Flaring Behavior of the Quasar 3C~454.3 across the Electromagnetic Spectrum

TL;DR

This study investigates the multi-wavelength flaring activity of quasar 3C 454.3 from 2005 to 2008, linking jet disturbances, optical outbursts, and high-energy emissions to understand jet dynamics and energy dissipation sites.

Contribution

It provides detailed analysis of jet disturbances, their relation to multi-wavelength outbursts, and the association of optical polarization rotation with flare stages in a blazar.

Findings

Jet disturbances have Lorentz factors >10 and correlate with millimeter-wave outbursts.

Optical outbursts precede millimeter peaks by 15-50 days and are linked to superluminal knot propagation.

Optical polarization rotation is common during early flare stages.

Abstract

We analyze the behavior of the parsec-scale jet of the quasar 3C~454.3 during pronounced flaring activity in 2005-2008. Three major disturbances propagated down the jet along different trajectories with Lorentz factors $\Gamma>$10. The disturbances show a clear connection with millimeter-wave outbursts, in 2005 May/June, 2007 July, and 2007 December. High-amplitude optical events in the $R$-band light curve precede peaks of the millimeter-wave outbursts by 15-50 days. Each optical outburst is accompanied by an increase in X-ray activity. We associate the optical outbursts with propagation of the superluminal knots and derive the location of sites of energy dissipation in the form of radiation. The most prominent and long-lasting of these, in 2005 May, occurred closer to the black hole, while the outbursts with a shorter duration in 2005 Autumn and in 2007 might be connected with the passage of a disturbance through the millimeter-wave core of the jet. The optical outbursts, which coincide with the passage of superluminal radio knots through the core, are accompanied by systematic rotation of the position angle of optical linear polarization. Such rotation appears to be a common feature during the early stages of flares in blazars. We find correlations between optical variations and those at X-ray and $\gamma$-ray energies. We conclude that the emergence of a superluminal knot from the core yields a series of optical and high-energy outbursts, and that the mm-wave core lies at the end of the jet's acceleration and collimation zone.