XMM-Newton EPIC-pn spectrum of the hard emitting region with a power-law model fit. The solid line is for the hard emission plus background spectra. Here, the background is the sum of the shell emission and the local emission. The background spectrum and shell spectrum were evaluated as described in Sect. 3.2.4. The background spectrum was not subtracted from the source spectrum but was modelled simultaneously and is included in the spectral model of the source spectrum. The contribution from the hard emitting region is represented in red. The bottom panel shows the residuals from the best-fit model.