Relativistic features from X-ray illuminated spots in AGN

Narrow spectral features in the 5-6 keV range were recently discovered in the X-ray spectra of a few AGN. We discuss the possibility that these features are redshifted iron lines from orbiting spots on the surface of the accretion disc, and compare numerical models with the observations. If the model is correct, these features can be used to measure the mass of Supermassive Black Holes in Active Galactic Nuclei, a task for future X-ray missions like Constellation-X