A quantitative study of the O stars in NGC 2244

Abstract

NGC 2244 located in the Rosette Nebula is a young open cluster composed of seven O-type stars. A first paper focused on the multiplicity of these stars, revealed only one binary system out of the seven studied stars. The minimum binary fraction of this cluster (∼ 14%) differs to the average fraction measured on the nearby clusters (∼ 44%). In order to better constrain this discrepancy, an analysis based on the determination of the stellar and wind parameters of these stars with the CMFGEN atmosphere code was performed. The main results confirm that all the stars have an age between 0 and 5 Myr, and that the N surface abundance appears to be consistent with the evolutionary models for a population of stars of the same age. Moreover, this investigation exhibits the existence of dynamical interactions inside this young open cluster sufficiently strong to eject the hottest component from its centre.