Investigating Active Galactic Nuclei Variability Using Combined
  Multi-Quarter Kepler Data
  We have used photometry from the Kepler satellite to characterize the
variability of four radio-loud active galactic nuclei (AGN) on timescales from
years to minutes. The Kepler satellite produced nearly continuous high
precision data sets which provided better temporal coverage than possible with
ground based observations. We have now accumulated eleven quarters of data,
eight of which were reported in our previous paper. In addition to constructing
power spectral densities (PSDs) and characterizing the variability of the last
three quarters, we have linked together the individual quarters using a
multiplicative scaling process, providing data sets spanning ~2.8 years with
>98% coverage at a 30 minute sampling rate. We compute PSDs on these connected
data sets that yield power law slopes at low frequencies in the approximate
range of -1.5 to -2.0, with white noise seen at higher frequencies. These PSDs
are similar to those of both the individual quarters and to those of ground
based optical observations of other AGN. We also have explored a PSD binning
method intended to reduce a bias toward shallow slope fits by evenly
distributing the points within the PSDs. This tends to steepen the computed PSD
slopes, especially when the low frequencies are relatively poorly fit. We
detected flares lasting several days in which the brightness increased by
~15-20% in one object, as well a smaller flare in another. Two AGN showed only
small, ~1-2%, fluctuations in brightness.
