Time-averaged differential squared visibility (top) and differential phases (bottom) around the Brγ line (left) and CO first overtone bandhead emission (right). Error bars shown represent statistical errors on the mean. A frame selection of 20 per cent was used for the visibilities and a selection rate of 80 percent was employed to obtain the averaged phases. The individual AMBER files were merged before frame selection was conducted. The dashed line alongside the CO emission represents the spectrum before telluric correction.