Institut für Astronomie und Astrophysik

Abteilung Astronomie

Preprint 09/97

Mass and radius of the white dwarf in the binary V471 Tau from ORFEUS and HIPPARCOS observations

K. Werner and T. Rauch

Institut für Astronomie und Astrophysik, Astronomie, Universität Tübingen, Waldhäuser Str. 64, D-72076 Tübingen, Germany

accepted by Astronomy & Astrophysics

Abstract. We present a model atmosphere analysis of the white dwarf component in the K2V/DA eclipsing binary system V471 Tau, based upon FUV spectra obtained by the ORFEUS satellite. This system is regarded as the prototype of a post-common envelope WD + MS binary and, hence, is of considerable importance for our understanding of close binary evolution.

From a line profile fit to the FUV hydrogen Lyman series we obtain T_eff=35125 K and log(g)=8.21. The HIPPARCOS trigonometric parallax measurement (21.37 +/- 1.62 mas) confirms the Hyades membership of V471 Tau and we can derive the white dwarf radius. Together with its astrometric mass, which is known from analyses of the orbital parameters and which is compatible with our spectroscopic surface gravity determination, we can compare this individual WD to the theoretical mass-radius relation.

Key words: stars: individual: V471 Tau - stars: fundamental parameters - stars: atmospheres -binaries: eclipsing - white dwarfs - ultraviolet: stars

Paper (110k gzip'ed Postscript including figures)

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Jürgen Barnstedt (barnstedt AT astro.uni-tuebingen.de) Last updated 04-Aug-1997