Properties of the binary neutron star merger GW170817

On August 17, 2017, the Advanced LIGOand Advanced Virgo gravitational-wavedetectors observed a low-mass compact binary inspiral. The initial sky localization of the source of the gravitational-wavesignal, GW170817, allowed electromagnetic observatories to identify NGC 4993 as the host galaxy. In this work, we improve initial estimates of the binary’s properties, including component masses, spins, and tidal parameters, using the known source location, improved modeling, and recalibrated Virgo data. We extend the range of gravitational-wavefrequencies considered down to 23 Hz, compared to 30 Hz in the initial analysis. We also compare results inferred using several signal models, which are more accurate and incorporate additional physical effects as compared to the initial analysis. We improve the localization of the gravitational-wavesource to a 90% credible region of 16     deg 2 . We find tighter constraints on the masses, spins, and tidal parameters, and continue to find no evidence for nonzero component spins. The component masses are inferred to lie between 1.00 and 1.89     M ⊙ when allowing for large component spins, and to lie between 1.16 and 1.60     M ⊙ (with a total mass 2.73 + 0.04 − 0.01     M ⊙ ) when the spins are restricted to be within the range observed in Galactic binary neutron stars. Using a precessing model and allowing for large component spins, we constrain the dimensionless spins of the components to be less than 0.50 for the primary and 0.61 for the secondary. Under minimal assumptions about the nature of the compact objects, our constraints for the tidal deformability parameter ˜ Λ are (0,630) when we allow for large component spins, and 300 + 420 − 230 (using a 90% highest posterior density interval) when restricting the magnitude of the component spins, ruling out several equation-of-state models at the 90% credible level. Finally, with LIGOand GEO600data, we use a Bayesian analysis to place upper limits on the amplitude and spectral energy density of a possible postmerger signal.