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The CIDA Variability Survey of Orion OB1. II. Demographics of the Young, Low-mass Stellar Populations
Berlind, Perry; Mateo, Mario; Bailey, John I., III +11 more
We present results of our large-scale, optical, multi-epoch photometric survey across ∼180 square degrees in the Orion OB1 association, complemented with extensive follow-up spectroscopy. Our focus is mapping and characterizing the off-cloud, low-mass, pre-main-sequence (PMS) populations. We report 2062 K- and M-type confirmed T Tauri members; 59%…
Exploring the Age-dependent Properties of M and L Dwarfs Using Gaia and SDSS
Angus, Ruth; Kiman, Rocio; Faherty, Jacqueline K. +3 more
We present a sample of 74,216 M and L dwarfs constructed from two existing catalogs of cool dwarfs spectroscopically identified in the Sloan Digital Sky Survey (SDSS). We cross-matched the SDSS catalog with Gaia DR2 to obtain parallaxes and proper motions and modified the quality cuts suggested by the Gaia Collaboration to make them suitable for l…
Anisotropy of the Milky Way’s Stellar Halo Using K Giants from LAMOST and Gaia
Bird, Sarah A.; Yang, Chengqun; Liu, Chao +3 more
The anisotropy parameter β characterizes the extent to which orbits in stellar systems are predominantly radial or tangential and is likely to constrain, for the stellar halo of the Milky Way, scenarios for its formation and evolution. We have measured β as a function of Galactocentric radius from 5 to 100 kpc for 7664 metal-poor ([Fe/H] < -1.3…
Reference Star Differential Imaging of Close-in Companions and Circumstellar Disks with the NIRC2 Vortex Coronagraph at the W. M. Keck Observatory
Matthews, Keith; Serabyn, Eugene; Absil, Olivier +11 more
Reference star differential imaging (RDI) is a powerful strategy for high-contrast imaging. Using example observations taken with the vortex coronagraph mode of Keck/NIRC2 in L‧ band, we demonstrate that RDI provides improved sensitivity to point sources at small angular separations compared to angular differential imaging (ADI). Applying RDI to i…
HD 1397b: A Transiting Warm Giant Planet Orbiting A V = 7.8 mag Subgiant Star Discovered by TESS
Henning, Thomas; Jordán, Andrés; Espinoza, Néstor +12 more
We report the discovery of a transiting planet first identified as a candidate in Sector 1 of the Transiting Exoplanet Survey Satellite (TESS), and then confirmed with precision radial velocities. HD 1397b has a mass of {M}{{P}} ={0.367}-0.023+0.022 {M}{{J}}, a radius of {R}{{P}}={1.023}-…
Spectrophotometric Parallaxes with Linear Models: Accurate Distances for Luminous Red-giant Stars
Hogg, David W.; Rix, Hans-Walter; Eilers, Anna-Christina
With contemporary infrared spectroscopic surveys like APO Galactic Evolution Experiment (APOGEE), red-giant stars can be observed to distances and extinctions at which Gaia parallaxes are not highly informative. Yet the combination of effective temperature, surface gravity, composition, and age—all accessible through spectroscopy—determines a gian…
Machine-learning Regression of Stellar Effective Temperatures in the Second Gaia Data Release
Bai, Yu; Wang, Song; Liu, JiFeng +2 more
This paper reports on the application of the supervised machine-learning algorithm to the stellar effective temperature regression for the second Gaia data release, based on the combination of the stars in four spectroscopic surveys: the Large Sky Area Multi-Object Fiber Spectroscopic Telescope, Sloan Extension for Galactic Understanding and Explo…
A Catalog of Wide Binary and Multiple Systems of Bright Stars from Gaia-DR2 and the Virtual Observatory
Solano, E.; Rodrigo, C.; Jiménez-Esteban, F. M.
Binary and multiple stars have long provided an effective empirical method of testing stellar formation and evolution theories. In particular, the existence of wide binary systems (separations >20,000 au) is particularly challenging to binary formation models as their physical separations are beyond the typical size of a collapsing cloud core (…
HATS-70b: A 13 MJ Brown Dwarf Transiting an A Star
Henning, T.; Mancini, L.; Rabus, M. +23 more
We report the discovery of HATS-70b, a transiting brown dwarf at the deuterium burning limit. HATS-70b has a mass of {M}p={12.9}-1.6+1.8 {M}Jup} and a radius of {R}p={1.384}-0.074+0.079 {R}Jup}, residing in a close-in orbit with a period of 1.89 days. The host …
LRG-BEASTS: Transmission Spectroscopy and Retrieval Analysis of the Highly Inflated Saturn-mass Planet WASP-39b
Kirk, James; López-Morales, Mercedes; Espinoza, Néstor +5 more
We present a ground-based transmission spectrum and comprehensive retrieval analysis of the highly inflated Saturn-mass planet WASP-39b. We obtained low-resolution spectra (R ≈ 400) of a transit of WASP-39b using the ACAM instrument on the 4.2 m William Herschel Telescope as part of the LRG-BEASTS survey. Our transmission spectrum is in good agree…