Structure and nuclear composition of general relativistic, magnetohydrodynamic outflows from neutrino-cooled disks

We compute the structure and degree of neutronization of general relativistic magnetohydrodynamic (GRMHD) outflows originating from the inner region of neutrino-cooled disks. We consider both, outflows expelled from a hydrostatic disk corona and outflows driven by disk turbulence. We show that in outflows driven thermally from a static disk the electron fraction quickly evolves to its equilibrium value which is dominated by neutrino capture. Those outflows are generally proton rich and, under certain conditions, can be magnetically dominated. They may also provide sites for effective production of Ni-56. Centrifugally driven outflows and outflows driven by disk turbulence, on the other hand, can preserve the large in-disk neutron excess. Those outflows are, quite generally, subrelativistic by virtue of the large mass flux driven by the additional forces. (c) 2007 Elsevier B.V. All rights reserved.