Black hole genealogy

Theoretical models say that in dense stellar environments like globular clusters allow black holes to collide not just once, but many times. In this paper, we introduce a phenomenological model for what we would expect the mass and spin distribution of black holes to look like if some black holes merge multiple times. We apply this method to the ten binary black holes in GWTC-1 and find that GW170729 may contain a second generation black hole.