SIMBAD references

We observed 14 methanol transitions near λ=2 mm in Galactic star-forming regions. Broad, quasi-thermal J₀-J_–1E methanol lines near 157 GHz were detected toward 73 sources. Together with the 6_–1-5₀E and 5_–2-6_–1E lines at 133 GHz and the 7₁-7₀E line at 166 GHz, they were used to study the methanol excitation. In the majority of the observed objects, the Class I 6_–1-5₀E transition is inverted, and the Class II 5_–2-6_–1E and 6₀-6_–1E transitions are overcooled. This is exactly as predicted by models of low-gain Class I masers. The absence of the inversion of Class II transitions 5_–2-6_–1E and 6₀-6_–1E means that quasi-thermal methanol emission in all objects arises in areas without a strong radiation field, which is required for the inversion.