Explosive nucleosynthesis in magnetohydrodynamical jets from collapsars. II: Heavy-element nucleosynthesis of s, p, r-processes

摘要

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 180Ta. In the explosive nucleosynthesis, elements of 90 A 160 are significantly overproduced relative to the solar values owing to the r-process, which is very different from the results of spherical explosion models. Only heavy p-elements (N 50) are overproduced via the p-process because of the low peak temperatures in the oxygen- and neon-rich layers. Compared with the previous study of r-process nucleosynthesis calculations in the collapsar model of 40 M- by Fujimoto et al. [S. Fujimoto, M. Hashimoto, K. Kotake and S. Yamada, Astrophys. J. 656 (2007), 382; S. Fujimoto, N. Nishimura and M. Hashimoto, Astrophys. J. 680 (2008), 1350], our jet model cannot contribute to the third peak of the solar r-elements and intermediate p-elements, which have been much produced because of the distribution of the lowest part of electron fraction in the ejecta. Averaging the overproduction factors over the progenitor masses with the use of Salpeter's IMF, we suggest that the 70 M 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] 0.4, which is different from that of a typical r-process-enriched star CS22892-052 ([Sr/Eu] 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). Tokyo 113-0033 JPN.