2008ApJ...682..784K

H.E.S.S. observed TeV blazar PKS 2155-304 in a strong flare state in 2006 July. The TeV flux varied on timescale as short as a few minutes, which sets strong constraints on the properties of the emission region. By use of the synchrotron self-Compton model, we found that models with the bulk Lorentz factor ∼100, the size of the emission region ∼10¹⁵ cm, and magnetic field ∼0.1 G explain the observed spectral energy distribution and the flare timescale of ∼a few minutes. This model with a large value of Γ accounts for the emission spectrum not only in the TeV band but also in the X-ray band. The major cooling process of electrons/positrons in the jet is inverse Compton scattering off synchrotron photons. The energy content of the jet is highly dominated by particle kinetic energy over magnetic energy.