Heavy element nucleosynthesis in jets from collapsars

We investigate nucleosynthesis in collapsars, based on long-term, magnetohydrodynamic simulations of a rapidly rotating massive star of 40M _⊙ during the core collapse. We have calculated detailed composition of magnetically driven jets ejected from the collapsars, in which the magnetic fields before the collapse, are uniform and parallel to the rotational axis of the star and the magnitudes of the fields, B₀, are 10¹⁰ G or 10¹² G. We follow the evolution of chemical composition up to about 4000 nuclides inside the jets from the collapse phase to the ejection phase through the jet generation phase with use of a large nuclear reaction network. We find that the r-process successfully operates in the jets from the collapsar of B₀ = 10¹² G, so that U and Th are synthesized abundantly. Abundance pattern inside the jets is similar to that of r-elements in the solar system. Furthermore, we find that p-nuclei are produced without seed nuclei: not only light p-nuclei, such as ⁷⁴Se, ⁷⁸Kr, ⁸⁴Sr, and ⁹²Mo, but also heavy p-nuclei, ¹¹³In, ¹¹⁵Sn, and ¹³⁸La, can be abundantly synthesized in the jets. The amounts of p-nuclei in the ejecta are much greater than those in core-collapse supernovae (SNe). In particular, ⁹²Mo, ¹¹³In, ¹¹⁵Sn, and ¹³⁸La deficient in the SNe, are significantly produced in the ejecta. On the other hand, in the jets from the collapsar of B₀ = 10¹⁰ G, the r-process cannot operate and ⁵⁶Ni, ²⁸Si, ³²S, and ⁴He are abundantly synthesized in the jets, as in ejecta from inner layers of Type II supernovae. An amount of ⁵⁶Ni is much smaller than that from SN 1987A.