A spine-sheath model for strong-line blazars

TL;DR

This paper introduces a spine-sheath jet model for strong-line blazars that explains their broad-band spectra, variability, and extreme gamma-ray events with a less power-demanding structure.

Contribution

The authors develop a quasi-analytical spine-sheath model that accounts for spectral features and variability in strong-line blazars, improving upon simpler one-zone models.

Findings

Reproduces broad-band spectra with magnetization near unity.

Explains large gamma-ray variability compared to optical.

Requires less jet power than traditional one-zone models.

Abstract

We have developed a quasi-analytical model for the production of radiation in strong-line blazars, assuming a spine-sheath jet structure. The model allows us to study how the spine and sheath spectral components depend on parameters describing the geometrical and physical structure of "the blazar zone". We show that typical broad-band spectra of strong-line blazars can be reproduced by assuming the magnetization parameter to be of order unity and reconnection to be the dominant dissipation mechanism. Furthermore, we demonstrate that the spine-sheath model can explain why gamma-ray variations are often observed to have much larger amplitudes than the corresponding optical variations. The model is also less demanding of jet power than one-zone models, and can reproduce the basic features of extreme gamma-ray events.