Contribution à l'étude des populations d'étoiles chaudes à grande vitesse observées par Hipparcos

In this thesis work, the origin of early-type stars with high velocity and/or large distance away from the galactic plane is studied, using Hipparcos satellite data. First, the influence of stellar rotation on absolute magnitudes computed using trigonometric parallaxes is analysed with a sample of normal main-sequence A-type stars. No significant effect is detected. A method for radial velocity determination is developed from the spectra observed with the Élodie spectrograph (OHP). It allows the calculation of the radial velocity with a precision of about 1-2 km/s without limitation due to the vsini of the observed star. In a second part, a sample of 35000 B-A-F type stars from the Hipparcos catalogue is analysed. 316 high velocity stars are identified and the various assumptions explaining their origin are discussed. In particular, the contribution of the blue stragglers is studied using a population synthesis model. It is shown that thin disc blue stragglers represent a source of high velocity stars primarily in B and early A-type stars whereas thick disc blue stragglers contribute to late A-type and F stars.