Determining the location of the GeV emitting zone in fast, bright blazars
The location of the GeV-flaring zone in bright Fermi blazars is an important topic of debate: is the GeV emitting region located inside the sub-pc broad line region (BLR) or farther out in the pc-scale molecular torus (MT)? We recently developed a diagnostic that uses on the energy dependence of the flare decay time to place the GeV flaring site in the BLR or the MT. Here we show results of our method, applied to bright flares of 3C 454.3, PKS 1510-089, and PKS 1222+216. We split each flare into high and low energy bands and fit an exponential rise and decay to each flare component. The resulting fit decay times indicate that the flaring site for these specific flares is generally located within a few pc from the central engine. We discuss analysis of the flares, the implications of the fit for the location of the GeV emitting zone, and future plans to apply this method to a wider survey of objects.