2011MNRAS.416.2857Z

In this paper, we study the structure of the broad emission-line regions (BLRs) of the well-known double-peaked emitter (an active galactic nucleus with broad double-peaked low-ionization emission lines) 3C 390.3. Besides the best-fitting results for the double-peaked broad optical Balmer lines of 3C 390.3 obtained from the theoretical disc model, we also try to find another way to further confirm that the double-peaked line originates from an accretion disc. Based on the long-period spectra in the optical band observed around 1995, collected by the AGN Watch project, the theoretical disc parameters of disc-like BLRs supposed by the elliptical accretion disc model have been well determined. Using theoretical disc-like BLRs, the characteristics of the observed light curves of the broad double-peaked Hα of 3C 390.3 can be reproduced well, based on the reverberation mapping technique. Thus, the accretion disc model is preferred as the better model for the BLRs of 3C 390.3. Furthermore, we find that different disc parameters should lead to some different results about the size of the BLRs of 3C 390.3 from those measured using observational data. This indicates that the measured disc parameters are valid for 3C 390.3. After this, with the precession of theoretical elliptical disc-like BLRs considered, we find that the line profile in 2000 expected by the theoretical model is consistent with the line profile observed by the Hubble Space Telescope around 2000. Based on the results, we believe that the broad double-peaked Balmer emission lines of 3C 390.3 originate from an accretion disc around a central black hole.