Gaia spectroscopic orbits validated with LAMOST and GALAH radial velocities

Abstract

The recently published Gaia DR3 catalogue of 181327 spectroscopic binaries (SB) includes the Keplerian elements of each orbit but not the measured radial velocities (RVs) and their epochs. Instead, the catalogue lists a few parameters that characterize the robustness of each solution. In this work, we use two external sources to validate the orbits – 17563 LAMOST DR6 and 6018 GALAH DR3 stars with measured RVs that have Gaia-SB orbits. We compare the expected RVs, based on the Gaia orbits, with the LAMOST and GALAH measurements. Finding some orbits that are inconsistent with these measurements, we constructed a function that estimates the probability of each of the Gaia orbits to be correct, using the published robust parameters. We devise a clean but still very large Gaia single-lined spectroscopic binaries (SB1) sample of 91740 orbits. The sample differs from the parent sample by the absence of – physically unlikely and hence presumably spurious – short-period binaries with high eccentricity. The clean SB1 sample offers the prospect of thorough statistical studies of the binary population after carefully modelling the remaining selection effects. At the first look, two possible features emerge from the clean sample – a paucity of short-period binaries with low-mass primaries, which might be a result of some observational bias, and a subsample of main-sequence binaries on circular orbits, probable evidence for circularization processes.

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