X-shooter spectra with model fit including Y⁺ lines with λ ≥ 700 nm for epochs 4 and 5. The blackbody continuum model is shown as a dashed black line, the blackbody plus the Sr⁺ P Cygni lines as a dotted purple line, and the full model including both Sr⁺ and Y⁺ as a solid red line. The partially transparent purple and red regions indicate the successive contributions to these models of the Sr⁺ and Y⁺ P Cygni lines, respectively. The grey hatched region indicates the overlapping noisy regions between the UVB and VIS arms of the spectrograph. The Y⁺ lines (from the 4d²–4d5p transitions) have fixed central wavelengths and their relative strengths are set by the LTE condition.