Line profile of HC₃N (cyanoacetylene) emission in G013.6562-00.5997 with rest frequency ν_lsr = 227.41891 GHz (the vertical red dot-dashed line in the top panel). The turquoise curve is the observed line with central frequency marked by the vertical grey dashed line. The black curve is the line corrected by V_lsr = 50.0 km s⁻¹ (Lumsden et al. 2013; Frimpong 2021). The red curve is the line corrected by V_lsr = 49.0 km s⁻¹. The bottom panel shows the cross-correlation function of the same source maximized at V_lsr = 49.0 km s⁻¹.