X-ray spectra of Cas A

An X-ray spectrum from Cas A taken by the EXOSAT GSPC detector. The resolution of this instrument was not as good as the Einstein SSS so the silicon and sulphur lines are not well resolved. However, the 6 keV line from iron shows clearly. The strength of this line provides an indication of the composition of the progenitor star. If the star had greater than solar abundances, then this line would be more prominant. The fact that the spectrum indicates stellar abundances, while other clues indicate a Type II SNe, is a puzzle. Courtesy of Nick White (formerly of ESTEC). Reproduced from figure 3-11 of Charles and Seward.

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