The correlation between the X-ray spectral slope and the FeKα line energy in radio-quiet active galactic nuclei

A significant correlation between the Fe Kalpha line energy and the X-ray spectral slope has been discovered among radio-quiet active galactic nuclei. The ionization stage of the bulk of the Fe Kalpha-emitting material is not the same in all active galactic nuclei and is related to the shape of the X-ray continua. Active galactic nuclei with a steep X-ray spectrum tend to have a fluorescence Fe Kalpha line from highly ionized material. In the narrow-line Seyfert 1 galaxies with a steeper X-ray spectrum (Gamma(x) greater than or similar to 2.1), the Fe Kalpha line originates from highly ionized material. In the Seyfert 1 galaxies and quasars with a flatter X-ray spectrum (Gamma(x) less than or similar to 2.1 ), the bulk of the Fe Kalpha emission arises from near-neutral or weakly ionized material. The correlation is an important observational characteristic related to the accretion process in radio-quiet active galactic nuclei and is driven by a fundamental physical parameter that is likely to be the accretion rate relative to the Eddington rate.