Sazuna/UAT_keywords huggingface dataset:
Evidence for Ammonia-bearing Species on the Uranian Satellite Ariel Supports Recent Geologic Activity. We investigated whether ammonia-rich constituents are present on the surface of the Uranian moon Ariel by analyzing 32 near-infrared reflectance spectra collected over a wide range of sub-observer longitudes and latitudes. We measured the band areas and depths of a 2.2 μm feature in these spectra, which has been attributed to ammonia-bearing species on other icy bodies. Ten spectra display prominent 2.2 μm features with band areas and depths &gt;2σ. We determined the longitudinal distribution of the 2.2 μm band, finding no statistically meaningful differences between Ariel's leading and trailing hemispheres, indicating that this band is distributed across Ariel's surface. We compared the band centers and shapes of the five Ariel spectra displaying the strongest 2.2 μm bands to laboratory spectra of various ammonia-bearing and ammonium-bearing species, finding that the spectral signatures of the Ariel spectra are best matched by ammonia-hydrates and flash frozen ammonia-water solutions. Our analysis also revealed that four Ariel spectra display 2.24 μm bands (&gt;2σ band areas and depths), with band centers and shapes that are best matched by ammonia ice. Because ammonia should be efficiently removed over short timescales by ultraviolet photons, cosmic rays, and charged particles trapped in Uranus' magnetosphere, the possible presence of this constituent supports geologic activity in the recent past, such as emplacement of ammonia-rich cryolavas and exposure of ammonia-rich deposits by tectonism, impact events, and mass wasting.

Keywords: Planetary surfaces, Uranian satellites, Surface processes, Surface composition, Surface ices
How Jupiters Save or Destroy Inner Neptunes around Evolved Stars. In about 6 Gyr our Sun will evolve into a red giant and finally end its life as a white dwarf. This stellar metamorphosis will occur to virtually all known host stars of exoplanetary systems and is therefore crucial for their final fate. It is clear that the innermost planets will be engulfed and evaporated during the giant phase and that planets located farther out will survive. However, the destiny of planets in-between, at ∼1 and 10 au, has not yet been investigated with a multiplanet tidal treatment. We here combine for the first time multiplanet interactions, stellar evolution, and tidal effects in an N-body code to study the evolution of a Neptune-Jupiter planetary system. We report that the fate of the Neptune-mass planet, located closer to the star than the Jupiter-mass planet, can be very different from the fate of a single Neptune. The simultaneous effects of gravitational interactions, mass loss, and tides can drive the planetary system toward mean motion resonances. Crossing these resonances affects particularly the eccentricity of the Neptune and thereby also its fate, which can be engulfment, collision with the Jupiter-mass planet, ejection from the system, or survival at a larger separation.

Keywords: Exoplanet dynamics, Exoplanet evolution, Tides, Evolved stars
What Determines Solar Flares Producing Interplanetary Type III Radio Bursts?. Energetic electrons accelerated by solar flares often give rise to type III radio bursts at a broad wave band and even interplanetary type III bursts (IT3) if the wavelength extends to a decameter-kilometer. In this Letter, we investigate the probability of the flares that produce IT3, based on the sample of 2272 flares above M-class observed from 1996 to 2016. It is found that only 49.6% of the flares are detected to be accompanied with IT3. The duration, peak flux, and fluence of the flares with and without IT3 both present power-law distributions in the frequency domain, but the corresponding spectral indices for the former (2.06 ± 0.17, 2.04 ± 0.18, and 1.55 ± 0.09) are obviously smaller than that for the latter (2.82 ± 0.22, 2.51 ± 0.19, and 2.40 ± 0.09), showing that the flares with IT3 have longer durations and higher peak fluxes. We further examine the relevance of coronal mass ejections (CMEs) to the two groups of flares. It is found that 58% (655 of 1127) of the flares with IT3 but only 19% (200 of 1078) of the flares without IT3 are associated with CMEs, and that the associated CMEs for the flares with IT3 are inclined to be wider and faster. This indicates that CMEs may also play a role in producing IT3, speculatively facilitating the escape of accelerated electrons from the low corona to the interplanetary space.

