The effect of pair-instability mass loss on black-hole mergers

Abstract

Mergers of two stellar origin black holes are a prime source of gravitational waves and are under intensive investigations. One crucial ingredient in their modeling has so far been neglected. Pair-instability pulsation supernovae with associated severe mass loss may suppress formation of massive black holes, decreasing black hole merger rates for the highest black hole masses. The mass loss associated with pair-instability pulsation supernovae limits the Population I/II stellar-origin black hole mass to 50 Msun, in tension with earlier predictions that the maximum black hole mass could be as high as 100 Msun. Suppression of double black hole merger rates by pair-instability pulsation supernovae is negligible for our evolutionary channel. Our standard evolutionary model with inclusion of pair-instability pulsation supernovae and with pair-instability supernovae is fully consistent with the LIGO detections of black hole mergers: GW150914, GW151226 and LVT151012. The LIGO observations seem to exclude high (>400 km/s) BH natal kicks. We predict the detection of several up to 60 BH-BH mergers with total mass 10--150 Msun (most likely range: 20--80 Msun) in the forthcoming 60 effective days of LIGO O2 observations.