Photometric data and inferred model for K2-233. Top: K2 extracted photometry (grey dots, see Sect. 2.1) and mean GP model (black dashed line). The transits for each individual planet are marked by upward triangles and colour-coded in the light curve. Middle: detrended light curve after removing the GP model and the spline high-frequency filtering (see Sect. 2.1) and including the median transit model obtained with PASTIS for the 4 planets in the system (grey solid line). Bottom: phase-folded lightcurves centred on the transit of each planet. The colour-coded symbols correspond to binned photometry with a bin size of 10% of the transit duration. The inferred transit models are shown as solid lines. The shaded regions correspond to 68.7% (dark colour) and 95% (light colour) confidence intervals.