This study is based on observations made with ROSAT and with the ESA Hipparcos astrometry satellite. The ROSAT project is supported by the Bundesministerium für Bildung, Wissenschaft, Forschung und Technologie (BMBF/DLR) and the Max-Planck-Gesellschaft (MPG). P.G. acknowledges support from a CNRS-MPG cooperation. R.N. acknowledges support from DFG. We are grateful to the Tycho Consortium for accessing the Tycho catalog in advance of publication.
© European Southern Observatory (ESO) 1998
Online publication: August 6, 1998