Hot and cold running water: Understanding evolved star winds
Journal article, 2017

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.

stars: winds

stars: late-type




A.M.S. Richards

University of Manchester

M. D. Gray

University of Manchester

A. Baudry

University of Bordeaux

E. Humphreys

European Southern Observatory (ESO)

S. Etoka

University of Manchester

L. Decin

KU Leuven

Ivan Marti-Vidal

Chalmers, Earth and Space Sciences, Onsala Space Observatory

A. M. Sobolev

Ural Federal University

Wouter Vlemmings

Galactic Astrophysics

Proceedings of the International Astronomical Union

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

Vol. 13 S336 347-350

Subject Categories

Meteorology and Atmospheric Sciences

Astronomy, Astrophysics and Cosmology

Other Physics Topics


Onsala Space Observatory



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