The ablation of gas clouds by blazar jets

¹ Ruhr Astroparticle and Plasma Physics Center (RAPP Center), Insitut für Theoretische Physik IV, Ruhr-Universität Bochum, 44780 Bochum, Germany
e-mail: hejo@tp4.rub.de
² Centre for Space Research, North-West University, Potchefstroom 2520, South Africa
e-mail: mzacharias.phys@gmail.com

Received: 11 March 2020
Accepted: 20 July 2020

Abstract

Context. Flaring activity in blazars can last for vastly different timescales, and it may be the result of density enhancements in the jet flow that result from the intrusion of an interstellar cloud into the jet.

Aims. We investigate the lightcurves expected from the ablation of gas clouds by the blazar jet under various cloud and jet configurations.

Methods. We derived the semi-analytical formulae describing the ablation process of a hydrostatic cloud and performed parameter scans of artificial set-ups over both cloud and jet parameter spaces. We then used parameters obtained from measurements of various cloud types to produce lightcurves of these cloud examples.

Results. 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 timescales.