Colliding winds in binaries: Observations

Colliding winds in binaries are discussed mainly from an observational point of view. Collisions are especially energetic in the case of hot, luminous stars, which drive strong, fast winds. Emphasis is therefore devoted to binaries containing Wolf-Rayet stars. The subject is divided up into (1) continuum radiation (X-ray and non-thermal radio from the hot bow shock head, IR from dust formed in some WC + O binaries far downstream in the collision shock cone) arid (2) line radiation (optical and UV, both from various regions downstream from the bow shock head). The latter is particularly useful in providing constraints on the velocity field and hence ultimately the geometry of the wind collision and the binary system itself.