We acknowledge the referee, P.O. Lindblad, whose suggestions helped us to improve the paper considerably. We are very grateful to F. Warin for her help in the data reduction, to J. Perea for making his cross-correlation program available to us and to D. Pelat for giving us his profile fitting programme. I. Márquez acknowledges financial support from the Spanish Ministerio de Educación y Ciencia.
© European Southern Observatory (ESO) 1998
Online publication: April 20, 1998