IUE observations of UB-bright stars in M 3.

Abstract

IUE UV observations of three "UV-bright" stars in M3 are presented. The brightest object - vZ1128 - is confirmed to be a bright Post-AGB star with logL/L_sun=3.09 and T_e=30,000 K, which contributes about 25% of the integrated UV light from the cluster at λ=1500Å. The nature of the two other stars, i.e. 524 (logL/L_sun=2.06, T_e=33,000 K) and 7561 (iogL/L_sun=2.04, T_e=35,000 K), is still controversial. They might be respectively AGB-manque' stars of the sort suggested by Greggio & Renzini (1990), or the result of mergers of binary systems according to Iben (1990), but other possibilities are considered and discussed.