EDP Sciences
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Volume 370, Number 1, April IV 2001
Page(s) 112 - 120
Section Formation, structure and evolution of stars
DOI http://dx.doi.org/10.1051/0004-6361:20010243

A&A 370, 112-120 (2001)
DOI: 10.1051/0004-6361:20010243

Evidence for TeV gamma ray emission from Cassiopeia A

F. Aharonian1, A. Akhperjanian2, J. Barrio3, K. Bernlöhr1, H. Börst4, H. Bojahr5, O. Bolz1, J. Contreras3, J. Cortina6, S. Denninghoff6, V. Fonseca3, J. Gonzalez3, N. Götting7, G. Heinzelmann7, G. Hermann1, A. Heusler1, W. Hofmann1, D. Horns7, A. Ibarra3, C. Iserlohe5, I. Jung1, R. Kankanyan1, M. Kestel6, J. Kettler1, A. Kohnle1, A. Konopelko1, H. Kornmeyer6, D. Kranich6, H. Krawczynski1, 8, H. Lampeitl1, M. Lopez3, E. Lorenz6, F. Lucarelli3, N. Magnussen5, 9, O. Mang4, H. Meyer5, R. Mirzoyan6, A. Moralejo3, E. Ona3, L. Padilla3, M. Panter1, R. Plaga6, A. Plyasheshnikov1, 10, J. Prahl7, G. Pühlhofer1, G. Rauterberg4, A. Röhring7, W. Rhode5, G. P. Rowell1, V. Sahakian2, M. Samorski4, M. Schilling4, F. Schröder5, M. Siems4, W. Stamm4, M. Tluczykont7, H. J. Völk1, C. A. Wiedner1 and W. Wittek6

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

(Received 23 November 2000 / Accepted 23 January 2001)

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 $\gamma$-ray emission was detected at the $5 \sigma$ level, and a flux of $(5.8 \pm 1.2_{\mathrm{stat}} \pm 1.2_{\mathrm{syst}}) 10^{-9}\
{ph} {m}^{-2} {s}^{-1}$ above 1 TeV was derived. The spectral distribution is consistent with a power law with a differential spectral index of $-2.5 \pm 0.4_{\mathrm{stat}} \pm 0.1_{\mathrm{syst}}$ between 1 and 10 TeV. As this is the first report of the detection of a TeV $\gamma$-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.

Key words: ISM: supernova remnants -- ISM: individual objects: Cassiopeia A -- cosmic rays -- gamma rays: observations

Offprint request: G. Pühlhofer, Gerd.Puehlhofer@mpi-hd.mpg.de

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