Paper detail

The catalogue of radial velocity standard stars for Gaia I. Pre-launch release

The Radial Velocity Spectrograph (RVS) on board of Gaia needs to be calibrated using stable reference stars known in advance. The catalogue presented here has being built for that purpose. It includes 1420 radial velocity standard star candidates selected on strict criteria in order to fulfill the Gaia-RVS requirements. A large programme of ground based observations is underway since 2006 to monitor these stars and verify their stability which has to be better than 300 m/s over several years. The observations have been made on the echelle spectrographs ELODIE and SOPHIE on the 1.93-m telescope at Observatoire de Haute-Provence (OHP), NARVAL on the Telescope 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 well as HARPS spectra from the ESO archive. We provide for each star a mean radial velocity in the SOPHIE scale, derived from the combination of velocities measured with those instruments, after having carefully estimated their differences of 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 fulfill a target stability criterion of 300 m/s. 343 stars are found to be constant at the level of 100 m/s over 10 years. Comparisons with the catalogues of Nidever et al.(2002) and Chubak et al.(2012) show an excellent agreement for FGK stars, with zero-point differences lower than 100 m/s and a remarkably low RMS scatter of 33 m/s in the case of Nidever et al.(2002), suggesting that the precision of the catalogue presented here is better than this value. This catalog will likely be useful for other large-scale spectroscopic surveys such as APOGEE, Gaia-ESO, HERMES and LAMOST.