HIPPARCOS Astrometric Observations of Symbiotic Stars

Abstract

The Hipparcos astrometric satellite has observed a number of symbiotic stars which are also known for being mapped at radio wavelengths. The radio emission generally arises from matter ejected by the binary system, which is made visible by the ionizing radiation of the system's hot component.

Hipparcos has provided the astrometric position (with milliarcsecond precision), proper motion, and distance (or a lower limit to it) of a few symbiotic stars. The most interesting results are those for CH Cygni and R Aquarii for which there is a significant displacement of the radio-continuum and optical position. The position of the radio maser emission of R Aqr is also discussed.

We shall also report the Hipparcos data for EG Andromedae, AG Draconis, AG Pegasi, and other peculiar variables.