Main-sequence B stars with strong winds in the core of NGC 6231.

Abstract

Low-dispersion IUE observations of 13 main sequence B0 - 2 stars in the Sco OB1 association are presented. Eleven of these are in the rich open cluster NGC 6231. Most of the NGC 6231 stars have strong UV resonance lines which are inconsistent with either their spectral types or the rest of their UV spectra. A high-dispersion IUE spectrum of one of the peculiar stars, CPD -41°7719, reveals an abnormally strong wind (M> 4×10^-9M_sun;yr^-1) with an unusual velocity law. The authors examine some possible causes of such a wind and conclude that an overabundance of carbon is the most likely origin. They discuss how the postulated abundance anomaly could originate and consider some implications of these results.