The behaviour of compact non-thermal sources with pair production

The behaviour of a compact source of hard non-thermal radiation may be strongly influenced by electron-positron pairs created by photon-photon collisions. We investigate the effects on the spectrum and variability of a source when the primary spectrum is due to the Compton scattering of blackbody soft photons by relativistic electrons injected with a fixed high Lorentz factor. Although the model spectra are successful in reproducing the power-law X-ray spectrum common to many Seyfert 1 galaxies, they produce an annihilation feature which is too strong to be acceptable. Many models also produce too many γ-rays. Further work, relaxing some of our assumptions, may alleviate these problems. The present study attempts to set up the basis from which future work can proceed. (author)