Growth of Intermediate-Mass Black Holes in Globular Clusters

We present results of numerical simulations of sequences of binary-single scattering events of black holes in dense stellar environments. The simulations cover a wide range of mass ratios from equal mass objects to 1000 : 10 : 10 M☉ and compare purely Newtonian simulations to simulations in which Newtonian encounters are interspersed with gravitational wave emission from the binary. In both cases, the sequence is terminated when the binary's merger time due to gravitational radiation is less than the arrival time of the next interloper. We find that black hole binaries typically merge with a very high eccentricity (0.93 ≤ e ≤ 0.95 pure Newtonian; 0.85 ≤ e ≤ 0.90 with gravitational wave emission) and that adding gravitational wave emission decreases the time to harden a binary until merger by ~30%-40%. We discuss the implications of this work for the formation of intermediate-mass black holes and gravitational wave detection.