A DOUBLE-SIDED RADIO JET FROM THE COMPACT GALACTIC-CENTER ANNIHILATOR 1E1740.7-2942

RECENT observations1,2 with the gamma-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 double-sided 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.