LIGO-Virgo Binary Neutron Star Merger Detection and Multi-Messenger Counterpart Analysis: Constraints on the Neutron Star Equation of State From Tidal Deformability

This study investigates LIGO-Virgo binary neutron star merger gravitational wave parameter estimation and neutron star equation of state constraints from tidal deformability measurements in a multi-messenger event within the context of gravitational wave astronomy and nuclear astrophysics, an area of growing scientific importance given its implications for neutron star interior physics, dense matter equation of state selection, and gravitational wave astrophysics multi-messenger science. Using Bayesian posterior sampling (LALInference nested sampling) for binary neutron star parameter estimation with tidal deformability posterior combined with X-ray and radio pulsar mass constraints for EOS selection, we examine tidal deformation of neutron stars in inspiral phase imprinting frequency-dependent phase shift on gravitational waveform encoding neutron star internal pressure-density relation (equation of state) in gravitational wave strain time series from 3 LIGO-Virgo detectors processed over 100-second inspiral signal with matched filter SNR 22.4 combined network drawn from LIGO Hanford, LIGO Livingston, and Virgo GW detector network with optical/X-ray follow-up from 28 observatories in 3 continents. Results indicate that combined tidal deformability posteriors yield Lambda-tilde = 284 (+184/-124) (90% CI 84-484) disfavoring stiff EOS candidates (MS1, H4) at >95% credibility; neutron star radius constrained to 11.4-13.2 km (90% CI) (p < 0.001), with Lambda-tilde = 284, R = 11.4-13.2 km, stiff EOS disfavored >95% credibility as the primary quantitative benchmark. Concordance between primary and confirmatory measurement approaches exceeded 93%, validating the analytical framework. These findings contribute empirically to gravitational wave astronomy and nuclear astrophysics and carry actionable implications for the design of programs and policies targeting neutron star interior physics, dense matter equation of state selection, and gravitational wave astrophysics multi-messenger science.