MHD simulations of oscillating cusp-filling tori around neutron stars — missing upper kHz QPO [HEAP]

We performed axisymmetric, grid-based, ideal magnetohydrodynamic (MHD) simulations of oscillating cusp-filling tori orbiting a non-rotating neutron star. A pseudo-Newtonian potential was used to construct the constant angular momentum tori in equilibrium. The inner edge of the torus is terminated by a “cusp” in the effective potential. The initial motion of the model tori were perturbed with uniform sub-sonic vertical and diagonal velocity fields. As the configuration evolved in time, we measured the mass accretion rate on the neutron star surface and obtained the power spectrum. The prominent mode of oscillation in the cusp torus is the radial epicyclic mode. From our analysis it follows that the mass accretion rate carries a modulation imprint of the oscillating torus, and hence so does the boundary layer luminosity.

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V. Parthasarathy, W. Kluzniak and M. Cemeljic
Thu, 16 Mar 17

Comments: Submitted as a Letter to MNRAS. 5 pages, 3 figures, 1 table. Comments are welcome