  Massive WR+O star systems produce high-temperature, shock-heated plasma where
the wind of the WR star and that of its binary companion collide - the
wind-collision region (WCR). The WCR is a source of thermal (e.g. hard X-rays)
and non-thermal (e.g. synchrotron) emission, the latter arising from electrons
and ions accelerated to relativistic energies. These colliding wind binaries
provide an excellent laboratory for the study of particle acceleration at
higher mass, photon and magnetic energy densities than exist in SNRs. Recent
models of the non-thermal emission from WR 140 have provided insight into this
process.
