First multi-wavelength campaign on the gamma-ray-loud active galaxy IC 310

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 Padova and INFN, 35131 Padova, Italy
⁵ Croatian MAGIC Consortium, Rudjer Boskovic Institute, University of Rijeka, University of Split – FESB, University of Zagreb – FER, University of Osijek, Croatia
⁶ Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Salt Lake, Sector-1, 700064 Kolkata, India
⁷ Max-Planck-Institut für Physik, 80805 München, Germany
⁸ Universidad Complutense, 28040 Madrid, Spain
⁹ Inst. de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain
¹⁰ Universidad de La Laguna, Dpto. Astrofísica, 38206 La Laguna, Tenerife, Spain
¹¹ University of Łódź, 90236 Lodz, Poland
¹² Deutsches Elektronen-Synchrotron (DESY), 15738 Zeuthen, Germany
¹³ Institut de Fisica d’Altes Energies (IFAE), The Barcelona Institute of Science and Technology, Campus UAB, 08193 Bellaterra ( Barcelona), Spain
¹⁴ Università di Siena, and INFN Pisa, 53100 Siena, Italy
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, 90014 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, 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, 606-8501 Kyoto, 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 and Department of Physics and Department of Astronomy, University of Maryland, College Park, MD 20742, USA
²⁸ Humboldt University of Berlin, Institut für Physik Newtonstr. 15, 12489 Berlin, Germany
²⁹ Also at University of Trieste, 34127 Trieste, Italy
³⁰ Now at École polytechnique fédérale de Lausanne (EPFL), 1085 Lausanne, Switzerland
³¹ Now at Finnish Centre for Astronomy with ESO (FINCA), 21500 Turku, Finland
³² Also at INAF-Trieste and Dept. of Physics & Astronomy, University of Bologna, 40126 Bologna, Italy
³³ GRAPPA & Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
³⁴ ASTRON, the Netherlands Institute for Radio Astronomy, PO Box 2, 7990 AA Dwingeloo, The Netherlands
³⁵ Dr. Remeis Sternwarte & ECAP, Universität Erlangen-Nürnberg, Sternwartstrasse 7, 96049 Bamberg, Germany
³⁶ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
³⁷ Departament d’Astronomia i Astrofísica, Universitat de València, C/Dr. Moliner 50, 46100 Burjassot, València, Spain
³⁸ Observatori Astronòmic, Universitat de València, C/Catedrático José Beltrán 2, 46980 Paterna, València, Spain
³⁹ NASA, Goddard Space Flight Center, Greenbelt, MD 20771, USA
⁴⁰ Department of Astrophysics/IMAPP, Radboud University Nijmegen, PO Box 9010, 6500 GL Nijmegen, The Netherlands
⁴¹ ESA/ESTEC, Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands
⁴² Aalto University Metsähovi Radio Observatory, Metsähovintie 114, 02540 Kylmälä, Finland
⁴³ Aalto University Department of Radio Science and Engineering, PO Box 13000, 00076 Aalto, Finland
⁴⁴ Department of Physics and Department of Astronomy, University of Maryland, College Park, MD 20742, USA
⁴⁵ Landessternwarte, Universität Heidelberg, Königstuhl, 69117 Heidelberg, Germany

^⋆ Corresponding author: D. Eisenacher Glawion, e-mail: dglawion@lsw.uni-heidelberg.de

Received: 23 December 2016
Accepted: 21 March 2017

Abstract

Context. The extragalactic very-high-energy gamma-ray sky is rich in blazars. These are jetted active galactic nuclei that are viewed at a small angle to the line-of-sight. Only a handful of objects viewed at a larger angle are so far known to emit above 100 GeV. Multi-wavelength studies of such objects up to the highest energies provide new insights into the particle and radiation processes of active galactic nuclei.

Aims. We aim to report the results from the first multi-wavelength campaign observing the TeV detected nucleus of the active galaxy IC 310, whose jet is observed at a moderate viewing angle of 10°−20°.

Methods. The multi-instrument campaign was conducted between 2012 November and 2013 January, and involved observations with MAGIC, Fermi, INTEGRAL, Swift, OVRO, MOJAVE and EVN. These observations were complemented with archival data from the AllWISE and 2MASS catalogs. A one-zone synchrotron self-Compton model was applied to describe the broadband spectral energy distribution.

Results. IC 310 showed an extraordinary TeV flare at the beginning of the campaign, followed by a low, but still detectable TeV flux. Compared to previous measurements in this energy range, the spectral shape was found to be steeper during the low emission state. Simultaneous observations in the soft X-ray band showed an enhanced energy flux state and a harder-when-brighter spectral shape behavior. No strong correlated flux variability was found in other frequency regimes. The broadband spectral energy distribution obtained from these observations supports the hypothesis of a double-hump structure.

Conclusions. The harder-when-brighter trend in the X-ray and VHE emission, observed for the first time during this campaign, is consistent with the behavior expected from a synchrotron self-Compton scenario. The contemporaneous broadband spectral energy distribution is well described with a one-zone synchrotron self-Compton model using parameters that are comparable to those found for other gamma-ray-emitting misaligned blazars.