Recompute cold-ejecta nucleosynthesis with a physical progenitor composition

Construct and perform a dedicated nucleosynthesis rerun for the cold ejecta using a physically motivated pre-collapse oxygen–neon–magnesium white-dwarf composition rather than free nucleons as the initial network composition, in order to determine its effect on the predicted $M(A{=}56)$, $M(A{=}44)$, and $M(A{=}60)$ yields.

Background

Cold ejecta do not undergo nuclear statistical equilibrium, so their final abundances depend on the assumed initial composition. The calculations use WinNet’s default free-nucleon composition, whereas the hydrodynamical equation-of-state treatment gives a surface composition associated with oxygen–neon–magnesium white-dwarf material. A sensitivity test indicates that a physically motivated composition can substantially change several radioactive-isotope proxy yields, especially the mass at A=60A=60; the authors therefore identify a corrected production calculation as unresolved work.

References

Ideally, nucleosynthesis calculations for these cold ejecta should be initialised with a more physically motivated composition, which we leave for future work.

— Nucleosynthesis in the Accretion-induced Collapse of magnetised, Rotating White Dwarfs  (2608.21000 - Thümmler et al., 21 Aug 2026) in Section 3.2, “Electron fraction and hot/cold ejecta”