Sazuna/UAT_keywords huggingface dataset:
An X-Ray Proper-motion Study of the Large Magellanic Cloud Supernova Remnant 0509-67.5. We present a third epoch of Chandra observations of the Type Ia Large Magellanic Cloud Supernova remnant 0509-67.5. With these new observations from 2020, the baseline for proper-motion measurements of the expansion has grown to 20 yr (from the earliest Chandra observations in 2000). We report here the results of these new expansion measurements. The lack of nearby bright point sources renders absolute image alignment difficult. However, we are able to measure the average expansion of the diameter of the remnant along several projection directions. We find that the remnant is expanding with an average velocity of 6120 (4900-7360) km s-1. This high shock velocity is consistent with previous works, and also consistent with the inference that 0509-67.5 is expanding into a very low density surrounding medium. At the distance of the LMC, this velocity corresponds to an undecelerated age of 600 yr, with the real age somewhat smaller.

Keywords: Supernova remnants, Interstellar medium
Orbital Flips Caused by the Eccentric Von Zeipel-Lidov-Kozai Effect in Nonrestricted Hierarchical Planetary Systems. The eccentric von Zeipel-Lidov-Kozai effect is widely applied to diverse astrophysical settings. In the restricted hierarchical three-body system, the topic of orbital flips has been extensively studied. However, it is far from being understood for nonrestricted circumstances. In this work, the dynamics of orbital flips are investigated under the Hamiltonian model at the octupole-level approximation for nonrestricted hierarchical planetary systems, where the outer planet is more massive than the inner one. Numerical distribution of flipping orbits shows that there are three major flipping regions, distributed in low-, intermediate-, and high-eccentricity spaces. Poincaré sections indicate that those islands of libration centered near i tot = 90° can lead to orbital flips. Thus, we refer to the behavior of orbital flips as a resonance phenomenon. From this viewpoint, dynamical models of orbital flips can be described by a separable Hamiltonian, which can be treated by a means of perturbation theory. The resonant model for orbital flips is formulated based on the adiabatic invariant approximation and then phase portraits are generated by plotting level curves of adiabatic invariants with the given Hamiltonian. By analyzing phase portraits, analytical boundaries of libration and circulation zones causing orbital flips are obtained. As expected, the numerical and analytical conditions that allow orbits to flip agree well with each other. The phenomenon of orbital flips in nonrestricted hierarchical problems can be well understood with the help of dynamical structures of secular resonance.

Keywords: Celestial mechanics, Perturbation methods, Three-body problem
The Arecibo Galaxy Environment Survey. XII. Optically Dark H I Clouds in the Leo I Group. Using data from the Arecibo Galaxy Environment Survey, we report the discovery of five H I clouds in the Leo I group without detected optical counterparts. Three of the clouds are found midway between M96 and M95, one is only ${10}^{{\prime} }$ from the southeast side of the well-known Leo Ring, and the fifth is relatively isolated. H I masses range from 2.6 × 106 M ⊙ to 9.0 × 106 M ⊙, and velocity widths (W50) range from 16 to 42 km s-1. Although a tidal origin is the most obvious explanation, this formation mechanism faces several challenges. For the most isolated cloud, the difficulties are its distance from neighboring galaxies and the lack of any signs of disturbance in the H I disks of those systems. Some of the clouds also appear to follow the baryonic Tully-Fisher relation between mass and velocity width for normal, stable galaxies, which is not expected if they are tidal in origin. Three clouds are found between M96 and M95 that have no optical counterparts but have otherwise similar properties and locations to the optically detected galaxy LeG 13. While overall we favor a tidal debris scenario to explain the clouds, we cannot rule out a primordial origin. If the clouds were produced in the same event that gave rise to the Leo Ring, they may provide important constraints on any model attempting to explain that structure.

