Comparison of model light curves based on the mean S2 emission and the modelled thermal emission of its bow shock (solid green and blue lines) with the observed L′-band emission of S2 (red points with errorbars). Upper panels: modelled thermal emission of the bow shock is associated with the extinction of A = 0.04 mag, which was inferred from the standard deviation of observed light curve points. We model the thermal dust emission of the ambient bow shock (solid green line in left panel) and the thermal emission of the stellar-wind shock (solid blue line in right panel) separately. The horizontal solid black line represents the light curve mean value, while the dashed black lines stand for the standard deviation. Lower panels: as in the upper panels, but for the extinction of A = 0.02 mag based on the excess variance of the observed light-curve points.