Spectral energy distributions of 3C 279 revisited:: BeppoSAX observations and variability models

We present the BeppoSAX observations of 3C 279 performed simultaneously during 1997 January 13-23 with gamma-ray pointings with EGRET on board the Compton Gamma Ray Observatory and optical observations at the Torino Observatory (1997 January 11-18). Infrared Space Observatory data close to this epoch are also available. We compare the derived spectral energy distribution (SED) with those obtained at all other epochs with adequate multiwavelength coverage. Simple spectral models fitted to the multiepoch SEDs suggest that changes in intensity can be ascribed mainly to the variation of the bulk Lorentz factor of the plasma in the jet.