We thank all staff members and students of Japanese VLBI group for their helps in operating J-Net array and correlator NAOCO. We are deeply indebted to Prof. S. Deguchi for his helpful discussions and valuable information and to Prof. M. Inoue and S. Enome for their encouraging comments. We have used, and acknowledge with thanks, data from the AAVSO International Database. We have to also express our thanks to Dr. J.A. Mattei for her kindness to check and send the AAVSO data. H. I. is financially supported by the Research Fellowship of the Japan Society for the Promotion of Science for Young Scientist.
© European Southern Observatory (ESO) 1997
Online publication: July 3, 1998