Correlated Variability in Blazars

TL;DR

This paper reviews recent multiwavelength observations of blazars, focusing on correlations between different emission components, and discusses how these observations constrain theoretical models of jet emission mechanisms.

Contribution

It provides a comprehensive review of observational evidence for correlated variability in blazars and analyzes how these correlations inform emission models.

Findings

Correlated variability observed in some blazars supports leptonic emission models.

Absence of correlation in certain cases challenges simple emission scenarios.

Quantitative analyses place constraints on jet emission parameters.

Abstract

Blazars are thought to emit highly-collimated outflows, so-called jets. By their close alignment to our line of sight, relativistic beaming effects enable us to observe these jets over the whole electromagnetic spectrum up to TeV energies, making them ideal laboratories for studying jet physics. In the last years multiwavelength observations of blazars provided us with detailed data sets which helped to characterize the two main components of the non-relativistic emission, peaking in the optical to X-ray and GeV/TeV energy region, respectively. In leptonic acceleration models, they are explained by synchrotron radiation of electrons and inverse-Compton emission from the same electron population and thus, correlations of both emission regimes are expected. We review recent observational results on the presence and absence of such correlations in blazars, and discuss constraints on emission models by quantitative correlation analyses.