In this work, we present a spectroscopic study of very massive stars found
outside the center of the massive stellar cluster NGC3603. From the analysis of
SOAR spectroscopic data and related optical-NIR photometry, we confirm the
existence of several very massive stars in the periphery of NGC 3603. The first
group of objects (MTT58, WR42e and RFS7) is compound by three new Galactic
exemplars of the OIf*/WN type, all of them with probable initial masses well
above 100 Msun and estimated ages of about 1 Myr. Based on Goodman blue-optical
spectrum of MTT68, we can confirm the previous finding in the NIR of the only
other Galactic exemplar (besides HD93129A) of the O2If* type known to date.
Based on its position relative to a set of theoretical isochrons in a
Hertzprung-Russel diagram, we concluded that the new O2If* star could be one of
the most massive (150 Msun) and luminous (Mv=-7.3) O-star in the Galaxy. Also,
another remarkable result is the discovery of a new O2V star (MTT31) that is
the first exemplar of the class so far identified in the Milk Way. From its
position in the Hertzprung-Russel diagram it is found that this new star
probably had an initial mass of 80 Msun, as well as an absolute magnitude
Mv=-6.0 corresponding to a luminosity similar to other known O2V stars in the
LMC. We also communicate the discovery of a new Galactic O3.5If* star (RFS8)
which case is quite intriguing. Indeed, It is located far to the south of the
NGC 3603 center, in apparent isolation at a large radial projected linear
distance of 62 pc. Its derived luminosity is similar to that of the other
O3.5If* (Sh18) found in the NGC 3603's innermost region. The fact that a such
high mass star is observed far isolated in the field led us to speculate that
perhaps it could have been expelled from the innermost parts of the complex by
a close fly-by dynamical encounter with a very massive hard binary system.Comment: 36 pages, 9 figures and 5 tables. Accepted for publication in the
Astrophysical Journa
