Composite spectra Paper 9: HR 5983

HR 5983 is a sixth-magnitude composite-spectrum binary system. It has a cir cular orbit and a period of 108 d. We separate the component spectra and sh ow that they are of types similar to G6 IIIa and A2.5 IV, with a mass ratio (giant:dwarf) of similar to 1.04. We find that the secondary has a mass cl ose to 2.6 M. and has already evolved somewhat from the main sequence, and that the primary appears to have reached the helium-burning 'blue loop' sta ge and is in synchronous rotation. The system resembles Capella in several respects, and may represent an earlier phase in the evolution of the latter .