$^{56}$Ni production in long-lived binary neutron star merger remnants
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arXiv
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| Auteurs principaux: | , , , , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866913751291133952 |
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| author | Jacobi, Maximilian Magistrelli, Fabio Loffredo, Eleonora Ricigliano, Giacomo Chiesa, Leonardo Bernuzzi, Sebastiano Perego, Albino Arcones, Almudena |
| author_facet | Jacobi, Maximilian Magistrelli, Fabio Loffredo, Eleonora Ricigliano, Giacomo Chiesa, Leonardo Bernuzzi, Sebastiano Perego, Albino Arcones, Almudena |
| contents | We investigate the nucleosynthesis and kilonova emission based on numerical-relativity binary neutron star merger simulations that incorporate a two-moment neutrino-transport scheme. Unlike in previous works with simpler neutrino treatments, a massive, fast (up to $v=0.3c$), proton-rich neutrino-driven wind develops in the post-merger phase of the simulations as long as the merger remnant does not collapse to a black hole. We evolve the ejecta for 100 days after the merger using 2D ray-by-ray radiation-hydrodynamics simulations coupled in-situ to a complete nuclear network. The most abundant nucleosynthesis products are He, $^{56}$Ni, and $^{56}$Co. We find a total yield of $\sim 10^{-3} M_\odot$ of $^{56}$Ni for all mergers that produce massive neutron star remnants, independently of the mass ratio and equation of state. After a few days, the decay of $^{56}$Ni and later $^{56}$Co becomes the primary source of heating in the matter expanding above the remnant. As a result, the kilonova light curve flattens on timescales of days for polar observation angles. The observation of this effect could serve as smoking gun for the presence of a long-lived neutron star remnant in future kilonova observations. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2503_17445 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | $^{56}$Ni production in long-lived binary neutron star merger remnants Jacobi, Maximilian Magistrelli, Fabio Loffredo, Eleonora Ricigliano, Giacomo Chiesa, Leonardo Bernuzzi, Sebastiano Perego, Albino Arcones, Almudena High Energy Astrophysical Phenomena We investigate the nucleosynthesis and kilonova emission based on numerical-relativity binary neutron star merger simulations that incorporate a two-moment neutrino-transport scheme. Unlike in previous works with simpler neutrino treatments, a massive, fast (up to $v=0.3c$), proton-rich neutrino-driven wind develops in the post-merger phase of the simulations as long as the merger remnant does not collapse to a black hole. We evolve the ejecta for 100 days after the merger using 2D ray-by-ray radiation-hydrodynamics simulations coupled in-situ to a complete nuclear network. The most abundant nucleosynthesis products are He, $^{56}$Ni, and $^{56}$Co. We find a total yield of $\sim 10^{-3} M_\odot$ of $^{56}$Ni for all mergers that produce massive neutron star remnants, independently of the mass ratio and equation of state. After a few days, the decay of $^{56}$Ni and later $^{56}$Co becomes the primary source of heating in the matter expanding above the remnant. As a result, the kilonova light curve flattens on timescales of days for polar observation angles. The observation of this effect could serve as smoking gun for the presence of a long-lived neutron star remnant in future kilonova observations. |
| title | $^{56}$Ni production in long-lived binary neutron star merger remnants |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2503.17445 |