Rapid Variability: What do we learn from correlated mm-/gamma-ray variability in jets ?

TL;DR

This study analyzes multi-frequency variability in the BL Lac object S5 0716+714, revealing correlated gamma-ray and radio flares with a time delay, providing insights into the location and physics of emission regions.

Contribution

It offers new evidence on the correlation and time delay between gamma-ray and radio flares, and models the shock-in-jet process with geometrical considerations.

Findings

Gamma-ray and radio flux variations are correlated.

A two-month delay suggests non-cospatial emission regions.

Shock-in-jet model explains flare evolution with geometrical effects.

Abstract

Densely time sampled multi-frequency flux measurements of the extreme BL Lac object S5 0716+714 over the past three years allow us to study its broad-band variability, and the detailed underlying physics, with emphasis on the location and size of the emitting regions and the evolution with time. We study the characteristics of some prominent mm-/gamma-ray flares in the context of the shock-in-jet model and investigate the location of the high energy emission region. The rapid rise and decay of the radio flares is in agreement with the formation of a shock and its evolution, if a geometrical variation is included in addition to intrinsic variations of the source. We find evidence for a correlation between flux variations at gamma-ray and radio frequencies. A two month time-delay between gamma-ray and radio flares indicates a non-cospatial origin of gamma-rays and radio flux variations in S5 0716+714.