Broadband spectral analysis of PKS 0528+134: A report on six years of Egret observations

The multiwavelength spectra of PKS 0528 + 134 during 6 yr of observations b y EGRET have been analyzed using synchrotron self-Compton (SSC) and externa l radiation Compton (ERC) models. We find that a two-component model, in wh ich the target photons are produced externally to the gamma-ray-emitting re gion, but also including an SSC component, is required to reproduce suitabl y the spectral energy distributions of the source. Our analysis indicates t hat there is a trend in the observed properties of PKS 0528 + 134, as the s ource goes from a gamma-ray low state to a flaring state. We observe that d uring the higher gamma-ray states, the bulk Lorentz factor of the jet incre ases and the ERC component dominates the high-energy emission. Our model ca lculations indicate the trend that the energies of the electrons giving ris e to the synchrotron peak decrease, and the power-ratio of the gamma-ray an d low-energy spectral components increases, as the source goes from a low t o a high gamma-ray state.