We study the locations of emission regions through modelling the quasi-simultaneous multi-frequency spectral energy distributions of 21 Fermi flat spectrum radio quasars ( FSRQs ) in the frame of a multi-component one-zone leptonic model .
In our calculations , we take the detailed broad line region ( BLR ) structure into account and discuss the effect of the uncertainty of the BLR structure on constraining the location of the emission regions for each FSQR , meanwhile we also include both the internal and external absorptions .
Our results indicate that ( 1 ) the contribution of external Compton-BLR component is important to \gamma -ray emission , and the energy density of external target photon fields depends on the location of the emission region , which can be derived through reproducing the observed \gamma -ray emission , and ( 2 ) the emission regions of FSRQs with relative low accretion disk luminosity lie in the region of 7.9 \times 10 ^ { 16 } – 1.3 \times 10 ^ { 18 } cm ( 300 – 4300 Schwarzschild radii ) from central black hole , and for FSRQs with high accretion disk luminosity , the emission regions locate in the larger region of 2.6 \times 10 ^ { 17 } – 4.2 \times 10 ^ { 18 } cm ( 300 – 5600 Schwarzschild radii ) .