paper

Tayler-Spruit dynamo in binary neutron star merger remnants

arXiv:2411.19328 · doi:10.1051/0004-6361/202453126

Abstract

In binary neutron star mergers, the remnant can be stabilized by differential rotation before it collapses into a black hole. Therefore, the angular momentum transport mechanisms are crucial for predicting the lifetime of the hypermassive neutron star. One such mechanism is the Tayler-Spruit dynamo, and recent simulations have shown that it could grow in proto-neutron stars formed during supernova explosions. We aim to investigate whether hypermassive neutron stars with high neutrino viscosity could be unstable to the Tayler-Spruit dynamo and study how magnetic fields would evolve in this context. Using a one-zone model based on the result of a 3D GRMHD simulation, we investigate the time evolution of the magnetic fields generated by the Tayler-Spruit dynamo. In addition, we analyze the dynamics of the 3D GRMHD simulation to determine whether the dynamo is present. Our one-zone model predicts that the Tayler-Spruit dynamo can increase the toroidal magnetic field to G and the dipole field to amplitudes G. The dynamo's growth timescale depends on the initial large-scale magnetic field right after the merger. In the case of a long-lived hypermassive neutron star, an initial magnetic field of G would be enough for the magnetic field to be amplified in a few seconds. However, we show that the resolution of the current GRMHD simulations is insufficient to resolve the Tayler-Spruit dynamo due to high numerical dissipation at small scales. We find that the Tayler-Spruit dynamo could occur in hypermassive neutron stars and shorten their lifetime, which would have consequences on multi-messenger observations.

13 pages, 9 figures, submitted to A&A

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