Particle acceleration in colliding wind binary systems

We present a new model for the particle acceleration believed to power the synchrotron emission observed in some Wolf-Rayet binaries. Particles are accelerated in a current sheet formed when the magnetic fields carried in the winds of the two stars are forced together as the winds collide. By modelling this current sheet we are able to determine, for a given magnetic field strength at the stellar surface, the speed to which particles will be accelerated over a given distance. We show that the observed GHz emission could be produced in systems with surface field strengths of only a few Gauss, in contrast to models of shock acceleration which require surface fields of some hundreds to thousands of Gauss.