Long Gamma-Ray Bursts (GRBs) are the most energetic explosions in the universe,
allowing their light to travel billions of light years before reaching the Earth.
Recently a long GRB was detected at redshift 8.2, meaning
it exploded when the universe was only 630 million years old.
The observation that nearby long GRB are often associated with SNe
show that they are produced by the death of a massive star.
However, the exact ingredients allowing massive stars to give birth to a long GRB are still debated.
In this talk I will show evolutionary calculations of single and binary stars including the effects of rotation and internal magnetic fields.
These stars, at the end of their life, fulfill the requirements of the collapsar scenario and can produce a long GRB.
The key ingredient is fast rotation, which allows stars to evolve in a non-canonical way (chemically homogeneous evolution).
This models predict long GRBs to occur preferentially at low metallicity, with no long GRBs predicted above a metallicity threshold.
We show that a possibly large fraction of long GRBs may occur in runaway stars, with important implications for the position of the burst in the sky.
Ref:
http://adsabs.harvard.edu/abs/2007A%26A...465L..29C
http://adsabs.harvard.edu/abs/2006A%26A...460..199Y
http://adsabs.harvard.edu/abs/2005A%26A...443..643Y
