COMPARISON OF RADIO AND OPTICAL POSITIONS OF RADIO STARS

A comparison between radio and optical positions of radio stars is presented. Eighty-eight "optical minus radio" differences from 56 stars are considered. To produce this comparison with high precision, a catalogue was compiled based on the Carlsberg Meridian Catalogues Nos. 4, 5, and 6, and on a catalogue of 221 radio stars observed with the Bordeaux automatic meridian circle. Most of the radio positions are from the VLA facilities. The overall average differences lead to a tie between the radio and optical frames at the level of 30 milliarcseconds. Also the relative orientation between the two frames is examined and is found to coincide within the limit of errors. Finally, it is found that different morphological types of radio stars give rise to different levels of agreement between the radio and optical systems.