Eccentricity of the eclipsing binary as a function of semi-major axis (top two plots) and period (bottom two plots). Plots b and d are zoomed versions of the a and c, respectively, showing the tightest binaries (P_bin< 12 d) with eccentricities compatible with zero. In the top plot the error in semi-major axis is shown, but this is excluded in the zoomed version for clarity. In the third figure (period vs. eccentricity, not zoomed) we use dashed lines to denote fits using the Meibom & Mathieu function in Eq. (11). The purple dashed line is a fit to all of the data where P_cut = 8.9 days, whilst the red dashed line is a fit to all binaries with M₁< 1.3 M_⊙ and no sign of a tertiary companion. In this latter case P_cut = 7.0 days.