2017MNRAS.467..524B

Stellar-remnant black holes (BH) in dense stellar clusters have always drawn attention due to their potential in a number of phenomena, especially the dynamical formation of binary black holes (BBH), which potentially coalesce via gravitational-wave radiation. This study presents a preliminary set of evolutionary models of compact stellar clusters with initial masses ranging over 1.0 x 10⁴-5.0 x 10⁴ M_☉, and half-mass radius of 2 or 1 pc, which is typical for young massive and starburst clusters. They have metallicities between 0.05 Z_☉ and Z_☉. Including contemporary schemes for stellar wind and remnant formation, such model clusters are evolved, for the first time, using the state-of-the-art direct N-body evolution program NBODY7, until their dissolution or at least for 10 Gyr. That way, a self-regulatory behaviour in the effects of dynamical interactions among the BHs is demonstrated. In contrast to earlier studies, the BBH coalescences obtained in these models show a prominence in triple-mediated coalescences while being bound to the clusters, compared to those occurring among the BBHs that are dynamically ejected from the clusters. A broader mass spectrum of the BHs and lower escape velocities of the clusters explored here might cause this difference, which is yet to be fully understood. Among the BBH coalescences obtained here, there are ones that resemble the detected GW151226, LVT151012 and GW150914 events and also ones that are even more massive. A preliminary estimate suggests few 10-100 s of BBH coalescences per year, originating due to dynamics in stellar clusters that can be detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO) at its design sensitivity.