General Relativistic Magnetohydrodynamic Simulations of Binary Neutron Star Mergers with the APR4 Equation of State

TL;DR

This paper reports on advanced general relativistic magnetohydrodynamic simulations of binary neutron star mergers, exploring gravitational wave signals, matter dynamics, and electromagnetic counterparts, with implications for understanding short gamma-ray burst engines.

Contribution

It introduces comprehensive simulations using the APR4 equation of state, including magnetic fields and thermal effects, to study merger outcomes and electromagnetic signals.

Findings

Different gravitational wave signatures identified.

Magnetic field evolution impacts post-merger dynamics.

Ejected mass and remnant properties vary with initial conditions.

Abstract

We present new results of fully general relativistic magnetohydrodynamic simulations of binary neutron star (BNS) mergers performed with the Whisky code. All the models use a piecewise polytropic approximation of the APR4 equation of state for cold matter, together with a 'hybrid' part to incorporate thermal effects during the evolution. We consider both equal and unequal-mass models, with total masses such that either a supramassive NS or a black hole is formed after merger. Each model is evolved with and without a magnetic field initially confined to the stellar interior. We present the different gravitational wave (GW) signals as well as a detailed description of the matter dynamics (magnetic field evolution, ejected mass, post-merger remnant/disk properties). Our simulations provide new insights into BNS mergers, the associated GW emission and the possible connection with the engine of short gamma-ray bursts (both in the 'standard' and in the 'time-reversal' scenarios) and other electromagnetic counterparts.