The authors would like to say Thank You to all the helpful CV-people in our institute and at MPA Garching, especially N. Drory, D. imi , E. Meyer-Hofmeister, F. Meyer, H. Ritter, H. Spruit and K. Ludwig for many fruitfull discussions. Also the comments of the referee which helped to improve the paper, are kindly acknowledged. This work is supported by the Deutsche Forschungsgemeinschaft (grant Ma 1693/4-1).
© European Southern Observatory (ESO) 1997
Online publication: April 6, 1998