A method for localizing energy dissipation in blazars using Fermi variability
Abstract
The distance of the Fermi-detected blazar gamma-ray emission site from the supermassive black hole is a matter of active debate. Here we present a method for testing if the GeV emission of powerful blazars is produced within the sub-pc scale broad line region (BLR) or farther out in the pc-scale molecular torus (MT) environment. If the GeV emission takes place within the BLR, the inverse Compton (IC) scattering of the BLR ultraviolet (UV) seed photons that produces the gamma-rays takes place at the onset of the Klein-Nishina regime. This causes the electron cooling time to become practically energy independent and the variation of the gamma-ray emission to be almost achromatic. If on the other hand the gamma-ray emission is produced farther out in the pc-scale MT, the IC scattering of the infrared (IR) MT seed photons that produces the gamma-rays takes place in the Thomson regime, resulting to energy-dependent electron cooling times, manifested as faster cooling times for higher Fermi energies. We demonstrate these characteristics and discuss the applicability and limitations of our method.
Cite
@article{arxiv.1209.2053,
title = {A method for localizing energy dissipation in blazars using Fermi variability},
author = {Amanda Dotson and Markos Georganopoulos and Demosthenes Kazanas and Eric S. Perlman},
journal= {arXiv preprint arXiv:1209.2053},
year = {2015}
}
Comments
Accepted by Astrophysical Journal Letters