Dependence of the optical/UV variability on the emission line properties
  and Eddington ratio in active galactic nuclei
  The dependence of the long-term optical/UV variability on the spectral and
the fundamental physical parameters for radio-quiet active galactic nuclei
(AGNs) is investigated. The multi-epoch repeated photometric scanning data in
the Stripe-82 region of the Sloan Digital Sky Survey (SDSS) are exploited for
two comparative AGN samples (mostly quasars) selected therein, a broad-line
Seyfert\,1 (BLS1) type sample and a narrow-line Seyfert\,1 (NLS1) type AGN
sample within redshifts 0.3--0.8. Their spectral parameters are derived from
the SDSS spectroscopic data. It is found that on rest-frame timescales of
several years the NLS1-type AGNs show systematically smaller variability
compared to the BLS1-type. In fact, the variability amplitude is found to
correlate, though only moderately, with the Eigenvector\,1 parameters, i.e.,
the smaller the \hb\ linewidth, the weaker the [O\,III] and the stronger the
\feii\ emission, the smaller the variability amplitude is. Moreover, an
interesting inverse correlation is found between the variability and the
Eddington ratio, which is perhaps more fundamental. The previously known
dependence of the variability on luminosity is not significant, and that on
black hole mass---as claimed in recent papers and also present in our
data---fades out when controlling for the Eddington ratio in the correlation
analysis, though these may be partly due to the limited ranges of luminosity
and black hole mass of our samples. Our result strongly supports that an
accretion disk is likely to play a major role in producing the opitcal/UV
variability.
