A NONTHERMAL X-RAY-SPECTRUM FROM THE SUPERNOVA REMNANT W-50

Hard X-ray properties of the supernova remnant W 50 are presented. The extended lobe structure is confirmed in the 0.7-10 keV energy band. The surface brightness in the 0.7-4 keV band has a clear peak at the region far from SS 433, similar to that obtained by the Einstein Observatory. The shape in the high energy band (4-10 keV) is roughly consistent with that in the low energy band (0.7-4 keV), but shows a flat top structure. The X-ray spectrum from the extended structure shows a non-thermal spectrum without apparent emission lines. The spectrum becomes harder as the distance from SS 433 decreases. We discuss the origin of the X-rays in terms of synchrotron emission.