Modelling the steady state spectral energy distribution of the BL-Lac Object PKS 2155-304 using a selfconsistent SSC model

Abstract

In this paper we present a fully selfconsistent SSC model with particle acceleration due to shock and stochastic acceleration (Fermi-I and Fermi-II-Processes respectively) to model the quiescent spectral energy distribution (SED) observed from PKS 2155. The simultaneous August/September 2008 multiwavelength data of H.E.S.S., Fermi, RXTE, SWIFT and ATOM give new constraints to the high-energy peak in the SED concerning its curvature. We find that, in our model, a monoenergetic injection of electrons at $\gamma_0 = 910$ into the model region, which are accelerated by Fermi-I- and Fermi-II-processes while suffering synchrotron and inverse Compton losses, finally leads to the observed SED of PKS 2155-30.4 shown in H.E.S.S. and Fermi-LAT collaborations (2009). In contrast to other SSC models our parameters arise from the jet's microphysics and the spectrum is evolving selfconsistently from diffusion and acceleration. The $\gamma_0$-factor can be interpreted as two counterstreaming plasmas due to the motion of the blob at a bulk factor of $\Gamma = 58$ and opposed moving upstream electrons at moderate Lorentz factors with an average of $\gamma_u \approx 8$.