Nucleosynthesis in the Innermost Ejecta of Neutrino-driven Supernova Explosions in Two Dimensions

We examine nucleosynthesis in the innermost neutrino-processed ejecta (a few {10}^-3 {M}_⊙ ) of self-consistent two-dimensional explosion models of core-collapse supernovae (CCSNe) for six progenitor stars with different initial masses. Three models have initial masses near the low-mass end of the SN range of 8.8 {M}_⊙ (e8.8; electron-capture SN), 9.6 {M}_⊙ (z9.6), and 8.1 {M}_⊙ (u8.1), with initial metallicities of 1, 0, and 10^-4 times the solar metallicity, respectively. The other three are solar-metallicity models with initial masses of 11.2 {M}_⊙ (s11), 15 {M}_⊙ (s15), and 27 {M}_⊙ (s27). The low-mass models e8.8, z9.6, and u8.1 exhibit high production factors (nucleosynthetic abundances relative to the solar abundances) of 100-200 for light trans-Fe elements from Zn to Zr. This is associated with an appreciable ejection of neutron-rich matter in these models. Remarkably, the nucleosynthetic outcomes for the progenitors e8.8 and z9.6 are almost identical, including interesting productions of ⁴⁸Ca and ⁶⁰Fe, irrespective of their quite different (O-Ne-Mg and Fe) cores prior to collapse. In the more massive models s11, s15, and s27, several proton-rich isotopes of light trans-Fe elements including the p-isotope ⁹²Mo (for s27) are made, up to production factors of ∼30. Both electron-capture SNe and CCSNe near the low-mass end can therefore be dominant contributors to the Galactic inventory of light trans-Fe elements from Zn to Zr and probably ⁴⁸Ca and live ⁶⁰Fe. The innermost ejecta of more massive SNe may have only subdominant contributions to the chemical enrichment of the Galaxy except for ⁹²Mo.