Observed spectrum of GQ Lup A (black) for the spectral order centred at 2345 nm, compared with a PHOENIX template (T_eff = 4300 K, log g = 4.0) that includes instrumental and rotational broadening. The mismatch between the observed line depths and the model without veiling is evident. The second panel shows the best-fit linear model (green), which incorporates a veiling continuum (pink) alongside the PHOENIX model (orange). Residuals of the best-fit model are presented in the third panel.