0320058

We propose a sensitive INTEGRAL ToO observation as part of a multifrequency campaign on the prominent gray blazar 3C279 during a flux high-state in the optical bandin order to measure 1) its high-state multifrequency spectrum 2) its X- and hard X-ray spectrum up to a about 200 keV and3) its variability behaviour at hard X-rays.The proposed INTEGRAL observation will increase our knowledge on the largely unknownhard X-ray properties of 3C 279. The comparison of the newly measuredhigh-state to the already observed low-state multifrequency spectrumwill reveal new insights in its overall emission scenario.Because the observed radiation of 3C 279 is almost purely of non-thermal origin we are studying jet physics and subsequently the physics of particle acceleration by the proposed observation. [truncated! Please see actual data for full text]