The evolution of close binary stars: conditions in the winds

The influence of mass transfer in an OB-type binary on the colliding wind characteristics of the following phase of WR binary is examined. We look to the changes in composition and orbital characteristics. Special attention is given to the formation of WR+OB systems and the colliding wind characteristics. The mass-luminosity behaviour after mass transfer is examined. We discuss the influence of the internal state, the composition of the wind, and rotational effects on the mass gainer. Recent models of both single stars and close binaries allow us to derive the dependence of these characteristics on the initial masses of the components. From this, constraints for the wind regimes at the WR+OB stage result.