On the dependence of the iron K-line profiles with luminosity in active galactic nuclei

We present evidence for changes in the strength and profile of the iron K alpha line in active galactic nuclei (AGNs), based on X-ray observations with ASCA. There is a clear decrease in the strength of the line with increasing luminosity. This relation is not due solely to radio power, as it persists when only radio-quiet AGNs are considered and therefore cannot be fully explained by relativistic beaming. In addition to the change in strength, the line profile also appears to be different in higher luminosity sources. We discuss these results in terms of a model where the accretion disk becomes ionized as a function of the accretion rate.