THE DENSE GALACTIC STARBURST NGC-3603 .1. HST/FOS SPECTROSCOPY OF INDIVIDUAL STARS IN THE CORE AND THE SOURCE OF IONIZATION AND KINETIC-ENERGY

We present spectrograms of 14 individual luminous stars in HD 97950, the core (r less than or equal to 4 ''=0.12 pc) of the dense galactic starburst NGC 3603, obtained with the Faint Object Spectrograph aboard the refurbished Hubble Space Telescope. In a volume of less than a cubic light year, three luminous hydrogen-rich WNL+abs stars cohabit with six O3 stars [including two O3 III (f*)] and other early O stars; KD 97950 is therefore the densest concentration of very massive stars known in the Galaxy. The close physical association between O3 and WNL+abs stars, as well as the evolution of spectroscopic features, suggests a direct evolutionary Link between them. The total output of Lyman continuum photons from these 14 stars alone accounts for more than 80% of what is required to ionize the surrounding nebula. The very small radius of the wind-driven bubble surrounding HD 97950 seems at odds with the tremendous power, L(w) similar to 3.2x10(38) erg s(-1), supplied by massive stars to the nebula. (C) 1995 American Astronomical Society.