The behaviour of compact non-thermal sources with pair production

Abstract

The behavior of a compact source of hard nonthermal radiation may be strongly influenced by electron-positron pairs created by photon-photon collisions. The effects on the spectrum and variability of a source are examined 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. Source variability is studied using power-spectral and cross-correlation analyses of the response of a model system to white noise. The characteristic lags which occur between different energy bands in the emergent spectrum are identified.