Carlos Palenzuela (UIB) — Formation of magnetically dominated jets in binary neutron star mergers with realistic initial magnetic fields

💡 A RES Success Story from the most extreme parts of the Universe💡 

📋"Formation of magnetically dominated jets in binary neutron star mergers with realistic initial magnetic fields" led by Carlos Palenzuela from Universitat de les Illes Balears

Since the detection of a binary neutron star (BNS) merger through a gravitational wave and an electromagnetic signal, which marked the beginning of the multimessenger era, it is believed that BNS mergers must be major sources of elements heavier than iron

🌌 Currently, the most accepted hypothesis for the formation of jets in this scenario is that the BNS merger produces a black hole and, during and after the process, the magnetic field is amplified and large scale magnetic structures are formed. However, several studies suggested another hypothesis: an ultra-strongly magnetized neutron star, instead of a black hole, drives the jets. 

Current realistic simulations are based in numerically solving the relativistic magnetohydrodynamics (MHD) equations for this scenario, but they lack precision to address the formation of jets even using high resolution. This happens due to unrealistically strong initial conditions for the magnetic fields and the limitations of the simulations using MHD.

🖥 Thanks to RES supercomputer #MareNostrum5 GPP , the research team could perform high-resolution Large-Eddy simulations of a long-lived hypermassive neutron star produced during BNS mergers. The simulations had a resolution of dx=60m and an associated computational cost of the order of 10 million CPU hours, which allowed them to reproduce the evolution of the remnant for 250ms. 

They did not observe any jet emerging from the remnant, but the simulations suggested that when considering realistic initial magnetic fields for the neutron star remnant, large-scale magnetic field structures require long timescales (of hundreds of milliseconds) to form. These structures arise from a slow inverse cascade, from smaller to larger scales, that organizes the highly turbulent magnetic configuration after the collision.

👇In the image, there is the evolution of the merger at three different times, showing the formation and development of large-scale structures.