On the Oscillations and Stability of Rotating Stellar Models. II. Rapidly Rotating White Dwarfs
Abstract
This paper deals with the stable and unstable oscillations of rapidly rotating, zerotemperature white dwarfs. The models are axisymmetric, and the angular velocity depends only on the distance from the axis of rotation. Approximate expressions for the lowest seven modes have been obtained for uniform'y and nonuniformly rotating models. We do not assume that rotational effects are small. It is shown that, for sufficiently high values of the ratio of kinetic to potential energy T/IWL, nonuniformly rotating white dwarfs may become overstable. This instability is directly analogous to an instability of the classical homogeneous Maclaurin spheroids that has been considered a precursor of fission A neutral mode, associated with a nonaxisymmetric Kelvin oscillation, can be found exactly and occurs when TI I W 0.14, the latter value being almost independent of the total mass and angularmomentum distribution. In cases where viscous forces are important, the models become secularly overstable when T/ I W > 0.14, but then adjacent triaxial configurations exist which carry on the stability. In the absence of viscosity, dynamical overstability occurs via the same nonaxisymmetric mode when T/ W > 0.26, almost in dependently of the total mass and angularmomentum distribution. Due to the fact that, for uniformly rotating white dwarfs, the kinetic energy is restricted to the range 0 «= T/IWI <0.06, these models are always stable with respect to nonaxisymmetric disturbances. All the white dwarf models constructed by Ostriker and Bodenheimer above the mass limit for nonrotating stars are dynamically stable to the modes considered. I. INTRODUCTIO
 Publication:

The Astrophysical Journal
 Pub Date:
 March 1969
 DOI:
 10.1086/149927
 Bibcode:
 1969ApJ...155..987O