The results of the C¹⁷O observed spectrum modelling with LOC are displayed. Left: observed spectrum of the C¹⁷O (1−0) (black). This spectrum is the result of a simulation using the original C¹⁷O fractional abundance profile at 5 × 10⁵ yr and the original pre-stellar core model (OM; dotted red) and the result of a simulation using the C¹⁷O fractional abundance profile at 5 × 10⁵ yr upscaled by a factor of 3 and the original pre-stellar core model (AM 1; solid red). The residuals are computed with the adopted model, and are shown in the lower panel. The dashed lines represent the 3σ levels. Right: observed spectrum of the C¹⁷O (1−0) (black) and the result of a simulation using the C¹⁷O fractional abundance profile at 5 × 10⁵ yr increased by a factor of 3 and a scaled-up velocity profile by 30% (AM 2; solid red). Residuals are computed with the adopted model and are shown in the lower panel. The dashed lines represent the 3σ levels.