Thermal radio emission from early-type binary systems

We investigate the effect of binarity on the thermal radio emission from early-type binary systems, finding that the presence of a companion with a substantial wind will tend to increase the expected thermal radio emission as compared toa single star with the same wind characteristics as the primary. While this is not surprising, the degree to which the radio emission is altered is a sensitive function of the wind parameters, and in particular the momentum ratio of the two winds. The hot gas created by the wind collision plays a substantial role in the excess radio emission. In the case of comparable winds the thermal radio emission can be increased by 50 per cent or more. In previous determinations of mass-loss rates of the components of binary systems via thermal radio emission, the effects of binarity have not been included in any rigorous way. This means that the mass-loss rates of some early-type stars in binary systems may have been systematically overestimated. In the light of our calculations, we discuss methods of more accurately estimating the mass-loss rates of both components of binary systems.