On computing the structure of critically rotating white dwarfs

A direct numerical simulation for determining the distorted structure of white dwarfs undergoing uniform critical rotation is presented. The novelty of this direct approach is that the Lane-Emden equation modelling a rotating white dwarf is coupled to an algebraic equation for the surface of the star and the condition for critical rotation. This allows for the computation of both the critical angular velocity and the corresponding equatorial radius simultaneously. Physical parameters (angular velocities, radii and masses) of critically rotating classical white dwarfs and polytropes for various values of the central density parameter, y0-2, are presented. Direct numerical simulation shows the development of cusps at higher latitudes than those found in models with Roche-like potentials. The results obtained in this paper are compared to numerical results obtained with the Hachisu Self Consistent Field method (HSCF) for polytropes and the Complex Iterative Technique (CIT) of Geroyannis and Papasotiriou for white dwarfs.