Results of a Cooperative Investigation of RY Scuti

Extract

Some preliminary results are given of a cooperative investigation of the highly interesting radio object RY Set. From spectroscopic data the mass-ratio was found to be q=m₂/m₁ ≈ 3.3. An attempt to determine the helium content by model-atmosphere techniques has shown that the atmosphere of the primary component has a large helium excess; the star has every characteristic of a helium star formed by mass exchange in case B. The analysis suggests that RY Set may offer a rare chance to observe a massive system at the stage when "switching of the roles" is complete and a helium remnant with a hydrogen shell is beginning to develop the characteristics of a WR-star.