Time series data and MLS power spectrum of the HARPS RVs and stellar activity indicators of GJ 1137. The left sub-panels show the individual RVs, the residuals of fitting the GJ 1137 b signal, and the two-Keplerian fit residuals including the long-period RV component. The rest are the HARPS activity indices as labelled in the panels. The vertical magenta line notates the HARPS-fibre change from which point we treat the pre- and post-HARPS data with a separate offset parameter. The right panel shows the individual MLP power spectrum in terms of ∆lnL as indicated in the sub-panels. The horizontal lines in the MLP periodograms show the FAP levels of 10%, 1%, and 0.1%, the latter of which is considered significant. The magenta vertical line indicates the orbital period of GJ 1137 b, whereas the red line indicates the best-fit long-term period seen in the one-planet Keplerian model residuals.