K. Iwasawa and Y. Taniguchi
Using the X-ray data of AGN obtained by the X-ray satellite Ginga, we have found that the equivalent width of the Fe K emission line at 6.4 keV, EW(Fe K), is inversely correlated with the X-ray luminosity in the 2-10 keV band. This inverse correlation is basically similar to the well-known relation known as the 'Baldwin effect', which means that the equivalent width of the C IV 1550 A emission line is inversely correlated with the UV continuum luminosity (Baldwin 1977). Hence, we may call our finding 'the X-ray Baldwin effect'. The X-ray Baldwin effect is pronounced for type 1 Seyfert galaxies. The obtained correlation is quite similar to those of the original Baldwin effects for type 1 Seyfert galaxies and quasars, implying that the Fe K emission mainly comes from the broad-line regions or from the regions whose geometrical configurations are nearly the same as those of broadline regions.