Very massive stars in not so massive clusters

Seungkyung Oh and Pavel Kroupa

Following André-Nicolas Chene et al. “Massive open star clusters using the VVV survey, IV. WR 62-2, a new very massive star in the core of the VVV CL041 cluster” Oh and Kroupa study the very massive star, WR62-2 ~80Msun, that violates the mmaxMecl relation that predicts a mass up to ~40 Msun. They study whether such a massive star can be formed via dynamically induced stellar collisions in a binary-rich star cluster that initially follows the mmaxMecl relation (C. WeidnerP. KroupaJ. Pflamm-Altenburg, 2013), which is the relation between the most massive star in a cluster, mmax, and the stellar mass of the embedded cluster, Mecl . They use N-body simulations for the first 5 Myr evolution of VVV CL041-like clusters and find the more than a half of their model clusters host a merger and 8 out of 100 form a star more massive than 80 Msun through multiple stellar collisions, this still supports the mmaxMecl relation which is related to the formation stage of the cluster.