The shock-heated atmosphere of an asymptotic giant branch star resolved by ALMA

The shock-heated atmosphere of an asymptotic giant branch star resolved by ALMA Our current understanding of the chemistry and mass-loss processes in Sun-like stars at the end of their evolution depends critically on the description of convection, pulsations and shocks in the extended stellar atmosphere 1 . Three-dimensional hydrodynamical stellar atmosphere models provide observational predictions 2 , but so far the resolution to constrain the complex temperature and velocity structures seen in the models has been lacking. Here we present submillimetre continuum and line observations that resolve the atmosphere of the asymptotic giant branch star W Hydrae. We show that hot gas with chromospheric characteristics exists around the star. Its filling factor is shown to be small. The existence of such gas requires shocks with a cooling time longer than commonly assumed. A shocked hot layer will be an important ingredient in current models of stellar convection, pulsation and chemistry at the late stages of stellar evolution. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Nature Astronomy Springer Journals
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Publisher
Nature Publishing Group UK
Copyright
Copyright © 2017 by The Author(s)
Subject
Physics; Physics, general; Astronomy, Astrophysics and Cosmology
eISSN
2397-3366
D.O.I.
10.1038/s41550-017-0288-9
Publisher site
See Article on Publisher Site

Abstract

Our current understanding of the chemistry and mass-loss processes in Sun-like stars at the end of their evolution depends critically on the description of convection, pulsations and shocks in the extended stellar atmosphere 1 . Three-dimensional hydrodynamical stellar atmosphere models provide observational predictions 2 , but so far the resolution to constrain the complex temperature and velocity structures seen in the models has been lacking. Here we present submillimetre continuum and line observations that resolve the atmosphere of the asymptotic giant branch star W Hydrae. We show that hot gas with chromospheric characteristics exists around the star. Its filling factor is shown to be small. The existence of such gas requires shocks with a cooling time longer than commonly assumed. A shocked hot layer will be an important ingredient in current models of stellar convection, pulsation and chemistry at the late stages of stellar evolution.

Journal

Nature AstronomySpringer Journals

Published: Oct 30, 2017

References

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