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Astron. Astrophys. 336, 953-959 (1998)

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

A.E. Gómez 1, X. Luri 1, 2, S. Grenier 1, F. Figueras 2, P. North 3, F. Royer 1, J. Torra 2 and M.O. Mennessier 4

1 Observatoire de Paris-Meudon, D.A.S.G.A.L., URA 335 du CNRS, F-92195 Meudon Cedex, France
2 Departament d'Astronomia i Meteorologia, Universitat de Barcelona, Avda. Diagonal 647, E-08028, Barcelona, Spain
3 Institut d'Astronomie de l'Université de Lausanne, CH-1290 Chavannes des Bois, Switzerland
4 Université Montpellier II, Groupe de Recherche en Astronomie et Astrophysique du Languedoc, URA 1368 du CNRS, F-34095 Montpellier Cedex 5, France

Received 22 January 1997 / Accepted 6 May 1998

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 (Luri, 1995; Luri, Mennessier et al., 1996) 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.

Key words: stars: chemically peculiar – stars: distances – stars: fundamental parameters – stars: Hertzsprung-Russell (HR) diagram – stars: kinematics

* 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/pub/cats/J/A+A/336/953 or via http://cdsweb.u-strasbg.fr/Abstract.html

Send offprint requests to: A.E. Gómez

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© European Southern Observatory (ESO) 1998

Online publication: July 27, 1998
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