Multiwavelength Observations of a Dramatic High-Energy Flare in the Blazar 3C 279
Maraschi, L.; Ghisellini, G.; Pian, E.; Falomo, R.; Johnson, W. N.; Madejski, G. M.; Thompson, D. J.; Tosti, G.; Villata, M.; Sikora, M.; Pohl, M.; Kondo, Y.; Treves, A.; Raiteri, C. M.; Stevens, J. A.; Kazanas, D.; McCollum, B.; Gear, W. K.; Wagner, S. J.; Tornikoski, M.; Celotti, A.; Urry, C. M.; Aller, H. D.; Aller, M. F.; Balonek, T. J.; Marscher, A. P.; Robson, E. I.; Sillanpää, A.; Smith, P. S.; Freudling, W.; McHardy, I. M.; Makino, F.; Sambruna, R. M.; Valtaoja, E.; Backman, D. E.; Hartman, R. C.; Pesce, J. E.; Thompson, R.; Wehrle, A. E.; Collmar, W.; Inoue, H.; Webb, J. R.; Bonnell, J.; Kii, T.; Lawson, A. J.; Aldering, G. S.; Boltwood, P.; Caplinger, J.; Dalton, J.; Drucker, A.; Fichtel, C. E.; Gonzales, N.; Hall, P.; Kidger, M. R.; Kollgaard, R. I.; Kurfess, J.; Lin, Y. C.; McNaron-Brown, K.; Nagase, F.; Nair, A. D.; Penton, S.; Renda, M.; Schirmer, A. F.; Shrader, C.; Stocke, J.; Takalo, L. O.; Teräsranta, H.; Turcotte, P.; Unwin, S. C.; Xu, W.; Yamashita, A.; Zook, A.
United States, Italy, United Kingdom, Japan, Germany, Canada, Spain, Poland, Finland
Abstract
The blazar 3C 279, one of the brightest identified extragalactic objects in the γ-ray sky, underwent a large (factor of ~10 in amplitude) flare in γ-rays toward the end of a 3 week pointing by Compton Gamma Ray Observatory (CGRO), in 1996 January-February. The flare peak represents the highest γ-ray intensity ever recorded for this object. During the high state, extremely rapid γ-ray variability was seen, including an increase of a factor of 2.6 in ~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 (ASCA; or, Astro-D), Roentgen Satellite (ROSAT), and International Ultraviolet Explorer (IUE) and from many ground-based observatories, covering most accessible wavelengths. The well-sampled, simultaneous RXTE light curve shows an outburst of lower amplitude (factor of ~=3) well correlated with the γ-ray flare without any lag larger than the temporal resolution of ~1 day. The optical-UV light curves, which are not well sampled during the high-energy flare, exhibit more modest variations (factor of ~2) and a lower degree of correlation. The flux at millimetric wavelengths was near a historical maximum during the γ-ray flare peak, and there is a suggestion of a correlated decay. We present simultaneous spectral energy distributions of 3C 279 prior to and near to the flare peak. The γ-rays vary by more than the square of the observed IR-optical flux change, which poses some problems for specific blazar emission models. The synchrotron self-Compton (SSC) model would require that the largest synchrotron variability occurred in the mostly unobserved submillimeter/far-infrared region. Alternatively, a large variation in the external photon field could occur over a timescale of a few days. This occurs naturally in the ``mirror'' model, wherein the flaring region in the jet photoionizes nearby broad emission line clouds, which, in turn, provide soft external photons that are Comptonized to γ-ray energies.