Variability along the Blazar-Sequence - Hints for extragalactic Cosmic Rays?

TL;DR

This study models the spectral energy distribution and variability of various blazars using a hybrid emission model, revealing differences in particle acceleration and suggesting certain active galactic nuclei as sources of extragalactic cosmic rays.

Contribution

It introduces a self-consistent, time-dependent lepto-hadronic model to distinguish emission processes in blazars and links variability signatures to cosmic ray origins.

Findings

BL Lac objects are modeled with leptonic processes.

Flat Spectrum Radio Quasars require hadronic components.

Active galactic nuclei with z > 0.5 are potential cosmic ray sources.

Abstract

The spectral energy distribution and variability of several blazars (Mkn 501, 1 ES 2344+51.4, PKS 2155-30.4, 1 ES 1218+30.4, 3C 454.3) along the blazar sequence is investigated using a selfconsistent and timedependent lepto-hadronic hybrid emission model. The BL Lac objects in the list are successfully modelled with purely leptonic radiation processes (essentially Synchrotron Self-Compton emission), while the Flat Spectrum Radio Quasar requires highly relativistic hadrons to be present within the jet. Variability is exploited as well with our model to distinguish between Self-Compton and hadronic gamma radiation making use of their different signatures in lightcurves. As a consequence active galactic nuclei with z > 0.5 are the best candidates as sources of extragalactic consmic rays, since High-Peaked BL Lac objects do not seem to accelerate protons to energies above thermal. Furthermore the parameters found during the modelling of the objects agree very well with obervations of e.g. superluminal motion or typical variability timescales.