Are the Variability Properties of the Kepler AGN Light Curves Consistent
  with a Damped Random Walk?
  We test the consistency of active galactic nuclei (AGN) optical flux
variability with the $\textit{damped random walk}$ (DRW) model. Our sample
consists of 20 multi-quarter $\textit{Kepler}$ AGN light curves including both
Type 1 and 2 Seyferts, radio-loud and -quiet AGN, quasars, and blazars.
$\textit{Kepler}$ observations of AGN light curves offer a unique insight into
the variability properties of AGN light curves because of the very rapid
($11.6-28.6$ min) and highly uniform rest-frame sampling combined with a
photometric precision of $1$ part in $10^{5}$ over a period of 3.5 yr. We
categorize the light curves of all 20 objects based on visual similarities and
find that the light curves fall into 5 broad categories. We measure the first
order structure function of these light curves and model the observed light
curve with a general broken power-law PSD characterized by a short-timescale
power-law index $\gamma$ and turnover timescale $\tau$. We find that less than
half the objects are consistent with a DRW and observe variability on short
timescales ($\sim 2$ h). The turnover timescale $\tau$ ranges from $\sim
10-135$ d. Interesting structure function features include pronounced dips on
rest-frame timescales ranging from $10-100$ d and varying slopes on different
timescales. The range of observed short-timescale PSD slopes and the presence
of dip and varying slope features suggests that the DRW model may not be
appropriate for all AGN. We conclude that AGN variability is a complex
phenomenon that requires a more sophisticated statistical treatment.
