Lines of CH₃CHS observed in TMC-1 (black histogram). The negative features correspond to artifacts caused by the frequency-switching technique. The line parameters are given in Table 1. In magenta we show the LTE calculated line profiles adopting a column density of 9.8 × 10¹⁰ cm⁻², a rotational temperature of 9.0 K, a full width at half maximum of 0.76 km s⁻¹ (the average of the values observed for the seven detected components; see Table 1), and a circular emission distribution with a diameter of 80″.