MAGIC observations of the giant radio galaxy M87 in a low emission state between 2005 and 2007

Abstract

We present the results of a long M87 monitoring campaign in very high energy $\gamma$-rays with the MAGIC-I Cherenkov telescope. A total of 150 hours of data was gathered between 2005 and 2007. No flaring activity was found during that time. Nevertheless, we have found an apparently steady and weak signal at the level of $7\sigma$. We present the spectrum between 100 GeV and 2 TeV, which is consistent with a simple power law with a spectral index $-2.21\pm0.21$ and a flux normalization (at 300 GeV) of $5.4\pm1.1 \times 10^{-8} \frac{1}{\mathrm{TeV s m}^{2}}$. It complements well with the previously published Fermi spectrum, covering an energy range of four orders of magnitude without apparent change in the spectral index.