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Fig. 4

image

Comparison of column densities between 2004 and 2015 summed over the three velocity components along with the 90% confidence intervals. The measurements by Blustin et al. (2007) are also presented. Only N+6, O+4, Fe+17, and S+12 appear to have changed, but three to four ions are expected to deviate considering the 90% uncertainties.

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