SIMBAD references

If supernova remnants (SNRs) are the site of cosmic-ray acceleration, the associated nuclear interactions should result in an observable flux of γ-rays for the nearest SNRs. Measurements of the TeV γ-ray flux from six nearby, radio-bright SNRs have been made with the Whipple Observatory imaging air Cerenkov telescope over the period September 1993 to June 1996. No significant emission has been detected and upper limits on the >300GeV flux are reported. Three of these SNRs (IC 443, γ-Cygni and W44) are spatially coincident with low-latitude otherwise unidentified sources detected with the Energetic Gamma-Ray Experiment Telescope (EGRET). If the EGRET γ-ray fluxes result from cosmic-ray interactions then the EGRET and Whipple data are found to be collectively inconsistent with a cosmic-ray source spectrum flatter than ∼E^–2.4. The Whipple upper limits for IC 443 and γ-Cygni are also inconsistent with a priori predictions if these remnants are indeed expanding into regions where the average density of the interstellar medium is enhanced by the presence of molecular clouds. These data weaken the case for the simplest models of shock acceleration and energy dependent propagation of cosmic rays.