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Preprint 13/02

The Rotational Velocity of Helium-rich Pre-White Dwarfs

T. Rauch (1,2), S. Köper (1), S. Dreizler (1), K. Werner (1), U. Heber (2), and I.N. Reid (3)

(1) Institut für Astronomie und Astrophysik, Astronomie, Universität Tübingen, Sand 1, D-72076 Tübingen, Germany
(2) Dr.-Remeis-Sternwarte, Bamberg, Germany
(3) STScI, Baltimore, MD, USA

To appear in: Stellar Rotation, Proceedings IAU Symposium No. 215 (2003)

Abstract. Previous investigations on hydrogen-rich white dwarfs generally yield only very small rotational velocities (v_rot sin i). We have analyzed line profiles in high-resolution optical spectra of eight hydrogen-deficient (pre-) white dwarfs and find deviations from the dominant Stark line broadening in five cases which, interpreted as an effect of stellar rotation, indicate projected rotational velocities of 40 - 70 km/sec. For the three least luminous stars upper limits of v_rot sin i = 15 - 25 km/sec could be derived only. The resulting velocities correlate with luminosity and mass. However, since the mass-loss rate is correlated to the luminosity of a star, the observed line profiles may be affected by a stellar wind as well. In the case of RX J2117.1+3412, this would solve discrepancies to results of pulsational modeling (v_rot sin i ~ 0).

Key words: -

Paper (132k gzip'ed Postscript including figures)

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