Observations of Mkn 421 with the MAGIC Telescope
Abstract
The MAGIC telescope studied very high energy $\gamma$-ray emission from the blazar Markarian 421 (Mkn 421) between November 2004 and April 2005. We present a combined analysis of data samples recorded under different observational conditions,down to $\gamma$-ray energies of 100 GeV. The flux was found to be variable, between low to moderate states (0.5 -- 2 Crab units, integrated above 200 GeV). The results at higher energies were found to be consistent with previous observations. A clear correlation is observed between $\gamma$-rays and X-rays fluxes, whereas no significant correlation between $\gamma$-rays and optical data is seen. The spectral energy distribution between 100 GeV and 3 TeV shows a clear deviation from a power law, consistent with previous observations. The deviation persists after correcting for the effect of attenuation by the extragalactic background light, and most likely is source--inherent. There is a possible indication of an inverse Compton peak around 100 GeV. The spectral energy distribution of Mkn 421 can be fitted by a one-zone synchrotron self-compton model suggesting once again a leptonic origin of the very high energy $\gamma$-ray emission from this blazar.Keywords
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