Spin‐up and Spin‐down of Rotating Magnetic White Dwarfs: A Straightforward Numerical Approach

Abstract

We compute constant-mass sequences of classical white dwarf models, distorted by rotation (either rigid or differential) and toroidal magnetic fields. Our numerical results show that a rapidly rotating white dwarf can spin up by angular momentum loss; if the mass of the white dwarf is large enough, this phenomenon is present even in rigidly rotating models. On the other hand, differential rotation seems to strengthen this phenomenon, while the presence of a strong toroidal magnetic field seems to reduce it. Furthermore, we discuss our results in connection with (1) the "accretion-induced collapse" scenario for accreting "oxygen-neon-magnesium" white dwarfs and (2) the X-ray pulsar 1E 2259+586, for which, in addition to our main numerical results, we calculate some significant physical parameters and give some estimates concerning its evolution.