We thank Kent Honeycutt for providing his RoboScope data as published in Robertson et al. (1997) in electronic format. JG and AvT are supported by the German Bundesministerium für Bildung, Wissenschaft, Forschung und Technologie (BMBF/DLR) under contract No. FKZ 50 QQ 9602 3 and 50 OR 96 09 8, respectively. The ROSAT project is supported by BMBF/DLR and the Max-Planck-Society. This research has made use of the Simbad database, operated at CDS, Strasbourg, France and the Digitized Sky Survey (DSS) produced at the Space Telescope Science Institute under US Government grant NAG W-2166.
© European Southern Observatory (ESO) 1998
Online publication: September 30, 1998