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We calculate the structure of accretion disk around a spinning black hole for accretion rates 0. 01 - 10 Mₛun/s. The model is fully relativistic and treats accurately the disk microphysics including neutrino emissivity, opacity, electron degeneracy, and nuclear composition. We find that the accretion flow always regulates itself to a mildly degenerate state with the proton-to-nucleon ratio Yₑ ~ 0. 1 and becomes very neutron-rich. The disk has a well defined "ignition" radius where neutrino flux raises dramatically, cooling becomes efficient, and Yₑ suddenly drops. We also calculate other characteristic radii of the disk, including the neutrino-opaque and neutrino-trapping radii, and show their dependence on the accretion rate. Accretion disks around fast-rotating black holes produce intense neutrino fluxes which may deposit enough energy above the disk to generate a GRB jet.
Chen et al. (Thu,) studied this question.