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The HR-diagram from HIPPARCOS data. Absolute magnitudes and kinematics of BP - AP stars
The HR-diagram of about 1000 Bp - Ap stars in the solar neighbourhoodhas been constructed using astrometric data from Hipparcos satellite aswell as photometric and radial velocity data. The LM method\cite{luri95,luri96} allows the use of proper motion and radial velocitydata in addition to the trigonometric parallaxes to obtain luminositycalibrations and improved distances estimates. Six types of Bp - Apstars 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 ofit (about 2 mag), just like normal stars in the same range of spectraltypes. Their kinematic behaviour is typical of thin disk stars youngerthan about 1 Gyr. A few stars found to be high above the galactic planeor to have a high velocity are briefly discussed. Based on data from theESA Hipparcos astrometry satellite and photometric data collected in theGeneva system at ESO, La Silla (Chile) and at Jungfraujoch andGornergrat Observatories (Switzerland). Tables 3 and 4 are onlyavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Distribution of B5 to A5 stars at (l, b) = (253 deg, -7 deg)
A study to V of about 12 mag is conducted for the distribution ofinterstellar extinction and early type stars (up to A5) in the (l, b) =(253 deg, -7 deg) field. The space density of B5, B8-A0, and A2-A5 starsis found to be normal for a field outside the galactic plane, and thestellar and extinction data indicate that the direction in question liesout of the matter plane of the Milky Way at least to 3 kpc. The higherextinction of Bochun 15 and the absence of background galaxies, however,suggest the possible presence of the galactic warp at -7 deg, atdistances beyond about 5 kpc, as well as a total higher extinction thanthe maximum of E(B-V) = 0.53 for d greater than 10 kpc, as found at (l,b) = (245 deg, zero deg).
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