Observations of the shell-type SNR Cassiopeia A at TeV energies with VERITAS

We report on observations of very high-energy gamma raysfrom the shell-type supernova remnant CassiopeiaA with the VERITAS stereoscopic array of four imaging atmospheric Cherenkov telescopes in Arizona. The total exposure time for these observations is 22 hours, accumulated between September and November of 2007. The gamma-raysource associated with the SNR CassiopeiaA was detected above 200 GeV with a statistical significance of 8.3 s.d. The estimated integral flux for this gamma-raysource is about 3% of the Crab-Nebulaflux. The photon spectrum is compatible with a power law dN/dE ~ E^(-Gamma) with an index Gamma = 2.61 +/- 0.24(stat) +/- 0.2(sys). The data are consistent with a point-like source. We provide a detailed description of the analysis results, and discuss physical mechanisms that may be responsible for the observed gamma-rayemission.