Abstract
GW170817 is the very first observation of gravitational waves originating from the coalescence of two compact objects in the mass range of neutron stars, accompanied by electromagnetic counterparts, and offers an opportunity to directly probe the internal structure of neutron stars. We perform Bayesian model selection on a wide range of theoretical predictions for the neutron star equation of state. For the binary neutron star hypothesis, we find that we cannot rule out the majority of theoretical models considered. In addition, the gravitational-wave data alone does not rule out the possibility that one or both objects were low-mass black holes. We discuss the possible outcomes in the case of a binary neutron star merger, finding that all scenarios from prompt collapse to long-lived or even stable remnants are possible. For long-lived remnants, we place an upper limit of 1.9 kHz on the rotation rate. If a black hole was formed any time after merger and the coalescing stars were slowly rotating, then the maximum baryonic mass of non-rotating neutron stars is at most , and three equations of state considered here can be ruled out. We obtain a tighter limit of for the case that the merger results in a hypermassive neutron star.
Highlights
On August 17, 2017, the Advanced LIGO [1] and Advanced Virgo [2] observatories detected a gravitational-wave signal, GW170817, from a low-mass compact binary system [3]
We expect the binary neutron star hypothesis with a common equation of state to be preferred over an independent equation of state hypothesis by a factor ∼5, as it uses one fewer param eter. This is in agreement with the results found in table 1 and as demonstrated in [49] for simulated binary neutron star signals
We employ Bayesian model selection as a tool to discriminate between different theoretical models for the neutron star equation of state using only the gravitational-wave data
Summary
On August 17, 2017, the Advanced LIGO [1] and Advanced Virgo [2] observatories detected a gravitational-wave signal, GW170817, from a low-mass compact binary system [3]. The signal was coincident with the gamma-ray burst GRB 170817A [4] and was followed by other observations spanning the electromagnetic spectrum [5] These electromagnetic observations, coupled with measurements of the component masses from the gravitational-wave observation [6, 7], provide compelling evidence that GW170817 was produced from the merger of two neutron stars. Information regarding the equation of state is encoded in the variation of the orbital evolution induced by tidal interactions and the deformation of the neutron stars under their own angular momenta [10,11,12,13,14] Such interactions are small at low frequencies but rapidly increase in strength in the final tens of gravitational-wave cycles before merger. No such post-merger signal was observed for GW170817 [6, 20, 22, 23]
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