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- Title
Patterns in water maser emission of evolved stars on the timescale of decades.
- Authors
Brand, Jan; Engels, Dieter; Winnberg, Anders
- Abstract
We present our past and current long-term monitoring program of water masers in the circumstellar envelopes of evolved stars, augmented by occasional interferometric observations. Using as example the Mira-variable U Her, we identify three types of variability: periodic (following the optical variation), long-term (years-decades) and short-term irregular (weeks-months). We show there are regions in the maser shell where excitation conditions are favourable, which remain stable for many years. Lifetimes of maser clouds in the wind-acceleration zone are of the order of up to a few years. Much longer lifetimes are found for the peculiar case of a maser cloud outside that zone (as in RT Vir), or in some cases where the motion of spectral features can be followed for the entire 2 decade monitoring period (as in red supergiant VX Sgr).
- Subjects
MASERS; ASYMPTOTIC giant branch stars
- Publication
Proceedings of the International Astronomical Union, 2022, Vol 18, Issue S380, p319
- ISSN
1743-9213
- Publication type
Article
- DOI
10.1017/S1743921323002144