AthenaK Simulations of Magnetized Binary Neutron Star Mergers

Abstract We present new numerical-relativity simulations of a magnetized binary neutron star merger performed with AthenaK . The simulations employ a temperature-and composition-dependent tabulated nuclear equation of state, with initially dipolar fields with a maximum initial strength of ∼10 16 G which extend outside the stars. We employ adaptive mesh refinement and consider three grid resolutions, with grid spacing down to Δ x min ≃ 92 m in the most refined region. When comparing the two highest resolution simulations, we find orbital dephasing of over 7 orbits until merger of only 0.06 radians. The magnetic field is amplified during the merger and we observe the formation of a magnetized funnel in the polar region of the remnant. Simulations are continued until about 30 milliseconds after merger. However, due to significant baryonic pollution, the binary fails to produce a magnetically-dominated outflow. Finally, we discuss possible numerical and physical effects that might alter this outcome.