GW170817: Measurements of Neutron Star Radii and Equation of State

Abstract

GW170817: Measurements of neutron star radii and equation of state The LIGO Scientific Collaboration and The Virgo Collaboration On August 17, 2017, the LIGO and Virgo observatories made the first direct detection of gravitational waves from the coalescence of a neutron star binary system. The detection of this gravitational wave signal, GW170817, offers a novel opportunity to directly probe the properties of matter at the extreme conditions found in the interior of these stars. The initial, minimal-assumption analysis of the LIGO and Virgo data placed constraints on the tidal effects of the coalescing bodies, which were then translated to constraints on neutron star radii. Here, we expand upon previous analyses by working under the hypothesis that both bodies were neutron stars that are described by the same equation of state and have spins within the range observed in Galactic binary neutron stars. Our analysis employs two methods: the use of equation-of-state-insensitive relations between various macroscopic properties of the neutron stars and the use of an efficient parameterization of the defining function p(ρ) of the equation of state itself. From the LIGO and Virgo data alone and the first method, we measure the two neutron star radii as R 1 = 10.8 +2.0 −1.7 km for the heavier star and R 2 = 10.7 +2.1 −1.5 km for the lighter star at the 90% credible level. If we additionally require that the equation of state supports neutron stars with masses larger than 1.97 M as required from electromagnetic observations and employ the equation of state parametrization, we further constrain R 1 = 11.9 +1.4 −1.4 km and R 2 = 11.9 +1.4 −1.4 km at the 90% credible level. Finally, we obtain constraints on p(ρ) at supranuclear densities, with pressure at twice nuclear saturation density measured at 3.5 +2.7 −1.7 × 10 34 dyn cm −2 at the 90% level.

Charge Radius of the Short-Lived Ni68 and Correlation with the Dipole Polarizability

“…The nuclear equation of state (EOS) plays a key role in supernova explosions and compact object mergers. In fact, the gravitational wave signal from the neutron star merger GW170817 has recently lead to constraints on the EOS of neutron-rich matter [1], which is consistent with our knowledge of nuclear physics. While the EOS of symmetric nuclear matter is well constrained around saturation density [2], the properties of neutron-rich matter are still rather uncertain.…”

Role of the crust in the tidal deformability of a neutron star within a unified treatment of dense matter

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XMM–Newton observations of a gamma-ray pulsar J0633+0632: pulsations, cooling and large-scale emission

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