I would like to express my warm thanks to Prof. M. Golay, who has initiated this study by examining the long-term trends in the Geneva photometric data, and to Dr. N. Cramer for the use of his photometric calibrations for the B-type stars. I am also grateful to my numerous colleagues who helped with the acquisition and reduction of the measurements at the Swiss station at the ESO Observatory of La Silla, to Dr. M. Burnet for the perfect maintenance of the photometric equipment, which allowed this kind of study, and to Dr. J. Zorec, the referee, for his careful reading of the paper and his very detailed comments. This work has been partly supported by the Swiss National Science Foundation.
© European Southern Observatory (ESO) 1999
Online publication: May 6, 1999