Abstract
Despite the growing evidence that long Gamma-Ray Bursts (GRBs) are associated with deaths of Wolf-Rayet stars, the evolutionary path of massive stars to GRBs and the exact nature of GRB progenitors remain poorly known. However, recent massive star evolutionary models indicate that — for sufficiently low metallicity — initially very rapidly rotating stars can satisfy the conditions for collapsar formation. Even though magnetic torques are included in these models, a strong core spin-down is avoided through quasi-chemically homogeneous evolution induced by rotational mixing. Here, we explore for which initial mass and spin-range single stars of Z = Zsolar/20 are expected to produce GRBs. We further find a dichotomy in the chemical structure of GRB progenitors, where lower initial masses end their lives with a massive helium envelope which still contains some amounts of hydrogen, while higher initial masses explode with C/O-dominated hydrogen-free atmospheres.
| Original language | Undefined/Unknown |
|---|---|
| Title of host publication | Stellar evolution at low metallicity : mass loss, explosions, cosmology : proceedings of a meeting held in Tartu, Estonia, 15-19 August 2005 |
| Editors | Henny J.G.L.M. Lamers |
| Place of Publication | San Francisco |
| Publisher | Astronomical Society of the Pacific |
| Pages | 63-69 |
| Number of pages | 7 |
| Publication status | Published - 15 Aug 2005 |