GW170817: Measurements of Neutron Star Radii and Equation of State

GW170817: Measurements of Neutron Star Radii and Equation of State

15 Oct 2018 | The LIGO Scientific Collaboration and The Virgo Collaboration
The LIGO and Virgo collaborations detected gravitational waves from the merger of a neutron star binary system on 17 August 2017, providing new insights into neutron star (NS) properties. By analyzing the data, they constrained the radii of the two neutron stars, finding R₁ = 10.8_{-1.7}^{+2.0} km and R₂ = 10.7_{-1.5}^{+2.1} km at the 90% credible level. When considering the equation of state (EOS) that supports NSs with masses above 1.97 M☉, the radii were further constrained to R₁ = 11.9_{-1.4}^{+1.4} km and R₂ = 11.9_{-1.4}^{+1.4} km. They also measured the pressure at twice nuclear saturation density as 3.5_{-1.7}^{+2.7} × 10³⁴ dyn cm⁻² at the 90% level. The analysis used two methods: one based on EOS-insensitive relations between macroscopic properties and another using a parametrized EOS. The results are consistent with previous studies and provide improved constraints on NS radii and EOS parameters. The findings suggest that NS radii are not large and that the EOS is likely soft. The results also support the observed maximum mass of a neutron star, PSR J0348+0432, at 2.01 M☉. The study highlights the importance of gravitational wave observations in probing extreme conditions in neutron star interiors.The LIGO and Virgo collaborations detected gravitational waves from the merger of a neutron star binary system on 17 August 2017, providing new insights into neutron star (NS) properties. By analyzing the data, they constrained the radii of the two neutron stars, finding R₁ = 10.8_{-1.7}^{+2.0} km and R₂ = 10.7_{-1.5}^{+2.1} km at the 90% credible level. When considering the equation of state (EOS) that supports NSs with masses above 1.97 M☉, the radii were further constrained to R₁ = 11.9_{-1.4}^{+1.4} km and R₂ = 11.9_{-1.4}^{+1.4} km. They also measured the pressure at twice nuclear saturation density as 3.5_{-1.7}^{+2.7} × 10³⁴ dyn cm⁻² at the 90% level. The analysis used two methods: one based on EOS-insensitive relations between macroscopic properties and another using a parametrized EOS. The results are consistent with previous studies and provide improved constraints on NS radii and EOS parameters. The findings suggest that NS radii are not large and that the EOS is likely soft. The results also support the observed maximum mass of a neutron star, PSR J0348+0432, at 2.01 M☉. The study highlights the importance of gravitational wave observations in probing extreme conditions in neutron star interiors.
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Understanding GW170817%3A Measurements of Neutron Star Radii and Equation of State.