Principle of Universality of γ-Process Nucleosynthesis in Core-Collapse Supernova Explosions

Abstract

Using core-collapse supernova explosion models, we investigate the principle of the universality of the gprocess, according to which the s/p abundance ratios produced by individual nucleosynthesis episode are almost constant over a wide range of atomic number. The universality originates from the shift of the g-process layers, the independence of the s/p abundance ratios of the nuclear reactions, and the weak s-process in presupernovae. Our calculations further suggest an extended universality in which the s/p ratios in the g-process layers are not only constant but also centered around a specific value of 3. To verify this, we propose an astronomical observation of indium isotopic abundance fractions.

La138-Ce138-Hayakawa1, Shizuma2, Kajino3 et al. 2008Phys. Rev. C

“…We calculated the γ process of core-collapse supernovae under various astrophysical conditions such as, metallicity, progenitor mass, and explosion energy and found that the scalings hold for individual nucleosyntheses independent of the astrophysical conditions assumed [27]. We presented a detailed mechanism why the scalings fold for various supernovae in our previous papers [27,28]. Our proposed chronometer is based on the universality of the scaling for the two p-nuclei.…”

“…In addition, we found a novel concept of "the universality of the γ process", wherein the scalings hold for nuclides produced in individual supernova γ processes under various astrophysical conditions [26]. We calculated the γ process of core-collapse supernovae under various astrophysical conditions such as, metallicity, progenitor mass, and explosion energy and found that the scalings hold for individual nucleosyntheses independent of the astrophysical conditions assumed [27]. We presented a detailed mechanism why the scalings fold for various supernovae in our previous papers [27,28].…”

Cosmic clock and thermometer for neutrino process

“…We found the empirical scaling law that the abundance ratios of N(1st p)/N(2nd p) is almost constant in a wide region of atomic number, where N is the solar abundance [4]. This empirical law leads to "the universality of the γ-process" that the scaling holds for nuclei produced in individual SNe [4,15]. If the abundances of 136,138 Ce and 138 La in a single sample produced mainly by a single supernova are measured, the time elapsed from a ν-process episode, T , can be calculated by 1) where N is the observed abundance in the sample, R pp is the initial N(1st p)/N(2nd p) ratio at the freezeout of the γ-process, and b is the branching ratio of the β − decay of 138 La: λ (β − ) / (λ (β − )+λ (EC)).…”

Universality of the p process

“…In our previous paper [14], we reported two empirical scaling laws in the solar system abundances, which are a piece of evidence that the most probable origin of the 27 p-nuclei is γ-process in SNe. These scalings lead to a novel concept of "the universality of the γ-process" [14,15]. The understanding of the mechanism of the universality is crucial for the γ-process and the Galactic chemical evolution (GCE) of the p-and s-nuclei.…”