Simulated projected radial profiles of the X-ray spectral parameters for four different models assuming spherical symmetry. Top panel: cut-off energy and the bottom one shows the spectral index in the 2−10 keV band as a function of the angular distance from the forward shock of the SNR. The distributions are obtained by extracting the spectrum for each region and fitting it with an exponential cut-off power law assuming a photon spectral index of Γ = 1.6(top panel) and with a simple power law (bottom panel). In both panels, green squares indicate the observational data (Kishishita et al. 2013).