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F.A. Aharonian, H. Krawczynski, G. Puehlhofer, G.P. Rowell (MPI-K, Heidelberg), HEGRA Collaboration
The HEGRA collaboration operates a system of 5 Imaging Atmospheric Cherenkov Telescopes for gamma-ray astronomy in the energy range above 500 GeV. Based on the method of stereoscopic air shower observations the system achieves an energy flux sensitivity at 1 TeV of approximately 10-12 ergs/cm2 sec for 100 hour of observation time as well as angular and energy resolutions of 0.1 degree and <20%, respectively. In this contribution we summarize and discuss recent results concerning the observations of Supernova Remnants (SNRs). Very deep observations of the SNR Cassiopeia A (232 h) revealed evidence at the 5 \sigma confidence level that the source emits TeV gamma-rays, indicating that the source accelerates particles up to energies of at least several TeV. Another important result in this field is the non-detection of TeV gamma-rays from Tycho. The flux upper limit based on 65 h observation time seriously constrains the parameter space of diffusive shock acceleration models of cosmic rays.