Wednesday, July 10, 2013

1307.2522 (Svetlana G. Jorstad et al.)

A Tight Connection between Gamma-Ray Outbursts and Parsec-Scale Jet Activity in the Quasar 3C 454.3    [PDF]

Svetlana G. Jorstad, Alan P. Marscher, Paul S. Smith, Valeri M. Larionov, Iván Agudo, Mark Gurwell, Ann E. Wehrle, Anne Lähteenmäki, Maria G. Nikolashvili, Gary D. Schmidt, Arkady A. Arkharov, Dmitry A. Blinov, Kelly Blumenthal, Carolina Casadio, Revaz A. Chigladze, Natatia V. Efimova, Joseph R. Eggen, José L. Gómez, Dirk Grupe, Vladimir A. Hagen-Thorn, Manasvita Joshi, Givi N. Kimeridze, Tatiana S. Konstantinova, Evgenia N. Kopatskaya, Omar M. Kurtanidze, Sofia O. Kurtanidze, Elena G. Larionova, Liudmilla V. Larionova, Sigua A. Lorand, Nicholas R. MacDonald, Jeremy D. Maune, Ian M. McHardy, H. Richard Miller, Sol N. Molina, Daria A. Morozova, Terri Scott, Brian Taylor, Merja Tornikoski, Ivan S. Troitsky, Clemens Thum, Gary Walker, Karen E. Williamson, Stephanie Sallum, Santina Consiglio, Vladimir Strelnitski
We analyze the multifrequency behavior of the quasar 3C 454.3 during three prominent \gamma-ray outbursts: 2009 Autumn, 2010 Spring, and 2010 Autumn. The data reveal a repeating pattern, including a triple flare structure, in the properties of each \gamma-ray outburst, which implies similar mechanism(s) and location for all three events. The multi-frequency behavior indicates that the lower frequency events are co-spatial with the \gamma-ray outbursts, although the \gamma-ray emission varies on the shortest timescales. We determine that the variability from UV to IR wavelengths during an outburst results from a single synchrotron component whose properties do not change significantly over the different outbursts. Despite a general increase in the degree of optical linear polarization during an outburst, the polarization drops significantly at the peak of the \gamma-ray event, which suggests that both shocks and turbulent processes are involved. We detect two disturbances (knots) with superluminal apparent speeds in the parsec-scale jet associated with the outbursts in 2009 Autumn and 2010 Autumn. The kinematic properties of the knots can explain the difference in amplitudes of the \gamma-ray events, while their millimeter-wave polarization is related to the optical polarization during the outbursts. We interpret the multi-frequency behavior within models involving either a system of standing conical shocks or magnetic reconnection events located in the parsec-scale millimeter-wave core of the jet. We argue that \gamma-ray outbursts with variability timescales as short as ~ 3 hr can occur on parsec scales if flares take place in localized regions such as turbulent cells.
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