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

摘要

New methanol maser lines at 72→63A-(86.6 GHz) and 72→63A+(86.9GHz) together with two candidate methanol maser lines at 72→81A-(80.99 GHz) and 72→81A+(111.29GHz) 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 A-type level system 72A→, 63A-and 81A-, as well as to the 72→81A- 80.99 GHz masers.