Multiepoch multiwavelength spectra and models for blazar 3C 279

Of the blazars detected by EGRET in GeV gamma -rays, 3C 279 is not only the best observed by EGRET but also one of the best monitored at lower frequen cies. We have assembled 11 spectra, from GHz radio through GeV gamma -rays, from the time intervals of EGRET observations. Although some of the data h ave appeared in previous publications, most are new, including data taken d uring the high states in early 1999 and early 2000. All of the spectra show substantial gamma -ray contribution to the total luminosity of the object; in a high state, the gamma -ray luminosity dominates over that at all othe r frequencies by a factor of more than 10. There is no clear pattern of tim e correlation; different bands do not always rise and fall together, even i n the optical, X-ray, and gamma -ray bands. The spectra are modeled using a leptonic jet, with combined synchrotron self-Compton plus external Compton gamma -ray production. Spectral variability of 3C 279 is consistent with v ariations of the bulk Lorentz factor of the jet, accompanied by changes in the spectral shape of the electron distribution. Our modeling results are c onsistent with the UV spectrum of 3C 279 being dominated by accretion disk radiation during times of low gamma -ray intensity.