Abstract:
We present the accretion disc-size estimates for a sample of 19 active galactic nuclei (AGNs) using the optical g-, r-, and i-band
light curves obtained from the Zwicky Transient Facility survey. All the AGNs have reliable supermassive black hole (SMBH)
mass estimates based on previous reverberation mapping measurements. The multiband light curves are cross-correlated, and
the reverberation lag is estimated using the Interpolated Cross-Correlation Function method and the Bayesian method using the
JAVELIN code. As expected from the disc-reprocessing arguments, the g − r band lags are shorter than the g − i band lags for
this sample. The interband lags for all, but five sources, are larger than the sizes predicted from the standard Shakura Sunyaev
(SS) analytical model. We fit the light curves directly using a thin disc model implemented through the JAVELIN code to get the
accretion disc sizes. The disc sizes obtained using this model are on an average 3.9 times larger than the prediction based on the
SS disc model. We find a weak correlation between the disc sizes and the known physical parameters, namely the luminosity
and the SMBH mass. In the near future, a large sample of AGNs covering broader ranges of luminosity and SMBH mass from
large photometric surveys would be helpful in a better understanding of the structure and physics of the accretion disc.
