IUE observations of UV bright stars in the globular clusters M15 and omega Cen.

Abstract

IUE spectra in the low dispersion mode are reported for three UV-bright stars. Two of them (stars K 559 and K 996) are members of the very metal poor cluster M15 and one (star ROA 5701) is a member of the populous cluster ω Cen. The authors find E(B-V) = 0.11 as a lower limit for the reddening of ω Cen whereas the reddening of M15 should not be larger than E(B-V) ≅ 0.08. Effective temperatures and bolometric magnitudes are evaluated for all the stars. Comparison with previous estimates shows that such temperatures tend to be generally lower than previously expected on a (B-V) basis. This difference is of the order of 2000K for ROA 5701, but it reaches more than 7000K for the two other stars. Evolutionary implications are discussed briefly.