engleski

MAGIC observations of the giant radio galaxy M 87 in a low-emission state between 2005 and 2007

We present the results of a long M 87 monitoring campaign in very high energy gamma- rays with the MAGIC-I Cherenkov telescope. We aim to model the persistent non-thermal jet emission by monitoring and characterizing the very high energy gamma-ray emission of M 87 during a low state. A total of 150 h of data were taken between 2005 and 2007 with the single MAGIC-I telescope, out of which 128.6 h survived the data quality selection. We also collected data in the X-ray and Fermi-LAT bands from the literature (partially contemporaneous). No flaring activity was found during the campaign. The source was found to be in a persistent low-emission state, which was at a confidence level of 7 sigma. We present the spectrum between 100 GeV and 2 TeV, which is consistent with a simple power law with a photon index GAMMA = 2.21 ± 0.21 and a flux normalization at 300 GeV of (7.7 +- 1.3) x 10^-8 TeV^-1 s^-1 m^-2. The extrapolation of the MAGIC spectrum into the GeV energy range matches the previously published Fermi-LAT spectrum well, covering a combined energy range of four orders of magnitude with the same spectral index. We model the broad band energy spectrum with a spine layer model, which can satisfactorily describe our data.

galaxies: individual: M 87; gamma rays: galaxies

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