Volume 595, November 2016
|Number of page(s)||11|
|Published online||04 November 2016|
Detection of very high energy gamma-ray emission from the gravitationally lensed blazar QSO B0218+357 with the MAGIC telescopes
1 ETH Zurich, 8093 Zurich, Switzerland
2 Università di Udine, and INFN Trieste, 33100 Udine, Italy
3 INAF National Institute for Astrophysics, 00136 Rome, Italy
4 Università di Siena, and INFN Pisa, 53100 Siena, Italy
5 Università di Padova and INFN, 35131 Padova, Italy
6 Croatian MAGIC Consortium, Rudjer Boskovic Institute, University of Rijeka, University of Split and University of Zagreb, Croatia
7 Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Salt Lake, Sector-1, 700064 Kolkata, India
8 Max-Planck-Institut für Physik, 80805 München, Germany
9 Universidad Complutense, 28040 Madrid, Spain
10 Inst. de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain
11 Universidad de La Laguna, Dpto. Astrofísica, 38206 La Laguna, Tenerife, Spain
12 University of Łódź, 90236 Lodz, Poland
13 Deutsches Elektronen-Synchrotron (DESY), 15738 Zeuthen, Germany
14 Institut de Fisica d’Altes Energies (IFAE), The Barcelona Institute of Science and Technology, Campus UAB, 08193 Bellaterra ( Barcelona), Spain
15 Universität Würzburg, 97074 Würzburg, Germany
16 Institute for Space Sciences (CSIC/IEEC), 08193 Barcelona, Spain
17 Technische Universität Dortmund, 44221 Dortmund, Germany
18 Finnish MAGIC Consortium, Tuorla Observatory, University of Turku and Astronomy Division, University of Oulu, Oulu, Finland
19 Unitat de Física de les Radiacions, Departament de Física, and CERES-IEEC, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
20 Universitat de Barcelona, ICC, IEEC-UB, 08028 Barcelona, Spain
21 Japanese MAGIC Consortium, ICRR, The University of Tokyo, Department of Physics and Hakubi Center, Kyoto University, Tokai University, The University of Tokushima, KEK, Japan
22 Inst. for Nucl. Research and Nucl. Energy, 1784 Sofia, Bulgaria
23 Università di Pisa, and INFN Pisa, 56126 Pisa, Italy
24 ICREA and Institute for Space Sciences (CSIC/IEEC), 08193 Barcelona, Spain
25 Also at the Department of Physics of Kyoto University, Japan
26 Now at Centro Brasileiro de Pesquisas Físicas (CBPF/MCTI), R. Dr. Xavier Sigaud, 150 – Urca, 22290-180 Rio de Janeiro – RJ, Brazil
27 Now at NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
28 Now at Department of Physics and Department of Astronomy, University of Maryland, College Park, MD 20742, USA
29 Humboldt University of Berlin, Institut für Physik Newtonstr. 15, 12489 Berlin Germany
30 Also at University of Trieste
31 Now at École polytechnique fédérale de Lausanne (EPFL), Lausanne, Switzerland
32 Now at Max-Planck-Institut fur Kernphysik, PO Box 103980, 69029 Heidelberg, Germany
33 Also at Japanese MAGIC Consortium
34 Now at Finnish Centre for Astronomy with ESO (FINCA), Turku, Finland
35 Also at INAF – Trieste and Dept. of Physics & Astronomy, University of Bologna, Italy
36 Also at ISDC – Science Data Center for Astrophysics, 1290 Versoix, Geneva
Received: 2 August 2016
Accepted: 31 August 2016
Context. QSO B0218+357 is a gravitationally lensed blazar located at a redshift of 0.944. The gravitational lensing splits the emitted radiation into two components that are spatially indistinguishable by gamma-ray instruments, but separated by a 10–12 day delay. In July 2014, QSO B0218+357 experienced a violent flare observed by the Fermi-LAT and followed by the MAGIC telescopes.
Aims. The spectral energy distribution of QSO B0218+357 can give information on the energetics of z ~ 1 very high energy gamma-ray sources. Moreover the gamma-ray emission can also be used as a probe of the extragalactic background light at z ~ 1.
Methods. MAGIC performed observations of QSO B0218+357 during the expected arrival time of the delayed component of the emission. The MAGIC and Fermi-LAT observations were accompanied by quasi-simultaneous optical data from the KVA telescope and X-ray observations by Swift-XRT. We construct a multiwavelength spectral energy distribution of QSO B0218+357 and use it to model the source. The GeV and sub-TeV data obtained by Fermi-LAT and MAGIC are used to set constraints on the extragalactic background light.
Results. Very high energy gamma-ray emission was detected from the direction of QSO B0218+357 by the MAGIC telescopes during the expected time of arrival of the trailing component of the flare, making it the farthest very high energy gamma-ray source detected to date. The observed emission spans the energy range from 65 to 175 GeV. The combined MAGIC and Fermi-LAT spectral energy distribution of QSO B0218+357 is consistent with current extragalactic background light models. The broadband emission can be modeled in the framework of a two-zone external Compton scenario, where the GeV emission comes from an emission region in the jet, located outside the broad line region.
Key words: gamma rays: galaxies / gravitational lensing: strong / galaxies: jets / radiation mechanisms: non-thermal / quasars: individual: QSO B0218+357
© ESO, 2016
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