The HR diagram from Hipparcos data. Absolute magnitudes and kinematics of Bp-Ap stars

Abstract

The HR-diagram of about 1000 Bp - Ap stars in the solar neighbourhood has been constructed using astrometric data from Hipparcos satellite as well as photometric and radial velocity data. The LM method \cite{luri95,luri96} allows the use of proper motion and radial velocity data in addition to the trigonometric parallaxes to obtain luminosity calibrations and improved distances estimates. Six types of Bp - Ap stars have been examined: He-rich, He-weak, HgMn, Si, Si+ and SrCrEu. Most Bp - Ap stars lie on the main sequence occupying the whole width of it (about 2 mag), just like normal stars in the same range of spectral types. Their kinematic behaviour is typical of thin disk stars younger than about 1 Gyr. A few stars found to be high above the galactic plane or to have a high velocity are briefly discussed. Based on data from the ESA Hipparcos astrometry satellite and photometric data collected in the Geneva system at ESO, La Silla (Chile) and at Jungfraujoch and Gornergrat Observatories (Switzerland). Tables 3 and 4 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html