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.

Accepted by Astrophysical Journal Letters

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• Fermi-Large Area Telescope Observations of the Exceptional Gamma-ray Flare from 3C 279 in 2015 June
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• Constraints of Flat Spectrum Radio Quasars in the hadronic model: the case of 3C 273
• Long term study of the light curve of PKS 1510-089 in GeV energies
• The Estimation of Fundamental Physics Parameters for Fermi-LAT Blazars
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• Locating the gamma-ray emission region in the brightest Fermi-LAT Flat Spectrum Radio Quasars
• Brightest Fermi-LAT Flares of PKS 1222+216: Implications on Emission and Acceleration Processes
• Fourier Analysis of Blazar Variability: Klein-Nishina Effects and the Jet Scattering Environment
• Parameter constraints in a near-equipartition model with multi-frequency \emph{NuSTAR}, \emph{Swift} and \emph{Fermi-LAT} data from 3C 279
• Multi-wavelength observations of the gamma-ray flaring quasar S4 1030+61 in 2009-2014
• A Method for Locating High Energy Dissipation Region in Blazar
• Localizing the $\gamma$-ray emitting region in the blazar TXS 2013+370
• Formation of very hard electron and gamma-ray spectra of flat spectrum radio quasar in fast-cooling regime
• Exploring the Nature of the 2016 γ-ray Emission in the Blazar 1749+096
• Investigating the connection between gamma-ray activity and relativistic jet in 3C273 during 2015-2019
• Locating the GeV Emission Region in the Jets of Blazars from Months-Timescale Multi-Wavelength Outbursts
• Constraining the $\gamma$-ray Emission Region for Fermi-Detected FSRQs by the Seed Photon Approach