Vol. 530In section 1. Letters

The VLT-FLAMES Tarantula Survey. II. R139 revealed as a massive binary system

The authors report the discovery that R139, one of the brightest stars in the 30 Doradus nebula, is a massive spectroscopic binary system. They obtained multi-epoch spectroscopy of this object as part of the VLT-FLAMES Tarantula Survey. The two members of the binary system are very similar: the primary is an O6.5 Iafc supergiant with a mass of 78 ± 8 Mo, and the secondary is an O6 Iaf supergiant with a mass of 66 ± 7 Mo, and they orbit each other with a period of 153.9 days. This is the most massive binary system known to contain two evolved Of supergiants.