Identifying stars of mass >150M ⊙ from their eclipse by a binary companion

Abstract

We examine the possibility that very massive stars greatly exceeding the commonly adopted stellar mass limit of 150M ⊙ may be present in young star clusters in the local universe. We identify 10 candidate clusters, some of which may host stars with masses up to 600M ⊙ formed via runaway collisions. We estimate the probabilities of these very massive stars being in eclipsing binaries to be ≳30 per cent. Although most of these systems cannot be resolved at present, their transits can be detected at distances of 3Mpc even under the contamination of the background cluster light, due to the large associated luminosities ~10 7 L ⊙ and mean transit depths of ~10 6 L ⊙ Discovery of very massive eclipsing binaries would flag possible progenitors of pair-instability supernovae and intermediate-mass black holes. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.