We thank the European Southern Observatory for generous allocation of observing time and the staff at La Silla for the kind assistance during the observations.
We are grateful to Christoph Gummersbach, Thomas Dumm, Thomas Gäng, Josef Kovács, Istvan Jankovics, Holger Lehmann, Holger Mandel, Jochen Peitz, Dominik Schäfer, Werner Schmutz, and Jörg Schweickhardt for carrying out part of observations with HEROS and to Conny Aerts, Martin Kürster, and Michelle Thaller for having taken additional spectra during their observing runs at other telescopes in 1997.
This work was supported by the Deutsche Forschungsgemeinschaft (Wo 296/20-1, 436 TSE 113/18) and Academy of Sciences and Grant Agency of the Czech Republic (436 TSE 113/18, 202/97/0326).
© European Southern Observatory (ESO) 1998
Online publication: April 15, 1998