Author/Authors :
Girma، M. نويسنده , , Akhperjanian، A. نويسنده , , Beilicke، M. نويسنده , , Bojahr، H. نويسنده , , Bolz، O. نويسنده , , Coarasa، T. نويسنده , , Denninghoff، S. نويسنده , , F. Aharonian، نويسنده , , K. Bernlohr، نويسنده , , H. G. Borst، نويسنده , , J. L. Contreras، نويسنده , , J. Cortina، نويسنده , , V. Fonseca، نويسنده ,
Abstract :
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 nightand 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 5.2(sigma) significance.
