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Issue A&A
Volume 393, Number 2, October II 2002
Page(s) 543 - 553
Section Formation, structure and evolution of stars
DOI http://dx.doi.org/10.1051/0004-6361:20021009



A&A 393, 543-553 (2002)
DOI: 10.1051/0004-6361:20021009

Predictions of variable mass loss for Luminous Blue Variables

Jorick S. Vink1, 2 and A. de Koter3

1  Imperial College, Blackett Laboratory, Prince Consort Road, London, SW7 2BZ, UK
2  Astronomical Institute, Utrecht University, PO Box 80000, 3508 TA Utrecht, The Netherlands
3  Astronomical Institute "Anton Pannekoek", University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands

(Received 16 April 2002 / Accepted 8 July 2002)

Abstract
We present radiation-driven wind models for Luminous Blue Variables (LBVs) and predict their mass-loss rates. We study the effects of lower masses and modified abundances in comparison to the normal OB supergiants, and we find that the main difference in mass loss is due to the lower masses of LBVs. In addition, we find that the increase in helium abundance changes the mass-loss properties by small amounts (up to about 0.2 dex in log $\dot{M}$), while CNO processing is relatively unimportant for the mass-loss rate. A comparison between our mass loss predictions and the observations is performed for four relatively well-studied LBVs. The comparison shows that (i) the winds of LBVs are driven by radiation pressure on spectral lines, (ii) the variable mass loss behaviour of LBVs during their S Doradus-type variation cycles is explained by changes in the line driving efficiency, notably due to the recombination/ionisation of Fe IV/III and Fe III/II, and finally, (iii) the winds of LBVs can be used to derive their masses, as exemplified by the case of AG Car, for which we derive a present-day mass of 35 .


Key words: stars: early-type -- stars: mass-loss -- stars: supergiants -- stars: winds, outflows -- stars: evolution

Offprint request: Jorick S. Vink, j.vink@ic.ac.uk

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© ESO 2002


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