Formation of a jet in the Galactic center black hole candidate 1E 1740.7-2942

The Galactic center object IE 1740.7-2942 is apparently a source of e⁺e^- annihilation radiation and has recently been associated with a double-sided radio jet at λ = 6 and λ = 20 cm. We here extend our earlier model for the y-ray continuum emission to encompass the formation of the jet, and discuss the ensuing jet structure. We find that due to γγ interactions in the intense radiation field produced within the inner ∼20 Schwarzschild radii (r_g) of the accretion disk, more than 5 × 10⁴³ pairs s^-1 stream outward and are accelerated by Compton scatterings to velocities as high as ∼0.7c. Roughly 90% of these pairs annihilate at the base of the nascent jet (within ∼40 r_g of the black hole) forming the broad (∼240 keV) annihilation line observed by SIGMA on GRANAT. The remainder (≲6 × 10⁴² pairs s^-1) escape into the enshrouding cloud and beyond, and presumably contribute to the formation of both the steady and the time-variable components of the narrow annihilation line observed from the bulge. However, before the pairs annihilate, they radiate via synchrotron emission as they spiral in the cloud's ambient magnetic field. We show that the physical conditions required to account for the broad γ-ray line seen in the high state and the implied conditions in the normal state are consistent with the pair density and velocity required to form the large-scale jet, the jet's shape, and its radio spectrum and luminosity.