H. Kunieda, Y. Terashima, K. Misaki, S. Tsuruta, A. Leroux

Abstract

The energy spectra from Seyfert galaxies have been explained by a power law model. However, following modulations have been found in these ten years; the reflection component above 10 keV, iron K emission line and edge structures, the warm absorbers, and the neutral absorbers (Galactic or intrinsic). At the same time, it is well established that global spectral feature is changing during the change of flux. Some are explained by the change of absorption including the warm absorbers, while others need the variation of the power index. In ASCA observations of some Seyfert galaxies (Mkn 841, MCG-63-15, NGC5548,,,,), light curves in different energy bands show different time variation, which indicate the variation of the apparent spectral slope. We collect X-ray data with similar spectral slope to obtain typical spectra with enough statistics. The spectral ratio of them is a useful method to distinguish the reasons to change the spectra. If it is due to the absorbtion, the ratio should match to the energy dependence of the absorption, without any change at high enegies. The warm ansorber makes a dip at 0.7-0.9 keV. On the other hand, the index change should give a straight slope in whole enrgy band.