Black Holes in Globular Clusters

We consider the implications of the presence of ∼ 1 stellar-mass black hole (BH) at the center of a dense globular cluster. We show that BH X-ray binaries formed through exchange interactions are likely to have extremely low duty cycles (< 10−3), consistent with the absence of BH X-ray transients in Galactic globular clusters. In contrast, we find that BH X-ray binaries formed through tidal capture would be persistent, bright X-ray sources. Given the absence of any such source and the very high interaction rates, we conclude that tidal capture of a main-sequence star by a BH most likely leads to the complete disruption of the star. Subject headings: accretion, accretion disks – binaries: close – black hole physics – globular clusters: general – stellar dynamics