Explosive Nucleosynthesis in Magnetohydrodynamical Jets from Collapsars. II : Heavy-Element Nucleosynthesis of s, p, r-Processes(Astrophysics and Cosmology)

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概要

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• We investigate the nucleosynthesis in a massive star of 70 M_<[○!・]> with solar metallicity in the main sequence stage. The helium core mass after hydrogen burning corresponds to 32 M_<[○!・]>. Nucleosynthesis calculations have been performed during the stellar evolution and the jetlike supernova explosion of a collapsar model. We focus on the production of elements heavier than iron group nuclei. Nucleosynthesis calculations have been accomplished consistently from hydrostatic to dynamic stages by using large nuclear reaction networks, 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, 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).

• 2012-10-25

著者

• Hashimoto Masa-aki

  Department Of Earth Science And Astronomy College Of Arts And Sciences University Of Tokyo

• Fujimoto Shin-ichiro

  Kumamoto National College Of Technology

• KOTAKE Kei

  Division of Theoretical Astronomy National Astronomical Observatory of Japan

• Yamada Shoichi

  Advanced Research Institute For Science And Engineering Waseda University

• ONO Masaomi

  Yukawa Institute for Theoretical Physics, Kyoto University

• KOTAKE Kei

  Division of Theoretical Astronomy/Center for Computational Astrophysics, National Astronomical Observatory of Japan:Center for Computational Astrophysics, National Astronomical Observatory of Japan

• ONO Masaomi

  Yukawa Institute for Theoretical Physics, Kyoto University:Department of Physics, Kyushu University

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• Explosive Nucleosynthesis in Magnetohydrodynamical Jets from Collapsars. II : Heavy-Element Nucleosynthesis of s, p, r-Processes(Astrophysics and Cosmology)
• Effects of a New Triple-α Reaction on the s-Process in Massive Stars
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• Explosive Nucleosynthesis in Magnetohydrodynamical Jets from Collapsars
• Heavy Elements Synthesized in an Accretion Disk around a Black Hole Associated with Gamma-Ray Bursts(Poster)

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