The collapse of rotating stellar cores: equilibria between white dwarf and neutron star densities

A simple analytical model is developed through which properties of a stellar core at the endpoint of its collapse can be estimated without performing a detailed collapse calculation. The model permits the range of physical conditions for which dynamical collapse to nuclear density will be prevented to be specified. The basic physical relations that allow the endpoint of collapse to be predicted are first outlined. The core is assumed to remain spherical during its collapse, even though it is rotating. A more accurate model of the endpoint of collapse is then obtained by allowing the core to acquire oblate spheroidal equilibrium structures. These analytical descriptions of the endpoint of core collapse require that collapse proceed along a fixed adiabat. The analysis is also performed without this assumption. An attempt is made to mimic the pressure-density conditions encountered during a hot core collapse, and final equilibrium conditions in the core are predicted for all possible initial core rotation rates.