0220146

3C273 is the brightest active galaxy in the sky in almost allwavebands from radio to low energy gamma-rays (eg Courvoisier etal1990). The large majority of its emission comes from a relativisticjet oriented towards the observer. The radio through optical emissionis synchrotron emission and the X- and Gamma-ray emission almostcertainly comes from Compton scattering of low energy seed photons byrelativistic particles in the jet. However the origin of the seedphotons and the way in which the scattering particles are acceleratedin the jet are unknown. INTEGRAL spectral quasi-monitoringobservations of 3C273 (10 observations of 50ksec each separated by 5days during one observing window) coupled withdaily X-ray monitoring with RXTE and ground based monitoring ofthe low energy synchrotron continuum provide the idea way to answerthese questions. Previous Gamma-ray observations have been completelyinadequate. Although not a major part of this proposal we will also be able to detect red and blue shiftedannihilation lines which will enable us to determine what the jet isactually made of. [truncated! Please see actual data for full text]