MAGIC search for VHE γ-ray emission from AE Aquarii in a multiwavelength context

¹ IFAE, Campus UAB, 08193 Bellaterra, Spain
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 Croatian MAGIC Consortium, Rudjer Boskovic Institute, University of Rijeka and University of Split, 10000 Zagreb, Croatia
⁶ Max-Planck-Institut für Physik, 80805 München, Germany
⁷ Universidad Complutense, 28040 Madrid, Spain
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 ETH Zurich, 8093 Zurich, Switzerland
¹² Universität Würzburg, 97074 Würzburg, Germany
¹³ Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, 28040 Madrid, Spain
¹⁴ Institute of Space Sciences, 08193 Barcelona, Spain
¹⁵ Technische Universität Dortmund, 44221 Dortmund, Germany
¹⁶ Università di Padova and INFN, 35131 Padova, Italy
¹⁷ Unitat de Física de les Radiacions, Departament de Física, and CERES-IEEC, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
¹⁸ Universitat de Barcelona, ICC, IEEC-UB, 08028 Barcelona, Spain
¹⁹ Japanese MAGIC Consortium, Division of Physics and Astronomy, 606-8501 Kyoto University, Japan
²⁰ Finnish MAGIC Consortium, Tuorla Observatory, University of Turku and Department of Physics, University of Oulu, 900147 Oulu, Finland
²¹ Inst. for Nucl. Research and Nucl. Energy, 1784 Sofia, Bulgaria
²² Università di Pisa, and INFN Pisa, 56126 Pisa, Italy
²³ ICREA and Institute of Space Sciences, 08193 Barcelona, Spain
²⁴ Università dell’Insubria and INFN Milano Bicocca, 22100 Como, Italy
²⁵ 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
²⁶ Now at: École polytechnique fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
²⁷ Now at: Institut für Astro- und Teilchenphysik, Leopold-Franzens-Universität Innsbruck, 6020 Innsbruck, Austria
²⁸ Now at: Finnish Centre for Astronomy with ESO (FINCA), Turku, University of Turku 21500 Piikkiö, Finland
²⁹ Now at: Astrophysics Science Division, Bhabha Atomic Research Centre, 400085 Mumbai, India
³⁰ Also at: INAF-Trieste, 34131 Trieste, Italy
³¹ Now at: School of Chemistry & Physics, University of Adelaide, 5005 Adelaide, Australia
³² Now at: Stockholm University, Oskar Klein Centre for Cosmoparticle Physics, 106 91 Stockholm, Sweden
³³ Astronomical Observatory Belgrade, 11060 Belgrade, Serbia
³⁴ Physics Department, College of Science, Sultan Qaboos University, PO Box 36, PC-123 Muscat, Oman
³⁵ Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, CA 95125, USA
³⁶ Physics Department, University of Crete, PO Box 2208, 71003, Heraklion, Greece
³⁷ Inst. de Astrofísica de Andalucía (CSIC), 18080 Granada, Spain

Received: 24 April 2014
Accepted: 18 June 2014

Abstract

Context. It has been claimed that the nova-like cataclysmic variable AE Aquarii (AE Aqr) is a very-high-energy (VHE, E> 100 GeV) source both on observational and theoretical grounds.

Aims. We search for VHE γ-ray emission from AE Aqr during different states of the source at several wavelengths to confirm or rule out previous claims of detection of γ-ray emission from this object.

Methods. We report on observations of AE Aqr performed by MAGIC. The source was observed during 12 h as part of a multiwavelength campaign carried out between May and June 2012 covering the optical, X-ray, and γ-ray ranges. Besides MAGIC, the other facilities involved were the KVA, Skinakas, and Vidojevica telescopes in the optical and Swift in X-rays. We calculated integral upper limits coincident with different states of the source in the optical. We computed upper limits to the pulsed emission limiting the signal region to 30% of the phaseogram and we also searched for pulsed emission at different frequencies applying the Rayleigh test.

Results. AE Aqr was not detected at VHEs during the multiwavelength campaign. We establish integral upper limits at the 95% confidence level for the steady emission assuming the differential flux proportional to a power-law function dφ/ dE ∝ E^{− Γ}, with a Crab-like photon spectral index of Γ = 2.6. The upper limit above 200 GeV is 6.4 × 10^-12 cm^-2 s^-1 and above 1 TeV is 7.4 × 10^-13 cm^-2 s^-1. We obtained an upper limit for the pulsed emission of 2.6 × 10^-12 cm^-2 s^-1 for energies above 200 GeV. Applying the Rayleigh test for pulsed emission at different frequencies we did not find any significant signal.

Conclusions. Our results indicate that AE Aqr is not a VHE γ-ray emitter at the level of emission previously claimed. We have established the most constraining upper limits for the VHE γ-ray emission of AE Aqr.