Elemental abundance analyses with DAO spectrograms - XVIII. The double-lined spectroscopic binary 46 Draconis
We present a study of the double-lined spectroscopic binary star 46 Draconis (46 Dra). The variations of the gamma-velocity indicate the presence of a third star which revolves around the mutual centre-of-mass of the close binary system with a period of 33.6 yr. Perhaps this third star is responsible for the observed X-ray radiation of 46 Dra. With a temperature difference of only 600 K, both components of the close binary are mercury-manganese stars. This system demonstrates the chemical evolution of two apparently metal-rich objects with the same initial composition, but with slightly different masses and resulting effective temperatures. Significant abundance differences are found for He, Al, S, Sc, Mn, Sr, Ga, Xe and Pt. These provide tests for the theories which purport to explain the anomalies.