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<SUB>sun</SUB>=3.09 and T<SUB>e</SUB>=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<SUB>sun</SUB>=2.06, T<SUB>e</SUB>=33,000 K) and 7561 (iogL/L<SUB>sun</SUB>=2.04, T<SUB>e</SUB>=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.