General relativistic radiation MHD simulations of super-Eddington accretion flows around a magnetized neutron star
Speaker: Akihiro Inoue (Osaka University)
Abstract:
Since neutron stars have strong magnetic and gravitational fields, they serve as natural laboratories for extreme plasma physics. When the neutron star is in a binary system, periodic X-ray pulsations are produced by the plasma accretion onto the neutron star. Such objects are called X-ray pulsars and thought to be ideal objects for investigating the extreme plasma physics. However, the magnetic field strength of the neutron star and the accretion rate remain uncertain since they cannot be observed directly.
We perform two-dimensional general relativistic radiation MHD simulations of super-Eddington accretion flows onto a magnetized neutron star, as modeling the X-ray pulsars at the super-Eddington rate. In our simulations, accretion disk, accretion flows along the neutron star’s magnetic field lines, and optically thick outflows driven by the strong radiation force appear. Such outflows can explain the thermal emission with a temperature of 1E+7 K and a blackbody radius of ~100 km detected in the super-Eddington X-ray pulsar, Swift J0243.6+6124. By comparing our models with observations, the magnetic field strength at the neutron star surface in Swift J0243.6+6124 is restricted to (0.3-4)E+12G. In this talk, we also present recent three-dimensional simulations, in which a non-axisymmetric accretion flows form.