Vol. 553
In section 7. Stellar structure and evolution

Three-dimensional orbits of the triple-O stellar system HD 150136

by H. Sana, J.-B. Le Bouquin, L. Mahy, O. Absil, M. De Becker, and E. Gosset A&A 553, A131

Direct mass estimates of high-mass stars are rare. The authors combine spectroscopic and interferometric observations to determine the orbits and masses of the three components of the triple-O star HD150136. This is the first direct measurement of the mass of an O3 star - an important reference point to test the evolution of massive stars. Although the error bars are still relatively high, they could be reduced by further monitoring of the system.