Electromagnetic Waves from Magnetar Collapse

Observed black holes cannot have currents and therefore, cannot have a magnetic field, indicating that the field of the precursor must be radiated away in some manner. Currently, numerical evidence suggests that the magnetic field radiates away within a few milliseconds, but it remains unclear how valid the approximations are that such studies depend on. Using AthenaK, an astrophysics code that performs general relativistic magnetohydrodynamics simulations in dynamical spacetimes, we model the collapse of an unstable magnetar, similar to the remnant of a binary neutron star merger. We present results on the radiation of the collapse of the magnetic field and discuss implications for the associated electromagnetic radiation.