0320044

Thanks to the BeppoSAX satellite unprecedentedly wide energy band extending up to 200 keV with the PDS instrument our knowledge of the spectra of blazars has improved substantially. However the results were limited by the PDS lack of imaging capabilities.In a number of blazars the PDS detected strong excesses in the 20-100 keV band with respect to the extrapolation from softer X-ray energies (0.5-10 keV). This implies either a new spectral component or a contaminating source that falls into the field of view of the PDS. We expect that the contaminant sources are mostly known objects that have a yet undiscovered bright emission in the hard X-ray band.With its spatial resolution in the 20-100 keV band INTEGRAL has the unique capability of disentangling the problem. If the excess is due to the blazar we will provide new input to our knowledge of the physics of this class of sources. If instead there is a serendipitous contaminating source we will be able to probe the still poorly studied 20-100 keV region and make significant progress in the understanding of the hard X-ray background. [truncated! Please see actual data for full text]