Differentially Rotating Equilibrium Models and the Collapse of Rotating Degenerate Configurations

Abstract

Using a recently developed method (Erlguchl and Muller, 1985a) two kind of problems involving axisymmetric, differentially rotating degenerate configurations are investigated: (I) Equilibrium models of rotating polytropes are used to estimate the properties of the degenerate core of a massive star M>8M⊙ at the endpoint of its collapse without performing a detailed collapse calculation. Our analysis shows (Erlguchl and Muller, 1985b) that a rotating stellar core will not collapse all the way to neutron star densities on a dynamical time-scale, if Its initial ratio of rotational to gravitational energy βl is larger than some minimum value: βmin=0.01, 0.03, and 0.08 for y=1.30, 1.25, and 1.20, respectively. Instead the collapse is stopped due to rotation at an intermediate, dynamically stable, axisymmetric equilibrium state. The further evolution will proceed on a secular time-scale. (II) Rotating, completely catalyzed, zero-temperature Newtonian configurations with central densities in the range 107gcm−3<Pc< 5.10 gem−3 are calculated. Based on these models we have then studied the question, if there exist evolutionary scenarios of rotating white dwarfs, where due to angular momentum losses a white dwarf with a mass larger than the Chandrasekhar mass will evolve towards a neutron star on a secular time-scale, i.e. without a sudden release of gravitational potential energy in the form of an optical supernova outburst.