Formation of jets in Galactic superluminal sources

A model of major ejection events in Galactic superluminal sources GRO J1655 -40 and GRS 1915-105 is proposed, in which episodes of pair creation give r ise to the formation of optically thick super-Eddington outflow acceleratin g protons to the limiting Lorentz factor of order 2-3. Probable source of p airs is pion production in proton-proton and proton-neutron collisions whic h may operate efficiently even for proton temperatures equal to several MeV . Gamma-ray spectral signatures of this mechanism are pointed out. Subseque nt deceleration of ejecta and formation of radio jets is analyzed in detail within a shock deceleration model, The detailed data available for GRO J16 55-40 are shown to be in good agreement with proposed scenario.