KW thanks Mordecai Mac Low, Guillermo García-Segura, and Norbert Langer for stimulating discussions. We thank the referee, Damien Hutsemékers, for his comments and suggestions. DJB acknowleges support from the Alexander von Humboldt Foundation through their Feodor Lynen Fellowship program. MDJ thanks the Brigham Young University Department of Physics and Astronomy for continued support of his research at CTIO. We thank Peter W. A. Roming for work done during the initial inspection of the optical imaging data, Richard Auer and Lisa Joner for editorial comments.
© European Southern Observatory (ESO) 1997
Online publication: June 30, 1998