Sinking of a magnetically confined mountain on an accreting neutron star

We perform ideal-magnetohydrodynamic axisymmetric simulations of magnetically confined mountains on an accreting neutron star, with masses ≲0.12 M_⊙. We consider two scenarios, in which the mountain sits atop a hard surface or sinks into a soft, fluid base. We find that the ellipticity of the star, due to a mountain grown on a hard surface, approaches ∼2 × 10^-4 for accreted masses ≳1.2 × 10^-3 M_⊙, and that sinking reduces the ellipticity by between 25 and 60 per cent. The consequences for gravitational radiation from low-mass X-ray binaries are discussed.