Double Gravitational Wave Mergers

Understand

In this paper we study the dynamical outcome in which black hole (BH) binary-single interactions lead to two successive gravitational wave (GW) mergers; a scenario we refer to as a `double GW merger'.

• The first GW merger happens during the three-body interaction through a two-body GW capture, where the second GW merger is between the BH formed in the first GW merger and the remaining bound single BH.
• We estimate the probability for observing both GW mergers, and for observing only the second merger that we refer to as a `prompt second-generation (2G) merger'.
• We find that the probability for observing both GW mergers is only notable for co-planar interactions with low GW kicks ($\lesssim 10^{1}-10^{2}$ kms$^{-1}$), which suggests that double GW mergers can be used to probe environments facilitating such interactions.