Gravity seminar - Alexis Reboul-Salze Seminar

Event details

Title: Large-scale magnetic field amplification in binary neutron star mergers

Abstract: The observation of GW170817/GRB 170817A confirmed that short gamma-ray bursts originate from binary neutron star (BNS) mergers. The presence of strong large-scale magnetic fields is necessary to lead to the production of a collimated relativistic outflow, which can be observed as short gamma-ray bursts. During the first few milliseconds after merger, the magnetic field is amplified due to the shear layer at the contact interface between the two neutron stars but the mechanism to generate large-scale magnetic fields in the long-lived remnant remains unclear. I will present two different mechanisms that plays a role in two different regions of the hypermassive neutron star: the magnetorotational instability (MRI) in the outer layers (>10 km) and the Tayler-Spruit (TS) dynamo in the core (<10km). I will first describe the physical mechanisms and properties of the dynamos driven by the MRI and the Tayler instabilities. I will present the latest comparison between our group's general relativity neutrino-radiation magnetohydrodynamic simulation of a hundred-millisecond-long BNS merger and magnetohydrodynamics models. I will also discuss the astrophysical consequences due to the high magnetic field generated by these dynamos. Overall, I will describe the latest results on the large-scale magnetic field amplification in hypermassive neutron stars and their observational consequences.