Grid results for SiS RT models for four stars of the sample. As in Fig. 1, but for ²⁸SiS (red), ²⁹SiS (green), ³⁰SiS (blue), and Si³⁴S (cyan). For IRAS 07454–7112, the contours shown are 2, 3, and 4σ (see Sect. 4.2.3). See Sect. 4.2 for descriptions of the hatched ‘best-fit’ regions for the individual sources. The x-axis ticks show ²⁸SiS abundances. The ²⁹SiS, ³⁰SiS, and Si³⁴S abundances at each point of the grid are given by its ²⁸SiS abundance divided by 20, 30, and 22, respectively (see Sect. 3.2).