RMS improvement of the ∆T_1/2(1,1) RV time series after linear detrending with different proxies. The markers represent detrending with either the S index alone (circles with orange edges), different 4-bin residuals (convex polygons with black edges), a multi-linear combination of all 4-bin residuals (crosses), or a multi-linear combination of all 4-bin residuals and the S index (stars). The marker sizes and colors indicate the same properties as described in Fig. 3.