Observational data were obtained at the 3.6m telescope at La Silla. We are grateful to the staff at the observatory for their assistance. Data reduction was performed in Munich and on the PPARC funded Northern Ireland STARLINK node, and some of the model atmosphere programs were made available through the PPARC supported Collaborative Computational Project No. 7. We would also like to acknowledge useful discussions with, and test calculations by, Rolf Kudritzki and Paco Najarro.
DJL is grateful for financial support from the Bundesminister für Forschung und Technologie under grant 010 R 90080.
NDME holds a post-graduate studentship from the Department of Education for Northern Ireland.
We are grateful to the British Council and the Deutsche Akademischer Austauschdienst for funding an ARC program of working visits between Munich and Belfast.
© European Southern Observatory (ESO) 1998
Online publication: December 8, 1997