Broad Iron Lines in Active Galactic Nuclei: A Possible Test of the Kerr Metric?

Abstract

The broad lines in Active Galactic Nuclei (AGN) discovered recently have been interpreted as evidence for emission close to a central black hole. We briefly describe the physical processes leading to the line emission, describe the computational methods used to compute the emerging line profiles, and summarize the qualitative behavior of these lines. We present the observational evidence for the relativistic lines, concentrating on the properties of the line in MCG-6-30-15, where the line profile shows strong indications that a Kerr black hole is present in the object. Finally, we show how future X-ray missions will help in deepening our understanding of the emission of broad iron lines from AGN.