0820018

We propose to continue the monitoring of the X-ray brightest Seyfert galaxy NGC 4151 with integral in order to measure its spectra as a function of the hard X-ray flux level. We will correlate the high energy spectral cutoff with other continuum parameters to determine the main physical mechanism driving the variability. We will also disentangle the contributions to the reflection hump from close and distant reflectors and correlate those with the narrow iron line variability to determine the nature of the thick reprocessing medium and the geometry of cold matter surrounding the source. We will finally probe for the existence of a hard non-thermal tail. We request four observations of 200 ks each for which we will propose four 10 ks accompanying XMM-Newton observations. [truncated! Please see actual data for full text]