Rotation velocities of white dwarfs determined from the Ca II K line

¹ Institut für Experimentelle und Angewandte Physik, University of Kiel, 24098 Kiel, Germany e-mail: berger@physik.uni-kiel.de
² Institut für Theoretische Physik und Astrophysik, University of Kiel, 24098 Kiel, Germany
³ Centre for Astrophysics Research, STRI, University of Hertfordshire, Hatfield AL10 9AB, UK
⁴ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
⁵ Department of Physics & Astronomy and Center for Astrobiology, UCLA, Los Angeles, CA 90095-1562, USA

Received: 29 April 2005
Accepted: 22 August 2005

Abstract

We determine projected rotation velocities  in DAZ white dwarfs, for the first time using the rotational broadening of the Ca II K line. The results confirm previous findings that white dwarfs are very slow rotators, and set even more stringent upper limits of typically less than 10 km s^-1. The few exceptions include 3 stars known or suspected to be variable ZZ Ceti stars, where the line broadening is very likely not due to rotation. The results demonstrate that the angular momentum of the core cannot be preserved completely between main sequence and final stage.