Fermi Gamma-ray Space Telescope

Acceleration Mechanisms in a Simplified Analytic Electron Distribution for Blazars

Tiffany Lewis
(Justin Finke, Peter Becker)


Blazar jet emission is often described as generated by a simple power-law electron distribution in one-zone leptonic models. However, these models both neglect a self-consistent expression of the acceleration mechanisms, and occasionally struggle to explain the high-energy spectra, detected by FermiLAT. The electron distribution is the key to understanding how particles are accelerated in the jet. We can calculate it using a relatively simple expression, which includes parameters for both first and second order Fermi acceleration. This provides flexibility in the functional form of the distribution, which in turn is apparent in the modeled spectrum. As a result, the model SED can explain key features in extreme blazar flares. For example, we analyze broadband spectra for the Dec 2013 gamma-ray flare of 3C 279, where the spectral hardening may be due to a significant increase in shock acceleration, while the extreme Compton dominance induced by the isolated gamma-ray flare, may indicate a sudden decrease in the magnetic field power and thus a departure from equipartition.