The variability of the quasar 3C 273: a radio to gamma-ray view
  We have analysed the first 15 months of Fermi/LAT data of the radio loud
quasar 3C 273. Intense gamma-ray activity has been detected, showing an average
flux of F(> 100 MeV) = 1.4e-6 ph/cm^2/s, with a peak at F(> 100 MeV) = 5.6e-6
ph/cm^2/s detected during a flare in September 2009. Together with the
brightening of the source, a possible hardening of the gamma-ray spectrum is
observed, pointing to a shift of the inverse Compton peak toward higher
energies than the 1-10 MeV range in which 3C 273 inverse Compton emission is
typically observed to peak. During the 15 months of observations the photon
index is measured to vary between 2.4 and 3.3, with an average value of 2.78
+/- 0.03. When compared to the observations at other wavelengths, the
gamma-rays show the largest flux variations and we discuss the possibility that
two different components are responsible for the inverse Compton hump emission
below and above the MeV peak.
