Frequency Spectrum of Gravitational Radiation from Global Hydromagnetic Oscillations of a Magnetically Confined Mountain on an Accreting Neutron Star

Recent time-dependent, ideal-magnetohydrodynamic (ideal-MHD) simulations ofpolar magnetic burial in accreting neutron stars have demonstrated that stable,magnetically confined mountains form at the magnetic poles, emittinggravitational waves at $f_{*}$ (stellar spin frequency) and $2 f_{*}$. GlobalMHD oscillations of the mountain, whether natural or stochastically driven, actto modulate the gravitational wave signal, creating broad sidebands (full-widthhalf-maximum $\sim 0.2f_*$) in the frequency spectrum around $f_{*}$ and $2f_{*}$. The oscillations can enhance the signal-to-noise ratio achieved by along-baseline interferometer with coherent matched filtering by up to 15 percent, depending on where $f_*$ lies relative to the noise curve minimum.Coherent, multi-detector searches for continuous waves from nonaxisymmetricpulsars should be tailored accordingly.Comment: 4 figures, accepted for publication in Ap