Sazuna/UAT_keywords huggingface dataset:
Refining the Census of the Upper Scorpius Association with Gaia. We have refined the census of stars and brown dwarfs in the Upper Sco association (∼10 Myr, ∼145 pc) by (1) updating the selection of candidate members from our previous survey to include the high-precision astrometry from the second data release of Gaia, (2) obtaining spectra of a few hundred candidate members to measure their spectral types and verify their youth, and (3) assessing the membership (largely with Gaia astrometry) of 2020 stars toward Upper Sco that show evidence of youth in this work and previous studies. We arrive at a catalog of 1761 objects that are adopted as members of Upper Sco. The distribution of spectral types among the adopted members is similar to those in other nearby star-forming regions, indicating a similar initial mass function. In previous studies, we have compiled mid-infrared photometry from the Wide-field Infrared Survey Explorer and the Spitzer Space Telescope for members of Upper Sco and used those data to identify the stars that show evidence of circumstellar disks; we present the same analysis for our new catalog of members. As in earlier work, we find that the fraction of members with disks increases with lower stellar masses, ranging from ≲10% for &gt;1 M☉ to ∼22% for 0.01-0.3 M☉. Finally, we have estimated the relative ages of Upper Sco and other young associations using their sequences of low-mass stars in ${M}_{{G}_{\mathrm{RP}}}$ versus GBP - GRP. This comparison indicates that Upper Sco is a factor of two younger than the β Pic association (21-24 Myr) according to both nonmagnetic and magnetic evolutionary models. * Based on observations made with the Two Micron All Sky Survey, the Gaia mission, the NASA Infrared Telescope Facility, Cerro Tololo Inter-American Observatory, Gemini Observatory, the Magellan Baade Telescope at Las Campanas Observatory, and the Bok Reflector at Steward Observatory.

Keywords: Brown dwarfs, Initial mass function, OB associations, Star formation, Protoplanetary disks, Low mass stars, Circumstellar disks, Stellar associations
Dimensionality Reduction of SDSS Spectra with Variational Autoencoders. High-resolution galaxy spectra contain much information about galactic physics, but the high dimensionality of these spectra makes it difficult to fully utilize the information they contain. We apply variational autoencoders (VAEs), a nonlinear dimensionality reduction technique, to a sample of spectra from the Sloan Digital Sky Survey (SDSS). In contrast to principal component analysis (PCA), a widely used technique, VAEs can capture nonlinear relationships between latent parameters and the data. We find that a VAE can reconstruct the SDSS spectra well with only six latent parameters, outperforming PCA with the same number of components. Different galaxy classes are naturally separated in this latent space, without class labels having been given to the VAE. The VAE latent space is interpretable because the VAE can be used to make synthetic spectra at any point in latent space. For example, making synthetic spectra along tracks in latent space yields sequences of realistic spectra that interpolate between two different types of galaxies. Using the latent space to find outliers may yield interesting spectra: in our small sample, we immediately find unusual data artifacts and stars misclassified as galaxies. In this exploratory work, we show that VAEs create compact, interpretable latent spaces that capture nonlinear features of the data. While a VAE takes substantial time to train (≈1 day for 48,000 spectra), once trained, VAEs can enable the fast exploration of large astronomical data sets.

Keywords: Astroinformatics, Galaxies, Neural networks, Galaxy classification systems, Spectroscopy, Dimensionality reduction
OSSOS XX: The Meaning of Kuiper Belt Colors. Observations show that 100 km class Kuiper Belt objects (KBOs) can be divided into (at least) two color groups, red (R; g - i &lt; 1.2) and very red (VR; g - i &gt; 1.2), reflecting a difference in their surface composition. This is thought to imply that KBOs formed over a relatively wide range of radial distance, r. The cold classicals at 42 au &lt; r &lt; 47 au are predominantly VR, and known Neptune Trojans at r ≃ 30 au are mostly R. Intriguingly, however, the dynamically hot KBOs show a mix of R and VR colors and no correlation of color with r. Here we perform migration/instability simulations where the Kuiper Belt is populated from an extended planetesimal disk. We find that the color observations can be best understood if R objects formed at r &lt; r* and VR objects at r &gt; r*, with 30 au &lt; r* &lt; 40 au. The proposed transition at 30 au &lt; r* &lt; 40 au would explain why the VR objects in the dynamically hot population have smaller orbital inclinations than the R objects, because the orbital excitation from Neptune weakens for orbits starting beyond 30 au. Possible causes of the R-VR color bimodality are discussed.

