Narrow-Line Seyfert 1 Galaxies with high-energy sharp spectral drops: reflection-versus absorption models

Abstract

With the launch of XMM-Newton in 1999, two Narrow-Line Seyfert 1 Galaxies (NLS1s) have been detected (IRAS 13224-3809 and 1H 0707-495) showing sharp spectral drops at energies equal or above the neutral Fe K edge at 7.1 keV without any narrow Fe K reemission. In this paper I summarize our present knowledge on the observed properties of sharp high-energy spectral drops. I list the problems presently arising from the reflection dominated and the optically thick disc models. Finally, I present an alternative solution which consists of a combination of the accretion disc model and the reflection dominated model. This might solve the problems of the standard accretion disc model.