U.K. would like to thank Roger Romani, Jim Truran and Hartmut Braun for helpful conversations, and Uwe Oberlack for providing up-to-date information on the status of COMPTEL data reduction. M.P. would like to thank Sumner Starrfield, Warren Sparks and Ron Webbink for very helpful discussions. M.P. would also like to warmly thank Dr. C. Keller at Los Alamos National Laboratory for his hospitality and for providing office space while visiting Los Alamos, where a portion of the work on this paper was completed. In addition, M.P. would like to warmly thank Drs. H. Ritter, F. Meyer and E. Meyer-Hofmeister at the Max-Planck-Institut für Astrophysik for their hospitality and support while visiting the Institut. Lastly, we are indebted to an anonymous referee whose comments and suggestions helped us to focus and improve our discussion.
© European Southern Observatory (ESO) 1997
Online publication: July 3, 1998