The blazar sequence revised

TL;DR

This paper proposes a simplified model explaining the blazar sequence by linking jet power, Lorentz factor, and spectral properties, supported by numerical simulations matching observed spectral energy distributions.

Contribution

It introduces a minimal-parameter model connecting jet energetics and spectral features, validated through detailed numerical simulations and comparison with observations.

Findings

Reproduces spectral energy distributions of blazars.

Shows correlation between jet power and spectral hardness.

Matches observed gamma-ray spectra and light-curves.

Abstract

We propose and test a fairly simple idea that could account for the blazar sequence: all jets are launched with similar energy per baryon, independently of their power. For instance, flat-spectrum radio quasars (FSRQs), the most powerful jets, manage to accelerate to high bulk Lorentz factor, as observed in the radio. As a result, the emission region will have a rather modest magnetization which will induce a steep particle spectra therein and a rather steep emission spectra in the gamma-rays; particularly in the \textit{Fermi}-LAT band. For the weaker jets, namely BL Lacertae objects (BL Lacs), the opposite holds true; i.e., the jet does not achieve a very high bulk Lorentz factor, leading to more magnetic energy available for non-thermal particle acceleration and harder emission spectra. Moreover, this model requires but a handful of parameters. By means of numerical simulations we have accomplished to reproduce the spectral energy distributions and light-curves from fiducial sources following the aforementioned model. With the a complete evolution of the broadband spectra we were able to study in detail the spectral features at any particular frequency band at any given stage. Finally numerical results are compared and contrasted with observations.