Explosive Nucleosynthesis in Magnetohydrodynamical Jets from Collapsars II. Heavy-Element Nucleosynthesis of s, r, p-Processes

TL;DR

This study models nucleosynthesis in a 70 solar mass collapsar, revealing overproduction of certain s, r, and p-elements, and suggesting such stars contribute to specific solar element abundances and the LEPP process.

Contribution

It provides detailed nucleosynthesis calculations for a 70 M_solar collapsar, highlighting its role in producing weak s-elements, neutron-rich elements, and light p-elements, expanding understanding of heavy element origins.

Findings

s-elements of 60 < A < 90 are highly overproduced

Elements of 90 < A < 160 are significantly overproduced via the r-process

Ejected matter shows [Sr/Eu]  -0.4, different from r-process stars

Abstract

We investigate the nucleosynthesis in a massive star of 70 M_solar with solar metallicity in the main sequence stage. The helium core mass after hydrogen burning corresponds to 32 M_solar. Nucleosynthesis calculations have been performed during the stellar evolution and the jetlike supernova explosion of a collapsar model, where the weak s-, p-, and r-processes are taken into account. We confirm that s-elements of 60 < A < 90 are highly overproduced relative to the solar abundances in the hydrostatic nucleosynthesis. During oxygen burning, p-elements of A > 90 are produced via photodisintegrations of seed s-elements. However, the produced p-elements are disintegrated in later stages except for ^{180}Ta. In the explosive nucleosynthesis, elements of 90 < A < 160 are significantly overproduced relative to the solar values owing to the r-process. Only heavy p-elements (N > 50) are overproduced via the p-process. Compared with the previous study of r-process nucleosynthesis calculations in the collapsar model of 40 M_solar by Fujimoto et al. 2007, 2008, our jet model cannot contribute to the third peak of the solar r-elements and intermediate p-elements. Averaging the overproduction factors over the progenitor masses with the use of Salpeter's IMF, we suggest that the 70 M_solar star could contribute to the solar weak s-elements of 60 < A < 90 and neutron-rich elements of 90 < A < 160. We confirm the primary synthesis of light p-elements in the ejected matter of high peak temperature. The ejected matter has [Sr/Eu] \sim -0.4, which is different from that of a typical r-process-enriched star CS22892-052 ([Sr/Eu] \sim -1). We find that Sr-Y-Zr isotopes are primarily synthesized in the explosive nucleosynthesis in a similar process of the primary production of light p-elements, which has been considered as one of the sites of a lighter element primary process (LEPP).