Letter to the Editor

White dwarf spins from low-mass stellar evolution models

¹ Astronomical Institute, Utrecht University, PO Box 80000, 3508 TA, Utrecht, The Netherlands e-mail: n.langer@astro.uu.nl
² Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95060, USA
³ Theoretical Astrophysics Group, T-6, MS B227, Los Alamos, NM 87545, USA
⁴ Keele Astrophysics Group, School of Physical and Geographical Sciences, Keele University, Staffordshire ST5 5BG, UK

Received: 17 January 2008
Accepted: 15 February 2008

Abstract

Context. The prediction of the spins of the compact remnants is a fundamental goal of the theory of stellar evolution.

Aims. Here, we confront the predictions for white dwarf spins from evolutionary models, including rotation with observational constraints.

Methods. We perform stellar evolution calculations for stars in the mass range 1... 3, including the physics of rotation, from the zero age main sequence into the TP-AGB stage. We calculate two sets of model sequences, with and without inclusion of magnetic fields. From the final computed models of each sequence, we deduce the angular momenta and rotational velocities of the emerging white dwarfs.

Results. While models including magnetic torques predict white dwarf rotational velocities between 2 and 10 km s^-1, those from the nonmagnetic sequences are found to be one to two orders of magnitude larger, well above empirical upper limits.

Conclusions. We find the situation analogous to that in the neutron star progenitor mass range, and conclude that magnetic torques may be required to understand the slow rotation of compact stellar remnants in general.