INTEGRAL observations of the blazar 3C 454.3 in outburst
Maraschi, L.; Tagliaferri, G.; Ghisellini, G.; Pian, E.; Gehrels, N.; Tosti, G.; Giommi, P.; Villata, M.; Tavecchio, F.; Walter, R.; Foschini, L.; Di Cocco, G.; Malaguti, G.; Treves, A.; Raiteri, C. M.; Tornikoski, M.; Barr, P.; Persic, M.; Courvoisier, T. J. -L.; Türler, M.; Fuhrmann, L.; Pursimo, T.; Beckmann, V.; Soldi, S.; Hudec, R.
Italy, United States, Switzerland, Spain, Finland, Netherlands, Czech Republic
Abstract
In Spring 2005, the blazar 3C 454.3 underwent a dramatic outburst at all wavelengths from mm to X-rays. This prompted INTEGRAL observations, accomplished in 15-18 May 2005. The source was detected by the INTEGRAL instruments from 3 to 200 keV in a bright state (∼ 5 × 10-10 erg s-1 cm-2), at least a factor of 2-3 higher than previously observed. This is one of the brightest blazar detections achieved by INTEGRAL. During the 2.5 days of INTEGRAL monitoring, we detected a ~20% decrease in the hard X-rays (20-40 keV), indicating that we have sampled the decaying part of the flare. The decrease is less apparent in the soft X-rays (5-15 keV). The simultaneous optical variations are weakly correlated with those at soft X-rays, and not clearly correlated with those at hard X-rays. The spectral energy distribution exhibits two components, as typically seen in blazars, which can be modeled with synchrotron radiation and inverse Compton scattering occurring in a region external to the broad line region.