Comparison between the line selection used in Dumusque (2018) and the new line selection described in this work. Top panel: line centres given by the HARPS K5 mask and window width fixed at 16 pixels (see Dumusque 2018). Bottom panel: lines are automatically found using an extremum localisation algorithm. The minima shown in red give the line centres, and the maxima shown in green define the maximum width allowed for the windows. Our windows are narrower than these maximum windows and are derived using the second derivative of the flux (see Appendix C for more details).