Keywords: Surface composition, Trans-Neptunian objects, Kuiper belt, Dynamical evolution
Orbits for Eight Binaries. The subject of the present paper is the analysis of the orbital solutions for eight binaries: WDS 02402+0436 = HDS 347, WDS 02552+5950 = MLR 520, WDS 03119+6131 = HDS 407, WDS 04570+7350 = YSC 145, WDS 05202+4105 = HDS 701, WDS 06467+0822 = HDS 940AB, WDS 08259-1623 = HDS 1199, and WDS 22550+5132 = HU 785. Seven orbits are determined for the first time, and the remaining orbit is a revision. The five binaries are HDS, discovered during the Hipparcos mission, two binaries were discovered before, 1902 and 1974, and one binary was discovered afterwards, 2009. All measured separations are less than 1 arcsecond, and in most studied pairs they are less than 0.4 arcseconds. The number of measurements is relatively small, from 9 to 16, except for one pair which has only been measured six times so far. The median orbital period is 95.1 yr, the shortest period is 12.5 yr, and the longest period is 362.7 yr. In addition to the orbital elements, we also give absolute magnitudes, spectral types, estimates of the masses, dynamical parallaxes, and $(O-C)$ residuals in θ and ρ.

Keywords: Fundamental parameters of stars, Visual binary stars
The Pre-He White Dwarfs in Eclipsing Binaries. I. WASP 0131+28. We report the first BV light curves and high-resolution spectra of the post-mass transfer binary star WASP 0131+28 to study the absolute properties of extremely low-mass white dwarfs. From the observed spectra, the double-lined radial velocities were derived, and the effective temperature and rotational velocity of the brighter, more massive primary were found to be ${T}_{\mathrm{eff},1}={\rm{10,000}}\pm 200$ K and ${v}_{1}\sin i$ = 55 ± 10 km s-1, respectively. The combined analysis of the Transiting Exoplanet Survey Satellite (TESS) archive data and ours yielded the accurate fundamental parameters of the program target. The masses were derived to about 1.0% accuracy and the radii to 0.6%, or better. The secondary component's parameters of ${M}_{2}=0.200\pm 0.002$ ${M}_{\odot }$ , ${R}_{2}=0.528\pm 0.003$ ${R}_{\odot }$ , ${T}_{\mathrm{eff},2}$ = 11,186 ± 235 K, and ${L}_{2}=3.9\pm 0.3$ ${L}_{\odot }$ are in excellent agreement with the evolutionary sequence for a helium-core white dwarf of mass 0.203 ${M}_{\odot }$ , and indicates that this star is halfway through the constant luminosity phase. The results presented in this article demonstrate that WASP 0131+28 is an EL CVn eclipsing binary in a thin disk, which is formed from the stable Roche-lobe overflow channel and composed of a main-sequence dwarf with a spectral type A0 and a pre-He white dwarf.

Keywords: CCD photometry, Fundamental parameters of stars, White dwarf stars, Spectroscopy, Eclipsing binary stars, Stellar evolution
Giant-planet Influence on the Collective Gravity of a Primordial Scattered Disk. Axisymmetric disks of high-eccentricity, low-mass bodies on near-Keplerian orbits are unstable to an out-of-plane buckling. This "inclination instability" exponentially grows the orbital inclinations, raises perihelion distances, and clusters in the argument of perihelion. Here we examine the instability in a massive primordial scattered disk including the orbit-averaged gravitational influence of the giant planets. We show that differential apsidal precession induced by the giant planets will suppress the inclination instability unless the primordial mass is ≳20 Earth masses. We also show that the instability should produce a "perihelion gap" at semimajor axes of hundreds of astronomical units, as the orbits of the remnant population are more likely to have extremely large perihelion distances ( ${ \mathcal O }(100\,\mathrm{au})$ ) than intermediate values.

Keywords: Celestial mechanics, Orbits, Solar system
The Hubble Space Telescope PanCET Program: An Optical to Infrared Transmission Spectrum of HAT-P-32Ab. We present a 0.3-5 μm transmission spectrum of the hot Jupiter HAT-P-32Ab observed with the Space Telescope Imaging Spectrograph and Wide Field Camera 3 instruments mounted on the Hubble Space Telescope, combined with Spitzer Infrared Array Camera photometry. The spectrum is composed of 51 spectrophotometric bins with widths ranging between 150 and 400 Å, measured to a median precision of 215 ppm. Comparisons of the observed transmission spectrum to a grid of 1D radiative-convective equilibrium models indicate the presence of clouds/hazes, consistent with previous transit observations and secondary eclipse measurements. To provide more robust constraints on the planet's atmospheric properties, we perform the first full optical to infrared retrieval analysis for this planet. The retrieved spectrum is consistent with a limb temperature of ${1248}_{-92}^{+92}$ K, a thick cloud deck, enhanced Rayleigh scattering, and ∼10× solar H2O abundance. We find log(Z/Z☉) = ${2.41}_{-0.07}^{+0.06}$ , and compare this measurement with the mass-metallicity relation derived for the solar system.

