Jet and accretion power in the most powerful Fermi blazars

Among the blazars detected by the Fermi satellite, we have selected the 23 blazars that in the three months of survey had an average γ–ray luminosity above 10 erg s. For 17 out of the 23 sources we found and analysed X–ray and optical–UV data taken by the Swift satellite. With these data, implemented by archival and not simultaneous data, we construct the spectral energy distributions, and interpreted them with a simple one–zone, leptonic, synchrotron and inverse Compton model. When possible, we also compare different high energy states of single sources, like 0528+134 and 3C 454.3, for which multiple good sets of multi–wavelength data are available. In our powerful blazars the high energy emission always dominates the electromagnetic output, and the relatively low level of the synchrotron radiation often does not hide the accretion disk emission. We can then constrain the black hole mass and the disk luminosity. Both are large (i.e. masses equal or greater than 109M⊙ and disk luminosities above 10% of Eddington). By modelling the non–thermal continuum we derive the power that the jet carries in the form of bulk motion of particles and fields. On average, the jet power is found to be slightly larger than the disk luminosity, and proportional to the mass accretion rate.