The catalogue of radial velocity standard stars forGaia

Abstract

The Radial Velocity Spectrograph (RVS) on board Gaia needs to be calibrated using stable reference stars known in advance. The catalogue presented here was built for that purpose. It includes 1420 radial velocity standard star candidates selected on strict criteria to fulfil the Gaia-RVS requirements. A large programme of ground-based observations has been underway since 2006 to monitor these stars and verify their stability, which has to be better than 300 m s −1 over several years. The observations were done on the echelle spectrographs ELODIE and SOPHIE on the 1.93-m telescope at Observatoire de Haute-Provence (OHP), NARVAL on the Télescope Bernard Lyot at Observatoire du Pic du Midi and CORALIE on the Euler-Swiss Telescope at La Silla. Data from the OHP and Geneva Observatory archives have also been retrieved as have HARPS spectra from the ESO archive. We provide a mean radial velocity in the SOPHIE scale for each star, derived from the combination of velocities measured with those instruments, after having carefully estimated their differences in zero points. In total, 10214 radial velocity measurements have been obtained for the 1420 stars. With a mean time baseline of 6.35 years, 92.9% of the candidates fulfil a target stability criterion of 300 m s −1 . Three hundred forty-three stars are found to be constant at the level of 100 m s −1 over 10 years. Comparisons with earlier catalogues show excellent agreement for FGK stars, with zero-point differences lower than 100 m s −1 and a remarkably low rms scatter of 33 m s −1 in one case, suggesting that the precision of the catalogue presented here is better than this value. This catalogue will likely be useful for other large-scale spectroscopic surveys, such as APOGEE, Gaia-ESO, HERMES, and LAMOST.

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