OBSERVATIONS OF THE SHELL-TYPE SUPERNOVA REMNANT CASSIOPEIA A AT TeV ENERGIES WITH VERITAS

Abstract

We report on observations of very high-energy gamma rays from the shell-type\nsupernova remnant Cassiopeia A with the VERITAS stereoscopic array of four\nimaging atmospheric Cherenkov telescopes in Arizona. The total exposure time\nfor these observations is 22 hours, accumulated between September and November\nof 2007. The gamma-ray source associated with the SNR Cassiopeia A was detected\nabove 200 GeV with a statistical significance of 8.3 s.d. The estimated\nintegral flux for this gamma-ray source is about 3% of the Crab-Nebula flux.\nThe photon spectrum is compatible with a power law dN/dE ~ E^(-Gamma) with an\nindex Gamma = 2.61 +/- 0.24(stat) +/- 0.2(sys). The data are consistent with a\npoint-like source. We provide a detailed description of the analysis results,\nand discuss physical mechanisms that may be responsible for the observed\ngamma-ray emission.\n