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Astron. Astrophys. 349, 29-44 (1999)


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The temporal characteristics of the TeV [FORMULA]-emission from Mkn 501 in 1997

II. Results from HEGRA CT1 and CT2

F. Aharonian 1, A.G. Akhperjanian 7, J.A. Barrio 2,3, K. Bernlöhr 1,8, H. Bojahr 6, I. Calle 3, J.L. Contreras 3, J. Cortina 3,2, A. Daum 1, T. Deckers 5, S. Denninghoff 2, V. Fonseca 3, J. Gebauer 2, J.C. Gonzalez 3, G. Heinzelmann 4, M. Hemberger 1, G. Hermann 1, M. Hess 1, A. Heusler 1, W. Hofmann 1, H. Hohl 6, D. Horns 4, A. Ibarra 3, R. Kankanyan 1, M. Kestel 2, O. Kirstein 5, C. Köhler 1, H. Kornmayer 2, D. Kranich 2, H. Krawczynski 1,4, H. Lampeitl 1, A. Lindner 4, E. Lorenz 2, N. Magnussen 6, H. Meyer 6, R. Mirzoyan 2, A. Moralejo 3, L. Padilla 3, M. Panter 1, D. Petry 2,6,9, R. Plaga 2, A. Plyasheshnikov 1, J. Prahl 4, G. Pühlhofer 1, G. Rauterberg 5, C. Renault 1, W. Rhode 6, A. Röhring 4, V. Sahakian 7, M. Samorski 5, D. Schmele 4, F. Schröder 6, W. Stamm 5, B. Wiebel-Sooth 6, C. Wiedner 1, M. Willmer 5, H. Wirth 1 and W. Wittek 2

1 Max-Planck-Institut für Kernphysik, Postfach 103980, D-69029 Heidelberg, Germany
2 Max-Planck-Institut für Physik, Föhringer Ring 6, D-80805 München, Germany
3 Universidad Complutense, Facultad de Ciencias Físicas, Ciudad Universitaria, E-28040 Madrid, Spain
4 Universität Hamburg, II. Institut für Experimentalphysik, Luruper Chaussee 149, D-22761 Hamburg, Germany
5 Universität Kiel, Institut für Kernphysik, Leibnitzstrasse 15, D-24118 Kiel, Germany
6 Universität Wuppertal, Fachbereich Physik, Gaussstrasse 20, D-42097 Wuppertal, Germany
7 Yerevan Physics Institute, Alikhanian Br. 2, 375036 Yerevan, Armenia
8 Now at Forschungszentrum Karlsruhe, P.O. Box 3640, D-76021 Karlsruhe, Germany
9 Now at Universidad Autónoma de Barcelona, Institut de Física d'Altes Energies, E-08193 Bellaterra, Spain

Received 2 February 1999 / Accepted 28 June 1999

Abstract

We present the results on the TeV gamma emission from Mkn 501 in 1997 obtained with the stand-alone Cherenkov telescopes CT1 and CT2 (threshold [FORMULA] and [FORMULA] resp.) of the HEGRA collaboration. The CT1 lightcurve has the most complete coverage of all TeV observations of Mkn 501 in 1997 due to the additional observations made under the presence of moonlight. CT2 - at the time of these observations a second generation Cherenkov telescope with relatively low imaging resolution - is a well tested instrument and its 85 hours of observational data on Mkn 501 in 1997 are useful for consistency checks and provide some additional daily data points. The Mkn 501 lightcurve data show significant correlation with the RXTE ASM X-ray data consistent with no time-lag. The spectral analysis shows a steepening spectrum extending beyond 10 TeV. No change of the spectral slope with the variation of the intensity was found. The results presented here are consistent with the results from the HEGRA Cherenkov telescope system presented in part I of this paper.

Key words: gamma rays: observations – galaxies: BL Lacertae objects: individual: Mkn 501


© European Southern Observatory (ESO) 1999

Online publication: August 25, 1999

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