Properties and nature of Be stars XX. Binary nature and orbital elements of gamma Cas

An analysis of accurate radial Velocities (RVs) of the Be star gamma Cas fr om 295 Reticon spectrograms secured between October 1993 and May 2000 allow ed us to prewhiten the RVs for the long-term changes and to obtain the firs t orbital RV curve of this star. The orbital period is 203(d).59 and the or bit has an eccentricity of 0.26. The orbital motion is detectable even in t he published velocities, based on photographic spectra. This implies that g amma Cas is a primary component of a spectroscopic binary. The secondary ha s a mass of about 1 M., appropriate for a white dwarf or a neutron star, bu t it could also be a normal late-type dwarf. The ultimate solution of the d ispute whether the observed X-ray emission is associated with the secondary or with the primary will need further dedicated studies.