Supernova remnants (SNRs) have long been considered the primary sites for the acceleration of cosmic rays up to 10³ TeV. The evidence lending support to this belief is based on several strong arguments. First, supernova blast shock are one of the few galactic sites capable of sustaining the cosmic ray population against loss by escape and nuclear interactions.
Second, shock acceleration models provide a plausible mechanism for converting this explosive energy into accelerated particles with energies ~10² - 10³ TeV. Finally, recent detections of non-thermal X-ray emission in SN 1006 (Koyama et al. 1995), IC 443 (Keohane et al. 1997) and CAS A (Allen et al. 1997) suggests the presence of electrons accelerated to 10 - 100 TeV. However, observations of electrons accelerated by strong shocks only provide indirect evidence of cosmic ray production.
If SNRs do contain significant accelerated proton populations these will inevitably interact with the swept up interstellar medium in the remnants to produce pi° gamma-rays (Drury et al. 1994). One critical test of the shock acceleration model for the origin of cosmic rays is the observation of gamma-rays. VERITAS will be able to make crucial measurements in this area as good angular resolution is required to map the emission region and good energy resolution is required to differentiate contributions to the gamma-ray flux by other mechanisms such as bremsstrahlung and inverse Compton.