Upper panel: time series of the log() chromospheric index as measured from HARPS-N spectra. Middle and lower panels: correlation analysis between the RV residuals, obtained by removing the Keplerian signal due to KELT-6 b from the original HARPS-N dataset, and two indicators of stellar activity derived from the HARPS-N spectra: the log() chromospheric index and the CCF bisector span. Over-plotted are the values of Spearman’s rank correlation coefficients, which show the absence of significant correlations and support the hypothesis that the origin of the observed RV long-term variations is Keplerian.