Issue |
A&A
Volume 442, Number 2, November I 2005
|
|
---|---|---|
Page(s) | 587 - 596 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20052862 | |
Published online | 07 October 2005 |
On the metallicity dependence of Wolf-Rayet winds
1
Imperial College, Blackett Laboratory, Prince Consort Road, London, SW7 2AZ, UK e-mail: jsv@astro.keele.ac.uk
2
Astronomical Institute “Anton Pannekoek”, University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
Received:
10
February
2005
Accepted:
13
July
2005
We have performed a pilot study of mass loss predictions
for late-type Wolf-Rayet (WR) stars as a function of metal
abundance, over a range between Z
. We
find that the winds of nitrogen-rich Wolf-Rayet stars are
dominated by iron lines, with a dependence of mass loss on Z
similar to that of massive OB stars. For more evolved, carbon-rich, WR
stars the wind strength is also found to be dependent on the Fe abundance,
so that they depend on the chemical environment of the host galaxy, but with a
mass loss metallicity dependence that is less steep than for OB stars.
Our finding that WR mass loss is Z-dependent is a new one, with
important consequences for black hole formation and X-ray population
studies in external galaxies.
A further finding of our study is that the Z dependence of
C-rich WR stars becomes weaker
at metallicities below
1/10, and mass loss
no longer declines once the metal abundance drops below (Z/
)
10-3.
This is the result of an increased importance of
radiative driving by intermediate mass elements, such as carbon.
In combination with rapid rotation and/or proximity to the
Eddington limit – likely to be relevant for massive Population iii stars – this effect
may indicate a role for mass loss in the appearance and evolution of these objects, as well as a potential role
for stellar winds in enriching the intergalactic medium of the early Universe.
Key words: stars: Wolf-Rayet / stars: early-type / stars: mass-loss / stars: winds, outflows / stars: evolution
© ESO, 2005
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