CO 6−5, CO 7−6, and ¹³CO 6−5 spectra observed with the APEX telescope. The central position of Cha-MMS1 is at (0,0). The directions parallel and perpendicular to the filament are shown as dashed and dotted arrows, respectively. The central spectra of the three transitions are plotted in the rightmost panel on the scale of the main-beam brightness temperature. The dotted line shows the systemic velocity of Cha-MMS1 derived from a seven-component hyperfine fit to the N₂H⁺ 1−0 multiplet and corrected for the 0.1 km s^-1 velocity shift (see Sect. 3.2.1).