Localising the gamma-ray emission region during the June 2014 outburst
  of 3C 454.3
  In May - July 2014, the flat spectrum radio quasar 3C 454.3 exhibited strong
flaring behaviour. Observations with the Large Area Telescope detector on-board
the Fermi Gamma-ray Space Telescope captured the $\gamma$-ray flux at energies
0.1 $\leq E_{\gamma}\leq$ 300 GeV increasing fivefold during this period, with
two distinct peaks in emission.
  The $\gamma$-ray emission is analysed in detail, in order to study the
emission characteristics and put constraints on the location of the emission
region. We explore variability in the spectral shape of 3C 454.3, search for
evidence of a spectral cutoff, quantify the significance of VHE emission and
investigate whether or not an energy-dependence of the emitting electron
cooling exists. $\gamma$-ray intrinsic doubling timescales as small as
$\tau_{int} = 0.68$ $\pm$ 0.01 h at a significance of > 5$\sigma$ are found,
providing evidence of a compact emission region. Significant $E_{\gamma,
emitted}\geq$ 35 GeV and $E_{\gamma, emitted}\geq$ 50 GeV emission is also
observed. The location of the emission region can be constrained to $r\geq1.3$
$\times$ $R_{BLR}^{out}$, a location outside the broad-line region. The
spectral variation of 3C 454.3 also suggests that these flares may be
originating further downstream of the supermassive black hole than the emission
before and after the flares.
