Prompt neutron star merger flares from turbulent amplification of magnetic field

Author: Jonathan Zrake

Abstract: The simultaneous detection of electromagnetic and gravitational wave emission from merging neutron star binaries would aid greatly in their discovery and interpretation. By studying turbulent amplification of magnetic fields in local high-resolution simulations of neutron star merger conditions, we demonstrate that eddies generated milliseconds before merger will naturally produce ∼ 1049 ergs of magnetic energy with magnetar-like field strengths. We demonstrate numerically converged magnetic field growth to ∼ 5 × 1016 G saturating on sufficiently short time-scales to occur repeatedly during the merger. We propose that magnetar-like flares will be generated that are observable within the Advanced LIGO detection volume. These flares emit promptly and are independent of any post-merger emission which may be produced by e.g. a short GRB from a black-hole accretion disk or magnetar. We suggest that merger flares may be present in the current sample of short GRBs and may be roughly isotropic on the sky since they are seen to distances where the cosmological matter distribution becomes homogeneous. Searches for merger flares should seek to identify short SGR-like flares among the short burst population. If mergers also produce short GRBs short-hard GRBs, then merger flares may constitute a precursor component of the emission.