GaiaData Release 3

Abstract

Context.The secondGaiadata release, DR2, contained radial velocities of stars with effective temperatures up toTeff = 6900 K. The third data release,GaiaDR3, extends this up toTeff = 14 500 K.Aims.We derive the radial velocities for hot stars (i.e., in theTeff = 6900 − 14 500 K range) from data obtained with the Radial Velocity Spectrometer (RVS) on boardGaia.Methods.The radial velocities were determined by the standard technique of measuring the Doppler shift of a template spectrum that was compared to the observed spectrum. The RVS wavelength range is very limited. The proximity to and systematic blueward offset of the calcium infrared triplet to the hydrogen Paschen lines in hot stars can result in a systematic offset in radial velocity. For the hot stars, we developed a specific code to improve the selection of the template spectrum, thereby avoiding this systematic offset.Results.With the improved code, and with the correction we propose to the DR3 archive radial velocities, we obtain values that agree with reference values to within 3 km s−1(in median). Because of the required S/N for applying the improved code, the hot star radial velocities in DR3 are mostly limited to stars with a magnitude in the RVS wavelength band ≤12 mag.