Stellar dynamics around black holes in galactic nuclei: collisional evolution of a rapidly rotating cluster

Recent observations suggest quite strongly that the nuclei of the nearby galaxies M31 and M32 contain central mass concentrations of ∼ 10 M''sun''. Assuming that these are black holes, the dynamics of the surrounding star cluster determines important processes like tidal disruption of stars by the black hole. A flattened and differentially rotating configuration of stars has already been suggested as a possible model. Estimates of its evolution under two-body gravitational encounters are made using Kuzmin's method of moments. Such a configuration may lead to a smaller rate of tidal disruption than in the spherical clusters usually considered. It evolves in such a manner that the two body relaxation time at every stage is comparable to the age. (author)