Bulk Comptonization spectra in blazars
Ghisellini G., and Celotti A.
We study the Bulk Compton (BC) process between a cold, relativistic shell of plasma moving along the jet and photons produced in the accretion disk and/or coming from the broad line region. BC of disk photons is unobservable, while BC of broad line photons yields a significant feature in the soft X-ray band. This helps to explain some X-ray properties of high z blazars, previously interpreted as due to absorption.We study