Location of a Sample of GeV and Optical Outbursts in the Jets of Blazars

TL;DR

This study determines the location of GeV and optical emission in blazar jets using a method based on outburst energy ratios, finding it consistently beyond the broad line region across multiple blazars.

Contribution

It applies a previously established method to a large sample of blazar outbursts, providing consistent evidence that emission occurs beyond the broad line region.

Findings

Emission is beyond the broad line region in all studied cases.

Results are consistent with other methods and studies.

Method applied to 47 outbursts in 10 blazars.

Abstract

The exact location of the $\gamma$-ray emitting region in blazar jets has long been a matter of debate. However, the location has important implications about the emission processes, geometric and physical parameters of the jet, as well as the nature of interaction of the jet with the interstellar and intergalactic medium. Diverse conclusions have been drawn by various authors based on a variety of methods applied to different data sets of many blazars, e.g., the location is less than 0.1 pc from the central engine within the broad line region (BLR) or a few or tens of pc downstream beyond the dusty torus or at some intermediate distance. Here we use a method, established in a previous work, in which the location of the GeV/optical emission is determined using the ratio of energy dissipated during contemporaneous outbursts at those wave bands. We apply it to a total of 47 multi-wavelength outbursts in 10 blazars. We find that the location of the GeV/optical emission is beyond the BLR for all cases. This result is consistent with other studies, in which the location has been determined for a large sample of blazars. We compare the location determined by our method for several GeV outbursts of multiple blazars to that obtained by other authors using different methods. We find that our results are consistent in such one-to-one comparison in most cases, for which the required data were available.