Keywords: Solar flares, Solar coronal mass ejections
A New Class of Roche Lobe-filling Hot Subdwarf Binaries. We present the discovery of the second binary with a Roche lobe-filling hot subdwarf transferring mass to a white dwarf (WD) companion. This 56 minute binary was discovered using data from the Zwicky Transient Facility. Spectroscopic observations reveal an He-sdOB star with an effective temperature of Teff = 33,700 ± 1000 K and a surface gravity of log(g) = 5.54 ± 0.11. The GTC+HiPERCAM light curve is dominated by the ellipsoidal deformation of the He-sdOB star and shows an eclipse of the He-sdOB by an accretion disk as well as a weak eclipse of the WD. We infer a He-sdOB mass of MsdOB = 0.41 ± 0.04 M☉ and a WD mass of MWD = 0.68 ± 0.05 M☉. The weak eclipses imply a WD blackbody temperature of 63,000 ± 10,000 K and a radius RWD = 0.0148 ± 0.0020 R☉ as expected for a WD of such high temperature. The He-sdOB star is likely undergoing hydrogen shell burning and will continue transferring mass for ≍1 Myr at a rate of 10-9 M☉ yr-1, which is consistent with the high WD temperature. The hot subdwarf will then turn into a WD and the system will merge in ≍30 Myr. We suggest that Galactic reddening could bias discoveries toward preferentially finding Roche lobe-filling systems during the short-lived shell-burning phase. Studies using reddening-corrected samples should reveal a large population of helium core-burning hot subdwarfs with Teff ≍ 25,000 K in binaries of 60-90 minutes with WDs. Though not yet in contact, these binaries would eventually come into contact through gravitational-wave emission and explode as a subluminous thermonuclear supernova or evolve into a massive single WD.

Keywords: White dwarf stars, B subdwarf stars, Compact binary stars, Stellar accretion, Stellar evolution
A Fast-growing Tilt Instability of Detached Circumplanetary Disks. Accretion disks in binary systems can exhibit a tilt instability, arising from the interaction between components of the tidal potential and dissipation. Using a linear analysis, we show that the aspect ratios and outer radii of circumplanetary disks provide favorable conditions for tilt growth. We quantify the growth rate of the instability using particle-based (PHANTOM) and grid-based (ATHENA++) hydrodynamic simulations. For a disk with outer aspect ratio H/r ≃ 0.1, initially moderate tilts double on a timescale of about 15-30 binary orbits. Our results imply that detached circumplanetary disks, whose evolution is not entirely controlled by accretion from the circumstellar disk, may commonly be misaligned to the planetary orbital plane. We discuss implications for planetary spin evolution, and possible interactions between the tilt instability and Kozai-Lidov dynamics.

Keywords: Planetary theory, Hydrodynamics, Natural satellite formation, Disk galaxies, Solar system planets, Planetary system formation, Pre-main sequence stars, Protoplanetary disks, Circumstellar disks, Stellar accretion disks, Exoplanet formation, Planet formation
The Effect of Massive Neutrinos on the Halo Spin Flip Phenomenon. The halo spin flip refers to the phenomenon that the spin axes of dark matter halos with masses above a certain threshold tend to be preferentially aligned perpendicular to the hosting large-scale filaments, while low-mass halos tend to have their spin axes aligned parallel to such structures. Extensive work has so far been conducted to understand this phenomenon under the assumption of cold dark matter and suggested that its origin should be closely related to the nonlinear evolution of the halo angular momentum in the anisotropic cosmic web. We present, for the first time, a numerical examination of this phenomenon assuming the presence of massive neutrinos, finding a clear and robust dependence of the threshold mass for the spin flip on the total neutrino mass. Our physical explanation is that the presence of more massive neutrinos retard the nonlinear evolution of the cosmic web, which in turn allows the halo spin vectors to better retain their memories of the initial tidal interactions in the nonlinear regime. Our finding implies that the statistical alignment of halo spins with the large-scale structures can be in principle used as a probe of the total neutrino mass.

Keywords: Large-scale structure of the universe
Search for Large-scale Anisotropy on Arrival Directions of Ultra-high-energy Cosmic Rays Observed with the Telescope Array Experiment. Motivated by the detection of a significant dipole structure in the arrival directions of ultra-high-energy cosmic rays above 8 EeV reported by the Pierre Auger Observatory (Auger), we search for a large-scale anisotropy using data collected with the surface detector array of the Telescope Array Experiment (TA). With 11 yr of TA data, a dipole structure in a projection of the R.A. is fitted with an amplitude of 3.3% ± 1.9% and a phase of 131° ± 33°. The corresponding 99% confidence-level upper limit on the amplitude is 7.3%. At the current level of statistics, the fitted result is compatible with both an isotropic distribution and the dipole structure reported by Auger.