Keywords: Galaxy environments, Galaxy dynamics, Galaxy kinematics, Galaxy groups, Galaxy evolution, Circumgalactic medium, Galaxies, Galaxy encounters
The Upper Edge of the Neptune Desert Is Stable Against Photoevaporation. Transit surveys indicate that there is a deficit of Neptune-sized planets on close-in orbits. If this "Neptune desert" is entirely cleared out by atmospheric mass loss, then planets at its upper edge should only be marginally stable against photoevaporation, exhibiting strong outflow signatures in tracers like the metastable helium triplet. We test this hypothesis by carrying out a 12-night photometric survey of the metastable helium feature with Palomar/WIRC, targeting seven gas-giant planets orbiting K-type host stars. Eight nights of data are analyzed here for the first time along with reanalyses of four previously published data sets. We strongly detect helium absorption signals for WASP-69b, HAT-P-18b, and HAT-P-26b; tentatively detect signals for WASP-52b and NGTS-5b; and do not detect signals for WASP-177b and WASP-80b. We interpret these measured excess absorption signals using grids of Parker wind models to derive mass-loss rates, which are in good agreement with predictions from the hydrodynamical outflow code ATES for all planets except WASP-52b and WASP-80b, where our data suggest that the outflows are much smaller than predicted. Excluding these two planets, the outflows for the rest of the sample are consistent with a mean energy-limited outflow efficiency of $\varepsilon ={0.41}_{-0.13}^{+0.16}$ . Even when we make the relatively conservative assumption that gas-giant planets experience energy-limited outflows at this efficiency for their entire lives, photoevaporation would still be too inefficient to carve the upper boundary of the Neptune desert. We conclude that this feature of the exoplanet population is a pristine tracer of giant planet formation and migration mechanisms.

Keywords: Exoplanets, Planetary atmospheres, Exoplanet astronomy, Exoplanet evolution, Exoplanet atmospheres
Simulating Reflected Light Coronagraphy of Earth-like Exoplanets with a Large IR/O/UV Space Telescope: Impact and Calibration of Smooth Exozodiacal Dust. Observing Earth-like exoplanets orbiting within the habitable zone of Sun-like stars and studying their atmospheres in reflected starlight requires contrasts of ~1e-10 in the visible. At such high contrast, starlight reflected by exozodiacal dust is expected to be a significant source of contamination. Here, we present high-fidelity simulations of coronagraphic observations of a synthetic solar system located at a distance of 10 pc and observed with a 12 m and an 8 m circumscribed aperture diameter space telescope operating at 500 nm wavelength. We explore different techniques to subtract the exozodi and stellar speckles from the simulated images in the face-on, the 30 deg inclined, and the 60 deg inclined case and quantify the remaining systematic noise as a function of the exozodiacal dust level of the system. We find that in the face-on case, the exozodi can be subtracted down to the photon noise limit for exozodi levels up to ~1000 zodi using a simple toy model for the exozodiacal disk, whereas in the 60 deg inclined case this only works up to ~50 zodi. We also investigate the impact of larger wave front errors and larger system distance, finding that while the former has no significant impact, the latter has a strong (negative) impact. Ultimately, we derive a penalty factor as a function of the exozodi level and system inclination that should be considered in exoplanet yield studies as a realistic estimate for the excess systematic noise from the exozodi.

Keywords: High contrast techniques, Exozodiacal dust, Exoplanet astronomy, Coronagraphic imaging, Direct imaging, Space telescopes, Exoplanet detection methods
Fragment Dynamics in Active Asteroid 331P/Gibbs. We present a dynamical analysis of the fragmented active asteroid 331P/Gibbs. Using archival images taken by the Hubble Space Telescope from 2015 to 2018, we measured the astrometry of the primary and the three brightest (presumably the largest) components. Conventional orbit determination revealed a high degree of orbital similarity between the components. We then applied a fragmentation model to fit the astrometry, obtaining key parameters including the fragmentation epochs and separation velocities. Our best-fit models show that Fragment B separated from the primary body at a speed of ~1 cm s-1 between 2011 April and May, whereas two plausible scenarios were identified for Fragments A and C. The former split either from the primary or from Fragment B, in 2011 mid June at a speed of ~8 cm s-1, and the latter split from Fragment B either in late 2011 or between late 2013 and early 2014, at a speed of ~0.7-0.8 cm s-1. The results are consistent with rotational disruption as the mechanism causing the cascading fragmentation of the asteroid, as suggested by the rapid rotation of the primary. The fragments constitute the youngest known asteroid cluster, providing us with a great opportunity to study asteroid fragmentation and formation of asteroid clusters.

