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  • Rani, B; Krichbaum, T P; Fuhrmann, L; Boettcher, M; Lott, B; Aller, H D; Aller, M F; Angelakis, E; Bach, U; Bastieri, D; Falcone, A D; Fukazawa, Y; Gabanyi, K E; Gupta, A C; Gurwell, M; Itoh, R; Kawabata, K S; Krips, M; Lähteenmäki, A A; Liu, X; Marchili, N; Max-Moerbeck, W; Nestoras, I; Nieppola, E; Quintana-Lacaci, G; Readhead, A C S; Richards, J L; Sasada, M; Sievers, A; Sokolovsky, K; Stroh, M; Tammi, J; Tornikoski, M; Uemura, M; Ungerechts, H; Urano, T; Zensus, J A

    arXiv.org, 01/2013
    Paper, Journal Article

    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.