MULTIWAVELENGTH OBSERVATIONS OF A DRAMATIC HIGH-ENERGY FLARE IN THE BLAZAR 3C-279

The blazar 3C 279, one of the brightest identified extragalactic objec ts in the gamma-ray sky, underwent a large (factor of similar to 10 in amplitude) flare in gamma-rays toward the end of a 3 week pointing by Compton Gamma Ray Observatory (CGRO), in 1996 January-February. The f lare peak represents the highest gamma-ray intensity ever recorded for this object. During the high state, extremely rapid gamma-ray variabi lity was seen, including an increase of a factor of 2.6 in similar to 8 hr, which strengthens the case for relativistic beaming. Coordinated multifrequency observations were carried out with Rossi X-Ray Timing Explorer (RXTE), Advanced Satellite for Cosmology and Astrophysics (AS CA; ol, Astro-D), Roentgen Satellite (ROSAT), and Intel national Ultra violet Explorer (IUE) and from many ground-based observatories, coveri ng most accessible wavelengths. The well-sampled, simultaneous RXTE li ght curve shows an outburst of lower amplitude (factor of similar or e qual to 3) well correlated with the gamma-ray flare without any lag la rger than the temporal resolution of similar to 1 day. The optical-UV light curves, which are not well sampled during the high-energy flare, exhibit more modest variations (factor of similar to 2) and a lower d egree of correlation. The flux at millimetric wavelengths was near a h istorical maximum during the gamma-ray flare peak, and there is a sugg estion of a correlated decay. We present simultaneous spectral energy distributions of 3C 279 prior to and near to the flare peak. The gamma -rays vary by more than the square of the observed IR-optical flux cha nge, which poses some problems for specific blazar emission models. Th e synchrotron self-Compton (SSC) model would require that the largest synchrotron variability occurred in the mostly unobserved submillimete r/far-infrared region. Alternatively, a large variation in the externa l photon held could occur over a timescale of a few days. This occurs naturally in the ''mirror'' model, wherein the flaring region in the j et photoionizes nearby broad emission line clouds, which, in turn, pro vide soft external photons that are Comptonized to gamma-ray energies.