Phase and amplitude of the 13.39 day signal as a function of the time centre of the window t₀ for the solar HARPS-N data, as described in Sect. 2.2 (solid red and green lines, respectively). Markers correspond to statistically independent estimates. Dashed red and green lines represent the average phase and amplitudes. The figures are all computed for a timescale of τ = 539 days, corresponding to τ∕T_obs = 1/9. Plots (a), (b), (c), and (d) are computed by adding iteratively the signals corresponding to the highest peaks to the base model.