Variability in the V magnitude and in the UD angular diameters in the near-continuum band, and in bands dominated by H₂O (2.05 μm) and CO 2–0 (2.29 μm). Also shown are sinusoidal fit results. The minimum continuum size tracks the maximum light, which can be understood by the increasing effective temperature when the star gets smaller. The minimum contribution of H₂O tracks the maximum light as well, which can be understood as the destruction of water vapour at maximum light and formation at minimum light. The contribution from CO instead is greatest at maximum light, indicating a different and more stable behaviour of CO compared to water vapour.