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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 amplified by a Kelvin-Helmholtz instability, but also during the inspiral, 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 B_0~10^{17}G, O<0.76 for stars with mass M~1.4Msun, dropping to O<0.67 for M~1.6Msun; in both cases O decreases further after the merger. These results shed light on the recent debate on whether the presence of magnetic fields can be detected during the inspiral and highlight that the use of higher-order methods is essential to draw robust conclusions on this complex process.