Photons and Particle Production in Cassiopeia A: Predictions from Nonlinear Diffusive Shock Acceleration

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We calculate particle spectra and continuum photon emission from the Cassiopeia A supernova remnant (SNR). The particle spectra, ion and electron, result from diffusive shock acceleration at the forward SNR shock and are determined with a nonlinear Monte Carlo calculation. The calculation self-consistently determines the shock structure under the influence of ion pressure, and includes a simple parameterized treatment of electron injection and acceleration. Our results are compared to photon observations, concentrating on the connection between the Radio and GeV-TeV gamma-ray range, and to cosmic ray ion observations. We include new upper limits from the Cherenkov Array at Themis (CAT) imaging Cherenkov telescope and the Whipple 10m gamma-ray telescope at > 400 GeV. These new limits support the suggestion (e.g. Cowsik & Sarkar 1980; Allen et. al. 1997) that energetic electrons are emitting synchrotron radiation in an extremely high magnetic field (1000 microGauss), far greater than values routinely assigned to the ISM, and help to constrain our model. The large magnetic field allows acceleration of cosmic ray ions to well above 10¹⁵ eV per nucleon in the 300 yr lifetime of Cas A.