Transitions in absorption system at z_abs = 1.6919 used to derive Δα/α in our second analysis approach. The Voigt profile model (green line) is plotted over the data (blue histogram). The velocity of each fitted component is marked with a vertical line, and the residuals between the data and model, normalized by the error spectrum, are shown above each transition. The top panel shows the composite residual spectrum − the mean spectrum of the normalized residuals for all transitions shown − in units of σ.