RADIO JETS AND UHE GAMMA-RAY EMISSION IN CYG X-3

The low-mass X-ray binary source Cyg X-3 has been extensively observed from radio to ultra-high-energy (UHE) gamma-ray energies (i.e., energ ies > 10(15)eV). In the radio, Cyg X-3 exhibits intense non-thermal ou tbursts (flares) and a double-sided relativistic jet morphology. Inter estingly, at energies above 1 TeV (10(12)eV), the gamma-ray emission i s highly variable and possibly correlated with the radio outbursts. Th is emission results primarily from the radiative decay of pi-degreess- mesons generated in inelastic collisions between relativistic nuclei ( predominantly protons) and the surrounding matter. The observed flux o f UHE gamma-rays from Cyg X-3 implies that Cyg X-3 is a localised acce lerator of such particles. We propose a model of Cyg X-3 wherein parti cles expelled by the source are accelerated by shockwaves in the relat ivistically expanding jets. Intense flaring episodes then lead to time variations in the ambient particle flux which account for the observe d features at UHE energies.