The X-ray and radio emission from SN 2002ap:: The importance of Compton scattering

The radio and X-ray observations of the Type Ic supernova SN 2002ap are modeled. We find that inverse Compton cooling by photospheric photons explains the observed steep radio spectrum, and also the X-ray flux observed by XMM-Newton. Thermal emission from the shock is insufficient to explain the X-ray flux. The radio-emitting region expands with a velocity of similar to70,000 km s(-1). From the ratio of X-ray to radio emission, we find that the energy densities of magnetic fields and relativistic electrons are close to equipartition. The mass-loss rate of the progenitor star depends on the absolute value of epsilon(B), and is given by (M) over dot approximate to 1 x 10(-8) (v(w)/1000 km s(-1))epsilon(B)(-1) M-. yr(-1).