Volume 568, August 2014
|Number of page(s)||8|
|Published online||29 August 2014|
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
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.
Key words: accretion, accretion disks / radiation mechanisms: non-thermal / novae, cataclysmic variables / gamma rays: stars
© ESO, 2014
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