Volume 410, Number 3, November II 2003
|Page(s)||813 - 821|
|Published online||17 November 2003|
TeV γ-ray light curve and energy spectrum of Mkn 421 during its 2001 flare as measured with HEGRA CT1*
Max-Planck-Institut für Kernphysik, Postfach 103980, 69029 Heidelberg, Germany
2 Yerevan Physics Institute, Alikhanian Br. 2, 375036 Yerevan, Armenia
3 Universität Hamburg, Institut für Experimentalphysik, Luruper Chaussee 149, 22761 Hamburg, Germany
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 Universidad Complutense, Facultad de Ciencias Físicas, Ciudad Universitaria, 28040 Madrid, Spain
8 Institut de Física d'Altes Energies, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
9 Now at Yale University, PO Box 208101, New Haven, CT 06520-8101, USA
10 Experimental Physics Dept., University of Łódź ul. Pomorska 149/153, 90-236 Łódź, Poland
Corresponding author: D. Kranich, J. Cortina, firstname.lastname@example.org;email@example.com
Accepted: 7 August 2003
In the first months of 2001 the AGN Mkn 421 showed highly variable, strong TeV activity at flux levels frequently exceeding 1 Crab. Here we present the light curve and energy spectrum of Mkn 421 as measured with the HEGRA stand alone telescope CT1. Around 30% of the data were taken under moonlight conditions. The spectrum shows a significant exponential energy cutoff at around 3.4 TeV. The results from the dark night- and the moon data are in excellent agreement with each other. A significant spectral shape variation depending on the flux level has been found. The TeV light curve is also found to be highly correlated with the X-ray light curve of the RXTE / ASM satellite, showing no significant time lag larger than 0.2 d. The derived correlation coefficient of 0.83 corresponds to a significance.
Key words: gamma rays: observations / BL Lacertae objects: individual: Mkn 421
© ESO, 2003
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