Simultaneous multiwavelength spectrum and variability of 3C 279 from 10(9) to 10(24) Hz

Data from a number of monitoring programs have been combined with data from the Compton Gamma Ray Observatory and the Ginga X-ray satellite to construct a spectrum covering nearly 15 decades in frequency during or near the time of the 3C 279 gamma-ray flare observed by EGRET in 1991 June. A much less complete spectrum is presented for 1991 October. Light curves from early 1991 to mid-1992 are presented for radio, millimeter, submillimeter, infrared, optical, and gamma-rays. Although the temporal coverage is incomplete, the only evidence for correlation in variability between the gamma-rays and lower frequencies is a flare in the optical R-band that peaks within similar to 1 day of the maximum in the gamma-ray light curve. The variability shows higher relative amplitude in gamma-rays than in the R band. We present spectral fits to the overall multi-wave band spectrum averaged over the 1991 June flare corresponding to two models: (i) synchrotron self-Compton (SSC) emission from a relativistic jet and (ii) inverse Compton scattering of seed photons originating external to the jet (ECS) by the synchrotron-emitting relativistic electrons in the jet. Either model can fit the observed spectra satisfactorily. The higher amplitude of the gamma-ray variations is as predicted by the SSC model and can be accommodated within the ECS model if the flare is caused by a temporary change in the bulk Lorentz factor of the gamma-ray-emitting plasma.