Orbit-averaged wind magnitude (w₀) as a function of MJD (data points) from fits of Eq. (9) to the residuals in each of the MJD bins shown in Fig. A.1. The solid grey line and the shaded area correspond to the linear fit to the data and the 1σ confidence interval of the best fit, respectively. The inset figure shows the 2D joint probability-density function of the rate of change of w₀ with time (a) and the reference MJD, t₀ (at which w₀ = 0), given the entire data set of residuals. The red star symbol corresponds to the location of the most likely values of a and t₀. The dashed line corresponds to the most probable function that describes the evolution of w₀ with time.