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Astron. Astrophys. 325, 1055-1062 (1997)

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White dwarfs observed by the HIPPARCOS satellite *

G. Vauclair 1, H. Schmidt 2, D. Koester 2 and N. Allard 3, 4

1 Observatoire Midi-Pyrénées, 14 av. Edouard-Belin, F-31400 Toulouse, France
2 Institut für Astronomie und Astrophysik der Universität Kiel, D-24098 Kiel, Germany
3 Observatoire de Paris-Meudon, Département Atomes et Molécules en Astrophysique, F-92195 Meudon Principal Cedex, France
4 CNRS Institut d'Astrophysique, 98 bis Boulevard Arago, F-75014 Paris, France

Received 30 January 1997 / Accepted 21 April 1997

Abstract

The HIPPARCOS satellite has measured trigonometric parallaxes for 20 white dwarfs. With the exception of one each of the spectral types DZ, DC, DB, DQ, the majority are of spectral type DA. We compare the parallaxes with the most recent ground-based determinations. From a spectroscopic analysis of new optical observations we determine atmospheric parameters [FORMULA] and [FORMULA]. From the angular diameters and the parallaxes radii are obtained, and masses are calculated from these radii and the spectroscopic [FORMULA]. These data are used to test the theoretical mass-radius relation. On the other hand, assuming this relation, including finite temperature evolutionary effects, we can derive radii and masses from the effective temperatures and parallaxes. From these we calculate surface gravities, which can be compared to the results of the spectroscopic analysis.

Key words: stars: distances – stars: fundamental parameters – stars: white dwarfs

* Based on data from the ESA HIPPARCOS astrometry satellite and on observations collected at the European Southern Observatory, La Silla, Chile, and at the German-Spanish Astronomical Center at Calar Alto, Spain

Send offprint requests to: H. Schmidt

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© European Southern Observatory (ESO) 1997

Online publication: April 28, 1998

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