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While it is very difficult to obtain quantitative spectral information from the HRI (i.e., , temperatures or power-law indices), it is still possible to obtain qualitative information on a scale of a few arc minutes using hardness (or softness) ratios. Wilson et al. Wilson-etal:ApJ:1992 showed that the extended emission in NGC1068 is harder than the nuclear component using a softness ratio defined by the channels [1:5]/[6:11]. Since the HRI gain varies temporally and spatially, the user may want to define the PHA boundaries on a case by case basis. For example, in the two observations of N132D shown in Fig. 5.19, the fraction of the total counts in PHA channels 6-11 decreased from 40% to 10%.
[Spectral fitting results for 3C 273] Spectral fitting results for 3C 273
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