ORIGIN OF THE ROTATION RATES OF SINGLE WHITE-DWARFS

I argue that the rotation of white dwarfs is not a remnant of the angu lar momentum of their main sequence progenitors but a result of the ma ss loss process on the AGE. Weak magnetic fields, if present in stella r interiors, are likely to maintain approximately uniform rotation in stars, both on the main sequence and on the giant branches. The nearly uniform rotation of the core of the Sun is evidence for the existence of such fields. Exactly axisymmetric mass loss on the AGE from unifor mly rotating stars would lead lead to white dwarfs with very long rota tion periods (> 10 yr). Small random non-axisymmetries (similar to 10( -3)) in the mass loss process, on the other hand, add sufficient angul ar momentum to explain the observed rotation periods around one day. T he process illustrated with a computation of the probability distribut ion of the rotation periods under the combined influence of random for cing by weak nonaxisymmetries and angular momentum loss in the AGE sup erwind. Such asymmetries can in principle be observed by proper motion studies of the clumps in interferometric images of SiO maser emission .