Datensatz

Zusammenfassung

In 2003, PKS 2155-304 has been significantly detected by H.E.S.S. at Very High Energies (VHE), with an average spectrum of = 3.3. Due to absorption by the Extragalactic Background Light (EBL), the intrinsic spectrum is heavily modified both in shape and intensity. To correct for this effect, and locate the Inverse Compton (IC) peak of the Spectral Energy Distribution (SED), we used three EBL models (representatives of three different flux levels for the stellar peak component). The resulting TeV spectrum has a peak around 1 TeV for stellar peak fluxes above the Primack (2001) calculation, while the spectrum is steeper than = 2 (thus locating the IC peak < 200 GeV) for fluxes below. With bulk Lorentz factors = 20 – 30 (typically used for this object), in the first case the IC peak is in the Klein-Nishina transition region, while in the other case it is in the Thompson regime, and in agreement with the commonly fitted source parameters (e.g. [17]). The constraint on given by transparency to 2 TeV photons is > 19 (for historical SED fluxes and 2 hours variability timescale). ©2005 American Institute of Physics