The missing link: Merging neutron stars naturally produce jet-like structures and can power short gamma-ray bursts

Short gamma-ray bursts (SGRBs) are among the most luminous explosions in the universe, releasing in less than one second the energy emitted by our Galaxy over one year. Despite decades of observations, the nature of their "central engine" remains unknown. Considering a binary of magnetized neutron stars and solving the Einstein equations, we show that their merger results in a rapidly spinning black hole surrounded by a hot and highly magnetized torus. Lasting over 35ms and much longer than previous simulations, our study reveals that magnetohydrodynamical instabilities amplify an initially turbulent magnetic field of ∼10¹²G to produce an ordered poloidal field of ∼10¹⁵G along the black hole spin axis, within a half-opening angle of ∼30°, which may naturally launch a relativistic jet. The broad consistency of our ab initio calculations with SGRB observations shows that the merger of magnetized neutron stars can provide the basic physical conditions for the central engine of SGRBs.