Results of the bootstrap analysis described in the text. The red histogram represents 1000 resampled bootstrap datasets from the INTEGRAL/SPI containing background data, whereas the blue histogram illustrates samples from a band centred at 478.0 keV with a 12 keV width. Comparing these two distributions reveals an ≈2.5σ significance level for the observed sky flux exceeding the background, indicating a substantial detection of the spectral line.