Cyg X-3: γ rays from a magnetic accretion disk

THE recent observation¹ of ∼ 100-MeV γ rays from Cygnus X-3, which have a comparable luminosity to the X-ray emission and which vary in phase with the 4.8-h period displayed by the X-ray and infrared emission, has been taken^{2, 3} as support for the suggestion ⁴ that the X-ray emission is produced by a very young pulsar in a short period binary system. In this letter, we show that the observed γ-ray luminosity can be produced by an accretion disk around a non-magnetic neutron star or low-mass black hole, in a magnetised corona which accelerates relativistic electrons that decay by inverse Compton losses modified through the photon-photon and pair-annihilation processes.