a) Hertzsprung-Russell diagram including sources in the SINFONI field of view. The M_K value of object 2 is corrected for its intrinsic infrared excess. b) and c) Detail of a), with PMS isochrones (dash-dotted lines) and evolutionary tracks (dotted lines) taken from Da Rio et al. (2009), calculated from the evolutionary models of Siess et al. (2000). Spectral types are indicated following the observational calibrations by Martins & Plez (2006, O stars) and Kenyon & Hartmann (1995, KH95, B0 and later). d) Age distribution of the classified stars (see text). The distribution peaks at 1.1 ± 0.6 Myr. When only considering sources with errors <1 Myr, the “tail” towards older ages disappears.