engleski

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

The nova-like cataclysmic variable (CV) AE Aquarii (AE Aqr) has been claimed to be a very-high-energy (VHE, E >100 GeV) source both on observational and theoretical grounds. Aims were to search for TeV gamma-ray emission from AE Aqr during different states of the source at several wavelengths and to confirm or rule out previous claims of detection of gamma-ray emission from this object. We report on observations of AE Aqr performed by MAGIC. The source was observed during 12 hours as a 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 KVA, Skinakas and Vidojevica telescopes in the optical and Swift in X-rays. 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 differential flux proportional to a power-law function dPHI/dE ~ E^(−GAMMA), with a Crab-like photon spectral index of GAMMA=2.6. The upper limit above 200 GeV is 6.4 x 10^(−12) cm^(−2) s^(−1) and above 1 TeV is 7.4 x 10^(−13) cm^(−2) s^(−1). We calculate integral upper limits coincident with different states of the source in the optical. We have also computed upper limits to the pulsed emission limiting the signal region to 30% of the phaseogram and obtaining an upper limit for the pulsed emission of 2.6 x 10^(−12) cm^(−2) s^(−1) for energies above 200 GeV. Finally, we search for pulsed emission at different frequencies applying the Rayleigh test and do not find any significant signal. Our results indicate that AE Aqr is not a very high energy gamma-ray emitter at the level of emission previously claimed. We have established the most constraining upper limits for the TeV gamma-ray emission of AE Aqr.

accretion: accretion disks; Radiation mechanisms: non-thermal; Novae: cataclysmic variables; Gamma rays: stars

The MAGIC Collaboration.