Supermassive black holes with high accretion rates in active galactic
  nuclei: X. Optical variability characteristics
  We compiled a sample of 73 active galactic nuclei (AGNs) with reverberation
mapping (RM) observations from RM campaigns including our ongoing campaign of
monitoring super-Eddington accreting massive black holes (SEAMBHs). This sample
covers a large range of black hole (BH) mass $(M_{\bullet}=10^{6-9}~M_\odot)$,
dimensionless accretion rates $(\dot{\mathscr{M}}=10^{-2.7}-10^{2.7})$ and
5100~\AA~luminosity $(L_{5100}=10^{42-46}~\rm erg~s^{-1})$, allowing us to
systematically study the AGN variability and their relations with BH mass,
accretion rates, and optical luminosity. We employed the damped random walk
(DRW) model to delineate the optical variability of continuum at 5100~\AA~and
obtained damped variability timescale ($\tau_{\rm d}$) and amplitude
($\sigma_{\rm d}$) using a Markov Chain Monte Carlo (MCMC) method. We also
estimated the traditional variability amplitudes ($F_{\rm var}$), which provide
a model-independent measure and therefore are used to test the DRW results. We
found that AGN variability characteristics are generally correlated with
$(M_{\bullet},\dot{\mathscr{M}},L_{5100})$. These correlations are smooth from
sub-Eddington to super-Eddington accretion AGNs, probably implying that the AGN
variability may be caused by the same physical mechanism.
