出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：The BL Lac object S5 0716+71 was a target of a coordinated and global multi-frequency campaign
to search for rapid and correlated variability, and signatures of the inverse-Compton (IC)
catastrophe. Here, we present first results obtained from a combined analysis of the cm- to submm
observations over a period of seven days, aiming at a detailed study of the intra- to inter-day
variability characteristics and to obtain constraints on the variability brightness temperatures and
Doppler factors comparing the radio data with the high-energy emission recorded by INTEGRAL.
A more detailed description of the whole cm- to sub-mm observations and our analysis/results will
be presented in a forthcoming paper. Our analysis reveals the source to be in a particularly shortterm
variability phase when compared to the past with a correlated &4 day time scale amplitude
increase of up to 35%, which is systematically more pronounced towards higher frequencies. The
obtained frequency-dependent variability amplitudes and time lags contradict expectations from
interstellar scintillation and strongly suggest an intrinsic origin of this inter-day variability. A
7-day spectral-evolution study indicate time-variable synchrotron self-absorption and expansion
of the emission region, consistent with standard models. Assuming relativistic boosting, our different
estimates of the Doppler factor yield robust lower limits of Dvar,IC > 5-22 using the IC-limit
and Dvar,eq > 8-33 using the equipartition argument. Although high, these values are in a good
agreement with Doppler factors obtained from recent VLBI studies and from the IC Doppler
factors DIC > 14-16 derived based on the X-ray emission seen by INTEGRAL at 3–200 keV.