Keywords: Extragalactic magnetic fields, Cosmic ray detectors, Cosmic ray astronomy, Cosmic ray showers, Cosmic ray sources, Extragalactic astronomy, Ultra-high-energy cosmic radiation, Cosmic rays
INTEGRAL Discovery of a Burst with Associated Radio Emission from the Magnetar SGR 1935+2154. We report on International Gamma-Ray Astrophysics Laboratory (INTEGRAL) observations of the soft γ-ray repeater SGR 1935+2154 performed between 2020 April 28 and May 3. Several short bursts with fluence of $\sim {10}^{-7}\mbox{--}{10}^{-6}$ erg cm-2 were detected by the Imager on-board INTEGRAL (IBIS) instrument in the 20-200 keV range. The burst with the hardest spectrum, discovered and localized in real time by the INTEGRAL Burst Alert System, was spatially and temporally coincident with a short and very bright radio burst detected by the Canadian Hydrogen Intensity Mapping Experiment (CHIME) and Survey for Transient Astronomical Radio Emission 2 (STARE2) radio telescopes at 400-800 MHz and 1.4 GHz, respectively. Its lightcurve shows three narrow peaks separated by ∼29 ms time intervals, superimposed on a broad pulse lasting ∼0.6 s. The brightest peak had a delay of 6.5 ± 1.0 ms with respect to the 1.4 GHz radio pulse (that coincides with the second and brightest component seen at lower frequencies). The burst spectrum, an exponentially cutoff power law with photon index ${\rm{\Gamma }}={0.7}_{-0.2}^{+0.4}$ and peak energy ${E}_{p}=65\pm 5\,\mathrm{keV}$ , is harder than those of the bursts usually observed from this and other magnetars. By the analysis of an expanding dust-scattering ring seen in X-rays with the Neil Gehrels Swift Observatory X-ray Telescope (XRT) instrument, we derived a distance of ${4.4}_{-1.3}^{+2.8}$ kpc for SGR 1935+2154, independent of its possible association with the supernova remnant G57.2+0.8. At this distance, the burst 20-200 keV fluence of $(6.1\pm 0.3)\times {10}^{-7}$ erg cm-2 corresponds to an isotropic emitted energy of $\sim 1.4\times {10}^{39}$ erg. This is the first burst with a radio counterpart observed from a soft γ-ray repeater and it strongly supports models based on magnetars that have been proposed for extragalactic fast radio bursts.

Keywords: Interstellar scattering, Magnetars, Soft gamma-ray repeaters, Radio bursts
Hidden AGNs in Dwarf Galaxies Revealed by MaNGA: Light Echoes, Off-nuclear Wanderers, and a New Broad-line AGN. Active galactic nuclei (AGNs) in dwarf galaxies could host the relics of those early universe seed black holes that did not grow into supermassive black holes. Using MaNGA integral field unit (IFU) spectroscopy we have found a sample of 37 dwarf galaxies that show AGN ionization signatures in spatially resolved emission line diagnostic diagrams. The AGN signatures are largely missed by integrated emission line diagnostics for 23 of them. The bolometric luminosity of these 23 new AGN candidates is ≲1040 erg s-1, fainter than that of single-fiber SDSS AGNs, X-ray AGNs, and radio AGNs in dwarf galaxies, which supports IFU spectroscopy as a powerful tool for identifying hidden and faint AGNs in dwarf galaxies. The AGN emission is in most cases offset from the optical center of the dwarf galaxy and shows a symmetric morphology, which indicates that either the AGNs are off-nuclear, that the central emission of the galaxy is dominated by star formation, or that the AGNs are turned off and we are observing a past ionization burst. One of the new AGNs shows a broad Hα emission line component, from which we derive a black hole mass in the realm of intermediate-mass black holes. This constitutes the first hidden type 1 AGN discovered in a dwarf galaxy based on IFU spectroscopy. The finding of this sample of hidden and faint AGNs has important implications for population studies of AGNs in dwarf galaxies and for seed black hole formation models.

