Patterns in water maser emission of evolved stars on the timescale of decades
Paper i proceeding, 2022

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).

AGB and post-AGB stars


water masers


J. Brand

Istituto di Radioastronomia

D. Engels

Universität Hamburg

Anders Winnberg

Chalmers, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik

Proceedings of the International Astronomical Union

1743-9213 (ISSN) 1743-9221 (eISSN)

Vol. 18 319-323


Astronomi, astrofysik och kosmologi



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