We would like to thank Martin Asplund, Bengt Edvardsson, Bengt Gustafsson and Oleg Kochukhov for stimulating and encouraging discussions. PB thanks Patrik Thorén for helping with MARCS model codes and Oleg Kochukhov for providing ATLAS models. We would like to thank the referee, Professor T. Gehren, for constructive suggestions. PB acknowledges the support of the Swedish Natural Science Research Council (NFR). NSO/Kitt Peak FTS data used here were produced by NSF/NOAO.
© European Southern Observatory (ESO) 2000
Online publication: December 5, 2000