Letter to the Editor

On the nature of an ejection event in the jet of 3C 111

¹ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany e-mail: perucho@mpifr-bonn.mpg.de
² Instituto de Astrofísica de Andalucía (CSIC), Apartado 3004, 18080 Granada, Spain
³ Dr. Karl Remeis-Observatory, University of Erlangen-Nuremberg, Sternwartstrasse 7, 96049 Bamberg, Germany
⁴ CRESST/NASA Goddard Space Flight Center, 662 Greenbelt, MD 20771, USA
⁵ Universities Space Research Association, 10211 Wincopin Circle, Suite 500 Columbia, MD 21044, USA
⁶ Astro Space Center of Lebedev Physical Institute, Profsoyuznaya 84/32, 117997 Moscow, Russia

Received: 30 June 2008
Accepted: 21 August 2008

Abstract

We present a possible scenario for the ejection of a superluminal component in the jet of the Broad Line Radio Galaxy 3C 111 in early 1996. VLBI observations at 15 GHz discovered the presence of two jet features on scales smaller than one parsec. The first component evolves downstream, whereas the second one fades out after 1 parsec. We propose the injection of a perturbation of dense material followed by a decrease in the injection rate of material in the jet as a plausible explanation. This scenario is supported by 1D relativistic hydrodynamic and emission simulations. The perturbation is modeled as an increase in the jet density, without modifying the original Lorentz factor in the initial conditions. We show that an increase of the Lorentz factor in the material of the perturbation fails to reproduce the observed evolution of this flare. We are able to estimate the lifetime of the ejection event in 3C 111 to be 36 ± 7 days.