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

TL;DR

This study models the spectral energy distribution of the quasar 3C 454.3 using a flat broad-line-region structure, revealing insights into jet energy balance, BLR geometry, and black hole mass during gamma-ray flares.

Contribution

It introduces a flat BLR model to explain gamma-ray outbursts in 3C 454.3, providing new estimates of BLR geometry and black hole mass based on multi-wavelength data.

Findings

Jet is near equipartition during outbursts.

Covering factor of BLR varies with emitting region location.

BLR aperture angle is approximately 45 degrees.

Abstract

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 $f_{\rm BLR}$ of the BLR is very small; as the emitting region goes into the BLR structure, $f_{\rm BLR}$ increases. (iii) The aperture angle $\alpha$ describing the BLR structure is about $45^{\circ}$; (iv) The central black hole (BH) mass is about $5\times 10^{8}$\,$M_{\odot}$ rather than $4.4\times 10^{9}$\,$M_{\odot}$.