Light bending models in AGNs

Abstract

We review the MCG-6-30-15 observations and results that provided the motivation for the light bending model. We present a summary of the main properties of the model and discuss its application to MCG-6-30-15 briefly mentioning other X-ray sources showing the same qualitative behaviour. Finally, we report on one of the most spectacular cases so far of short-timescale variability of a redshifted Fe K line in the Seyfert galaxy NGC 3516, most likely due to an orbiting spot or flare in the relativistic region of the accretion disc.