Portion of an X-shooter spectrum of J0019–0137 featuring H₂ absorption bands. The solid red line shows the overall absorption model, and the contribution from non-H₂ lines (H I, metals and lines from intervening systems) is shown as a dashed profile. The blue segments connect lines from different rotational levels (shown here for convenience from J = 0 to J = 5) of a given band (indicated by the label above, ’L’ for Lyman, ’W’ for Werner, and the following number is the upper vibrational level.