Draft version November 13, 2018 A Preprint typeset using LTEX style emulateapj v. 5/2/11 BLACK HOLE TRIPLE DYNAMICS: BREAKDOWN OF THE ORBIT AVERAGE APPROXIMATION AND IMPLICATIONS FOR GRAVITATIONAL WAVE DETECTIONS Fabio Antoninia, Norman Murraya & Seppo Mikkolab aCanadian Institute for Theoretical Astrophysics, University of Toronto, 60 George St., Toronto, Ontario M5S 3H8, Canada bTuorla Observatory, University of Turku, Vais¨ al¨ antie¨ 20, Piikkio¨ FI-21500, Finland E-mail:
[email protected] Draft version November 13, 2018 Abstract Coalescing black hole (BH) binaries forming via dynamical interactions in the dense core of globu- lar clusters (GCs) are expected to be one the brightest and most numerous sources of gravitational wave (GW) radiation, detectable by the upcoming generation of ground based laser interferometers. Favorable conditions for merger are initiated by the Kozai resonance in which the gravitational in- teraction with a third distant object, typically another BH, induces quasi-periodic variations of the inner BH binary eccentricity. In this paper we perform high precision 3-body simulations of the long term evolution of hierarchical BH triples and investigate the conditions that lead to the merging of the BH binary and the way it might become an observable source of GW radiation. We find that the secular orbit average treatment, adopted in previous works, does not reliably describe the dynamics of these systems if the binary is orbited by the outer BH on a highly inclined orbit with a periapsis distance less than 10 times the inner binary semi-major axis. During the high eccentricity phase of a Kozai cycle the∼ torque due to the outer BH can drive the binary to extremely large eccentricities in a fraction of the binary’s orbital period.