Synchrotron Self-Compton Model for PKS 2155-304

TL;DR

This paper models the rapid TeV flare of blazar PKS 2155-304 using a synchrotron self-Compton framework, constraining emission region properties and jet composition based on observed variability and spectrum.

Contribution

It introduces a detailed SSC model with high Lorentz factor and specific emission region parameters to explain the flare's spectral and temporal features.

Findings

High Lorentz factor (~100) explains rapid variability.

Emission region size ~10^15 cm consistent with observations.

Jet energy dominated by particles over magnetic fields.

Abstract

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 $\sim 100$, the size of the emission region $\sim 10^{15}$ cm, and magnetic field $\sim 0.1$ G explain the observed spectral energy distribution and the flare timescale $\sim$ a few minutes. This model with a large value of $\Gamma$ 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.