MAGIC upper limits to the VHE gamma-ray flux of 3C 454.3 in high emission state

¹ ETH Zurich, 8093 Switzerland
² INAF National Institute for Astrophysics, 00136 Rome, Italy
³ Universidad Complutense, 28040 Madrid, Spain e-mail: Fabrizio.Tavecchio@brera.inaf.it
⁴ Technische Universität Dortmund, 44221 Dortmund, Germany
⁵ Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
⁶ Max-Planck-Institut für Physik, 80805 München, Germany
⁷ Università di Padova and INFN, 35131 Padova, Italy
⁸ Inst. de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain
⁹ University of Łódź, 90236 Lodz, Poland
¹⁰ Deutsches Elektronen-Synchrotron (DESY), 15738 Zeuthen, Germany
¹¹ Università di Siena, and INFN Pisa, 53100 Siena, Italy
¹² Universitat de Barcelona (ICC/IEEC), 08028 Barcelona, Spain
¹³ Universität Würzburg, 97074 Würzburg, Germany
¹⁴ IFAE, Edifici Cn., Campus UAB, 08193 Bellaterra, Spain
¹⁵ Depto. de Astrofisica, Universidad, 38206 La Laguna, Tenerife, Spain
¹⁶ Università di Udine, and INFN Trieste, 33100 Udine, Italy
¹⁷ Institut de Cienciès de l'Espai (IEEC-CSIC), 08193 Bellaterra, Spain
¹⁸ now at: Centro de Investigaciones Energticas, Medioambientales y Tecnolgicas (CIEMAT), Madrid, Spain
¹⁹ Inst. de Astrofísica de Andalucia (CSIC), 18080 Granada, Spain
²⁰ University of California, Davis, CA-95616-8677, USA
²¹ Tuorla Observatory, Turku University, 21500 Piikkiö, Finland
²² Inst. for Nucl. Research and Nucl. Energy, 1784 Sofia, Bulgaria
²³ Humboldt-Universität zu Berlin, 12489 Berlin, Germany
²⁴ now at: University of California, Santa Cruz, CA 95064, USA
²⁵ INAF/Osservatorio Astronomico and INFN, 34143 Trieste, Italy
²⁶ ICREA, E-08010 Barcelona, Spain
²⁷ Università di Pisa, and INFN Pisa, 56126 Pisa, Italy
²⁸ INAF/IASF–Milano, via E. Bassini 15, 20133 Milano, Italy
²⁹ INAF/IASF–Roma, via Fosso del Cavaliere 100, 00133 Roma, Italy
³⁰ Dip. di Fisica, Univ. “Tor Vergata”, via della Ricerca Scientifica 1, 00133 Roma, Italy

Received: 11 November 2008
Accepted: 6 February 2009

Abstract

Aims. We report upper limits to the very high energy flux ( GeV) of the flat spectrum radio quasar 3C 454.3 () derived by the Cherenkov telescope MAGIC during the high states of July/August and November/December 2007. We compare the upper limits derived in both time slots with the available quasi-simultaneous MeV-GeV data from the AGILE γ-ray satellite and interpret the observational results in the context of leptonic emission models.

Methods. The source was observed with the MAGIC telescope during the active phases of July-August 2007 and November-December 2007 and the data were analyzed with the MAGIC standard analysis tools. For the periods around the ends of July and November, characterized by the most complete multifrequency coverage, we constructed the spectral energy distributions using our data together with nearly simultaneous multifrequency (optical, UV, X-ray and GeV) data.

Results. Only upper limits can be derived from the MAGIC data. The upper limits, once corrected for the expected absorption by the extragalactic background light, together with nearly simultaneous multifrequency data, allow us to constrain the spectral energy distribution of 3C 454.3. The data are consistent with the model expectations based on inverse Compton scattering of the ambient photons from the broad line region by relativistic electrons, which robustly predicts a sharp cut-off above 20–30 GeV.