PRIMORDIAL BLACK-HOLES IN GLOBULAR-CLUSTERS

IT HAS recently been recognized1 that significant numbers of medium-ma ss black holes (of order 10 solar masses) should form in globular clus ters during the early stages of their evolution. Here we explore the d ynamical and observational consequences of the presence of such a prim ordial black-hole population in a globular cluster. The holes initiall y segregate to the cluster cores, where they form binary and multiple black-hole systems. The subsequent dynamical evolution of the black-ho le population ejects most of the holes on a relatively short timescale : a typical cluster will retain between zero and four black holes in i ts core, and possibly a few black holes in its halo. The presence of b inary, triple and quadruple black-hole systems in cluster cores will d isrupt main-sequence and giant stellar binaries; this may account for the observed2 anomalies in the distribution of binaries in globular cl usters. Furthermore, tidal interactions between a multiple black-hole system and a red-giant giant star can remove much of the red giant's s tellar envelope, which may explain the puzzling absence3 of larger red giants in the cores of some very dense clusters.