Keywords: Dwarf galaxies, Active galactic nuclei
Detection of Fe I Emission in the Dayside Spectrum of WASP-33b. We analyze the high-resolution emission spectrum of WASP-33b taken using the High Dispersion Spectrograph (R ≈ 165,000) on the 8.2 m Subaru telescope. The data cover λ ≈ 6170-8817 Å, divided over 30 spectral orders. The telluric and stellar lines are removed using a de-trending algorithm, SYSREM, before cross-correlating with planetary spectral templates. We calculate the templates assuming a 1D plane-parallel hydrostatic atmosphere including continuum opacity of bound-free H- and Rayleigh scattering by H2 with a range of constant abundances of Fe I. Using a likelihood-mapping analysis, we detect an Fe I emission signature at 6.4σ located at ${K}_{{\rm{p}}}$ of 226.0 ${}_{-2.3}^{+2.1}$ km s-1 and vsys of -3.2 ${}_{-1.8}^{+2.1}$ km s-1—consistent with the planet's expected velocity in the literature. We also confirm the existence of a thermal inversion in the dayside of the planet, which is very likely to be caused by the presence of Fe I and previously detected TiO in the atmosphere. This makes WASP-33b one of the prime targets to study the relative contributions of both species to the energy budget of an ultra-hot Jupiter. * Based on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

Keywords: High resolution spectroscopy, Exoplanet atmospheric composition , Exoplanet atmospheres
Discovery of the Optical Afterglow and Host Galaxy of Short GRB 181123B at z = 1.754: Implications for Delay Time Distributions. We present the discovery of the optical afterglow and host galaxy of the Swift short-duration gamma-ray burst (SGRB) GRB 181123B. Observations with Gemini-North starting ≍9.1 hr after the burst reveal a faint optical afterglow with i ≍ 25.1 mag at an angular offset of 0"59 ± 0"16 from its host galaxy. Using grizYJHK observations, we measure a photometric redshift of the host galaxy of $z={1.77}_{-0.17}^{+0.30}$ . From a combination of Gemini and Keck spectroscopy of the host galaxy spanning 4500-18000 Å, we detect a single emission line at 13390 Å, inferred as Hβ at z = 1.754 ± 0.001 and corroborating the photometric redshift. The host galaxy properties of GRB 181123B are typical of those of other SGRB hosts, with an inferred stellar mass of ≍9.1 × 109 M☉, a mass-weighted age of ≍0.9 Gyr, and an optical luminosity of ≍0.9L*. At z = 1.754, GRB 181123B is the most distant secure SGRB with an optical afterglow detection and one of only three at z &gt; 1.5. Motivated by a growing number of high-z SGRBs, we explore the effects of a missing z &gt; 1.5 SGRB population among the current Swift sample on delay time distribution (DTD) models. We find that lognormal models with mean delay times of ≍4-6 Gyr are consistent with the observed distribution but can be ruled out to 95% confidence, with an additional ≍one to five Swift SGRBs recovered at z &gt; 1.5. In contrast, power-law models with ∝t-1 are consistent with the redshift distribution and can accommodate up to ≍30 SGRBs at these redshifts. Under this model, we predict that ≍1/3 of the current Swift population of SGRBs is at z &gt; 1. The future discovery or recovery of existing high-z SGRBs will provide significant discriminating power on their DTDs and thus their formation channels.

Keywords: Gamma-ray bursts
Detectability of Molecular Signatures on TRAPPIST-1e through Transmission Spectroscopy Simulated for Future Space-based Observatories. Discoveries of terrestrial, Earth-sized exoplanets that lie within the habitable zone (HZ) of their host stars continue to occur at increasing rates. Transit spectroscopy can potentially enable the detection of molecular signatures from such worlds, providing an indication of the presence of an atmosphere and its chemical composition, including gases potentially indicative of a biosphere. Such planets around nearby M-dwarf stars—such as TRAPPIST-1—provide a relatively good signal, high signal-to-noise ratio, and frequent transits for follow-up spectroscopy. However, even with these advantages, transit spectroscopy of terrestrial planets in the HZ of nearby M-stars will still be a challenge. Herein, we examine the potential for future space observatories to conduct such observations, using a global climate model, a photochemical model, and a radiative transfer suite to simulate modern-Earth-like atmospheric boundary conditions on TRAPPIST-1e. The detectability of biosignatures on such an atmosphere via transmission spectroscopy is modeled for various instruments of the James Webb Space Telescope, Large UV/Optical/Infrared Surveyor, Habitable Exoplanet Observatory, and Origins. We show that only CO2 at 4.3 μm would be detectable at the &gt;5σ level in transmission spectroscopy, when clouds are included in our simulations. This is because the impact of clouds on scale height strongly limits the detectability of molecules in the atmosphere. Synergies between space- and ground-based spectroscopy may be essential in order to overcome these difficulties.

