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

TL;DR

This paper reports the detection of very high-energy gamma rays from the supernova remnant Cassiopeia A using VERITAS, providing insights into its emission mechanisms and spectral properties.

Contribution

First detection of TeV gamma-ray emission from Cassiopeia A with detailed spectral analysis and discussion of possible physical origins.

Findings

Gamma-ray emission detected above 200 GeV with 8.3 sigma significance.

The gamma-ray flux is about 3% of the Crab Nebula flux.

The photon spectrum follows a power law with index ~2.61.

Abstract

We report on observations of very high-energy gamma rays from the shell-type supernova remnant Cassiopeia A 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-ray source associated with the SNR Cassiopeia A was detected above 200 GeV with a statistical significance of 8.3 s.d. The estimated integral flux for this gamma-ray source is about 3% of the Crab-Nebula flux. 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-ray emission.