Vol. 539
In section 4. Extragalactic astronomy

A multiwavelength view of the flaring state of PKS 2155-304 in 2006

by A. Abramowski, F. Acero, et al. (H.E.S.S. collaboration) A&A 539, A149

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The paper provides a comprehensive view of an active state of the prototypical blazar PKS 2155-304 covering the interval from centimeter radio to TeV and combining ground-based and satellite data. The authors construct time-dependent spectral energy distributions. This campaign is also discussed in the context of the multi-year behavior of the source, providing a detailed overview of its activity. A major new result is the strong correlation during flaring between the X-rays and very high-energy gamma-ray flux variations. This is not found for the low-activity state that is modeled well by a self-Compton synchrotron model. A two-zone model is successfully applied to these data and will serve as a baseline for any future modeling.