We present a Bayesian surrogate model for the analysis of periodic or
quasi-periodic time series data. We describe a computationally e±cient implemen-
tation that enables Bayesian model comparison. We apply this model to simulated
and real exoplanet observations. We discuss the results and demonstrate some of
the challenges for applying our surrogate model to realistic exoplanet data sets. In
particular, we ¯nd that analyses of real world data should pay careful attention to
the e®ects of uneven spacing of observations and the choice of prior for the \jitter"
parameter.