IUE OBSERVATIONS OF BLUE HORIZONTAL-BRANCH STARS IN THE GLOBULAR-CLUSTERS M-3 AND NGC-6752

IUE observations of 3 blue horizontal branch (BHB) stars in M 3 and 4 stars in NGC 6752 are presented. In addition, unpublished IUE archive data have been used for 5 more BHB stars in NCC 6752. Using the most r ecent model atmospheres (Kurucz 1992) the physical parameters of these stars have been derived, and compared with the ZAHB evolutionary trac ks by Dorman et al. (1993). All the stars, including those that appear to be evolved off the ZAHB, are consistent with the theoretical predi ctions. The present results are compared with those obtained in previo us similar analyses: the possible presence of some low-gravity stars i s confirmed in M 3, while no clear indication is found of multiple ste llar populations on the HE of NGC 6752. However different populations, if any, would be difficult to identify in the logg-logT(e) plane beca use of the simultaneous effect of various parameters and the poor accu racy of the gravity estimates from IUE data.