Authors thank Dr. A. Obayashi for providing with details her observations before publication. They also express their gratitude to Dr. Kevin Volk for his careful reading of the manuscript and useful suggestions. This work has been partly supported by grant 2.P03D.002.13 of the Polish State Committee for Scientific Research and by the International Collaboration Bureau of Chinese Academy of Sciences. R Sz acknowledges also support from the JSPS Invitation Fellowship Program for Research in Japan.
© European Southern Observatory (ESO) 2000
Online publication: October 30, 19100