Lidov-Kozai Cycles with Gravitational Radiation: Merging Black Holes in Isolated Triple Systems

Understand

We show that a black-hole binary with an external companion can undergo Lidov-Kozai cycles that cause a close pericenter passage, leading to a rapid merger due to gravitational-wave emission.

• This scenario occurs most often for systems in which the companion has mass comparable to the reduced mass of the binary and the companion orbit has semi-major axis within a factor of $\sim 10$ of the binary semi-major axis.
• Using a simple population-synthesis model and 3-body simulations, we estimate the rate of mergers in triple black hole systems in the field to be about six per Gpc$^3$ per year in the absence of natal kicks during black hole formation.
• This value is within the low end of the 90\% credible interval for the total black-hole black-hole merger rate inferred from the current LIGO results.