Left panel: Event lists scaled to R₅₀₀ and stacked on the coordinates of each source from the sample described in Section 2. The red circle indicates R₅₀₀. Central panel: Stacked spectrum in the 0.5–2 keV energy range. The fit using GADEM with the mean temperature provided in the title is shown by the red dashed line. Right panel: Histograms of temperatures from the bootstrapping analysis with background subtraction (green) and background modeling (blue). The title displays the mean temperature and the 3σ deviation for the background modeling histogram.