Keywords: Small Solar System bodies, Asteroids, Main-belt comets, Solar system, Asteroid belt, Comets
More Evidence for Variable Helium Absorption from HD 189733b. We present a new Keck/NIRSPEC observation of metastable helium absorption from the upper atmosphere of HD 189733b, a hot Jupiter orbiting a nearby moderately active star. We measure an average helium transit depth of 0.420% ± 0.013% integrated over the [-20, 20] km s-1 velocity range. Comparing this measurement to eight previously published transit observations with different instruments, we find that our depth is 32% (9σ) lower than the average of the three CARMENES transits, but only 16% (4.4σ) lower than the average of the five GIANO transits. We perform 1D hydrodynamical simulations of the outflow, and find that XUV variability on the order of 33%-common for this star-can change the helium absorption depth by up to 60%, although a more typical change is 15%. We conclude that changes in stellar XUV flux can explain the observational variability in helium absorption, but that variability in the stellar He line cannot be excluded. 3D models are necessary to explore other sources of variability, such as shear instability and changing stellar wind conditions.

Keywords: Exoplanet atmospheric composition , Exoplanet atmospheric variability, Exoplanet atmospheres
A Jupiter Analog Orbiting The Nearby M Dwarf GJ 463. We report the detection of a long-period giant planetary companion to the nearby M3V star GJ 463 (=Ross 690). The detection is based on over ten years of highly-precise radial velocity measurements with the High Resolution Spectrograph at the Hobby-Eberly Telescope and the HIRES spectrograph at Keck. With an orbital period of 10 yr and a minimum mass of 1.55 ± 0.15 M Jup, GJ 463 b has a comparable orbital period to Jupiter and hence qualifies as a Jupiter analog around a low-mass star. We demonstrate that the radial velocity signal is not produced by a magnetic activity cycle of the host star. GJ 463 was observed with TESS, and we searched the light curve for any possible signals of stellar or planetary origin, but detected none. This planet is a candidate for possible direct detection with the coronagraph of the upcoming Nancy Grace Roman Space Telescope. We compared Gaia EDR3 with Hipparcos astrometry and detected a significant acceleration, which is likely caused by this long-period planetary companion at a = 3.53 ± 0.07 au.

Keywords: Extrasolar gaseous planets, Exoplanets
Roaring Storms in the Planetary-mass Companion VHS 1256-1257 b: Hubble Space Telescope Multiepoch Monitoring Reveals Vigorous Evolution in an Ultracool Atmosphere. The photometric and spectral variability of brown dwarfs probes heterogeneous temperature and cloud distributions and traces the atmospheric circulation patterns. We present a new 42 hr Hubble Space Telescope (HST) Wide Field Camera 3 G141 spectral time series of VHS 1256-1257 b, a late L-type planetary-mass companion that has been shown to have one of the highest variability amplitudes among substellar objects. The light curve is rapidly evolving and best fit by a combination of three sine waves with different periods and a linear trend. The amplitudes of the sine waves and the linear slope vary with the wavelength, and the corresponding spectral variability patterns match the predictions by models invoking either heterogeneous clouds or thermal profile anomalies. Combining these observations with previous HST monitoring data, we find that the peak-to-valley flux difference is 33% ± 2% with an even higher amplitude reaching 38% in the J band, the highest amplitude ever observed in a substellar object. The observed light curve can be explained by maps that are composed of zonal waves, spots, or a mixture of the two. Distinguishing the origin of rapid light curve evolution requires additional long-term monitoring. Our findings underscore the essential role of atmospheric dynamics in shaping brown-dwarf atmospheres and highlight VHS 1256-1257 b as one of the most favorable targets for studying the atmospheres, clouds, and atmospheric circulation of planets and brown dwarfs.

Keywords: Brown dwarfs, Atmospheric clouds, Atmospheric circulation, Planetary atmospheres, L dwarfs, Spectroscopy, Time series analysis, Atmospheric variability
Ephemerides of the Irregular Saturnian Satellites from Earth-based Astrometry and Cassini Imaging. We report a new determination of the orbits of the irregular Saturnian satellites. We fit their numerically integrated orbits to a data set containing Earth-based observations and imaging data from the Cassini spacecraft. We include the statistics of the observation residuals, the satellites' orbital elements, and projected accuracies of the satellites' positions. We also provide astrometric positions derived from the Cassini imaging. Two of the satellites are considered lost because they have not been observed for more than one epoch and have indeterminate uncertainties in their positions. Three of the satellites appear to be in a Kozai resonance, with one being the first irregular satellite of any planet found to be in a 270° rather than 90° resonance. *

