Can the Fe K-alpha Line Reliably Predict Supernova Remnant Progenitors?

Abstract The centroid energy of the Fe K α line has been used to identify progenitors supernova remnants (SNRs). These investigations generally considered derived from spectrum entire remnant. Here we use XMM-Newton data investigate in 6 SNRs: 3C 397, N132D, W49B, DEM L71, 1E 0102.2-7219, and Kes 73. In 73 fail detect any emission. We report a tentative first detection emission SNR L71 with consistent its Type Ia designation. remaining remnants, spatial spectral sensitivity is sufficient variations centroid. find N132D W49B that centroids different regions are those overall spectrum, although not necessarily remnant type identified via other means. However, statistically significant variation up 100 eV, aligning density structure around span intermediate space between energies signifying core-collapse (CC) remnants. Shifting dividing downwards by 50 eV can place all CC region, but contradicts obtained Our results show caution must be when employing as sole diagnostic for typing