The measurement of precise radial velocities of early type stars

Abstract

Methods are discussed which have made it possible to measure radial velocities to within 1-3 km/s for O, B, and A spectral-type stars of all v sin i. The methods are based on the premise that neither the spectral type nor the rotation velocity of a star need be well known prior to the velocity measurement. This makes them particularly suitable for survey studies or programs dealing with very heterogeneous samples of early stars. Observations of early type members of the Pleiades and Alpha Persei open clusters at 3787 A shown that the radial-velocity zero point used here for the early type stars is consistent with that for late-type stars to about 1 km/s for all spectral types and projected rotation velocities.