PRODUCTION OF ALL THE r-PROCESS NUCLIDES IN THE DYNAMICAL EJECTA OF NEUTRON STAR MERGERS

Journal Article · Thu Jul 10 00:00:00 EDT 2014 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/789/2/L39· OSTI ID:22365641

Wanajo, Shinya ^[1]; Sekiguchi, Yuichiro; Kiuchi, Kenta; Shibata, Masaru ^[2]; Nishimura, Nobuya ^[3]; Kyutoku, Koutarou ^[4]

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1. iTHES Research Group, RIKEN, Wako, Saitama 351-0198 (Japan)
2. Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502 (Japan)
3. Astrophysics, EPSAM, Keele University, Keele ST5 5BG (United Kingdom)
4. Department of Physics, University of Wisconsin-Milwaukee, P.O. Box 413, Milwaukee, WI 53201 (United States)

Recent studies suggest that binary neutron star (NS-NS) mergers robustly produce heavy r-process nuclei above the atomic mass number A ∼ 130 because their ejecta consist of almost pure neutrons (electron fraction of Y {sub e} < 0.1). However, the production of a small amount of the lighter r-process nuclei (A ≈ 90-120) conflicts with the spectroscopic results of r-process-enhanced Galactic halo stars. We present, for the first time, the result of nucleosynthesis calculations based on the fully general relativistic simulation of a NS-NS merger with approximate neutrino transport. It is found that the bulk of the dynamical ejecta are appreciably shock-heated and neutrino processed, resulting in a wide range of Y {sub e} (≈0.09-0.45). The mass-averaged abundance distribution of calculated nucleosynthesis yields is in reasonable agreement with the full-mass range (A ≈ 90-240) of the solar r-process curve. This implies, if our model is representative of such events, that the dynamical ejecta of NS-NS mergers could be the origin of the Galactic r-process nuclei. Our result also shows that radioactive heating after ∼1 day from the merging, which gives rise to r-process-powered transient emission, is dominated by the β-decays of several species close to stability with precisely measured half-lives. This implies that the total radioactive heating rate for such an event can be well constrained within about a factor of two if the ejected material has a solar-like r-process pattern.

• OSTI ID: 22365641
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 2 Vol. 789; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
APPROXIMATIONS
BINARY STARS
COMPUTERIZED SIMULATION
DIAGRAMS
ELECTRONS
HEATING RATE
MILKY WAY
NEUTRINOS
NEUTRON STARS
NEUTRONS
NUCLEOSYNTHESIS
R PROCESS
RELATIVISTIC RANGE
TRANSIENTS