GAIA Spectroscopy and Radial Velocities

Abstract

GAIA spectroscopic and radial velocity performances are reviewed onthe base of ground-based test observations and simulations. Theprospects for accurate analysis of stellar atmospheres (temperature,gravity, chemical abundances, rotation, peculiarities) and preciseradial velocities (single stars, binaries, pulsating stars) arecolourful provided the spectral dispersion is high enough. A higherdispersions also favors a given precision of radial velocities to bereached at fainter magnitudes: for example, with current parametersfor GAIA spectrograph, a 1 km s^-1 accuracy on individual epochRVs of a K0 star is reached at V~13.0 mag with 0.25 Å/pixdispersion spectra, at V~10.3 mag for 0.5 Å/pix, andV~6.7 mag for 1 Å/pix. GAIA radial velocities for singlestars can match the ~0.5km s^-1 mean accuracy oftangential motions at V=15 mag, provided the observations areperformed at a dispersion not less than 0.5 Å/pix.