Keywords: Exoplanet atmospheric composition , Hot Jupiters, Exoplanet atmospheres, Exoplanets
A Spectroscopic Classification Survey to Search for New ρ Puppis Stars. The ρ Puppis stars are mid-F-type stars that show peculiar chemical-abundance patterns similar to those of the Am stars. Typically they exhibit overabundances of iron-peak elements such as Fe and Ni and s- and r-process elements such as Sr and Eu, and underabundances of certain other elements including He, Ca, and Sc. It has been proposed that these stars are evolving Am stars passing through the short-lived phase that occurs between the re-establishment of convection and the consequent erasure of their chemical peculiarities. In this paper we suggest a second hypothesis: these stars may have acquired their peculiar abundance patterns in a fashion similar to the Barium stars, i.e., they may have gained the s-process element enhancements via mass transfer from a once asymptotic giant-branch companion star, now turned white dwarf. This study will detail our efforts to investigate the ρ Puppis stars with regard to these two hypotheses, with a view to understanding these stars and their significance in terms of stellar evolution. We have performed a spectral classification survey, and a detailed chemical-abundance analysis of selected ρ Puppis stars. This paper gives an overview of the ρ Puppis stars and describes the spectral classification survey which has increased the number of ρ Puppis stars currently known from 6 to 49. A future paper will describe the chemical-abundance analysis which should provide insight into the nature of these stars.

Keywords: Am stars, Stellar classification, Barium stars, Chemically peculiar stars
Two Intermediate-mass Transiting Brown Dwarfs from the TESS Mission. We report the discovery of two intermediate-mass transiting brown dwarfs (BDs), TOI-569b and TOI-1406b, from NASA's Transiting Exoplanet Survey Satellite mission. TOI-569b has an orbital period of P = 6.55604 ± 0.00016 days, a mass of Mb = 64.1 ± 1.9 ${M}_{{\rm{J}}}$ , and a radius of Rb = 0.75 ± 0.02 ${R}_{{\rm{J}}}$ . Its host star, TOI-569, has a mass of M⋆ = 1.21 ± 0.05 $\,{M}_{\odot }$ , a radius of R⋆ = 1.47 ± 0.03 $\,{R}_{\odot }$ , $[\mathrm{Fe}/{\rm{H}}]=+0.29\pm 0.09$ dex, and an effective temperature of Teff = 5768 ± 110 K. TOI-1406b has an orbital period of P = 10.57415 ± 0.00063 days, a mass of Mb = 46.0 ± 2.7 ${M}_{{\rm{J}}}$ , and a radius of Rb = 0.86 ± 0.03 ${R}_{{\rm{J}}}$ . The host star for this BD has a mass of M⋆ = 1.18 ± 0.09 $\,{M}_{\odot }$ , a radius of R⋆ = 1.35 ± 0.03 $\,{R}_{\odot }$ , $[\mathrm{Fe}/{\rm{H}}]=-0.08\pm 0.09$ dex, and an effective temperature of Teff = 6290 ± 100 K. Both BDs are in circular orbits around their host stars and are older than 3 Gyr based on stellar isochrone models of the stars. TOI-569 is one of two slightly evolved stars known to host a transiting BD (the other being KOI-415). TOI-1406b is one of three known transiting BDs to occupy the mass range of 40-50 ${M}_{{\rm{J}}}$ and one of two to have a circular orbit at a period near 10 days (with the first being KOI-205b). Both BDs have reliable ages from stellar isochrones, in addition to their well-constrained masses and radii, making them particularly valuable as tests for substellar isochrones in the BD mass-radius diagram.

Keywords: Brown dwarfs, Substellar companion stars, Spectroscopy, Photometry, Radial velocity, Transit photometry
Feasibility of Observing Gamma-Ray Polarization from Cygnus X-1 Using a CubeSat. Instruments flown on CubeSats are small. Meaningful applications of CubeSats in astronomical observations rely on the choice of a particular subject that is feasible for CubeSats. Here we report the result of a feasibility study for observing gamma-ray polarization from Cygnus X-1 using a small Compton polarimeter on board a 3U CubeSat. Silicon detectors and cerium bromide scintillators were employed in the instrument models that we discuss in this study. Through Monte Carlo simulations with a Geant4-based MEGAlib package, we found that, with a 10 Ms on-axis, zenith-direction observation in a low-inclination, low-altitude, Earth-orbit radiation background environment, the minimum detectable polarization degree can be down to about 10% in 160-250 keV, 20% in 250-400 keV, and 65% in 400-2000 keV. A 3U CubeSat dedicated to observing Cygnus X-1 can therefore yield useful information on the polarization state of gamma-ray emissions from the brightest persistent X-ray black hole binary in the sky.

