We thank the Geneva team (especially Dr. G. Burki) for the telescope time put at our disposal in June 1990 and September 1991. Dr. Sperl is kindly acknowledged for making the programme Period98 available for this application. We appreciate the help of Dr. L. Eyer (Geneva Observatory) in the selection of the Hipparcos Epoch Photometry data. We thank our colleague, Dr. J. Cuypers, for a critical reading and the referee, Dr. P. North, for constructive comments on this manuscript. The Geneva data can be requested from the Geneva photometry team. The ESO data are available on request from the authors. This work has made use of the Simbad database, operated by the Centre de Données astronomiques de Strasbourg (France).
© European Southern Observatory (ESO) 2000
Online publication: April 17, 2000