THE EXTRAORDINARY GAMMA-RAY FLARE OF THE BLAZAR 3C 454.3

We present the gamma-ray data of the extraordinary flaring activity above 100 MeV from the flat spectrum radio quasar 3C 454.3 detected by AGILE during the month of 2009 December. 3C 454.3, which has been among the most active blazars of the FSRQ type since 2007, has been detected in the gamma-ray range with a progressively rising flux since 2009 November 10. The gamma-ray flux reached a value comparable with that of the Vela pulsar on 2009 December 2. Remarkably, between 2009 December 2 and 3, the source more than doubled its gamma-ray emission and became the brightest gamma-ray source in the sky with a peak flux of F(gamma,p) = (2000 +/- 400) x 10 (8) ph cm (2) s (1) for a 1 day integration above 100 MeV. The gamma-ray intensity decreased in the following days with the source flux remaining at large values near F(gamma) similar or equal to (1000 +/- 200) x 10(-8) ph cm(-2) s(-1) for more than a week. This exceptional gamma-ray flare dissipated among the largest ever detected intrinsic radiated power in gamma-rays above 100 MeV (L(gamma,source,peak) similar or equal to 3 x 10(46) erg s(-1), for a relativistic Doppler factor of delta similar or equal to 30). The total isotropic irradiated energy of the month-long episode in the range 100 MeV-3 GeV is E(gamma,iso) similar or equal to 10(56) erg. We report the intensity and spectral evolution of the gamma-ray emission across the flaring episode. We briefly discuss the important theoretical implications of our detection.