Transition Elements in Supernova Presolar Grains: Condensation versus Implantation

Kuljeet K. Marhas and Piyush Sharda

The Astrophysical Journal, Volume 853, Number 1


“We compute the concentrations of five transition elements (Cr, Fe, Co, Ni, and Zn) via condensation and implantation in supernova presolar grains (Silicon Carbide Type X) from the time they condense until the end of the free expansion (or pre-Sedov) phase. We consider relative velocities of these elements with respect to grains as they condense and evolve at temperatures lesssim2000 K; use zonal nucleosynthesis yields for three core collapse supernovae models −15 M ⊙, 20 M ⊙, and 25 M ⊙; and use an ion target simulator SDTrimSP to model their implantation onto the grains. Simulations from SDTrimSP show that maximal implantation in the core of the grain is possible, contrary to previous studies. Among the available models, we find that the 15 M ⊙ model best explains the measured concentrations of SiC X grains obtained from the Murchison meteorite. For grains where measured concentrations of Fe and Ni are gsim300 ppm, we find the implantation fraction to be lesssim0.25 for most probable differential zonal velocities in this phase, which implies that condensation is more dominant than implantation. We show that radioactive corrections and mixing from the innermost Ni and Si zones are required to explain the excess Ni (condensed as well as implanted) in these grains. This mixing also explains the relative abundances of Co and Ni with respect to Fe simultaneously. The model developed can be used to predict concentrations of all other elements in various presolar grains condensed in supernova ejecta and compared with measured concentrations in grains found in meteorites.”