Spectroscopic orbits of symbiotic stars - Preliminary results

Preliminary results of a systematic search for radial-velocity variations due to orbital motion in symbiotic stars are reported. Seventeen symbiotics were observed and radial-velocity variations in the M-giant primary were observed in nine. In eight of the stars, the photospheric absorption lines of the M giant could not be seen clearly and radial velocities could not be measured. The observed radial-velocity curves are commensurate with those expected from a group of binaries having random sin i and ≡20 km s-1 orbital velocities. The curves suggest orbital periods for seven stars. Knowledge of the orbits allows identification of those symbiotics that are close to filling their Roche lobes.