Characterizing the gamma-ray variability of the brightest flat spectrum radio quasars observed with the Fermi LAT

Almost 10 years of observations with the Fermi Large Area Terlescope (LAT) have revealed extreme gamma-ray outbursts from flat spectrum radio quasars (FSRQs), temporarily making these objects the brightest gamma-ray emitters in sky. Yet, the location and mechanisms of the gamma-ray emission remain elusive. Here, we characterize the brightest flares of six FSRQs observed with the LAT. We find evidence for variability on timescales as short as minutes in four sources, which suggests that extremely compact emission regions are a common feature in FSRQs. We do not find any signs for gamma-ray absorption in the broad line region (BLR), which indicates that the gamma-rays are produced away from the black hole by hundreds of gravitational radii. This is further supported by a correlation analysis between radio and gamma-ray light curves. We propose two possible scenarios, which we will quantitatively investigate in the future, that could explain these observations: the gamma-ray emission region might be screened from BLR photons or the gamma rays could be synchrotron emission from electron-positron pairs produced by proton interactions in the BLR.