Issue |
A&A
Volume 443, Number 2, November IV 2005
|
|
---|---|---|
Page(s) | 643 - 648 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20054030 | |
Published online | 04 November 2005 |
Evolution of rapidly rotating metal-poor massive stars towards gamma-ray bursts
1
Astronomical Institute “Anton Pannekoek”, University of Amsterdam, Kruislaan 403, 1098 SJ, Amsterdam, The Netherlands e-mail: scyoon@science.uva.nl
2
Astronomical Institute, Utrecht University, Princetonplein 5, 3584 CC, Utrecht, The Netherlands e-mail: n.langer@astro.uu.nl
Received:
10
August
2005
Accepted:
14
September
2005
Recent models of rotating massive stars including magnetic fields prove
it difficult for the cores of single stars
to retain enough angular momentum to produce a collapsar and gamma-ray burst.
At low metallicity, even very massive stars may retain a massive
hydrogen envelope due to the weakness of the stellar winds,
posing an additional obstacle to the collapsar model.
Here, we consider the evolution of massive, magnetic stars where rapid rotation
induces almost chemically homogeneous evolution.
We find that in this case, the requirements of the collapsar model
are rather easily fulfilled if the metallicity is sufficiently small:
1) rapidly rotating helium stars are formed without the need to
remove the hydrogen envelope, avoiding mass-loss induced spin-down.
2) Angular momentum transport from the helium core to hydrogen envelope
by magnetic torques is insignificant. We demonstrate this by calculating
evolutionary models of massive stars with various metallicities,
and derive an upper metallicity limit for this scenario based on
currently proposed mass loss rates. Our models also suggest the existence
of a lower CO-core mass limit of about – which relates to an
initial mass of only about
within our scenario – for GRB production.
We argue that the relative importance of the considered
GRB progenitor channel, compared to any channel related to binary stars,
may increase with decreasing metallicity, and
that this channel might be the major path to GRBs from first stars.
Key words: stars: rotation / stars: evolution / stars: Wolf-Rayet / supernovae: general / gamma rays: bursts
© ESO, 2005
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