Can magnetic fields be detected during the inspiral of binary neutron stars?

TL;DR

This study uses general-relativistic simulations to evaluate how magnetic fields influence gravitational waves from neutron star mergers, finding that realistic magnetic fields have negligible effects on inspiral waveforms detectable by current instruments.

Contribution

It provides a quantitative analysis showing that magnetic fields below 10^{14}G do not significantly affect gravitational wave signals during inspiral, highlighting the limited detectability of magnetic effects with current detectors.

Findings

Magnetic fields amplify after merger due to Kelvin-Helmholtz instability.

Magnetic tension reduces tidal deformation for extremely large magnetic fields.

Current detectors are unlikely to detect magnetic effects during inspiral.

Abstract

Using accurate and fully general-relativistic simulations we assess the effect that magnetic fields have on the gravitational-wave emission produced during the inspiral and merger of magnetized neutron stars. In particular, we show that magnetic fields have an impact after the merger, because they are amplified by a Kelvin-Helmholtz instability, but also during the inspiral, most likely because the magnetic tension reduces the stellar tidal deformation for extremely large initial magnetic fields, B_0>~10^{17}G. We quantify the influence of magnetic fields by computing the overlap, O, between the waveforms produced during the inspiral by magnetized and unmagnetized binaries. We find that for any realistic magnetic field strength B_0<~10^{14}G the overlap during the inspiral is O>~0.999 and is quite insensitive to the mass of the neutron stars. Only for unrealistically large magnetic fields like B_0~10^{17}G the overlap does decrease noticeably, becoming at our resolutions O<~0.76/0.67 for stars with baryon masses M_b~1.4/1.6 Msun, respectively. Because neutron stars are expected to merge with magnetic fields ~10^{8}-10^{10}G and because present detectors are sensitive to O<~0.995, we conclude that it is very unlikely that the present detectors will be able to discern the presence of magnetic fields during the inspiral of neutron stars.