Discovery of VHE γ-rays from the blazar 1ES 1215+303 with the MAGIC telescopes and simultaneous multi-wavelength observations

¹ IFAE, Edifici Cn., Campus UAB, 08193 Bellaterra, Spain
² Universidad Complutense, 28040 Madrid, Spain
³ INAF National Institute for Astrophysics, 00136 Rome, Italy
⁴ Università di Siena, and INFN Pisa, 53100 Siena, Italy
⁵ Technische Universität Dortmund, 44221 Dortmund, Germany
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 Depto. de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Spain
¹¹ Deutsches Elektronen-Synchrotron (DESY), 15738 Zeuthen, Germany
¹² ETH Zurich, 8093 Zurich, Switzerland
¹³ Universität Würzburg, 97074 Würzburg, Germany
¹⁴ Universitat de Barcelona (ICC/IEEC), 08028 Barcelona, Spain
¹⁵ Università di Udine, and INFN Trieste, 33100 Udine, Italy
¹⁶ Institut de Ciències de l’Espai (IEEC-CSIC), 08193 Bellaterra, Spain
¹⁷ Inst. de Astrofísica de Andalucía (CSIC), 18080 Granada, Spain
¹⁸ Croatian MAGIC Consortium, Rudjer Boskovic Institute, University of Rijeka and University of Split, 10000 Zagreb, Croatia
¹⁹ Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
²⁰ Tuorla Observatory, University of Turku, 21500 Piikkiö, Finland
²¹ Inst. for Nucl. Research and Nucl. Energy, 1784 Sofia, Bulgaria
²² Japanese MAGIC Consortium, Division of Physics and Astronomy, Kyoto University, Japan
²³ INAF/Osservatorio Astronomico and INFN, 34143 Trieste, Italy
²⁴ Università dell’Insubria, Como, 22100 Como, Italy
²⁵ Università di Pisa, and INFN Pisa, 56126 Pisa, Italy
²⁶ ICREA, 08010 Barcelona, Spain
²⁷ Now at: Écolepolytechnique fédérale de Lausanne (EPFL), Lausanne, Switzerland
²⁸ Supported by INFN Padova Italia
²⁹ Now at: Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), Madrid, Spain
³⁰ Now at: KIPAC, SLAC National Accelerator Laboratory, USA
³¹ Now at: Institut für Experimentalphysik, University of Hamburg, Germany
³² Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Finland
³³ Aalto University Metsähovi Radio Observatory, Metsähovintie 114, 02540, Kylmälä, Finland
³⁴ Department of Physics, Stockholm University, AlbaNova, 106 91 Stockholm, Sweden
³⁵ The Oskar Klein Centre for Cosmoparticle Physics, AlbaNova, 106 91 Stockholm, Sweden
³⁶ Department of Astronomy, Stockholm University, 106 91 Stockholm, Sweden
Corresponding authors: jbecerra@iac.es, elilin@utu.fi, colin@mppmu.mpg.de, colin@mppmu.mpg.de, saverio.lombardi@pd.infn.it, jsitarek@ifae.es

Received: 29 February 2012
Accepted: 22 May 2012

Abstract

Context. We present the discovery of very high energy (VHE, E > 100 GeV) γ-ray emission from the BL Lac object 1ES 1215+303 by the MAGIC telescopes and simultaneous multi-wavelength data in a broad energy range from radio to γ-rays.

Aims. We study the VHE γ-ray emission from 1ES 1215+303 and its relation to the emissions in other wavelengths.

Methods. Triggered by an optical outburst, MAGIC observed the source in 2011 January − February for 20.3 h. The target was monitored in the optical R-band by the KVA telescope that also performed optical polarization measurements. We triggered target of opportunity observations with the Swift satellite and obtained simultaneous and quasi-simultaneous data from the Fermi Large Area Telescope and from the Metsähovi radio telescope. We also present the analysis of older MAGIC data taken in 2010.

Results. The MAGIC observations of 1ES 1215+303 carried out in 2011 January − February resulted in the first detection of the source at VHE with a statistical significance of 9.4σ. Simultaneously, the source was observed in a high optical and X-ray state. In 2010 the source was observed in a lower state in optical, X-ray, and VHE, while the GeV γ-ray flux and the radio flux were comparable in 2010 and 2011. The spectral energy distribution obtained with the 2011 data can be modeled with a simple one zone SSC model, but it requires extreme values for the Doppler factor or the electron energy distribution.