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oai:docta.ucm.es:20.500.14352/509092024-09-05T17:49:08Zcom_20.500.14352_14col_20.500.14352_15

00925njm 22002777a 4500 dc Antoranz Canales, Pedro author Barrio Uña, Juan Abel author Contreras González, José Luis author Fonseca González, María Victoria author López Moya, Marcos author Miranda Pantoja, José Miguel author 2007-07-01 The MAGIC telescope took data of very high energy gamma-ray emission from the blazar Markarian 421 ( Mrk 421) between 2004 November and 2005 April. 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 vary between 0.5 and 2 crab ( integrated above 200 GeV), considered a low state when compared to known data. Although the flux varied day by day, no short-term variability was observed, although there is some indication that not all nights show an equally quiescent state. The results at higher energies were found to be consistent with previous observations. A clear correlation is observed between gamma-ray and X-ray fluxes, whereas no significant correlation between gamma-ray and optical data is seen. The spectral energy distribution between 100 GeVand 3 TeV shows a clear deviation from a power law, more clearly and at lower flux than previous observations at higher energies. The deviation persists after correcting for the effect of attenuation by the extragalactic background light, and most likely is source- inherent. There is a rather clear indication of an inverse Compton peak around 100 GeV. The spectral energy distribution of Mrk 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. 0004-637X 10.1086/518221 https://hdl.handle.net/20.500.14352/50909 http://dx.doi.org/10.1086/518221 http://iopscience.iop.org http://arxiv.org/abs/astro-ph/0603478 Observations of Markarian 421 with the MAGIC telescope