The U/Th production ratio from extended independent model

Abstract

The Meyer and Schramm (M&S) independent model formalism is developed to determine the production ratio of actinide chronometers in the nucleosynthesis era of the Galaxy formation. The production ratio of U/Th is calculated, considering the non-radioactive mass reduction rate of chronometers together with a new production of r-process nuclides over the time interval between the last r-process event and the solidification of meteorites. In the first approach, we considered two extra terms rather than M&S formalism, and the average U/Th production ratio over the duration of nucleosynthesis in stars and supernovas was measured to be $0.5378 \pm_{0.0005}^{0.0006}$ and $0.5942_{ - 0.0474}^{ + 0.0491}$. Considering only one extra term rather than M&S original model led to the average production ratio of $0.5603 \pm 0.0007$ and $0.5994 \pm_{0.0472}^{0.0487}$. The calculated results from both approaches are compatible with those of used stellar models and chronometric methods. The advantages of our extended model are in precise determining of actinides production ratios and evaluating a narrow down range for the Galaxy age rather than M&S formalism.