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 Dr aconis (46 Dra). The variations of the gamma-velocity indicate the pre sence 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 thir d 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 chemi cal evolution of two apparently metal-rich objects with the same initi al composition, but with slightly different masses and resulting effec tive temperatures, Significant abundance differences are found for He, Al, S, Sc, Mn, Sr, Ga, Xe and Pt. These provide tests for the theorie s which purport to explain the anomalies.