Further studies of particle acceleration in cassiopeia A

We have further investigated models for statistical particle acceleration in the supernova remnant Cas A. Simple (three-parameter) models involving continuous second order Fermi acceleration and variable relativistic particle injection can reproduce the observed radio properties of Cas A, including the low-frequency flux anomaly first noted by Erickson and Perley. Models dominated by adiabatic expansion losses are preferable to those dominated by particle escape. The gain time determined from these models agrees well with that predicted from the hydrodynamic situation in Cas A. A model predicting the high-frequency nonthermal spectrum of Cas A indicates that the spectrum turns down in the optical regime due to synchrotron losses. The maximum relativistic particle energy content of Cas A was probably about several times 1049-1050 ergs, which can be compared with an estimated initial kinetic energy in the range 0.24 to 1.0 x 1052 ergs. If relativistic particles can escape from Cas A, their spectra will have certain characteristics: the electron spectrum will have a turnover due to synchrotron losses and the proton spectrum will have a cutoff due to the particle gyroradii becoming larger than the sizes of the magnetic scattering centers. The observed bend in the galactic cosmic ray spectrum could be due to energy losses within the source remnant itself instead of losses incurred during propagation through the Galaxy. We also comment on other models for the relativistic electron content of Cas A