CH₃¹⁸OH spectra (black line) observed at the CH₃¹⁸OH peaks (a) MeOH1 and (b) MeOH2 in the rest frame, and CH₃¹⁷OH spectra (black line) observed at (c) MeOH1 and (d) MeOH2. The system velocities are assumed to be V_LSR = 7.50 km s⁻¹ and 7.55 km s⁻¹ for MeOH1 and MeOH2, respectively. The spectra were obtained after the angular resolutions of observation data were convolved to be the 2″.0 × 2″.0 beam. The solid red line in (c) and (d) is the experimentally measured CH₃¹⁷OH spectrum obtained in a laboratory (Tamanai et al. 2025) with an arbitrary intensity scale. The dashed red lines are the positions of CH₃¹⁸OH and CH₃¹⁷OH and the dashed black lines are those of other molecules. Molecular names with a question mark, “?,” indicate the potential molecular species. “U” indicates an unidentified emission line. Blue lines are model spectra of CH₃¹⁸OH and CH₃¹⁷OH predicted with the LTE model by using the column densities estimated in Table 3 and the line parameters listed in Table 2. The line width is assumed to be 2.5 km s⁻¹ and 2.1 km s⁻¹ for MeOH1 and MeOH2, respectively; these values were evaluated from the Gaussian fitting to the CH₃¹⁸OH (5₀–4₀, E) line. The Sμ² and E_u values are taken from Tamanai et al. (2025).