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| Paper: |
Water Vapour Masers in the Mira Variable U Herculis |
| Volume: |
445, Why Galaxies Care about AGB Stars II: Shining Examples and Common Inhabitants |
| Page: |
375 |
| Authors: |
Winnberg, A.; Brand, J.; Engels, D. |
| Abstract: |
The H2O maser line at 22 GHz from the Mira variable U Her has
been monitored for more than 20 years. Additional interferometric
observations were made at four epochs covering a period of 3 years.
We found that the maser components have an average lifetime of
0.5–1 year and are distributed in a ring with distances from
12 to 25 AU from the star. The strongly varying shape of the
single-dish maser spectra is the result of a superposition of many
short-lived maser components with randomly varying intensities.
The integrated flux is dominated by the random variations but varies
also in response to the large-amplitude light variations with a
period of 406 days. |
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