Evidence for ellipsoidal variations of the Be star binary HD 50123.

Abstract

On the basis of 8 years of photoelectric monitoring in the Stroemgren system we were able to establish that HD50123 is an interacting binary consisting of a B6Ve primary and an early K giant secondary which fills its Roche lobe. The orbital period is 28.601days. The secondary contributes considerably to the flux in the y and b bands, in which the double-sinusoidal light curve typical for ellipsoidal variables is seen. A few published radial velocities of the primary are consistent with a semiamplitude of K_1_=25+/-6km/s, and a mass function f(M)=0.046+/-0.026M_sun_. Preliminary estimates of the stellar masses give 5 and 1.5M_sun_, respectively, for primary and secondary. Some implications for the binary interpretation of Be stars, as well as for the period distribution of ellipsoidal variables, are discussed.