  Characteristic variability timescales in blazar gamma-ray light curves can
provide insight into the physical processes responsible for the gamma-ray
variability. The power spectral density (PSD) is capable of revealing such
timescales, which may appear as breaks or periodicities. Continuous-time
autoregressive moving-average (CARMA) models can be used to accurately estimate
a light curve's PSD. Through a lightcurve simulation study, we develop a
methodology to identify PSD breaks using CARMA models. Using this methodology,
we study the gamma-ray light curves of 13 bright blazars observed with the
Fermi Large Area Telescope in the 0.1-300 GeV band over 9.5 years. We present
the blazar gamma-ray PSDs, which provide evidence for low-frequency breaks on
timescales ~1 year in four sources, and an additional high-frequency break on a
timescale ~9 days in one source.
