In this catalogue the stellar data and keys to data retrieval are supplied of the presently 66 cardinal radio stars that have the potential of connecting optical and radio celestial reference frames. The catalogue is thought to be an aid of studies on linking frames, and of repeated observations of the radio stars of this core in view of the maintenance of the link. A survey of supplementary radio star candidates is urged for enlarging the core in order to obtain better uniformity of the spatial distribution, the distribution of spectral types and apparent magnitudes. More diversification of the types of radio stars will diminish the risk of biases.
Acknowledgements
This research has made use of the SIMBAD data base, operated at CDS, Strasbourg, France. C.d.V. wants to thank the Bundesministerium für Bildung, Wissenschaft, Forschung und Technologie (BMBF) for financial support under grant No.50008810 (Hipparcos).