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The Presence of Water Masers in Color-Selected IRAS Sources

Published online by Cambridge University Press:  19 July 2016

B. M. Lewis
Affiliation:
NAIC, Arecibo Observatory
D. Engels
Affiliation:
Hamburger Sternwarte

Abstract

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Eder, Lewis, and Terzian (1987) examined ∼ 400 sources from the IRAS Point Source Catalogue with colors appropriate to OH/IR stars, for the presence of 1612 MHz emission. We examined a proportion of these objects at Effelsberg for the presence of water-maser emission. In sources with |bII| > 10° which are therefore relatively local, we find a 68% detection rate for water-masers among objects associated with 1612 MHz masers, as opposed to a 17% detection rate among sources with similar colors but without 1612 MHz emission. Those conditions in a circumstellar shell that favor the presence of water-masers also favor the presence of a 1612 MHz maser. These results are consistent with most Type II masers being associated with water-masers. Since Cooke and Elitzur (1985) show that water-masers are collisionally excited, this result excludes stirring of the envelope by a companion star with an associated loss of velocity coherence, as the primary cause for the existence of the color-analogue sources without 1612 MHz masers. We discuss an alternative scenario.

Type
V. Origin of Planetaries
Copyright
Copyright © Kluwer 1989