Top: total intensity FORS2 spectrum I (black) together with the normalised circular polarisation P_V (red) and the null profile N_V (blue) obtained by combining all data taken on 2014-06-05 for LS IV-14°116. The null profile is offset by −0.5% for display purposes, the 1σ errors expected from photon noise being represented by the light blue error bars. The green (magenta) marked wavelength ranges indicate the portions of the spectrum used for the analysis based on the H (metal) lines. Bottom: P_V (left) and N_V plotted as a function of the quantity indicated on the x-axis. The slope of P_V in this diagram is proportional to the mean longitudinal magnetic field ⟨ B_z ⟩. The plots refer to the results obtained from using the H lines (green portions of the wavelength range in the top plot) and the metal lines (magenta portions) as indicated.