The 0.1–200 keV spectrum of the blazar PKS 2005–489 during an active state

The bright BL Lac object PKS 2005–489 was observed by BeppoSAX on November 1–2, 1998, following an active X–ray state detected by RossiXTE. The source, detected between 0.1 and 200 keV, was in a very high state with a continuum well fitted by a steepening spectrum due to synchrotron emission only. Our X–ray spectrum is the flattest ever observed for this source. The different X–ray spectral slopes and fluxes, as measured by various satellites, are consistent with relatively little changes of the peak frequency of the synchrotron emission, always located below 10 Hz. We discuss these results in the framework of synchrotron self–Compton models. We found that for the BeppoSAX observation, the synchrotron peak frequency is between 10 and 2.5 × 10 Hz, depending on the model assumptions.