Accurate muonic interactions in neutron star mergers and impact on heavy-element nucleosynthesis

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Main Authors: Ng, Harry Ho-Yin, Musolino, Carlo, Tootle, Samuel D., Rezzolla, Luciano
Format: Preprint
Published: 2024
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author Ng, Harry Ho-Yin
Musolino, Carlo
Tootle, Samuel D.
Rezzolla, Luciano
author_facet Ng, Harry Ho-Yin
Musolino, Carlo
Tootle, Samuel D.
Rezzolla, Luciano
contents The abundances resulting from $r$-process nucleosynthesis as predicted by simulations of binary neutron star (BNS) mergers remain an open question as the current state of the art is still restricted to three-species neutrino transport. We present the first BNS merger simulations employing a moment-based general-relativistic neutrino transport with five neutrino species, thus including (anti)muons and advanced muonic $β$-processes, and contrast them with traditional three-neutrino-species simulations. Our results show that a muonic trapped-neutrino equilibrium is established, forming a different trapped-neutrino hierarchy akin to the electronic equilibrium. The formation of (anti)muons and the muonization via muonic $β$-processes enhance the neutrino luminosity, leading to rapid cooling in the early postmerger phase. Since muonic processes redirect part of the energy otherwise used for protonization by electronic processes, they yield a cooler remnant and disk, together with neutrino-driven winds that are more neutron-rich. Importantly, the unbound ejected mass is smaller than three-species simulations, and, because of its comparatively smaller temperature and proton fraction, it can enhance lanthanide production and reduce the overproduction of light $r$-process elements for softer equations of state. This finding underlines the importance of muonic interactions and five neutrino species in long-lived BNS remnants.
format Preprint
id arxiv_https___arxiv_org_abs_2411_19178
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Accurate muonic interactions in neutron star mergers and impact on heavy-element nucleosynthesis
Ng, Harry Ho-Yin
Musolino, Carlo
Tootle, Samuel D.
Rezzolla, Luciano
High Energy Astrophysical Phenomena
General Relativity and Quantum Cosmology
The abundances resulting from $r$-process nucleosynthesis as predicted by simulations of binary neutron star (BNS) mergers remain an open question as the current state of the art is still restricted to three-species neutrino transport. We present the first BNS merger simulations employing a moment-based general-relativistic neutrino transport with five neutrino species, thus including (anti)muons and advanced muonic $β$-processes, and contrast them with traditional three-neutrino-species simulations. Our results show that a muonic trapped-neutrino equilibrium is established, forming a different trapped-neutrino hierarchy akin to the electronic equilibrium. The formation of (anti)muons and the muonization via muonic $β$-processes enhance the neutrino luminosity, leading to rapid cooling in the early postmerger phase. Since muonic processes redirect part of the energy otherwise used for protonization by electronic processes, they yield a cooler remnant and disk, together with neutrino-driven winds that are more neutron-rich. Importantly, the unbound ejected mass is smaller than three-species simulations, and, because of its comparatively smaller temperature and proton fraction, it can enhance lanthanide production and reduce the overproduction of light $r$-process elements for softer equations of state. This finding underlines the importance of muonic interactions and five neutrino species in long-lived BNS remnants.
title Accurate muonic interactions in neutron star mergers and impact on heavy-element nucleosynthesis
topic High Energy Astrophysical Phenomena
General Relativity and Quantum Cosmology
url https://arxiv.org/abs/2411.19178