Accretion disk assembly and survival during the disruption of a neutron star by a black hole

We study the formation of accretion disks resulting from dynamical three dimensional binary coalescence calculations, where a neutron star is tidally disrupted before being swallowed by its black hole companion. By subsequently assuming azimuthal symmetry we are able to follow the time dependence of the disk structure for a few tenths of a second. Although the disruption of a neutron star leads to a situation where violent instabilities redistribute mass and angular momentum within a few dynamical timescales, enough gas mass remains in the orbiting debris to catalyse the extraction of energy from the hole at a rate adequate to power a short-lived gamma ray burst.