Vol 7, No 6 (2007): (743-844) / Liu

Generation of Interstellar Class II 72–81A+ and 72–81A- Methanol Masers

Han-Ping Liu, Jin Sun


New methanol maser lines at 72→63A(86.6 GHz) and 72→63A+(86.9 GHz) together with two candidate methanol maser lines at 72→81A(80.99 GHz) and 72→81A+(111.29 GHz) have been detected in W3(OH). We use a pumping mechanism, i.e., methanol masers without population inversion, to explain the formation of weak methanol masers of 72→81A+ and 72→81A. We explain well why the line-shape of the transition 72→81A+ is not typical. A similar argument can be applied to the Λ-type level system 72A, 63A and 81A, as well as to the 72→81A 80.99 GHz masers.

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DOI: https://doi.org/10.1088/1009-9271/7/6/07


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