pattern of FRBs contains essential information about their physical nature and emission mechanisms. Using the two largest samples of FRB 20121102 and FRB 20201124A, we report that the sources of the two FRBs reveal memory over a large range of timescales, from a few minutes to about an hour. The memory is detected from the coherent growths in burst-rate structures and the Hurst exponent. The waiting time distribution displays an approximate power-law tail, which is consistent with a Poisson model with a time-varying rate. From cellular automaton simulations, we find that these characteristics can be well understood within the physical framework of a self-organized criticality system driven in a correlation way, such as random walk functions. These properties indicate that the triggers of bursts are correlated, preferring the crustal failure mechanism of neutron stars.

Keywords: radio transient sources; radio bursts; magnetars
Ejecta Evolution Following a Planned Impact into an Asteroid: The First Five Weeks

The impact of the Double Asteroid Redirection Test spacecraft into Dimorphos, moon of the asteroid Didymos, changed Dimorphos's orbit substantially, largely from the ejection of material. We present results from 12 Earth-based facilities involved in a world-wide campaign to monitor the brightness and morphology of the ejecta in the first 35 days after impact. After an initial brightening of ~1.4 mag, we find consistent dimming rates of 0.11-0.12 mag day-1 in the first week, and 0.08-0.09 mag day-1 over the entire study period. The system returned to its pre-impact brightness 24.3-25.3 days after impact though the primary ejecta tail remained. The dimming paused briefly eight days after impact, near in time to the appearance of the second tail. This was likely due to a secondary release of material after re-impact of a boulder released in the initial impact, though movement of the primary ejecta through the aperture likely played a role.

Keywords: asteroids; near-earth objects; impact phenomena; asteroid satellites
Further Evidence for the Minifilament-eruption Scenario for Solar Polar Coronal Jets

We examine a sampling of 23 polar-coronal-hole jets. We first identified the jets in soft X-ray (SXR) images from the X-ray telescope (XRT) on the Hinode spacecraft, over 2014-2016. During this period, frequently the polar holes were small or largely obscured by foreground coronal haze, often making jets difficult to see. We selected 23 jets among those adequately visible during this period, and examined them further using Solar Dynamics Observatory's (SDO) Atmospheric Imaging Assembly (AIA) 171, 193, 211, and 304 Å images. In SXRs, we track the lateral drift of the jet spire relative to the jet base's jet bright point (JBP). In 22 of 23 jets, the spire either moves away from (18 cases) or is stationary relative to (4 cases) the JBP. The one exception where the spire moved toward the JBP may be a consequence of line-of-sight projection effects at the limb. From the AIA images, we clearly identify an erupting minifilament in 20 of the 23 jets, while the remainder are consistent with such an eruption having taken place. We also confirm that some jets can trigger the onset of nearby "sympathetic" jets, likely because eruption of the minifilament field of the first jet removes magnetic constraints on the base-field region of the second jet. The propensity for spire drift away from the JBP, the identification of the erupting minifilament in the majority of jets, and the magnetic-field topological changes that lead to sympathetic jets, all support or are consistent with the minifilament-eruption model for jets.

Keywords: solar filament eruptions; solar x-ray emission; solar extreme ultraviolet emission; solar activity
The Infrared Database of Extragalactic Observables from Spitzer. II. The Database and Diagnostic Power of Crystalline Silicate Features in Galaxy Spectra

We present the Infrared Database of Extragalactic Observables from Spitzer (IDEOS), a homogeneous, publicly available, database of 77 fitted mid-infrared observables in the 5.4-36 μm range, comprising measurements for 3335 galaxies observed in the low-resolution staring mode of the Infrared Spectrometer on board the Spitzer Space Telescope. Among the included observables are polycyclic aromatic hydrocarbon fluxes and their equivalent widths, the strength of the 9.8 μm silicate feature, emission-line fluxes, solid-state features, rest-frame continuum fluxes, synthetic photometry, and a mid-infrared spectral classification. The IDEOS spectra were selected from the Cornell Atlas of Spitzer-IRS Sources. To our surprise, we have detected at a >95% confidence level crystalline silicates in the spectra of 786 IDEOS galaxies. The detections range from single-band detections to detections of all fitted crystalline bands (16, 19, 23, 28, and 33 μm). We find the strength of the crystalline silicate bands to correlate with the amorphous silicate strength and the change from an emission to an absorption feature to occur at higher obscuration as the wavelength of the crystalline silicate band is longer. These observed characteristics are consistent with an origin for the amorphous and crystalline silicate features in a centrally heated dust geometry, either an edge-on disk or a cocoon. We find the 23 and 33 μm crystalline silicate bands to be well suited to classify the obscuration level of galactic nuclei, even in the presence of strong circumnuclear star formation. Based on our detection statistics, we conclude that crystalline silicates are a common component of the interstellar medium of galactic nuclei.

