0220151

It has been known for many years that the X-ray spectral indices ofSeyfert galaxies in the 2-10 keV band become steeper as the fluxincreases. Recently we and others have defined the shape of theflux/spectral index relationship very precisely and in particular itis noted that the spectral index reaches an asymptotic level at highfluxes.There are two main possible explanations for this relationship. Thefirst possibility is that the spectrum could consist of twocomponents a relatively hard component of approximately constantflux and a soft component of variable flux. The second possibilityis that there is intrinsic spectral variability in the component whichdominates the X-ray flux such that the spectrum does becomeintrinsically softer at high fluxes perhaps pivoting about some highenergy (100keV).Determining which possibility is actually the case has importantimplications for the physics of the high energy emission regionand is the main aim of the present proposal. Integral is ideallysuited to this programme. [truncated! Please see actual data for full text]