2013MNRAS.435L..73R

In this Letter, we communicate the identification of a new Galactic O2If* star (MTT 68) isolated at a projected linear distance of 3pc from the centre of the starburst cluster NGC 3603. From its optical photometry, I computed a bolometric luminosity MBol = -10.7, which corresponds to a total stellar luminosity of 1.5x10⁶ L_☉. It was found to be an interesting similarity between MTT 68 and the well-known multiple system HD 93129. From Hubble Space Telescope (HST) F656N images of the NGC 3603 field, it was found that MTT 68 is actually a visual binary system with an angular separation of 0.38arcsec, which corresponds to a projected (minimum) linear distance of rA-B = 1.4x10^–2pc. This value is similar to that for the HD 93129A (O2If*) and HD 93129B (O3.5) pair, rA-B = 3.0x10^–2pc. On the other hand, HD 93129A has a third closer companion named HD 93129Ab (O3.5) at only 0.053arcsec, and taking into account that the X-ray to total stellar luminosity ratio for the MTT 68 system (LX/LBol ∼ 1x10^–5) is about two orders of magnitude above the canonical value expected for single stars, I suspect that the MTT 68 system probably hosts another massive companion possibly to close to be properly resolved by the HST archive images.