HARD X-RAY-EMISSION FROM THE VELA SUPERNOVA REMNANT

We report the first hard (2.5-25 keV) X-ray images of the Vela supernova remnant (SNR), resulting from observations with the University of Birmingham coded mask telescope flown on the Spacelab 2 mission in 1985. The emission from the region around the pulsar is resolved; the diffuse emission extends approximately 1-degrees to the north-east and south-west, roughly aligned along the direction of the pulsar spin axis, and produces about 48 per cent of the total emission in the 4-25 keV band. We suggest that this region, which overlaps the peak of the Vela-X radio source, is a synchrotron nebula. The power required to produce the relativistic electrons in the nebula is estimated to be 75 per cent of the rotational energy loss of the pulsar. Emission from a number of bright knots in the shell is also detected; whilst these generally correlate with bright features in the lower energy Einstein Observatory and the H-alpha-images, the features at different wavelengths are not coincident, suggesting the presence of blobs of material at a wide range of temperatures.