The ablation of gas clouds by blazar jets

TL;DR

This paper models how gas clouds are ablated by blazar jets, producing diverse lightcurves that depend on cloud and jet properties, helping interpret observed blazar flares.

Contribution

It introduces semi-analytical formulae for cloud ablation in blazar jets and explores how different parameters affect flare lightcurves.

Findings

Cloud and jet parameters significantly influence flare duration and intensity.

The scale height of the cloud is crucial in shaping the lightcurve.

Different cloud configurations can produce a wide variety of symmetrical flares.

Abstract

Flaring activity in blazars can last for vastly different time-scales, and may be the result of density enhancements in the jet flow that result from the intrusion of an interstellar cloud into the jet. We investigate the lightcurves expected from the ablation of gas clouds by the blazar jet under various cloud and jet configurations. We derive the semi-analytical formulae describing the ablation process of a hydrostatic cloud, and perform parameter scans of artificial set-ups over both cloud and jet parameter spaces. We then use parameters obtained from measurements of various cloud types to produce lightcurves of these cloud examples. The parameter scans show that a vast zoo of symmetrical lightcurves can be realized. Both cloud and emission region parameters significantly influence the duration, and strength of the flare. The scale height of the cloud is one of the most important parameters, as it determines the shape of the lightcurve. In turn, important cloud parameters can be deduced from the observed shape of a flare. The example clouds result in significant flares lasting for various time scales.