Keywords: Saturnian satellites
Constructing the Milky Way Stellar Halo in the Galactic Center by Direct Orbit Integration. The halo stars on highly-radial orbits should inevitably pass the center regions of the Milky Way. Under the assumption that the stellar halo is in "dynamical equilibrium" and is axisymmetric, we integrate the orbits of ~10,000 halo K giants at 5 ≤ r ≤ 50 kpc cross-matched from LAMOST DR5 and Gaia DR3. By carefully considering the selection function, we construct the stellar halo distribution at the entire regions of r ≤ 50 kpc. We find that a double-broken power-law function well describes the stellar halo's density distribution with shallower slopes in the inner regions and the two breaks at r = 10 kpc and r = 25 kpc, respectively. The stellar halo becomes flatter from outer to inner regions but has q ~ 0.5 at r ≲ 5 kpc. The stellar halo becomes isotropic with a slight prograde rotation in the inner 5 kpc, and reaches velocity dispersions of ~250 km s-1. We get a weak negative metallicity gradient of -0.005 dex kpc-1 at 5 ≤ r ≤ 50 kpc, while there is an excess of relative metal-rich stars with [Fe/H] &gt; -1 in the inner 10 kpc. The halo interlopers at r ≤ 5 kpc from integration of our sample has a mass of ~1.2 × 108 M ⊙ (~4.7×107 M ⊙ at [Fe/H] &lt; 1.5), which can explain 50-100% of the metal-poor stars with [Fe/H] &lt; -1.5 directly observed in the Galactic central regions.

Keywords: Milky Way stellar halo, Galactic center, Milky Way dynamics, Galactic bulge
Refining the Masses and Radii of the Star Kepler-33 and its Five Transiting Planets. Kepler-33 hosts five validated transiting planets ranging in period from 5 to 41 days. The planets are in nearly coplanar orbits and exhibit remarkably similar (appropriately scaled) transit durations indicative of similar impact parameters. The outer three planets have a radius of 3.5 ≲ R p/R ⊕ ≲ 4.7 and are closely packed dynamically, and thus transit timing variations can be observed. Photodynamical analysis of transit timing variations provide 2σ upper bounds on the eccentricity of the orbiting planets (ranging from &lt;0.02 to &lt;0.2) and the mean density of the host star ( ${0.39}_{-0.02}^{+0.01}\,{\rm{g}}\,{\mathrm{cm}}^{-3}$ ). We combine Gaia Early Data Release 3 parallax observations, the previously reported host-star effective temperature and metallicity, and our photodynamical model to refine properties of the host star and the transiting planets. Our analysis yields well-constrained masses for Kepler-33 e ( ${6.6}_{-1.0}^{+1.1}\,{M}_{\oplus }$ ) and f ( ${8.2}_{-1.2}^{+1.6}\,{M}_{\oplus }$ ) along with 2σ upper limits for planets c (&lt;19 M ⊕) and d (&lt;8.2 M ⊕). We confirm the reported low bulk densities of planet d (&lt;0.4 g cm-3), e (0.8 ± 0.1 g cm-3), and f (0.7 ± 0.1 g cm-3). Based on comparisons with planetary evolution models, we find that Kepler-33 e and f exhibit relatively high envelope mass fractions of ${f}_{\mathrm{env}}={7.0}_{-0.5}^{+0.6} \% $ and f env = 10.3% ± 0.6%, respectively. Assuming a mass for planet d ~4 M ⊕ suggests that it has f env ≳ 12%.

Keywords: Exoplanet dynamics, Exoplanets, Exoplanet systems, Exoplanet astronomy, Transit photometry
NGC 6153: Reality is Complicated. We study the kinematics of emission lines that arise from many physical processes in NGC 6153 based upon deep, spatially resolved, high-resolution spectra acquired with the UVES spectrograph at the European Southern Observatory Very Large Telescope. Our most basic finding is that the plasma in NGC 6153 is complex, especially its temperature structure. The kinematics of most emission lines defines a classic expansion law, with the outer part expanding fastest (normal nebular plasma). However, the permitted lines of O I, C II, N II, O II, and Ne II present a constant expansion velocity that defines a second kinematic component (additional plasma component). The physical conditions imply two plasma components, with the additional plasma component having lower temperature and higher density. The [O II] density and the [N II] temperature are anomalous, but may be understood considering the contribution of recombination to these forbidden lines. The two plasma components have very different temperatures. The normal nebular plasma appears to have temperature fluctuations in part of its volume (main shell), but only small fluctuations elsewhere. The additional plasma component contains about half of the mass of the N2+ and O2+ ions, but only 3%-5% of the mass of H+ ions, so the two plasma components have very different chemical abundances. We estimate abundances of $12+\mathrm{log}({{\rm{O}}}^{2+}/{{\rm{H}}}^{+})\sim 9.2$ dex and He/H ~ 0.13. Although they are all complications, multiple plasma components, temperature fluctuations, and the contributions of multiple physical processes to a given emission line are all part of the reality in NGC 6153, and should generally be taken into account. *Based on observations collected at the European Southern Observatory under ESO program(s) 69.D-0174(A).

