Speaker
Toshio Suzuki
(Nihon University)
Description
R-process nucleosynthesisin core-collapse supernova explosions (CCSNe) and binary neutron star mergers (NSMs), both of which are promissing candidates for the r-process sites, are studied using new beta-decay half-lives for the waiting-point nuclei obtained by shell-model calculations.
We here investigate how the change of beta-decay half-lives affects the r-process nucleoasynthesis. Beta decay rates for exotic nuclei with neutron magic number of N=126 are evaluated up to Z=78 by including the contributions from both the Gamow-Teller and first-forbidden transitions. The half-lives obtained prove to be short compared to a standard finite-range-droplet model (FRDM), in particular near $^{208}$Pb region due to the effects of the first-forbidden transitions.
The element abundances for the r-process in neutrino-driven wind CCSNe, magnethydrodynamic jet CCSNe and binary NSMs are obtained up to the third peak as well as beyond the peak region up to thorium and uranium. The position of the third peak is found to be shifted toward a higher mass region in both CCSNe and NSMs. We find that thorium and uranium elements are produced more with the shorter shell-model half-lives and their abundances come closer to the observed values in CCSNe. In case of binary NSMs, thorium and uranium are produced as much as consistent with the observed values independent of the half-lives. This suggests that NSMs are promissing robust r-process sites for producing very heavy elements such as thorium and uranium.
Primary author
Toshio Suzuki
(Nihon University)
Co-authors
Dr
Ryota Shibagaki
(National Astronomical Observatory of Japan)
Prof.
Taka Kajino
(National Astronomical Observatory of Japan, The University of Tokyo)
Prof.
Takaharu Otsuka
(Department of Physics and Center for Nuclear Study, University of Tokyo)
Dr
Takashi Yoshida
(Department of Astronomy, the University of Tokyo)
