Example ∼ MeV gamma-ray light curve L_γ(t) of r-process ejecta, calculated based on a multizone ejecta model from A. Patel et al. (2025), with M_ej ≈ 1.2 × 10⁻⁶ M_⊙, M_r ≈ 7 × 10⁻⁷ M_⊙, ﹩\bar{v}=0.15c﹩, and β = 6, f_Ω = 3/4. Attenuation is treated approximately following K. Hotokezaka et al. (2016) for an assumed constant opacity κ_γ = 0.1 cm² g⁻¹. Shown with a purple line is the late-time MeV light curve of the SGR 1806–20 giant flare detected by INTEGRAL ACS (S. Mereghetti et al. 2005) over the time window 675–12,000 s, with the best-fit decay rate ∝ t^−1.2±0.1 in dark purple above the light curve to guide the eye (Figure 4; Appendix A). The top panel shows the cumulative fluence for an assumed source distance d = 8.7 kpc (J. L. Bibby et al. 2008) in comparison to the estimated total fluence based on measurements from ACS and RHESSI (S. E. Boggs et al. 2007; Appendix A).