FLARING BEHAVIOR OF THE QUASAR 3C 454.3 ACROSS THE ELECTROMAGNETIC SPECTRUM

Abstract

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