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Hot and cold running water: understanding evolved star winds

Published online by Cambridge University Press:  16 July 2018

A. M. S. Richards
Affiliation:
JBCA, School of Physics & Astronomy, University of Manchester, M13 9PL, UK contact email: amsr@jb.man.ac.uk
M. D. Gray
Affiliation:
JBCA, School of Physics & Astronomy, University of Manchester, M13 9PL, UK contact email: amsr@jb.man.ac.uk
A. Baudry
Affiliation:
Laboratoire d’astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, F-33615 Pessac, France
E. M. L. Humphreys
Affiliation:
ESO Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
S. Etoka
Affiliation:
JBCA, School of Physics & Astronomy, University of Manchester, M13 9PL, UK contact email: amsr@jb.man.ac.uk
L. Decin
Affiliation:
Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, 3001 Leuven, Belgium
I. Marti-Vidal
Affiliation:
Dept. of Earth, Space and Environment, Chalmers University of Technology, Onsala Space Observatory, SE 439 92 Onsala, Sweden
A. M. Sobolev
Affiliation:
Ural Federal University, Ekaterinburg, Russia
W. Vlemmings
Affiliation:
Dept. of Earth, Space and Environment, Chalmers University of Technology, Onsala Space Observatory, SE 439 92 Onsala, Sweden
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Abstract

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Outstanding problems concerning mass-loss from evolved stars include initial wind acceleration and what determines the clumping scale. Reconstructing physical conditions from maser data has been highly uncertain due to the exponential amplification. ALMA and e-MERLIN now provide image cubes for five H2O maser transitions around VY CMa, at spatial resolutions comparable to the size of individual clouds or better, covering excitation states from 204 to 2360 K. We use the model of Gray et al. 2016, to constrain variations of number density and temperature on scales of a few au, an order of magnitude finer than is possible with thermal lines, comparable to individual cloud sizes or locally almost homogeneous regions. We compare results with the models of Decin et al. 2006 and Matsuura et al. 2014 for the circumstellar envelope of VY CMa; in later work this will be extended to other maser sources.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2018 

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