B. Rani, T. P. Krichbaum, L. Fuhrmann, M. Boettcher, B. Lott, H. D. Aller, M. F. Aller, E. Angelakis, U. Bach, D. Bastieri, A. D. Falcone, Y. Fukazawa, K. E. Gabanyi, A. C. Gupta, M. Gurwell, R. Itoh, K. S. Kawabata, M. Krips, A. A. Lähteenmäki, X. Liu, N. Marchili, W. Max-Moerbeck, I. Nestoras, E. Nieppola, G. Quintana-Lacaci, A. C. S. Readhead, J. L. Richards, M. Sasada, A. Sievers, K. Sokolovsky, M. Stroh, J. Tammi, M. Tornikoski, M. Uemura, H. Ungerechts, T. Urano, J. A. Zensus
We present the results of a series of radio, optical, X-ray and gamma-ray observations of the BL Lac object S50716+714 carried out between April 2007 and January 2011. The multi-frequency observations were obtained using several ground and space based facilities. The intense optical monitoring of the source reveals faster repetitive variations superimposed on a long-term variability trend at a time scale of ~350 days. Episodes of fast variability recur on time scales of ~ 60-70 days. The intense and simultaneous activity at optical and gamma-ray frequencies favors the SSC mechanism for the production of the high-energy emission. Two major low-peaking radio flares were observed during this high optical/gamma-ray activity period. The radio flares are characterized by a rising and a decaying stage and are in agreement with the formation of a shock and its evolution. We found that the evolution of the radio flares requires a geometrical variation in addition to intrinsic variations of the source. Different estimates yield a robust and self-consistent lower limits of \delta > 20 and equipartition magnetic field B_eq > 0.36 G. Causality arguments constrain the size of emission region \theta < 0.004 mas. We found a significant correlation between flux variations at radio frequencies with those at optical and gamma-rays. The optical/GeV flux variations lead the radio variability by ~65 days. The longer time delays between low-peaking radio outbursts and optical flares imply that optical flares are the precursors of radio ones. An orphan X-ray flare challenges the simple, one-zone emission models, rendering them too simple. Here we also describe the spectral energy distribution modeling of the source from simultaneous data taken through different activity periods.
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http://arxiv.org/abs/1301.7087
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