FAR-ULTRAVIOLET LUMINOSITY FUNCTIONS FOR THE GLOBULAR-CLUSTERS M3 ANDM13

Far-ultraviolet images of the globular clusters M3 (NGC 5272) and M13 (NGC 6205) obtained with the Ultraviolet Imaging Telescope during the 1990 December Astro-1 mission are presented. 74 sources are detected d own to an FUV limiting magnitude of 16.0 in M3, and 56 sources to magn itude 14.2 in M13. Although the two clusters are similar in total popu lation, luminosity, and metallicity, M13 has a much larger population of stars with FUV magnitudes brighter than the zero age horizontal bra nch. The relative numbers of UV-bright stars in the two clusters are i n good agreement with theoretical post-HB evolutionary tracks for norm al, non-binary stars given the amount of red giant branch mass loss in ferred from the optical color-magnitude diagrams. (C) 1995 American As tronomical Society.