Keywords: infrared galaxies; starburst galaxies; active galaxies; interstellar medium; silicate grains; polycyclic aromatic hydrocarbons; astrochemistry; galaxy spectroscopy; liner galaxies; ultraluminous infrared galaxies; dust continuum emission
Clouds in Three-dimensional Models of Hot Jupiters over a Wide Range of Temperatures. I. Thermal Structures and Broadband Phase-curve Predictions

Using a general circulation model (GCM), we investigate trends in simulated hot Jupiter atmospheres for a range of irradiation temperatures (1500-4000 K), surface gravities (10 and 40 m s-2), and cloud conditions. Our models include simplified temperature-dependent clouds with radiative feedback and show how different cloud compositions, vertical thicknesses, and opacities shape hot Jupiter atmospheres by potentially increasing planetary albedos, decreasing photospheric pressures and nightside temperatures, and in some cases producing strong dayside thermal inversions. With decreasing irradiation, clouds progressively form on the nightside and cooler western limb, followed by the eastern limb and central dayside. We find that clouds significantly modify the radiative transport and affect the observable properties of planets colder than Tirr ≈ 3000 K (Teq ≈ 2100 K) depending on the clouds' vertical extent. The precise strength of expected effects depends on the assumed parameters, but trends in predicted phase curves emerge from an ensemble of simulations. Clouds lead to larger phase-curve amplitudes and smaller phase-curve offsets at IR wavelengths, compared to cloud-free models. At optical wavelengths, we predict mostly westward phase-curve offsets at intermediate temperatures (Tirr ≈ 2000-3500 K) with clouds confined to the nightside and western limb. If clouds are vertically compact (i.e., on the order of a pressure scale height in thickness), their distributions and effects become more complicated as different condensates form at different heights—some too deep to significantly affect the observable atmosphere. Our results have implications for interpreting the diversity of phase-curve observations of planets with Tirr ≲ 3000 K.

Keywords: exoplanet atmospheres; exoplanet atmospheric variability; exoplanets
Neutron Star-Black Hole Mergers from Gravitational-wave Captures

LIGO's third observing run (O3) has reported several neutron star-black hole (NSBH) merger candidates. From a theoretical point of view, NSBH mergers have received less attention in the community than either binary black holes, or binary neutron stars. Here we examine single-single (sin-sin) gravitational wave (GW) captures in different types of star clusters—galactic nuclei, globular clusters, and young stellar clusters—and compare the merger rates from this channel to other proposed merger channels in the literature. There are currently large uncertainties associated with every merger channel, making a definitive conclusion about the origin of NSBH mergers impossible. However, keeping these uncertainties in mind, we find that sin-sin GW capture is unlikely to significantly contribute to the overall NSBH merger rate. In general, it appears that isolated binary evolution in the field or in clusters, and dynamically interacting binaries in triple configurations, may result in a higher merger rate.

Keywords: neutron stars; stellar mass black holes; gravitational wave sources; young star clusters; globular star clusters; galactic center; stellar dynamics
Detections of [C II] 158 μm and [O III] 88 μm in a Local Lyman Continuum Emitter, Mrk 54, and Its Implications to High-redshift ALMA Studies

We present integral field, far-infrared (FIR) spectroscopy of Mrk 54, a local Lyman continuum emitter, obtained with FIFI-LS on the Stratospheric Observatory for Infrared Astronomy. This is only the second time, after Haro 11, that [C II] 158 μm and [O III] 88 μm spectroscopy of the known LCEs have been obtained. We find that Mrk 54 has a strong [C II] emission that accounts for ~1% of the total FIR luminosity, whereas it has only moderate [O III] emission, resulting in the low [O III]/[C II] luminosity ratio of 0.22 ± 0.06. In order to investigate whether [O III]/[C II] is a useful tracer of f esc (LyC escape fraction), we examine the correlations of [O III]/[C II] and (i) the optical line ratio of O32 ≡ [O III] 5007 Å/[O II] 3727 Å, (ii) specific star formation rate, (iii) [O III] 88 μm/[O I] 63 μm ratio, (iv) gas-phase metallicity, and (v) dust temperature based on a combined sample of Mrk 54 and the literature data from the Herschel Dwarf Galaxy Survey and the LITTLE THINGS Survey. We find that galaxies with high [O III]/[C II] luminosity ratios could be the result of high ionization (traced by O32), bursty star formation, high ionized-to-neutral gas volume filling factors (traced by [O III] 88 μm/[O I] 63 μm), and low gas-phase metallicities, which is in agreement with theoretical predictions. We present an empirical relation between the [O III]/[C II] ratio and f esc based on the combination of the [O III]/[C II] and O32 correlation, and the known relation between O32 and f esc. The relation implies that high-redshift galaxies with high [O III]/[C II] ratios revealed by the Atacama Large Millimeter/submillimeter Array may have f esc ≳ 0.1, significantly contributing to the cosmic reionization. * Based on observations done with FIFI-LS on SOFIA.

Keywords: far infrared astronomy; dwarf galaxies; markarian galaxies
Absorption-line Environments of High-redshift BOSS Quasars

The early stage of massive galaxy evolution often involves outflows driven by a starburst or a central quasar plus cold mode accretion (infall), which adds to the mass build-up in the galaxies. To study the nature of these infall and outflows in the quasar environments, we have examined the correlation of narrow absorption lines (NALs) at positive and negative velocity shifts to other quasar properties, such as their broad absorption-line (BAL) outflows and radio-loudness, using spectral data from SDSS-BOSS DR12. Our results show that the incidence of associated absorption lines (AALs) and outflow AALs is strongly correlated with BALs, which indicates most AALs form in quasar-driven outflows. Multiple AALs are also strongly correlated with BALs, demonstrating quasar outflows tend to be highly structured and can create multiple gas components with different velocity shifts along our line of sight. Infall AALs appear less often in quasars with BALs than quasars without BALs. This suggests that BAL outflows act on large scale in host galaxies and inhibit the infall of gas from the IGM, supporting theoretical models in which quasar outflow plays an important role in the feedback to host galaxies. Despite having larger distances, infall AALs are more highly ionized than outflow AALs, which can be attributed to the lower densities in the infall absorbers.

Keywords: quasar absorption line spectroscopy; quasars