We have made use of the ROSAT Data Archive of the Max Planck Institut für Extraterrestrische Physik at Garching; of the SIMBAD database operated at Centre de Données astronomiques in Strasbourg; and of the Digitized Sky Surveys. For Hipparcos and Tycho data the CD-ROM Celestia, provided by ESA, was very helpful. We further thank Lucien Kuiper for discussions about the Maximum Likelihood algorithms, Marten van Kerkwijk for help with use of the Digitized Sky Surveys, and Dr. Asai for communication of the re-determination of the position of the ASCA source in Liller 1.
© European Southern Observatory (ESO) 2000
Online publication: June 20, 2000