Gaia Data Release 2: The catalogue of radial velocity standard stars

TL;DR

This paper presents a catalogue of 4,813 stable stars with well-measured radial velocities, calibrated using asteroid observations, to ensure accurate zero points for Gaia's RVS instrument in Data Release 2.

Contribution

It provides a large, validated catalogue of radial velocity standard stars for Gaia DR2, calibrated with asteroid data to improve measurement accuracy.

Findings

Median standard deviation of 15 m/s in measurements

Seven observations per star on average over six years

Catalogue used for calibration and validation of Gaia RVS data

Abstract

Aims. The Radial Velocity Spectrometer (RVS) on board the ESA satellite mission Gaia has no calibration device. Therefore, the radial velocity zero point needs to be calibrated with stars that are proved to be stable at a level of 300 m/s during the Gaia observations. Methods. We compiled a dataset of ~71000 radial velocity measurements from five high-resolution spectrographs. A catalogue of 4813 stars was built by combining these individual measurements. The zero point was established using asteroids. Results. The resulting catalogue has seven observations per star on average on a typical time baseline of six years, with a median standard deviation of 15 m/s. A subset of the most stable stars fulfilling the RVS requirements was used to establish the radial velocity zero point provided in Gaia Data Release 2. The stars that were not used for calibration are used to validate the RVS data.