Combining Electromagnetic and Gravitational-Wave Constraints on Neutron-Star Masses and Radii

Area of Science:

• Astrophysics
• Nuclear Physics
• Gravitational-wave Astronomy

Background:

• Neutron stars are extreme astrophysical objects with properties governed by the equation of state (EOS) at supra-nuclear densities.
• Understanding the neutron-star mass-radius relationship is crucial for constraining the EOS.
• Multiple observational datasets, including gravitational waves and X-ray binaries, offer complementary probes of neutron-star structure.

Purpose of the Study:

• To jointly infer neutron-star mass and radius constraints using a comprehensive dataset.
• To assess the impact of prior distributions on the derived mass-radius curves and EOS.
• To analyze the consistency between gravitational-wave and electromagnetic observations of neutron stars.

Main Methods:

• Joint Bayesian inference was performed on data from GW170817, quiescent low-mass X-ray binaries (QLMXBs), photospheric radius expansion X-ray bursting sources, and NICER observations of J0030+0451.
• The influence of prior distribution forms on posterior mass-radius curves and EOS was evaluated.
• Electromagnetic data consistency was analyzed by incorporating an intrinsic scattering term into the uncertainties.

Main Results:

• The combined dataset yields consistent constraints on the neutron-star mass-radius curve and EOS.
• The impact of prior distributions on the posterior results is reduced compared to analyses using QLMXBs alone.
• Including intrinsic scattering in electromagnetic data analysis results in only a slight broadening of the posterior distributions.

Conclusions:

• Gravitational-wave and electromagnetic observations provide a consistent picture of neutron-star structure.
• The joint analysis strengthens our understanding of the neutron-star equation of state.
• Future studies can build upon this consistent framework to further refine neutron-star physics.