A model for GRO J1655–40 is described in which the hard X/γ-ray behavior, and long delay between the X/γ and radio outbursts, are explained by processes which occur when the accretion rate approaches and exceeds the Eddington limit. The principal feature of the model is a dense, optically thick, super-Eddington wind ejected from the center of the accretion disk. The wind is responsible for determining the luminosity and spectral evolution of the object and for suppressing the formation of a fast, relativistic jet while the accretion rate is above the Eddington limit.
Our model makes use of the “magnetic switch” mechanism we recently discovered with MHD simulations of jet production in magnetized accretion disk coronae. A fast jet can be turned on (or off) by increasing (or decreasing) the Alfvén velocity in the corona relative to a critical value. Examination of models of sub- and super-Eddington disks shows that V
remains below the critical value while the wind is present, but could exceed it when the wind disappears and a hot, optically thin corona forms.