Fermi Gamma-ray Space Telescope

Characterizing the brightest gamma-ray flares of flat spectrum radio quasars

Manuel Meyer
(Jeffrey Scargle, Roger Blandford, for the Fermi-LAT collaboration)


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, which indicates that the gamma-rays are produced hundreds of gravitational radii away from the black hole. This is further supported by a correlation analysis between radio and gamma-ray light curves. The gamma-ray light curves of these sources on different temporal scales provide us with a rich data set that can be compared to theoretical models of emission and particle cooling scenarios.