Line profiles of CH₃¹⁸OH and CH₃¹⁷OH (Table 1) at the two methanol peaks, MeOH1 (left: a–h) and MeOH2 (right: i–o). The spectra were obtained after the angular resolutions of observation data were convolved to be the 2″.0 × 2″.0 beam for fair comparisons. The vertical scale is the brightness temperature. The vertical dashed lines indicate the system velocities of V_LSR = 7.50 km s⁻¹ and 7.55 km s⁻¹ for MeOH1 and MeOH2, respectively.