Periodograms of the synthetic CO spectrum and the K giant spectrum per MRS band, before and after residual fringe correction. The curves are colour-coded (see insets): ‘ff’ stands for extended fringe flat and ‘rfc’ for extended fringe flat+residual fringe correction. The frequency range shown is the range where the residual_fringe pipeline algorithm searches for frequencies to remove. The red arrows indicate the largest peaks that are removed by the algorithm.