Constraints on orbital variations. Variations in the orbital period ΔP_b (panel a), the epoch of the ascending node ΔT_ASC (panel b), and the projected semi-major axis of the orbit Δx (panel c) are plotted against time for 180-, 360-, and 720-day segments. Here ΔP_b = 0 refers to the orbital period in Table 2 found for the full span and similarly for the other parameters. The right-hand panels show distributions of the variations for each segment length. The dotted lines denote the mean of the uncertainty on the measurements. The uncertainties are generally of the same order of magnitude as the standard deviations on the variations and the measurements do not show any clear trends.