OBSERVATIONS OF PKS 2155-304 WITH THE EXTREME-ULTRAVIOLET EXPLORER

We present a high-accuracy light curve for the BL Lac object PKS 2155- 304, observed with the Extreme Ultraviolet Explorer. The light curve s hows variations of about 10% over a 1.3 day observing period. The obse rved EUV flux is a factor of 1.7 fainter than when PKS 2155-304 was ob served by the ROSAT Wide Field Camera (WFC) during the EUV survey. The optical flux during our observations is about a factor of fainter tha n during the WFC observations, so we conclude that the overall spectra l shape is invariant as the flux varies. These observations support th e model in which the spectrum from the optical to the X-ray band is gi ven by a synchrotron spectrum. Extrapolating an X-ray power-law spectr um with an energy index of 1.66 into the EUV only slightly over-predic ts the observed EUV count rates so that changing any one of several sp ectral parameters within the uncertainties gives an acceptable model.