Evidence for TeV gamma ray emission from Cassiopeia A

¹ Max-Planck-Institut für Kernphysik, Postfach 103980, 69029 Heidelberg, Germany
² Yerevan Physics Institute, Alikhanian Br. 2, 375036 Yerevan, Armenia
³ Universidad Complutense, Facultad de Ciencias Físicas, Ciudad Universitaria, 28040 Madrid, Spain
⁴ Universität Kiel, Institut für Experimentelle und Angewandte Physik, Leibnizstraße 15-19, 24118 Kiel, Germany
⁵ Universität Wuppertal, Fachbereich Physik, Gaußstr. 20, 42097 Wuppertal, Germany
⁶ Max-Planck-Institut für Physik, Föhringer Ring 6, 80805 München, Germany
⁷ Universität Hamburg, II. Institut für Experimentalphysik, Luruper Chaussee 149, 22761 Hamburg, Germany
⁸ Now at Yale University, PO Box 208101, New Haven, CT 06520-8101, USA
⁹ Now at IFAE, Unversitat Autònoma de Barcelona, Spain
¹⁰ On leave from Altai State University, Dimitrov Street 66, 656099 Barnaul, Russia

Corresponding author: G. Pühlhofer, Gerd.Puehlhofer@mpi-hd.mpg.de

Received: 23 November 2000
Accepted: 23 January 2001

Abstract

232 hours of data were accumulated from 1997 to 1999, using the HEGRA Stereoscopic Cherenkov Telescope System to observe the supernova remnant Cassiopeia A. TeV γ-ray emission was detected at the level, and a flux of above 1 TeV was derived. The spectral distribution is consistent with a power law with a differential spectral index of between 1 and 10 TeV. As this is the first report of the detection of a TeV γ-ray source on the "centi-Crab"scale, we present the analysis in some detail. Implications for the acceleration of cosmic rays depend on the details of the source modeling. We discuss some important aspects in this paper.