Neutrino-cooled Accretion Disks around Spinning Black Holes

Abstract. We calculate the structure of accretion disk around a spinning black hole for accretion rates Ṁ = 0.01− 10M⊙ s−1. 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 protonto-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 ν-opaque and ν-trapping radii, and show their dependence on Ṁ. Accretion disks around fast-rotating black holes produce intense neutrino fluxes which may deposit enough energy above the disk to generate a GRB jet.