Relative deviation between simulated and observed ON–OFF-to-interferometric flux ratio, , as a function of CS lifetime. The different colour lines represent the different physical conditions assumed in the model, which are presented in Table 7 (T = 50–125 K′ for the T_var temperature model). The grey shaded region corresponds to the 1-σ observed value. The CS default photo-dissociation rate (β₀ = 2.5 × 10⁻⁵ s⁻¹) is indicated by a vertical dashed line. CS is assumed to come from the photo-dissociation of CS₂.