X-RAY-SPECTRUM OF THE BL-LACERTAE OBJECT PKS-0548-322 OBSERVED WITH GINGA

The BL Lac object PKS 0548-322 was observed in X-rays with Ginga five times between 1990 January and 1991 March. The 2-20 keV flux varied by a factor of 2.5, and the spectral energy index a showed a significant change of between 0.8+/-0.02 and 1.03+/-0.04. No simple relation has been found between the flux and the spectral index. An upper limit for the equivalent width of the iron K line is 83 eV at 90% confidence. B ased on the spectral results, we propose a simple scheme to interpret the variation of the X-ray spectrum in terms of the synchrotron emissi on. This gives new constraints on the properties of the emission regio n.