Keywords: Cosmic abundances, Chemical abundances, Astronomical techniques, Planetary nebulae, Spectroscopy, Interstellar medium, Stellar evolution
NICMOS Kernel-phase Interferometry. I. Catalogue of Brown Dwarfs Observed in F110W and F170M. Filling out the dearth of detections between direct imaging and radial velocity surveys will test theories of planet formation and (sub)stellar binarity across the full range of semimajor axes, connecting formation of close- to wide-separation gas giants and substellar companions. Direct detection of close-in companions is notoriously difficult: coronagraphs and point-spread function subtraction techniques fail near the λ/D diffraction limit. We present a new faint companion detection pipeline called Argus that analyzes kernel phases, an interferometric observable analogous to closure phases from nonredundant aperture masking but utilizing the full unobscured telescope aperture. We demonstrate the pipeline, and the power of interferometry, by performing a companion search on the entire HST/NICMOS F110W and F170M image archive of 114 nearby brown dwarfs (observed in seven different programs). Our pipeline is able to detect companions down to flux ratios of ~102 at half the classical diffraction limit. We discover no new companions, but recover and refine astrometry of 19 previous imaging companions (two with multiple epochs) and confirm two previous kernel-phase detections. We discuss the limitations of this technique with respect to nondetections of previously confirmed or proposed companions. We present contrast curves to enable population studies to leverage nondetections and to demonstrate the strength of this technique at separations inaccessible to classical imaging techniques. The binary fraction of our sample ( ${\epsilon }_{b}={14.4}_{-3.0}^{+4.7}$ %) is consistent with previous binary surveys, even with sensitivity to much tighter separation companions.

Keywords: Brown dwarfs, Direct detection interferometry, Hubble Space Telescope, Near infrared astronomy, Direct imaging, Interferometry
Weak Lensing in the Blue: A Counter-intuitive Strategy for Stratospheric Observations. The statistical power of weak lensing measurements is principally driven by the number of high-redshift galaxies whose shapes are resolved. Conventional wisdom and physical intuition suggest this is optimized by deep imaging at long (red or near-IR) wavelengths, to avoid losing redshifted Balmer-break and Lyman-break galaxies. We use the synthetic Emission Line ("EL")-COSMOS catalog to simulate lensing observations using different filters, from various altitudes. Here were predict the number of exposures to achieve a target z ≳ 0.3 source density, using off-the-shelf and custom filters. Ground-based observations are easily better at red wavelengths, as (more narrowly) are space-based observations. However, we find that SUPERBIT, a diffraction-limited observatory operating in the stratosphere, should instead perform its lensing-quality observations at blue wavelengths.

Keywords: Galaxy clusters, Observational astronomy, Weak gravitational lensing, Galaxy cluster counts, High altitude balloons, Gravitational lensing, Limiting magnitude
A Statistical Analysis on the Morphology and Color of Galaxies Hosting Radio-loud Active Galactic Nuclei. The properties of galaxies hosting radio-loud active galactic nuclei (AGN) have been investigated in order to find out the relation between morphology and color of galaxies and radio loudness. The concentration index is used to map the morphology of galaxies as early or late type. 4000 Å break strength and star-formation rate are used to quantify the state of galaxies as blue star forming or red quenched. Due to the environmental dependence of these properties, galaxies with the same environment have been considered. The results show that the prevalence of radio-loud AGN in early-type galaxies is independent of environment. This is confirmed by comparing a sample of galaxies hosting radio-loud AGN with a sample of galaxies hosting radio-quiet AGN or with a randomly selected galaxy sample from the total population of galaxies used in this study. In addition, it is shown that galaxies hosting radio-loud AGN are bluer indicating the role of cold gas in triggering AGN activity. Finally, the optically-selected radio-loud AGN show to have higher [O III] luminosities compared with their radio-quiet counterparts. We argue the relation between radio size and luminosity with the [O III] luminosity.

Keywords: Radio continuum emission, Galaxy interactions, Active galactic nuclei, Radio active galactic nuclei