High resolution radio studies of WR colliding-wind systems

High resolution radio observations with MERLIN and the VLA spatially resolve the thermal and non-thermal emission in WR147 and WR146. In both of these systems, the WR stars have massive companions. The relative positions of the radio emission and the stellar components is consistent with the non-thermal emission originating in the region where the two stellar winds in the system collide. In total eleven WR star systems are known to be non-thermal emitters, of which ten have massive companions, strongly supporting the hypothesis that nonthermal emission in WR stars requires a massive binary system. VLBI presents the exciting prospect of imaging the structure of the non-thermal plasma within the wind-collision region on AU scales, potentially having a major impact on our understanding of colliding-wind systems.