We test the consistency of active galactic nuclei ( AGN ) optical flux variability with the damped random walk ( DRW ) model .
Our sample consists of 20 multi-quarter Kepler AGN light curves including both Type 1 and 2 Seyferts , radio-loud and -quiet AGN , quasars , and blazars . 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 .