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Abstract In nuclear matter in isolated neutron stars, the flavor content (e.g., proton fraction) is subject to weak interactions, establishing flavor (β-)equilibrium. However, there can be deviations from this equilibrium during the merger of two neutron stars. We study the resulting out-of-equilibrium dynamics during the collision by incorporating direct and modified Urca processes (in the neutrino-transparent regime) into general-relativistic hydrodynamics simulations with a simplified neutrino transport scheme. We demonstrate how weak-interaction-driven bulk viscosity in postmerger simulations can emerge and assess the bulk viscous dynamics of the resulting flow. We further place limits on the impact of the postmerger gravitational-wave strain. Our results show that weak-interaction-driven bulk viscosity can potentially lead to a phase shift of the postmerger gravitational-wave spectrum, although the effect is currently on the same level as the numerical errors of our simulation.
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Bulk viscosity transport coefficients in neutron star mergers
We compute first and second-order bulk-viscous transport properties due to weak-interaction processes innpematter in the neutrino transparent regime. The transport coefficients characterize the out-of-beta-equilibrium pressure corrections, which depend on the weak-interaction rates and the equation of state. We calculate these coefficients for realistic equations of state and show they are sensitive to changes in the nuclear symmetry energyJand its slopeL.
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- Award ID(s):
- 2103680
- PAR ID:
- 10637147
- Editor(s):
- Bellwied, R; Geurts, F; Rapp, R; Ratti, C; Timmins, A; Vitev, I
- Publisher / Repository:
- EPJ
- Date Published:
- Journal Name:
- EPJ Web of Conferences
- Volume:
- 296
- ISSN:
- 2100-014X
- Page Range / eLocation ID:
- 03003
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1051/epjconf/202429603003
