Posterior distributions of parameters of model 1C fit with an MCMC to HARPS-N N1 (blue), HARPS-N N2 (orange), CARMENES N1 (red), CARMENES N2 (green), HARPS-N N3 (purple), and all five nights combined (black). Lower panels: normalised posteriors (higher peak for better constrained parameters), and the marked improvement obtained when combining all data sets. Upper panels: 1σ (dark colour) and 2σ (light colour) confidence intervals obtained from the corresponding posteriors in the lower panels.