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Variability of water masers in evolved stars on timescales of decades

Published online by Cambridge University Press:  16 July 2018

Jan Brand ,
Dieter Engels  and
Anders Winnberg
Jan Brand
Affiliation:
INAF-Istituto di Radioastronomia & Italian ALMA Regional Centre, Bologna, Italy email: brand@ira.inaf.it
Dieter Engels
Affiliation:
Hamburger Sternwarte, Hamburg, Germany;
Anders Winnberg
Affiliation:
Onsala Rymdobservatorium, Onsala, Sweden
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Abstract

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For several decades (1987-2015) we have been carrying out observations of water masers in the circumstellar envelopes (CSE’s) of Mira variables, Red Supergiants (RSG’s) and Semi-Regular Variables (SRV’s) with the Medicina 32-m and Effelsberg 100-m antennas. The single-dish monitoring observations provide evidence for strong H2O maser profile variations, which likely are connected to structural changes in the maser shells. Such variations include strong flares in intensity lasting several (tens of) months and systemic velocity gradients of maser components developing over years, as well as other secular variations which are superimposed on periodic variations following the stellar light variations.

When complemented with interferometric observations, it is possible to derive the 3-D distribution of the maser spots, and their lifetime, as we have done for RX Boo (Winnberg et al. 2008) and U Her (Winnberg et al. 2011; Brand et al. in prep.).

Keywords

stars: AGB and post-AGBstars: variables: othermasersflare
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 13 , Symposium S336: Astrophysical Masers: Unlocking the Mysteries of the Universe , September 2017 , pp. 393 - 394
Copyright
Copyright © International Astronomical Union 2018 

References

Brand, J., Felli, M., Cesaroni, R., et al. 2007, IAU Symp. 242 (eds. Chapman & Baan), p. 223CrossRefGoogle Scholar
Winnberg, A., Brand, J., & Engels, D. 2011, ASP Conf. Ser. 445 (eds. Kerschbaum, Lebzelter, & Wing), p. 375Google Scholar
Winnberg, A., Engels, D., Brand, J., Baldacci, L., & Walmsley, C. M., 2008, A&A, 482, 831Google Scholar