SPECKLE MASKING OBSERVATIONS OF HD-97950 WITH 75 MAS RESOLUTION - EVOLUTION OF THE STELLAR CORE OF THE STARBURST CLUSTER NGC-3603

We present diffraction-limited speckle masking observations of the cen tral object HD 97950 in the giant H II region and starburst cluster NG C 3603. In the reconstructed images 28 stellar components with V magni tudes in the range from 11.40 to 15.85 were detected in the 6.''3 x 6. ''3 (similar to 0.2 pc x 0.2 pc) field of view. Four different fitters were used for the selection of distinct spectral regions comprising H alpha emission, the main Wolf-Rayet and Of-type emission lines, and t wo continuum bands. The angular resolutions of the four reconstructed images are 0.''080 (RG 695 filter), 0.''075 (658 nm), 0.''079 (545 nm) , and 0.''174 (471 nm). Two WN stars and two further stars with mild W N-type characteristics were found. A colour-magnitude diagram has been constructed. Isochrone fits taken from the new grids of stellar model s from Schaller et al. (1992), yield a cluster age of about 3.2 Myr wh ich is in accordance with the time-scale of Wolf-Rayet star evolution and places NGC 3603 in the Carina nebula phase of young stellar aggreg ates. The initial mass function IMF of HD 97950 has a fairly steep slo pe of x = 1.59, in contrast to other Local Group giant H II regions an d to starburst galaxies. HD 97950 has, compared to the cores of extrag alactic H II regions, a similar, but high number ratio of WN to OB-typ e stars, indicating an instantaneous burst of star formation. HD 97950 hosts OB-type stars with a total mass of about 1000 M., corresponding to a mass density of similar to 10(5) M. pc(-3). Thus, HD 97950 is ev en more compact than R 136a, the core of the giant H II region 30 Dor in the LMC.