Observed J = 6 − 5 line of HCNS with the IRAM 30m (top panel) and Yebes 40m (middle panel) radio telescopes. The data of the Yebes telescope have been scaled to those of IRAM using the line N = 8 − 7 J = 15/2 − 13/2 of CCC¹³CH at 73819.18 MHz that appears in both sets of data with a S/N of ∼10 in the IRAM data and of ∼5 in the Yebes data. The merged spectrum was obtained by averaging both sets of data weighted as 1/σ² and has a sensitivity of 1 mK. The derived line parameters for this transition of HCNS are given in Table A.1. The red line corresponds to the computed synthetic spectra (see Sect. 3). The vertical blue line corresponds to the measured frequency for a v_LSR of 5.83 km s⁻¹.