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

Abstract

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.more » 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.« less

Authors:
 [1]; ; ;  [2];  [3];  [4]
  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)
Publication Date:
OSTI Identifier:
22365641
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 789; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; APPROXIMATIONS; BINARY STARS; COMPUTERIZED SIMULATION; DIAGRAMS; ELECTRONS; HEATING RATE; MILKY WAY; NEUTRINOS; NEUTRON STARS; NEUTRONS; NUCLEOSYNTHESIS; R PROCESS; RELATIVISTIC RANGE; TRANSIENTS

Citation Formats

Wanajo, Shinya, Sekiguchi, Yuichiro, Kiuchi, Kenta, Shibata, Masaru, Nishimura, Nobuya, and Kyutoku, Koutarou, E-mail: shinya.wanajo@riken.jp. PRODUCTION OF ALL THE r-PROCESS NUCLIDES IN THE DYNAMICAL EJECTA OF NEUTRON STAR MERGERS. United States: N. p., 2014. Web. doi:10.1088/2041-8205/789/2/L39.
Wanajo, Shinya, Sekiguchi, Yuichiro, Kiuchi, Kenta, Shibata, Masaru, Nishimura, Nobuya, & Kyutoku, Koutarou, E-mail: shinya.wanajo@riken.jp. PRODUCTION OF ALL THE r-PROCESS NUCLIDES IN THE DYNAMICAL EJECTA OF NEUTRON STAR MERGERS. United States. doi:10.1088/2041-8205/789/2/L39.
Wanajo, Shinya, Sekiguchi, Yuichiro, Kiuchi, Kenta, Shibata, Masaru, Nishimura, Nobuya, and Kyutoku, Koutarou, E-mail: shinya.wanajo@riken.jp. Thu . "PRODUCTION OF ALL THE r-PROCESS NUCLIDES IN THE DYNAMICAL EJECTA OF NEUTRON STAR MERGERS". United States. doi:10.1088/2041-8205/789/2/L39.
@article{osti_22365641,
title = {PRODUCTION OF ALL THE r-PROCESS NUCLIDES IN THE DYNAMICAL EJECTA OF NEUTRON STAR MERGERS},
author = {Wanajo, Shinya and Sekiguchi, Yuichiro and Kiuchi, Kenta and Shibata, Masaru and Nishimura, Nobuya and Kyutoku, Koutarou, E-mail: shinya.wanajo@riken.jp},
abstractNote = {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.},
doi = {10.1088/2041-8205/789/2/L39},
journal = {Astrophysical Journal Letters},
number = 2,
volume = 789,
place = {United States},
year = {Thu Jul 10 00:00:00 EDT 2014},
month = {Thu Jul 10 00:00:00 EDT 2014}
}