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Abstract: Binary neutron stars NSNS are expected to be among the leading sources ofgravitational waves observable by ground-based laser interferometers and may bethe progenitors of short-hard gamma ray bursts. We present a series of generalrelativistic NSNS coalescence simulations both for unmagnetized and magnetizedstars. We adopt quasiequilibrium initial data for circular, irrotationalbinaries constructed in the conformal thin-sandwich CTS framework. We adoptthe BSSN formulation for evolving the metric and a high-resolutionshock-capturing scheme to handle the magnetohydrodynamics. Our simulations ofunmagnetized binaries confirm the results of Shibata, Taniguchi and Uryu2003. In cases in which the mergers result in a prompt collapse to a blackhole, we are able to use puncture gauge conditions to extend the evolution anddetermine the mass of the material that forms a disk. We find that the diskmass is less than 2% of the total mass in all cases studied. We then add asmall poloidal magnetic field to the initial configurations and study thesubsequent evolution. For cases in which the remnant is a hypermassive neutronstar, we see measurable differences in both the amplitude and phase of thegravitational waveforms following the merger. For cases in which the remnant isa black hole surrounded by a disk, the disk mass and the gravitationalwaveforms are about the same as the unmagnetized cases. Magnetic fieldssubstantially affect the long-term, secular evolution of a hypermassive neutronstar driving `delayed collapse- and an accretion disk around a nascent blackhole.

Author: Yuk Tung Liu, Stuart L. Shapiro, Zachariah B. Etienne, Keisuke Taniguchi UIUC


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