Accurate evolutions of inspiralling and magnetized neutron-stars: equal-mass binaries

TL;DR

This paper presents advanced simulations of magnetized, equal-mass neutron-star binaries, revealing how magnetic fields influence post-merger evolution, black hole formation, and potentially detectable gravitational-wave signals with future detectors.

Contribution

It provides the first detailed numerical analysis of magnetic field effects in equal-mass neutron-star mergers, including their impact on collapse times and gravitational-wave signatures.

Findings

Magnetic fields can accelerate the collapse of hypermassive neutron stars to black holes.

Post-merger magnetic fields develop both toroidal and poloidal components of similar strength.

Magnetic effects on gravitational waves are marginal for current detectors but could be detectable with future, more sensitive observatories.

Abstract

By performing new, long and numerically accurate general-relativistic simulations of magnetized, equal-mass neutron-star binaries, we investigate the role that realistic magnetic fields may have in the evolution of these systems. In particular, we study the evolution of the magnetic fields and show that they can influence the survival of the hypermassive-neutron star produced at the merger by accelerating its collapse to a black hole. We also provide evidence that even if purely poloidal initially, the magnetic fields produced in the tori surrounding the black hole have toroidal and poloidal components of equivalent strength. When estimating the possibility that magnetic fields could have an impact on the gravitational-wave signals emitted by these systems either during the inspiral or after the merger we conclude that for realistic magnetic-field strengths B<~1e12 G such effects could be detected, but only marginally, by detectors such as advanced LIGO or advanced Virgo. However, magnetically induced modifications could become detectable in the case of small-mass binaries and with the development of gravitational-wave detectors, such as the Einstein Telescope, with much higher sensitivities at frequencies larger than ~2 kHz.