Clues from the photonuclear time scale on the nature of particle accelerators in Cygnus X-3 and Vela X-1

The author has calculated the attenuation times of protons and heavier nuclei in the radiation fields of the stellar companions to the Cyg X-3 and Vela X-1 compact objects. The maximum observed γ-ray energy enables an upper limit to be put on the acceleration time scale of protons at 3 x 1016 eV of 104-3 x 105 s for Cyg X-3 and 105 s for Cyg X-3 and 105 s for Vela X-1. This result can be used to put some constraints on the nature of the particle accelerator. If binary X-ray sources are contributing significantly to the cosmic rays, the cosmic-ray abundances will be affected by photonuclear interactions. (author)