Model fits to our data. Upper panels: best fit models (black curves) to the observations (“+” signs surrounded by diamonds). Fit residuals are represented by asterisks. Lower panels: parametric contour plots of the reduced chi squared goodness-of-fit statistic (). Contours at the 1σ, 2σ, and 3σ levels are plotted. The best fit value is indicated by a “+” sign while the ephemeris prediction is indicated by a cross.