Modelling 20 years of synchrotron flaring in the jet of 3C 273

TL;DR

This paper introduces a comprehensive jet model that successfully reproduces 20 years of multi-wavelength variability in quasar 3C 273, supporting shock-based emission mechanisms and linking outbursts to jet features.

Contribution

It extends the shock model to include accelerating, decelerating, curved, and non-adiabatic jets, enabling detailed decomposition of long-term light curves into individual outbursts.

Findings

Model accurately reproduces 20-year light curves of 3C 273.

Supports the shock model as a key mechanism in quasar jet variability.

Links outbursts to superluminal jet features.

Abstract

We present a phenomenological jet model which is able to reproduce well the observed variations of the submillimetre-to-radio emission of the bright quasar 3C 273 during the last 20 years. It is a generalization of the original shock model of Marscher & Gear (1985), which is now able to describe an accelerating or decelerating shock wave, in a curved, non-conical and non-adiabatic jet. The model defines the properties of a synchrotron outburst which is expected to be emitted by the jet material in a small region just behind the shock front. By a proper parameterization of the average outburst's evolution and of the peculiarities of individual outbursts, we are able to decompose simultaneously thirteen long-term light-curves of 3C 273 in a series of seventeen distinct outbursts. It is the first time that a model is so closely confronted to the long-term multi-wavelength variability properties of a quasar. The ability of the model to reproduce the very different shapes of the submillimetre-to-radio light curves of 3C 273 gives strong support to the shock model of Marscher & Gear (1985). Indirectly, it also reinforces the idea that the outbursts seen in the light-curves are physically linked to the distinct features observed to move along the jet with apparently superluminal velocities.