Observation of Gaia (DR2) Red and White Dwarf Binary Stars in the Solar Neighborhood (Abstract)

Volume 48 number 2 (2020)

Rick Wasson

Orange County Astronomers; ricksshobs@verizon.net

Abstract

(Abstract only) The Gaia satellite combines astrometric, parallax, photometric, and spectroscopic measurements of stellar properties—with greater accuracy than ever before. In 2018 Gaia Data Release 2 (DR2) made preliminary but consistent data available for an extraordinary number of stars: 1.3 Billion! Red and White Dwarf stars are intrinsically very faint—only the nearest and brightest are visible in the eyepiece of a small telescope. Although many can be recorded in long exposure images, they are less well studied than brighter stars. Red Dwarfs are the most common type, but are faint because of their small size, slow nuclear fusion, and cool red color; White Dwarfs are hot but very small and relatively rare. Even in the Solar Neighborhood, between 10 and 100 parsecs (33–326 light-years), all the stars of these two types have not yet been found. In 2019 a campaign was begun to identify and observe “new Gaia binary” candidate systems containing a red or white dwarf star. Binaries offer the chance to define stellar properties more completely by deriving masses from their orbit. The Orange County Astronomers’ 22-inch Kuhn Telescope was used, together with Speckle Interferometry techniques, to achieve higher resolution than either the Gaia satellite or large deep surveys. The goals of this project were: 1. Confirm new binary systems discovered by Gaia and add measurements of their orbit. 2. Discover possible new red dwarf components in multiple star systems. New red dwarf binary candidates are defined as not listed in the Washington Double Star (WDS) catalog. A “data mining” search of DR2 was made with the following Gaia parameters: two stars with separation < 10°, parallax greater than 10 mas (i.e., within 100 parsecs of the Sun), similar proper motion, and at least one component with Gaia color index (Bp-Rp) > 2.0 (i.e., late K or M spectral type). More than 800 Gaia candidate binaries have been identified within 100 parsecs in the northern sky; about three-quarters of them have a Red Dwarf component, and a handful of White Dwarfs are also included. Thirty-five of the brighter systems have been observed so far; about half of these do not appear in the WDS Catalog and are thus believed to be “new” Gaia binaries. Observation methods and results are presented and discussed.