Masking equation of state effects in binary neutron star mergers

TL;DR

This study demonstrates that magnetic fields in binary neutron star mergers can cause frequency shifts in gravitational wave signals, complicating the identification of equation of state features like phase transitions.

Contribution

It reveals that magnetic fields can mimic or mask equation of state effects in gravitational wave spectra, highlighting the need for including magnetic effects in data interpretation.

Findings

Magnetic fields induce frequency shifts similar to those caused by equation of state features.

Magnetic effects can mask or nullify the signatures of phase transitions.

Interpretation of gravitational wave data requires accounting for magnetic field influences.

Abstract

Recent nonmagnetized studies of binary neutron star mergers have indicated the possibility of identifying equation of state features, such as a phase transition or a quark-hadron crossover, based on the frequency shift of the main peak in the postmerger gravitational wave spectrum. By performing a series of general relativistic, magnetohydrodynamic simulations we show that similar frequency shifts can be obtained due to the effect of the magnetic field. The existing degeneracy can either mask or nullify a shift due to a specific equation of state feature, and therefore the interpretation of observational data is more complicated than previously thought, requiring a more complete treatment that would necessarily include the neutron star's magnetic field.