I thank Dr.R.P.Fender for important comments. I thank the Indian National Science Academy for a Senior Scientist Fellowship. I thank the Director of the Tata Institute of Fundamental Research for allowing me the use of their Library and other facilities for this research. I thank my colleagues at the University of Bombay, particularly Prof.S.B.Patel.
© European Southern Observatory (ESO) 2000
Online publication: February 25, 2000