Masses of the components of SB2 binaries observed with Gaia. I. Selection of the sample and mass ratios of 20 new SB2s discovered with Sophie

Jean-Louis Halbwachs, Frédéric Arenou, Dimitri Pourbaix, Benoît Famaey, Patrick Guillout, Yveline Lebreton, Jean-Baptiste Salomon, Lev Tal-Or, Rodrigo Ibata, Tsevi Mazeh

Published 2014-09-04Version 1

In anticipation of the Gaia astrometric mission, a large sample of spectroscopic binaries is being observed since 2010 with the Sophie spectrograph at the Haute--Provence Observatory. Our aim is to derive the orbital elements of double-lined spectroscopic binaries (SB2s) with an accuracy sufficient to finally obtain the masses of the components with relative errors as small as 1% when the astrometric measurements of Gaia are taken into account. Simultaneously, the luminosities of the components in the Gaia photometric band G will also be obtained. Our observation program started with 200 SBs, including 152 systems that were only known as single-lined. Thanks to the high efficiency of the Sophie spectrograph, an additional component was found for 25 SBs. After rejection of 5 multiple systems, 20 new SB2s were retained, including 8 binaries with evolved primary, and their mass ratios were derived. Our final sample contains 68 SB2s, including 2 late-type giants and 10 other evolved stars.