The Spectral Sequence of Blazars - Status and Perspectives

TL;DR

This paper reviews the current understanding of the blazar spectral sequence, discusses recent findings challenging or supporting it, and highlights how upcoming gamma-ray observations from the GLAST satellite will expand our knowledge of blazar populations and their spectral properties.

Contribution

It provides an updated overview of the blazar spectral sequence status and discusses how future gamma-ray observations will enhance the understanding of blazar diversity.

Findings

The original blazar spectral sequence still holds despite new searches.

Upcoming GLAST data will significantly increase the detectable blazar population.

GLAST will enable study of lower power and less beamed blazar jets.

Abstract

The present status of the blazar spectral sequence is discussed, including new findings about blazars selected with different criteria than the original complete radio-samples. Despite extensive searches of blazars "breaking" the sequence, the original idea proposed 10 years ago, still seems to hold. On the other hand the forthcoming launch of the GLAST satellite will provide a new selection band for blazars and blazar related populations as well as fantastic progress on the spectra and variability behaviour of presently known blazars. The order of magnitude increase in sensitivity of GLAST will allow to detect gamma-rays from jets with lower power and/or lower beaming factor, thus sampling a much wider population.