Iron KαLine Emission in Active Galactic Nuclei

The iron K line can be produced in a variety of X-ray illuminated material, and in hot plasma in active galactic nuclei.It provides an important diagnostic of the physical state and the geometry of gas in the active galactic nucleus, as well as the nature of the gravitational potential in the central engine.In this talk, we review the physics of the iron line formation and the recent observational progress in this area.