Wolf-Rayet stars in the Magellanic clouds. VI: Spectroscopic orbits of WC binaries and implications for W-R evolution

In addition to obtaining spectroscopic orbits for the three largest WC + O binary systems in the LMC, an improved orbit has been determined for the SMC's bright WO + O system. The very short periods noted in two of the LMC binary systems indicate that orbital angular momentum must have been lost from the system, in addition to the momentum associated with the extreme mass loss of the present WC components, although this need not have occurred through mass transfer. A continuous decrease of mass ratio is noted with WC subtype; this implies that WC stars can evolve from WN stars and from cooler to hotter subtypes within the WC sequence. 38 refs.