Burial of the polar magnetic field of an accreting neutron star and gravitational wave emission

Abstract

We present detailed, ab initio numerical simulations of the distorted magnetic structure of an accreting neutron star as a function of accreted mass Ma: (i) we evolve an initial dipole through a quasi-static sequence of Grad-Shafranov equilibria while maintaining strict fluX-freezing for the first time and (ii) we import these equilibria into the time-dependent, ideal-magnetohydrodynamic (MHD) code ZEUS-3D and load additional mass on to the star dynamically. We investigate the stability of these hydromagnetic equilibria by perturbing them in ZEUS-3D in two and three dimeinsions. Surprisingly, in both cases, the equilibria are marginally stable for all Ma ≤ 6 × 10-4M⊙. On extending the ZEUS-3..