It is a pleasure to thank Artemio Herrero and the staff of the Isaac Newton telescope for helping us to carry out the observations. DM acknowledges the support by the Spanish Dirección General de Investigación Científica y Técnica (DGICYT) under grant PB94-0263. E.M. acknowledges financial support from EU grant ERBCHBG-CT93-0315 for visiting FORTH in Heraklion (Crete) during 1995.
© European Southern Observatory (ESO) 1997
Online publication: July 3, 1998