Water Vapor Maser "Turn-On" in the HII Region W3 (OH)

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Science  16 Dec 1977:
Vol. 198, Issue 4322, pp. 1153-1155
DOI: 10.1126/science.198.4322.1153


A line in the water vapor maser spectrum of the HII region W3(OH) was observed to increase in brightness over an 8-day period and then decline to its original intensity over the following 4 weeks. The intensity variation can be explained by a simple maser model, with an impulse of energy suddenly applied. The observed time scale and energy output are consistent with a maser on the outskirts of a dust cocoon surrounding an O5 star, with a momentary "leak," lasting a day or. two, supplying the necessary energy.