Empirical Solar Abundance Scaling Laws of Supernova γ Process Isotopes

Analyzing the solar system abundances, we have found two empirical abundance scaling laws concerning the p‐ and s‐nuclei with the same atomic number. They are evidence that the 27 p‐nuclei are synthesized by the supernova γ‐process. The scalings lead to a novel concept of “universality of γ‐process” that the s/p and p/p ratios of nuclei produced by individual γ‐processes are almost constant, respectively. We have calculated the ratios of materials produced by the γ‐process based on core‐collapse supernova explosion models under various astrophysical conditions and found that the scalings hold for individual γ‐processes independent of the conditions assumed. The results further suggest an extended universality that the s/p ratios in the γ‐process layers are not only constant but also centered on a specific value of 3. With this specific value and the scaling of the s/p ratios, we estimate that the ratios of the s‐process abundance contributions from the AGB stars to the massive stars are almost 6.7 for the s‐nuclei of $A>90$ in the solar system.