Eccentricity distributions of eccentric binary black holes in galactic nuclei

Understand

Galactic nuclei are expected to be one of the main sites for formations of eccentric binary black holes (EBBHs), with an estimated detection rate of $\mathcal{O}(1-100$ yr$^{-1})$ with Advanced LIGO (aLIGO) detectors operating at design sensitivity.

• The two main formation channels of these binaries are gravitational capture and the secular Kozai-Lidov mechanism, with expectedly commensurable formation rates.
• We used Monte Carlo simulations to construct the eccentricity distributions of EBBHs formed through these channels in galactic nuclei, at the time their gravitational-wave signals enter the aLIGO band at $10$ Hz.
• We have found that the proportion of binary black holes entering the aLIGO band with eccentricities larger than $0.1$ is $\sim 10$ percent for the secular Kozai-Lidov mechanism, and $\sim 75$ percent for gravitational capture.