Computing the delayed collapse of hot neutron stars to black holes

We perform dynamical simulations of the delayed collapse of hot neutron stars to black holes. Using our recently developed code for spherical collapse in general relativity, we can follow this collapse to completion, i.e., until the last fluid elements have approached the event horizon. Therefore, we can study the very late stages of the collapse and determine, for example, the neutrino signature of this event. We adopt a hot kaon condensate equation of state and model neutrino transport with a relativistic diffusion equation. In our simulations, we evolve hot neutron stars with masses greater than the maximum mass of cold neutron stars. These stars are initially stabilized by thermal pressure. However, as the stars emit neutrinos and cool down, they eventually reach the onset of instability and catastrophically collapse to black holes. We track the entire evolution, from the quasi-static onset of collapse to the final dynamical implosion. This calculation is meant to serve as a prototype for more detailed calculations of delayed collapse, but nevertheless it does illustrate all the physical features that we expect to find when more detailed calculations are performed.