Detection of very high energy gamma-ray emission from NGC 1275 by the MAGIC telescopes

6 páginas, 5 figuras.-- Accepted on ApJ Letters as part of the special Sunrise issue.-- MAGIC Collaboration: et al.We report on the detection with the MAGIC telescopes of very high energy -rays from IC 310, a head-tail radio galaxy in the Perseus galaxy cluster, observed during the interval November 2008 to February 2010. The Fermi satellite has also detected this galaxy. The source is detected by MAGIC at a high statistical significance of 7.6 in 20.6 hr of stereo data. The observed spectral energy distribution is flat with a differential spectral index of −2.00 ± 0.14. The mean flux above 300 GeV, between October 2009 and February 2010, (3.1±0.5)×10−12 cm−2 s−1, corresponds to (2.5±0.4)% of Crab Nebula units. Only an upper limit, of 1.9% of Crab Nebula units above 300 GeV, was obtained with the 2008 data. This, together with strong hints (> 3 ) of flares in the middle of October and November 2009, implies that the emission is variable. The MAGIC results favour a scenario with the very high energy emission originating from the inner jet close to the central engine. More complicated models than a simple one-zone SSC scenario, e.g. multi-zone SSC, external Compton or hadronic, may be required to explain the very flat spectrum and its extension over more than three orders of magnitude in energy.The support of the German BMBF and MPG, the Italian INFN, the Swiss National Fund SNF, and the Spanish MICINN is gratefully acknowledged. This work was also supported by the Marie Curie program, by the CPAN CSD2007-00042 and MultiDark CSD2009-00064 projects of the Spanish Consolider-Ingenio 2010 programme, by grant DO02-353 of the Bulgarian NSF, by grant 127740 of the Academy of Finland, by the YIP of the Helmholtz Gemeinschaft, by the DFG Cluster of Excellence “Ori- gin and Structure of the Universe”, and by the Polish MNiSzW Grant N N203 390834.Peer reviewe