Keywords: Gamma-ray sources, Gamma-ray detectors, Gamma-ray telescopes, Astronomical instrumentation, Polarimeters, Gamma-ray astronomy, Astrophysical black holes
CosTuuM: Polarized Thermal Dust Emission by Magnetically Oriented Spheroidal Grains. We present the new open-source C++-based Python library COSTUUM that can be used to generate infrared absorption and emission coefficients for arbitrary mixtures of spheroidal dust grains that are (partially) aligned with a magnetic field. We outline the algorithms underlying the software, demonstrate the accuracy of our results using benchmarks from literature, and use our tool to investigate some commonly used approximative recipes. We find that the linear polarization fraction for a partially aligned dust grain mixture can be accurately represented by an appropriate linear combination of perfectly aligned grains and grains that are randomly oriented, but that the commonly used picket fence alignment breaks down for short wavelengths. We also find that for a fixed dust grain size, the absorption coefficients and linear polarization fraction for a realistic mixture of grains with various shapes cannot both be accurately represented by a single representative grain with a fixed shape, but that instead an average over an appropriate shape distribution should be used. Insufficient knowledge of an appropriate shape distribution is the main obstacle in obtaining accurate optical properties. COSTUUM is available as a standalone Python library and can be used to generate optical properties to be used in radiative transfer applications.

Keywords: Interstellar dust, Polarimetry, Dust continuum emission, Radiative transfer simulations, Magnetic fields
New Candidates for Planetary-mass Brown Dwarfs in IC 348. We have used infrared images obtained with the Wide Field Camera 3 on board the Hubble Space Telescope to search for planetary-mass brown dwarfs in the star-forming cluster IC 348. In those images, we have identified 12 objects that have colors indicative of spectral types later than M8, corresponding to masses of ≲30 MJup at the age of IC 348. The four brightest candidates have been observed with spectroscopy, all of which are confirmed to have late types. Two of those candidates appear to be young, and thus are likely members of the cluster, while the ages and membership of the other two candidates are uncertain. One of the former candidates is the faintest known member of IC 348 in extinction-corrected Ks and is expected to have a mass of 4-5 MJup based on evolutionary models and an assumed age of 3 Myr. Four of the remaining eight candidates have ground-based photometry that further supports their candidacy as brown dwarfs, some of which are fainter (and potentially less massive) than the known members.

Keywords: Hubble Space Telescope, Star forming regions, Brown dwarfs, Initial mass function
Visual Orbits of Spectroscopic Binaries with the CHARA Array. III. HD 8374 and HD 24546. We present the visual orbits of two long-period spectroscopic binary stars, HD 8374 and HD 24546, using interferometric observations acquired with the CHARA Array and the Palomar Testbed Interferometer. We also obtained new radial velocities from echelle spectra using the APO 3.5 m and Fairborn 2.0 m telescopes. By combining the visual and spectroscopic observations, we solve for the full, three-dimensional orbits and determine the stellar masses and distances to within 3% uncertainty. We then estimate the effective temperature and radius of each component star through Doppler tomography and spectral energy distribution analyses, in order to compare the observed stellar parameters to the predictions of stellar evolution models. For HD 8374, we find masses of M1 = 1.636 ± 0.050M☉ and M2 = 1.587 ± 0.049M☉, radii of R1 = 1.84 ± 0.05R☉ and R2 = 1.66 ± 0.12R☉, temperatures of ${T}_{\mathrm{eff}1}=7280\pm 110$ K and ${T}_{\mathrm{eff}2}=7280\pm 120$ K, and an estimated age of 1.0 Gyr. For HD 24546, we find masses of M1 = 1.434 ± 0.014M☉ and M2 = 1.409 ± 0.014M☉, radii of R1 = 1.67 ± 0.06R☉ and R2 = 1.60 ± 0.10R☉, temperatures of ${T}_{\mathrm{eff}1}=6790\pm 120$ K and ${T}_{\mathrm{eff}2}=6770\pm 90$ K, and an estimated age of 1.4 Gyr. HD 24546 is therefore too old to be a member of the Hyades cluster, despite its physical proximity to the group.

