MAGIC search for VHE gamma-ray emission from AE Aquarii in a multiwavelength context
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2014
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Abstract
Context. It has been claimed that the nova-like cataclysmic variable (CV) 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 gamma-ray emission from AE Aqr during diferent states of the source at several wavelengths to confirm or rule out previous claims of detection of gamma-ray emission from this object.
Methods. We report on observations of AE Aqr performed by MAGIC. The source was observed during 12 hours as part of a multiwavelength campaign carried out between May and June 2012 covering the optical, X-ray, and gamma-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 diferent 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 diferent frequencies applying the Rayleigh test.
Results. AE Aqr was not detected at VHE energies during the multiwavelength campaign. We establish integral upper limits at the 95% confidence level for the steady emission assuming the diferential flux proportional to a power-law function dф /dE α E^(-Γ) with a Crab-like photon spectral index of Γ =2.6. The upper limit above 200 GeV is 6.4X10^(-12) cm^(-2)s^(-1) and above 1 TeV is 7.4X10^(-13) cm^(-2)s^(-1). We obtained an upper limit for the pulsed emission of 2.6X10^(-12) cm^(-2)s^(-1) for energies above 200 GeV. Applying the Rayleigh test for pulsed emission at diferent frequencies we did not find any significant signal.
Conclusions. Our results indicate that AE Aqr is not a VHE gamma-ray emitter at the level of emission previously claimed. We have established the most constraining upper limits for the VHE gamma-ray emission of AE Aqr.
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© ESO 2014. We would like to thank the Instituto de Astrofísica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The support of the German BMBF and MPG, the Italian INFN, the Swiss National Fund SNF, and the Spanish MINECO is gratefully acknowledged. This work was also supported by the CPAN CSD2007-00042 and MultiDark CSD2009-00064 projects of the Spanish Consolider-Ingenio 2010 program, by grant 127740 of the Academy of Finland, by the DFG Cluster of Excellence “Origin and Structure of the Universe”, by the Croatian Science Foundation (HrZZ) Project 09/176, by the DFG Collaborative Research Centers SFB823/C4 and SFB876/C3, and by the Polish MNiSzW grant 745/N-HESSMAGIC/2010/0. CWM’s contribution to this work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. MB acknowledges support from the Serbian MESTD through grant ON176021. The authors thank N. Gehrels for approving our request for target-of-opportunity observations and the Swift Science Operations Team for scheduling them. This research made use of data provided by the HEASARC, which is a service of the Astrophysics Science Division at NASA/GSFC and the High Energy Astrophysics Division of the Smithsonian Astrophysical Observatory. This research made use of the XRT Data Analysis Software (XRTDAS) developed under the responsibility of the ASI Science Data Center (ASDC), Italy. We would also like to thank the American Association of Variable Star Observers for supporting optical observations during the campaign.