The strength and width of Fe Kalpha lines in Seyferts and their correlations with the X-ray slope

Abstract

We study properties of Fe K lines of a large sample of Seyfert 1s observed by ASCA. Fits with power laws and Gaussian lines yield the average linewidth and equivalent width of 0.22+-0.03 keV and 0.13+-0.01 keV, respectively. Thus, the typical lines are weak and narrow. We then obtain the average line profile of all our spectra, and find it to consist of a narrow core and blue and red wings, with the red wing being much weaker than that of, e.g., MCG-6-30-15. We obtain three average spectra of Seyferts grouped according to the hardness, and find the equivalent width of the core (originating in a remote medium) to be about 50 eV in all three cases. The wings are well fitted by a broad line from a disc with strong relativistic effects. Its equivalent width correlates with the slope, increasing from ~70 eV for the hardest spectrum to ~120 eV for the softest one. The inner disc radius decreases correspondingly from ~40 to ~10 gravitational radii, and the fitted disc inclination is ~45 degrees. The obtained correlation between the slope and the strength of the broad Fe K line is found to be consistent with the previously found correlation of the slope and Compton reflection.