Optical and ultraviolet observations of 3C 279 during outburst

An ongoing program of photometric monitoring of selected active galactic nuclei has revealed a significant outburst in the optically violently variable (OVV) quasi-steller object (QSO) 3C 279. The event occurred during May and June of 1992, and was characterized by a peak amplitude of 2.3 mag in the R band. We obtained nearly simultaneous optical and ultraviolet spectroscopy from 1150 to 8600 A of the source at the approximate midpoint of the outburst. The outburst spectrum is well represented by a power law with index alpha = -1.77 (where F(sub nu) varies as nu (exp alpha) which is relatively flat in comparison with typical quiescent spectra for this source. No emission features are discernable in our data, nor is there any significant Lyman-edge absorption. The observations and data analysis procedures are described, and the resulting photometric light curves and spectra are presented. We also present a long baseline photometric light curve for context. Comparisons with previously published optical-UV outburst and quiescent spectra are made, and luminosity-dependent spectral variations are discussed.