TP-16

Mass loss from a magnetically driven wind emitted by a disk orbiting a stellar mass black hole.

Frederic Daigne and Robert Mochkovitch
Institut d'Astrophysique de Paris

The source of Gamma-Ray Bursts (GRBs) is usually believed to be a stellar mass black hole accreting material from a thick disk. The mechanism of production of a relativistic wind by such a system is still unknown. We investigate here one proposal where the disk energy is extracted by a magnetic field amplified by differential rotation to very large values. With some very simple assumptions we compute the mass loss rate along magnetic field lines and then estimate the Lorentz factor Gamma at infinity. We find that Gamma can reach high values only if severe constraints on the field geometry and the conditions of energy injection are satisfied. We discuss the results in the context of different scenarios for GRBs.