HIPPARCOS ASTROMETRY AND RADIO MAPPING OF PECULIAR BINARY SYSTEMS R. Viotti

We report Hipparcos observations of a number of binary systems, symbiotic stars and bright long period binaries, which are known also for being radio sources. In these systems the matter ejected from the component(s) is generally made visible in the radio by the ionizing radiation of the hot component of the system. Shocks from wind collision may also play a role, especially in those objects which are known for being X--ray sources. Hipparcos has shown that in most cases the astrometric position is very close to the core of the radio source. In particular, in the case of multiple radio sources, the Hipparcos position is close to the central source of CH Cyg, to the brightest source of AG Dra, and to the SiO maser emission of R Aqr. Key words: radio emission; space astrometry; symbiotic stars; VV Cep stars. 1. INTRODUCTION Symbiotic stars are long period interactive binary systems, characterized by a late type giant primary (of K or M type, or a Mira variable), and a misterious compact ..