Summary of the hierarchical model. Shown are the upper bounds on the ²²Na ejecta masses (left axis) for individual objects (black) as a function of the population width τ, together with the complete pooling estimate (τ → 0, dashed orange), and the population mean μ (solid orange). Individual objects of interest (best (blue) worst (aqua) bound, diffuse emission (red)) are indicated. As τ → ∞, each upper bound converges to its no pooling value (Table B.1). Given the SPI flux posteriors, a population width of (right axis, grey shaded) is found. This value is dominated by the flux uncertainties.