Hertzsprung-Russell diagram (HRD) of the massive stars in W49. The solid line represents the zero age main sequence isochrone from Lejeune & Schaerer (2001). The dashed lines are main-sequence isochrones for 1, 1.5, 2, and 3 Myr from Ekström et al. (2012) and Yusof et al. (2013). The stars are dereddened using the extinction law of Indebetouw et al. (2005). Three very massive stars are indicated by red dots, while OB main sequence stars are indicated by black dots.