Results from the one- and two-Gaussian fit to the HC₃N (10−9) emission at the position of the protostar B5-IRS1. Top: HC₃N (10−9) emission spectrum at the position of B5-IRS1, together with the best fit results using one and two Gaussian curves. The vertical dashed line represents the central velocity of the protostar from P15. Bottom: residuals from the fit in terms of S/N. The dashed purple line represents the residuals after the 1 Gaussian fit, whereas the solid purple line, the residuals after the 2 Gaussian fit. The horizontal blue dashed lines mark the S/N = 3 and −3 levels.