A double-sided radio jet from the compact Galactic Centre annihilator 1E1740.7-2942

RECENT observations^1,2 with the γ-ray telescope SIGMA, on the GRANAT satellite, indicated that the hard X-ray source 1E1740.7 - 2942 may be the source of the strongest outbursts of 511-keV electron-positron annihilation radiation from the Galactic Centre region³. We have observed this source using the Very Large Array, and find that its radio structure is that of a doublesided jet emanating from a compact and variable core. The changes in flux density and spectral index of the core are correlated with variations in the hard X-ray output. The jets are symmetrical about the core, and end in edge-brightened radio lobes; they are probably a result of synchrotron emission of electrons and positrons from the compact core. Our observation suggest that 1E1740.7 - 2942 is a 'microquasar' stellar remnant near the Galactic Centre, which ejects positrons that travel more than a parsec before slowing and annihilating in the interstellar gas.