Quadrupole moment of a magnetically confined mountain on an accreting neutron star: Effect of the equation of state

Abstract

Magnetically confined mountains on accreting neutron stars are promising sources of continuous-wave gravitational radiation and are currently the targets of directed searches with long-baseline detectors like the Laser Interferometer Gravitational Wave Observatory (LIGO). In this paper, previous ideal-magnetohydrodynamic models of isothermal mountains are generalized to a range of physically motivated, adiabatic equations of state. It is found that the mass ellipticity ε drops substantially, from ε≈ 3 × 10-4 (isothermal) to ε≈ 9 × 10-7 (non-relativistic degenerate neutrons), 6 × 10-8 (relativistic degenerate electrons) and 1 × 10-8 (non-relativistic degenerate electrons) (assuming a magnetic..