Fermi Gamma-ray Space Telescope

Time-Dependent, Multi-Wavelength Models for Active Flares of Fermi Blazars

Matthew Baring
(Markus Boettcher (North-West University, South Africa), Errol J. Summerlin (NASA's Goddard Space Flight Center))


Jets in blazars are an excellent forum for studying acceleration at relativistic shocks using the highly-variable emission seen across the electromagnetic spectrum. Our recent work on combining multi-wavelength leptonic emission models with complete simulated distributions from shock acceleration theory has resulted in new insights into plasma conditions in Fermi blazars. This has demonstrated the ability to infer the plasma density, and suggested the interpretation that turbulence levels decline with remoteness from jet shocks. In this paper, we extend this program to a two-zone, time-evolving construction, modeling together both extended, enhanced emission states from larger radiative regions, and prompt flare events in the Fermi-LAT and TeV blazars Mrk 501 and 3C 279. With impulsive injection episodes from the shock zone, as the acceleration first proceeds and then abates, we find spectral hysteresis in the hardness-flux diagram in all wavebands, including the GeV one. Possible diagnostics using Fermi data are identified. Interestingly, flaring during the acceleration epoch for the GeV-band SSC emission is more pronounced for the HBL blazar Mrk 501 than is the external Compton signal employed for the LBL blazar 3C 279 to supply flux in the Fermi window. The results are interpreted in the light of the shock acceleration paradigm.