Alok C. Gupta, T. P. Krichbaum, P. J. Wiita, B. Rani, K. V. Sokolovsky, P. Mohan, A. Mangalam, N. Marchili, L. Fuhrmann, I. Agudo, U. Bach, R. Bachev, M. Böttcher, K. E. Gabanyi, H. Gaur, K. Hawkins, G. N. Kimeridze, O. M. Kurtanidze, S. O. Kurtanidze, C. -U. Lee, X. Liu, B. McBreen, R. Nesci, G. Nestoras, M. G. Nikolashvili, J. M. Ohlert, N. Palma, S. Peneva, T. Pursimo, E. Semkov, A. Strigachev, J. R. Webb, H. Wiesemeyer, J. A. Zensus
We report results from a 1 week multi-wavelength campaign to monitor the BL Lac object S5 0716+714 (on December 9-16, 2009). In the radio bands the source shows rapid (~ (0.5-1.5) day) intra-day variability with peak amplitudes of up to ~ 10 %. The variability at 2.8 cm leads by about 1 day the variability at 6 cm and 11 cm. This time lag and more rapid variations suggests an intrinsic contribution to the source's intraday variability at 2.8 cm, while at 6 cm and 11 cm interstellar scintillation (ISS) seems to predominate. Large and quasi-sinusoidal variations of ~ 0.8 mag were detected in the V, R and I-bands. The X-ray data (0.2-10 keV) do not reveal significant variability on a 4 day time scale, favoring reprocessed inverse-Compton over synchrotron radiation in this band. The characteristic variability time scales in radio and optical bands are similar. A quasi-periodic variation (QPO) of 0.9 - 1.1 days in the optical data may be present, but if so it is marginal and limited to 2.2 cycles. Cross-correlations between radio and optical are discussed. The lack of a strong radio-optical correlation indicates different physical causes of variability (ISS at long radio wavelengths, source intrinsic origin in the optical), and is consistent with a high jet opacity and a compact synchrotron component peaking at ~= 100 GHz in an ongoing very prominent flux density outburst. For the campaign period, we construct a quasi-simultaneous spectral energy distribution (SED), including gamma-ray data from the FERMI satellite. We obtain lower limits for the relativistic Doppler-boosting of delta >= 12-26, which for a BL\,Lac type object, is remarkably high.
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http://arxiv.org/abs/1207.5942
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