The Hipparcos mission, active from November 1989 to March 1993, measured very precise astrometrical data for 118000 stars. These results are published in The Hipparcos Catalogue (ESA 1997). Up to the Hipparcos magnitude 9, the median precision of positions, parallaxes and proper motions are better than 1 mas and 1 masyr-1 respectively.
An ESO key-program (Gerbaldi et al. 1989) was allocated to obtain complementary radial velocity data as well as fundamental parameters for early-type stars nearer than 100 pc observed by the Hipparcos satellite. The major aims were the detailed study of the HR-diagram, in particular the calibration of the absolute magnitude Mv and the determination of age and mass in order to study the kinematics and evolution of these stars. A first determination of Mv, age and mass of these stars has been made by Sabas (1997) and applied in Sabas et al. (1998). The same spectra have been used for a detailed independent analysis of the A0-type stars performed by Gerbaldi et al. (1998), giving the determination and the discussion about the effective temperature () and the gravity (g). The projected rotational velocity (vsini) has been determined by Royer et al. (1998). We limited the sample to normal stars between B8 and F2 and luminosity classes V to III, excluding known chemically peculiar stars.
Radial velocities have been obtained using a cross-correlation method with synthetic spectra. Their precision strongly depends on vsini and of the star. New binaries have been detected from the analysis of the shape of correlation peaks and from the variable radial velocities. These results, which have been compared with Hipparcos data about double and multiple systems, are often complementary in terms of separation, magnitude difference and orbital period.
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