THE RADIO STRUCTURE OF SUPERNOVA REMNANT 0540-693

We present an Australia Telescope Compact Array multifrequency study o f the supernova remnant 0540 693 which is the youngest known remnant, after SN 1987A, in the Large Magellanic Cloud. The radio observations reveal that it consists of a central synchrotron nebula of diameter 1. 4 pc which is powered by the 50 ms pulsar PSR B0540-69, and a nearly c ircular low-surface brightness annulus of diameter 17.5 pc. The centra l nebula has a flatter spectrum than the annular emission and is the r adio counterpart of the synchrotron nebula previously detected at opti cal and X-ray wavelengths. Its properties are very similar to those of the Crab Nebula. The annular emission is similar to other young super nova remnant shells and is generated b the interaction of the supernov a ejecta with the circumstellar medium.