Abstract

We have measured the light curve and spectrum of NGC 5548 obtained with the Extreme Ultraviolet Explorer (EUVE) during a period when the galaxy was also intensively monitored with the Hubble Space Telescope, the International Ultraviolet Explorer, and ground-based telescopes. NGC 5548 was observed with EUVE for a total of about 20 days spread over a period of 2 months. The broadband extreme ultraviolet (EUV) light curve showed several factor of 2 variations on 0.5 day timescales and one factor of 4 decrease over 2 days. The normalized variability index was smaller than in the EUVE observation of Mrk 478. Cross-correlation of the EUV light curve with the contemporaneous ultraviolet light curve indicates that the EUV and UV/optical variations are, to within the limitations of these data, simultaneous, although the amplitude in the EUV is twice that in the UV.

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