Keywords: Spectroscopic binary stars, Visual binary stars, Fundamental parameters of stars
ALMA Band-to-band Phase Referencing: Imaging Capabilities on Long Baselines and High Frequencies. High-frequency long-baseline experiments with the Atacama Large Millimeter/submillimeter Array were organized to test the high angular resolution imaging capabilities in the submillimeter wave regime using baselines up to 16 km. Four experiments were conducted, two Band 7 (289 GHz) and two Band 8 (405 GHz) observations. Phase correction using band-to-band (B2B) phase referencing was used with a phase calibrator only $0\buildrel{\circ}\over{.} 7$ away observed in Band 3 (96 GHz) and Band 4 (135 GHz), respectively. In Band 8, we achieved the highest resolution of 14 × 11 mas. We compared the synthesis images of the target quasar using 20 and 60 s switching cycle times in the phase referencing. In Band 7, the atmosphere had good stability in phase rms (&lt;0.5 rad over 2 minutes), and there was little difference in image coherence between the 20 and 60 s switching cycle times. One Band 8 experiment was conducted under a worse phase rms condition (&gt;1 rad over 2 minutes), which led to a significantly reduced coherence when using the 60 s switching cycle time. One of our four experiments indicates that the residual phase rms error after phase referencing can be reduced to 0.16 rad at 289 GHz in using the 20 s switching cycle time. Such conditions would meet the phase correction requirement of image coherence of &gt;70% in Band 10, assuming a similar phase calibrator separation angle, emphasizing the need for such B2B phase referencing observing at high frequencies.

Keywords: Submillimeter astronomy, Long baseline interferometry, Phase error
A Wide and Deep Exploration of Radio Galaxies with Subaru HSC (WERGS). III. Discovery of a z = 4.72 Radio Galaxy with the Lyman Break Technique. We report a discovery of a z = 4.72 radio galaxy, HSC J083913.17+011308.1, using the Lyman break technique with the Hyper Suprime-Cam Subaru Strategic Survey (HSC-SSP) catalog for Very Large Array Faint Images of the Radio Sky at Twenty centimeter radio sources. The number of known high-z radio galaxies (HzRGs) at z &gt; 3 is quite small to constrain the evolution of HzRGs so far. The deep and wide-area optical survey by HSC-SSP enables us to apply the Lyman break technique to a large search for HzRGs. For an HzRG candidate among pre-selected r-band dropouts with a radio detection, a follow-up optical spectroscopy with the Gemini Multi-Object Spectrographs (GMOS)/Gemini has been performed. The obtained spectrum presents a clear Lyα emission line redshifted to z = 4.72. The spectral energy distribution fitting analysis with the rest-frame UV and optical photometries suggests the massive nature of this HzRG with $\mathrm{log}{M}_{* }/{M}_{\odot }=11.4$ . The small equivalent width of Lyα and the moderately red UV colors indicate its dusty host galaxy, implying a chemically evolved and dusty system. The radio spectral index does not meet a criterion for an ultra-steep spectrum, ${\alpha }_{1400}^{325}$ of -1.1 and ${\alpha }_{1400}^{150}$ of -0.9, demonstrating that the HSC-SSP survey compensates for a subpopulation of HzRGs that are missed in surveys focusing on an ultra-steep spectral index.

Keywords: Active galaxies, Radio galaxies, Spectroscopy, Lyman-break galaxies, High-redshift galaxies
Dynamic Observing and Tiling Strategies for the DESI Legacy Surveys. The Dark Energy Spectroscopic Instrument Legacy Surveys, a combination of three ground-based imaging surveys, have mapped 16,000 deg2 in three optical bands (g, r, and z) to a depth 1-2 mag deeper than the Sloan Digital Sky Survey. Our work addresses one of the major challenges of wide-field imaging surveys conducted at ground-based observatories: the varying depth that results from varying observing conditions at Earth-bound sites. To mitigate these effects, the Legacy Surveys (the Dark Energy Camera Legacy Survey, or DECaLS; the Mayall z-band Legacy Survey, or MzLS; and the Beiijing-Arizona Sky Survey, or BASS) employed a unique strategy to dynamically adjust the exposure times as rapidly as possible in response to the changing observing conditions. We present the tiling and observing strategies used by the first two of these surveys. We demonstrate that the tiling and dynamic observing strategies jointly result in a more uniform-depth survey that has higher efficiency for a given total observing time compared with the traditional approach of using fixed exposure times.

Keywords: Sky surveys, Astronomical methods