Keywords: Transmission spectroscopy, Astrobiology, Low mass stars, Biosignatures, Habitable zone, Exoplanet atmospheres
A First Spectroscopic Measurement of the Magnetic-field Strength for an Active Region of the Solar Corona. For all involved in astronomy, the importance of monitoring and determining astrophysical magnetic-field strengths is clear. It is also a well-known fact that the corona magnetic fields play an important part in the origin of solar flares and the variations of space weather. However, after many years of solar corona studies, there is still no direct and continuous way to measure and monitor the solar magnetic-field strength. We present here a scheme that allows such a measurement, based on a careful study of an exotic class of atomic transitions, known as magnetic induced transitions, in Fe9+. In this contribution we present a first application of this methodology and determine a value of the coronal field strength using the spectroscopic data from Hinode.

Keywords: The Sun, Active sun, Atomic spectroscopy, Astronomical techniques, Solar magnetic fields, Solar corona, Spectroscopy
A New Method for Studying Exoplanet Atmospheres Using Planetary Infrared Excess. To date, the ability for observers to reveal the composition or thermal structure of an exoplanet's atmosphere has rested on two techniques: high-contrast direct imaging and time-series observations of transiting exoplanets. The former is currently limited to characterizing young, massive objects while the latter requires near 90° orbital inclinations, thus limiting atmospheric studies to a small fraction of the total exoplanet population. Here we present an observational and analysis technique for studying the atmospheres of non-transiting exoplanets that relies on acquiring simultaneous, broad-wavelength spectra and resolving planetary infrared emission from the stellar spectrum. This method could provide an efficient means to study exoplanet atmospheric dynamics using sparsely sampled phase curve observations or a mechanism to search for signs of life on non-transiting exoplanets orbiting the nearest M-dwarf stars (such as Proxima Centauri). If shown to be effective with James Webb Space Telescope observations, the method of measuring planetary infrared excess would open up the large population of nearby, non-transiting exoplanets for atmospheric characterization.

Keywords: Exoplanet detection methods, Exoplanet atmospheres
Observations of Small-scale Magnetic Reconnections within a Magnetic Flux Rope in Earth's Magnetosheath. The small-scale magnetic reconnection, which has been observed in turbulent plasma, is detected in the interior regions of an ion-scale flux rope in the magnetosheath. Reconnecting current sheets are configured with a nearly symmetric inflow boundary condition and a large guide field of six times the asymptotic field. The evidence of ongoing reconnection is consistent with the standard reconnection model, except no ion flow is detected. In this study, the electron shear flow near the current sheets allows the reconnections to occur. Strong dissipation with these reconnections indicate that electromagnetic energy can be effectively transformed into electron heating and kinetic energy. In particular, the small-scale reconnections do not result in an increase in high-energy electrons, but are responsible for an increase in electron flux over a lower energy range of 100-200 eV. Observations indicate that small-scale reconnection is very common and provides an important channel for energy dissipation in the magnetosheath plasma.

Keywords: Space plasmas
A Low-mass Stellar-debris Stream Associated with a Globular Cluster Pair in the Halo. There are expected to be physical relationships between the globular clusters (GCs) and stellar substructures in the Milky Way, not all of which have yet been found. We search for such substructures from a combined halo sample of SDSS blue horizontal-branch and SDSS+LAMOST RR Lyrae stars, cross-matched with astrometric information from Gaia DR2. This is a sample of old stars which are also excellent tracers of structures, ideal for searching for ancient relics in the outer stellar halo. By applying the neural-network-based method STARGO to the full 4D dynamical space of our sample, we rediscover the Sagittarius Stream, and find the debris of the Gaia-Enceladus-Sausage and the Sequoia events in the outer halo, as well as their linkages with several GCs. Most importantly, we find a new, low-mass, debris stream associated with a pair of GCs (NGC 5024 and NGC 5053), which we dub LMS-1. This stream has a very polar orbit, and occupies a region between 10 to 20 kpc from the Galactic center. NGC 5024 (M53), the more massive of the associated GC pair, is very likely the nuclear star cluster of a now-disrupted dwarf galaxy progenitor, based on the results from N-body simulations.

Keywords: Globular star clusters, Milky Way stellar halo