Afterglow of binary neutron star merger

TL;DR

This paper uses numerical simulations to show that binary neutron star mergers produce a hypermassive neutron star that emits highly luminous electromagnetic radiation due to dynamic magnetic field variations.

Contribution

It demonstrates the dynamic evolution of magnetic fields in hypermassive neutron stars and predicts their electromagnetic luminosity during post-merger phases.

Findings

Electromagnetic luminosity can reach ~10^{47} ergs/s.

Magnetic field profiles are dynamically varied during HMNS evolution.

Luminosity is comparable to quasar brightness.

Abstract

The merger of two neutron stars results often in a rapidly and differentially rotating hypermassive neutron star (HMNS). We show by numerical-relativity simulation that the magnetic-field profile around such HMNS is dynamically varied during its subsequent evolution, and as a result, electromagnetic radiation with a large luminosity ~ 0.1 B^2 R^3 Omega is emitted with baryon (B, R, and Omega are poloidal magnetic-field strength at stellar surface, stellar radius, and angular velocity of a HMNS). The predicted luminosity of electromagnetic radiation, which is primarily emitted along the magnetic-dipole direction, is ~ 10^{47} (B/10^{13} G)^2(R/10 km)^3(Omega/10^4 rad/s) ergs/s, that is comparable to the luminosity of quasars.