Gamma-Ray excess from a stacked sample of high- and intermediate-frequency peaked blazars observed with the MAGIC telescope



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Antoranz Canales, Pedro and Barrio Uña, Juan Abel and Contreras González, José Luis and Fonseca González, Mª Victoria and Miranda Pantoja, José Miguel and Nieto, Daniel (2011) Gamma-Ray excess from a stacked sample of high- and intermediate-frequency peaked blazars observed with the MAGIC telescope. Astrophysical journal, 729 (2). ISSN 0004-637X

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Between 2004 and 2009, a sample of 28 X-ray selected high-and intermediate-frequency peaked blazars with an X-ray flux larger than 2 mu Jy at 1 keV in the redshift range from 0.018 to 0.361 was observed with the MAGIC telescope at energies above 100 GeV. Seven among them were detected and the results of these observations are discussed elsewhere. Here we concentrate on the remaining 21 blazars which were not detected during this observation campaign and present the 3 sigma (99.7%) confidence upper limits on their flux. The individual flux upper limits lie between 1.6% and 13.6% of the integral flux from the Crab Nebula. Applying a stacking method to the sample of non-detections with a total of 394.1 hr exposure time, we find evidence for an excess with a cumulative significance of 4.9 standard deviations. It is not dominated by individual objects or flares, but increases linearly with the observation time as for a constant source with an integral flux level of similar to 1.5% of that observed from the Crab Nebula above 150 GeV.

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© The American Astronomical Society. Supported by INFN Padova.We would like to thank the Instituto de Astrofisica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. 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 Polish MNiSzW Grant N N203 390834, by the YIP of the Helmholtz Gemeinschaft, and by grant DO02-353 of the Bulgarian National Science Fund.

Uncontrolled Keywords:BL-LAC Objects, Crab-Nebula, Cherenkov Telescope, Discovery, Emission, Constraints, Radiation, Model, Hess, JET.
Subjects:Sciences > Physics > Electronics
Sciences > Physics > Electricity
Sciences > Physics > Nuclear physics
ID Code:22145
Deposited On:29 Jul 2013 12:05
Last Modified:10 Dec 2018 14:58

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