Wind anisotropies and GRB progenitors

Aims. We study the effect of wind anisotropies on the stellar evolution leading to collapsars. Methods. Rotating models of a 60 M-circle dot star with Omega/Omega(crit) = 0.75 on the ZAMS, accounting for shellular rotation and a magnetic field, with and without wind anisotropies, are computed at Z = 0.002 until the end of the core He-burning phase. Results. Only the models accounting for the effects of the wind anisotropies retain enough angular momentum in their core to produce a Gamma Ray Burst (GRB). The chemical composition is such that a type Ic supernova event occurs. Conclusions. Wind anisotropies appear to be a key physical ingredient in the scenario leading to long GRBs.