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arXiv · 2407.20335

Delayed jet launching in binary neutron star mergers with realistic initial magnetic fields

Ricard Aguilera-Miret·Carlos Palenzuela·Federico Carrasco·Stephan Rosswog·Daniele Viganò
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Abstract

We analyze a long-lived hyper-massive neutron star merger remnant (post-merger lifetime $>250$ ms) that has been obtained via large eddy simulations with a gradient subgrid-scale model. We find a clear helicoidal magnetic field structure that is governed by the toroidal component of the magnetic field. Although no jet emerges during the simulation time, we observe at late times a significant increase of the poloidal component of the magnetic field at all scales. We also compare with the results of several binary neutron star simulations with moderate resolution of $120$~m, that are evolved up to $50$~ms after the merger, which differ in terms of the initial topology and strength of the magnetic field. We find that the best choice is an isotropic small-scale magnetic field distribution that mimics the turbulent state that generically develops during the merger. This initial configuration reaches a closer agreement with our high-resolution simulation results than the purely dipolar large-scale fields that are commonly employed in these type of simulations. This provides a recipe to perform such simulations avoiding the computationally expensive grids required to faithfully capture the amplification of the magnetic field by Kelvin-Helmholtz instabilities.

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Ricard Aguilera-Miret, Carlos Palenzuela, Federico Carrasco, Stephan Rosswog, Daniele Viganò. 2024-07-29. Delayed jet launching in binary neutron star mergers with realistic initial magnetic fields. https://arxiv.org/abs/2407.20335

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