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Postmerger MassEjection of Low-massBinary Neutron Stars Sho FujibayashiShinya WanajoKenta Kiuchi2020 год

Postmerger Mass Ejection of Low-mass Binary Neutron Stars
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Аннотация: We study the post-merger mass ejection of low-mass binary neutron stars (NSs) with the system mass of $2.5\, M_\odot$, and subsequent nucleosynthesis by performing general-relativistic, neutrino-radiation viscous-hydrodynamics simulations in axial symmetry. We find that the merger remnants are long-lived massive NSs surviving more than several seconds, irrespective of the nuclear equations of state (EOSs) adopted. The ejecta masses of our fiducial models are $\sim 0.06$-$0.1\, M_\odot$ (depending on the EOS), being $\sim 30\%$ of the initial disk masses ($\sim 0.15$-$0.3\, M_\odot$). Post-processing nucleosynthesis calculations indicate that the ejecta is composed mainly of light $r$-process nuclei with small amounts of lanthanides (mass fraction $\sim 0.002$-$0.004$) and heavier species due to the modest average electron fraction ($\sim 0.32$-$0.34$) for a reasonable value of the viscous coefficient. Such abundance distributions are incompatible with the solar $r$-process-like abundance patterns found in all measured $r$-process-enhanced metal-poor stars. Therefore, low-mass binary NS mergers should be rare. If such low-mass NS mergers occur, their electromagnetic counterparts, kilonovae, will be characterized by an early bright blue emission because of the large ejecta mass as well as the small lanthanide fraction. We also show, however, that if the effective turbulent viscosity is very high, or there is an efficient mass ejection working in the early post-merger phase, the electron fraction of the ejecta could be low enough that the solar $r$-process-like abundance pattern is reproduced and the lanthanide fraction becomes so high that the kilonova would be characterized by early bright blue and late bright red emissions.
Год издания: 2020
Авторы: Sho Fujibayashi, Shinya Wanajo, Kenta Kiuchi, Koutarou Kyutoku, Yuichiro Sekiguchi, Masaru Shibata
Издательство: IOP Publishing
Источник: The Astrophysical Journal
Ключевые слова: Pulsars and Gravitational Waves Research, Gamma-ray bursts and supernovae, Astrophysical Phenomena and Observations
Другие ссылки: The Astrophysical Journal (PDF)
The Astrophysical Journal (HTML)
arXiv (Cornell University) (PDF)
arXiv (Cornell University) (HTML)
MPG.PuRe (Max Planck Society) (PDF)
MPG.PuRe (Max Planck Society) (HTML)
DataCite API (HTML)