Multiple inverse Compton scatterings and the blazar sequence

TL;DR

This paper investigates the role of multiple inverse Compton scatterings in blazars, proposing that such processes better explain observed spectral features and correlations than single scattering models, with implications for understanding the blazar sequence.

Contribution

It introduces a multiple scattering model for blazar emissions, challenging the traditional single scattering assumption and explaining spectral features and correlations more effectively.

Findings

Multiple scatterings dominate in the Klein-Nishina limit.

Blazar sequence is primarily governed by electron energy density.

X-ray minima can be explained by extended one-zone models.

Abstract

The high frequency component in blazars is thought to be due to inverse Compton scattered radiation. Recent observations by Fermi-LAT are used to evaluate the details of the scattering process. A comparison is made between the usually assumed single scattering scenario and one in which multiple scatterings are energetically important. In the latter case, most of the radiation is emitted in the Klein-Nishina limit. It is argued that several of the observed correlations defining the blazar sequence are most easily understood in a multiple scattering scenario. Observations indicate also that, in such a scenario, the blazar sequence is primarily governed by the energy density of relativistic electrons rather than that of the seed photons. The pronounced X-ray minimum in the spectral energy distribution often observed in the most luminous blazars is discussed. It is shown how this feature can be accounted for in a multiple scattering scenario by an extension of standard one-zone models.