On the phenomenological classification of continuum radio spectra variability patterns of Fermi blazars

TL;DR

This study classifies the variability patterns of Fermi blazars' radio spectra into five types based on multi-frequency observations, linking spectral changes to physical models and simulations.

Contribution

It introduces a phenomenological classification of blazar radio spectral variability and models these patterns with a simple two-component system.

Findings

Five variability types identified among 78 blazars.

Spectral evolution dominated types modeled by a two-component system.

Achromatic variability attributed to different mechanisms.

Abstract

The F-GAMMA program is a coordinated effort to investigate the physics of Active Galactic Nuclei (AGNs) via multi-frequency monitoring of {\em Fermi} blazars. The current study is concerned with the broad-band radio spectra composed of measurement at ten frequencies between 2.64 and 142 GHz. It is shown that any of the 78 sources studied can be classified in terms of their variability characteristics in merely 5 types of variability. The first four types are dominated by spectral evolution and can be reproduced by a simple two-component system made of the quiescent spectrum of a large scale jet populated with a flaring event evolving according to Marscher & Gear (1985). The last type is characterized by an achromatic change of the broad-band spectrum which must be attributed to a completely different mechanism. Here are presented, the classification, the assumed physical system and the results of simulations that have been conducted.