Modeling the spectral-energy-distribution of 3C 454.3 in a "flat" broad-line-region scenario

The broad-line region (BLR) of flat-spectrum radio quasars (FSRQs) could have a “flat” geometrical structure to allow GeV gamma-ray photons escape, to produce the observed gamma-ray flares with short timescales. In this paper, we collect the quasi-simultaneous spectral energy distributions (SEDs) of the FSRQ 3C 454.3 obtained by the multi-wavelength campaigns spanning from 2007 July to 2011 January, and use a model with the “flat” structure BLR, the accretion disc and the dust torus to explain the SEDs of gamma-ray outbursts. We obtain the following results: (i) The jet is almost in equipartition between magnetic and particle energy densities during the outbursts; (ii) When the emitting region locates inside the cavity of the BLR, the covering factor $f_{\mathrm{B}\mathrm{L}\mathrm{R}}$ of the BLR is very small; as the emitting region goes into the BLR structure, $f_{\rm BLR}$increases\mathrm{.}(iii)Theapertureangle$\alpha$ describing the BLR structure is about ${45}^{\circ }$; (iv) The central black hole (BH) mass is about $5\times 10^{8}$$M_{\odot}$ratherthan$4.4\times 10^{9}$$M_{\odot}$.