We thank Christian Henkel for critically reading the manuscript and Andrea Tarchi for help with part of the observations. FW acknowledges NSF grant AST 96-13717. The KOSMA 3 m telescope is operated by the University of Cologne, Germany, and supported by the DFG grant SFB 301, as well as special funding from the Land NRW, Germany. The observatory is administered by the Internationale Stiftung Hochalpine Forschungsstationen Jungfraujoch und Gornergrat, Bern, Switzerland.
© European Southern Observatory (ESO) 2000
Online publication: October 2, 2000