2016ApJ...830..162B

A prominent outburst of the flat spectrum radio quasar 3C 454.3 was observed in 2014 June with the Fermi Large Area Telescope. This outburst was characterized by a three-stage light-curve pattern-plateau, flare, and post-flare-that occurred from 2014 May to July, in a similar pattern as observed during the exceptional outburst in 2010 November. The highest flux of the outburst reported in this paper occurred during 2014 June 7-29, showing a multiple-peak structure in the light-curves. The average flux in these 22 days was found to be F[E>100 MeV]=(7.2±0.2)×10^–6 ph cm^–2 s^–1, with a spectral index, for a simple power law, of Γ=2.04±0.01. That made this outburst the first γ-ray high state of 3C 454.3 ever to be detected by Fermi with such a hard spectrum over several days. The highest flux was recorded on 2014 June 15, in a 3 hr bin, at MJD 56823.5625, at a level of F[E>100 MeV]=(17.6±1.9)×10^–6 ph cm^–2 s^–1. The rise time of one of the short subflares was found to be T_r=1200±700 s at MJD = 56827, when the flux increased from 4 to 12 x 10^–6 ph cm^–2 s^–1. Several photons above 20 GeV were collected during this outburst, including one at 45 GeV on MJD 56827, constraining the γ-ray emission region to be located close to the outer boundary of the broad-line region, leading to fast flux variability.