ON THE SPREAD OF AGES AMONG THE YOUNG STARS IN THE LMC ASSOCIATION NGC-1948

The ages of the young associations located at the border of the superg iant shell LMC 4 are essential parameters to understand the formation and the evolution of that supergiant shell. We present spectra in the UV and the optical wavelength range of eleven stars in NGC 1948 in ord er to establish the location of the top of the main sequence more accu rately than possible from photometry alone. From the present data we d erive an age for NGC 1948 of 5 - 10 Myr, a much tighter range than der ived earlier by Vallenari et al. (1993), but located at the lower bord er of the age range given by those authors. Two stars seem to be as ol d as 40 Myr, but from their location at the border of the association they may be non-members. The given range of ages corresponds to a real spread in the ages of the sample stars and not to an error estimate o f a precisely fixed age.