Stages of the power spectrum analysis for a template (SN2017iuu / ZTF18aajwbhh) with a host previously identified by the sigma clipping method described in Sect. 3.2. From left to right, the panels show the template image, the mask, and the mask populated with noise. The right-most panel shows the distribution of Wasserstein distances between the original template and shuffled noised masks (gray) and between random pairs of shuffled noised masks (rose). The distributions were generated using 1000 different shuffles of the noised masks within the central patch of 7 × 7 pixels.