Observed transitions of CH₃C₆H in TMC-1. The right component corresponds to K = 0 transitions and the left component to K = 1 transitions. The abscissa corresponds to local standard of rest frequencies. Central frequencies and intensities for the observed lines are given in Table A.1. The ordinate is the antenna temperature, corrected for atmospheric and telescope losses, in milli Kelvin. The quantum numbers of each transition are indicated in the corresponding panel. The red lines show the computed synthetic spectrum for this species for T_rot = 9 K and a column density of 7 × 10¹¹ cm⁻². The green line shows the computed synthetic spectrum assuming T_rot = 6 K and a N=3.1 × 10¹² cm⁻²(Remijan et al. 2006). Blanked channels correspond to negative features produced when folding the frequency-switched data.