A radio-emitting X-ray "bullet" ejected by the Vela supernova

Abstract

A massive star that explodes as a supernova produces an expanding remnant-a shell of gas-and leaves behind a neutron star. It has been suggested that instabilities during these explosions may create high-density clumps of ejecta 1,2 , but such fragments have never been found in a remnant containing a pulsar. Here we present X-ray and radio observations of a feature outside the shock-wave boundary of the Vela supernova remnant (associated with the pulsar PSR0833-45), which appears to be an ejected fragment, with a wake 3 . The feature, which has travelled nearly 50 pc from the site of PSR0833-45 but is only one parsec across, is a clear-cut case of a «bullet» of ejecta moving supersonically through the surrounding medium. The radio observations show non-thermal emission along the leading edge of the X-ray feature, indicating particle acceleration at the fragment's shock front