HARPS-N RV (top panel), Call S-index (middle panel), and FWHM (bottom panel) measurements of HAT-P-11 during the four HAT-P-11 b transit nights for atmospheric characterisation. The three time series are highly correlated showing the same long-term trend, with no apparent shifts in the minima of variations. The vertical dashed line indicates the predicted periastron time of the hypothetical planet c, and the grey area shows its 1σ error bar accounting for the uncertainty on the orbital period from Yee et al. (2018). Note: The HARPS-N radial velocities were divided by their median of −63420.4 m s⁻¹, to make a straightforward comparison with the HIRES radial velocities in Fig. 4.