2013MNRAS.433..712R

In this paper, we report on the discovery of an O2 If*/WN6 star probably still partially embedded in its parental cocoon in the starburst cluster NGC 3603. From the observed size of the associated compact Hii region, it has been possible to derive a probable dynamic age of no more than 600 000 yr. Using the computed visual extinction value AV ∼ 6.0±0.2 mag, an absolute visual magnitude MV = -5.7 mag has been obtained. For the assumed heliocentric distance of 7.6 kpc, this results in a bolometric luminosity of 8x105 L☉. Also, from the V magnitude and the V - I colour of the new star, and from previous models for the massive star population of NGC 3603, we estimate the mass of the binary (O2 If*/WN6 + O3 If) and the single star (O2 If*/WN6). For the binary, we find that the initial masses of each component possibly exceed 80 and 40 M☉, respectively, while for the single star the initial mass of MTT 58 is possibly in excess of 100 M☉.