Invisible Plasma Content in Blazars? The Case of Markarian 421

TL;DR

This paper investigates the presence of unseen plasma, such as protons and thermal pairs, in blazar jets like Mrk 421 by comparing theoretical models with observed spectra, suggesting a significant invisible plasma component.

Contribution

It provides evidence for substantial invisible plasma in blazar jets and proposes that the blazar sequence may result from variations in plasma composition.

Findings

Existence of copious invisible plasma in Mrk 421's jet

Blazar sequence linked to plasma composition variations

Comparison of internal shock model with observed spectra

Abstract

Invisible plasma content in blazar jets such as protons and/or thermal electron-positron ($e^{\pm}$) pairs is explored through combined arguments of dynamical and radiative processes. By comparing physical quantities required by the internal shock model with those obtained through the observed radio-to-gamma-ray spectra for Mrk 421, we find the existence of a copious amount of invisible plasma in the jet. We speculate that the blazar sequence could arise from variations of total amount and/or blending ratio of $e^{\pm}$ pair and electron-proton plasma.