Direct comparison of flux profiles in different regions of G15.9+0.2. Each panel is labeled with the letter corresponding to the respective region. Top and middle sub-panels: exposure corrected images at the early and late epoch, and the white rectangle outlines the measurement region. Bottom sub-panel: one-dimensional flux profiles F_i(x) at the early (red) and late (blue) epoch. The x coordinate increases outward along the radial direction of the SNR. The markers display the binned distribution, and the solid line reflects the flux profile smoothed with a Gaussian kernel. The dashed red line corresponds to the profile of the early epoch, shifted and rescaled by the parameters indicated in the upper right corner, with the shaded area displaying the associated uncertainty.