Radio and x-ray emission from type II supernovae

The interaction of the outer parts of a supernova envelope with circumstellar matter gives rise to a high-energy density shell. The equation of motion of the shell is deduced based on the approximations that the shell is thin and that the supernova density profile is a power law in radius. The density structure in the shell is Rayleigh-Taylor unstable, and the energy density created by the instability can be a substantial fraction of the original thermal energy density. The instability can drive turbulent motions, and these may amplify the magnetic field and accelerate relativistic electrons. If the efficiency of these processes is comparable to that inferred for the Cassiopeia A supernova remnant, the observed radio luminosity from SN 1980k and SN 1979c can be reproduced. Several mechanisms are considered for the early low-frequency absorption of the radio emission. Free-free absorption by circumstellar matter is the most likely mechanism because of the steep time dependence of the radio emission and the magnitude of the absorption effect. If the circumstellar matter is smoothly distributed, it is inferred that the presupernova star of SN 1980k had a mass loss rate of about 10-5 M/sub sun/ yr-1 and that of SN 1979c about 5 x 10-5 M/sub sun/ yr-1. Clumping of the matter would reduce the estimated mass loss rates. It is also inferred that SN 1979c had more high velocity matter than did SN 1980k. Thermal X-ray emission is expected from both the shocked circumstellar medium and the shocked supernova matter. The shocked supernova matter dominates the emission in the band observed with the Einstein Observatory, and it can produce the X-ray flux observed from SN 1980k. Inverse Compton emission is another possibility for the observed X-ray emission, but it is less likely because it would decrease the number of radio-emitting electrons