A search for very high energy gamma rays from Cygnus X-3

Abstract

Cygnus X-3 is an x-ray binary system approximately 10kpc away from the earth, lying in the plane of the galactic disc. Since the observation of intense radio jets emanating from the system, it has continued to confound experimentalists and theorists alike. In certain models of -y-ray production Cygnus X-3 could supply the power necessary to sustain the high energy (E> 10^17eV ) galactic cosmic ray population against leakage (Hillas 1984a). By any model, the experimental results indicate that it is the most intense source of high energy cosmic rays observed. This thesis represents an attempt to verify the previous observations, and elucidate the nature of the -y-ray emission. Taking a conservative viewpoint we set an upper limit to the time averaged flux from Cygnus X-3 of 5.8 x 10^-1lγ'scm^-2s^-1 above 300GeV. However there is evidence, of low statistical significance (20'), that Cygnus X-3 is a sporadic emitter of γ-rays, with a measured :flux of (3.3 ± 0.7) x 10-10-γ'scm^-2s^-1, and a duty cycle of 6% (consistent with previous observations]; though it appears that this emission is not correlated with the 4.8hr x-ray period (in contradiction to previous observations). We also see no evidence of the reported 12.59ms pulsations, and note that the published world data is now consistent with this hypothesis at the 2% level.