The X-ray spectrum of the supernova remnant W 49B from EXOSAT.

X-ray observations of the supernova remnant W49B made by the medium-energy detector and gas scintillation propotional counter experiments on board Exosat are presented. The detection of a very strong emission line feature at 6.7 keV indicates a thermal origin of the X-rays. Fitting the spectral data with an optically thin thermal plasma model indicates a temperature of 2 keV for the remnant. From a consideration of Exosat, Einstein, and radio data, it is suggested that the dominant observed X-ray emission comes from a reverse shock.