The merger of neutron stars drives a relativistic jet which can be observed as a short gamma-ray burst. A strong large-scale magnetic field is necessary to launch the relativistic jet. However, the magnetohydrodynamical mechanism to build up this magnetic field remains uncertain. Here we show that the αΩ dynamo mechanism driven by the magnetorotational instability builds up the large-scale magnetic field inside the long-lived binary neutron star merger remnant by performing an {\it ab initio} super-high resolution neutrino-radiation magnetohydrodynamics merger simulation in full general relativity. As a result, the magnetic field induces the Poynting-flux dominated relativistic outflow with the luminosity ∼1051\,erg/s and magnetically-driven post-merger mass ejection with the mass ∼0.1M⊙. Therefore, the magnetar scenario in binary neutron star mergers is possible. These can be the engines of short-hard gamma-ray bursts and very bright kilonovae. Therefore, this scenario is testable in future observation.
@article{arxiv.2306.15721,
title = {A large-scale magnetic field produced by a solar-like dynamo in binary neutron star mergers},
author = {Kenta Kiuchi and Alexis Reboul-Salze and Masaru Shibata and Yuichiro Sekiguchi},
journal= {arXiv preprint arXiv:2306.15721},
year = {2024}
}