Nucleosynthesis in Jets from Collapsars

We investigate nucleosynthesis inside magnetically driven jets ejected from collapsars, or rotating magnetized stars collapsing to a black hole, based on two‐dimensional magnetohydrodynamic simulation of the collapsars during the core collapse. We follow the evolution of the abundances of about 4000 nuclides from the collapse phase to the ejection phase using a large nuclear reaction network. We find that the r‐process successfully operates only in the energetic jets (>1051 erg), so that U and Th are synthesized abundantly, even when the collapsars have a relatively small magnetic field (1010 G) and a moderately rotating core before the collapse. The abundance patterns inside the jets are similar to that of the r‐elements in the solar system. The higher energy jets have larger amounts of 56Ni. Less energetic jets, which have small amounts of 56Ni, could induce GRB without supernova, such as GRB060505 and GRB060614.