Figure 8: Evolution of the separation of a black hole binary with mass ratio . The initial separation here was  pc and the disc/secondary mass ratio is . The solid curve shows the case where the disc is allowed to fragment and form stars, whereas the dotted line shows where star formation ignored. Star formation severely depletes the disc, and the remaining disc mass is not large enough to induce a black hole merger within a Hubble time. The figure taken from Lodato et al. [16].