Collisional Dynamics around Binary Black Holes in Galactic Centers

We follow the sinking of two massive black holes in a spherical stellarsystem where the black holes become bound under the influence of dynamicalfriction. Once bound, the binary hardens by three-body encounters withsurrounding stars. We find that the binary wanders inside the core, providingan enhanced supply of reaction partners for the hardening. The binary evolvesinto a highly eccentric orbit leading to coalescence well beyond a Hubble time.These are the first results from a hybrid ``self consistent field'' (SCF) anddirect Aarseth N-body integrator (NBODY6), which combines the advantages of thedirect force calculation with the efficiency of the field method. The code isdesigned for use on parallel architectures and is therefore applicable tocollisional N-body integrations with extraordinarily large particle numbers (>10^5). This creates the possibility of simulating the dynamics of both globularclusters with realistic collisional relaxation and stellar systems surroundingsupermassive black holes in galactic nuclei.Comment: 38 pages, 13 figures, submitted to ApJ, accepted, revised text and added figure