THE MULTIFREQUENCY SPECTRAL EVOLUTION OF BLAZAR 3C 345 DURING THE 1991 OUTBURST

The blazar 3C 345 underwent a 2.5 mag optical outburst between 1990 No vember and 1991 May. We have obtained 10 nearly simultaneous multifreq uency spectra during the course of the outburst in order to study the multifrequency spectral variations of 3C 345 as a function of time. Al though our observations were not sampled frequently enough to complete ly resolve the variations in every frequency band, the general rise an d decline of the outburst were seen in the UV through radio with diffe ring rise times. Simulations of an electron distribution injected into a tangled magnetic field show a relationship between frequency and ch aracteristic timescale that was also observed in the radio variations of 3C 345. The two X-ray observations made during the monitoring perio d showed no evidence of variability. The multifrequency spectrum was m odeled with two major components: a relativistic jet and a relativisti c thermal accretion disk. Models calculated for each spectrum indicate that the outburst can be explained in terms of these models by varyin g the high-energy cutoff of the injected electron distribution in the jet model, while also varying the mass accretion rate in the disk mode l. There is marginal evidence that the inferred accretion rate varies with the jet luminosity.