Journal Article

Saturation and spectral asymmetry in 1612 MHz shell masers

M. D. Gray, D. A. Howe and B. M. Lewis

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 391, issue 1, pages 334-342
Published in print November 2008 | ISSN: 0035-8711
Published online November 2008 | e-ISSN: 1365-2966 | DOI:
Saturation and spectral asymmetry in 1612 MHz shell masers

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At least one ‘dying’ asymptotic giant branch star has been observed to show a strong spectral asymmetry in the decay of its 1612 MHz OH maser spectrum, with the red peak decaying substantially more rapidly than the blue peak. We have tested a model which explains the general behaviour of such stars to see if it can also explain asymmetry of this type. We find that it is actually very difficult to overcome a natural propensity for the blue peak to decay more rapidly, which is tied to the distribution of OH molecules and pumping radiation in the model. A possible solution is the presence of strongly saturating rays in the blue peak from a large stellar radiosphere, which decay more slowly than an almost unsaturated red peak.

Keywords: masers; molecular processes; stars: AGB and post-AGB; stars: mass-loss; radio lines: stars

Journal Article.  7782 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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