Model-Independent Determination of the Tidal Deformability of a 1.4 $M_{\odot}$ Neutron Star from Gravitational-Wave Measurements

Abstract: Tidal deformability of a 1.4 $M_\odot$ neutron star provides a pivotal window into the physics of dense nuclear matter, bridging gravitational-wave(GW), electromagnetic observations and nuclear physics. In this work, we present a novel, data-driven approach to constrain $\Lambda_{1.4}$ without invoking specific equation-of-state(EOS) models. By interpolating directly over the mass--tidal-deformability posteriors from GW170817, we obtain an EOS-independent constraint of $$\Lambda_{1.4} \;=\; 222.89_{-98.85}^{+420.33}.$$ We further combine these GW-based results with the X-ray EOS-independent constraint from \cite{Huang_2025}, deriving a multimessenger limit of $$\Lambda_{1.4} \;=\; 265.18_{-104.38}^{+237.88},$$ which remains largely EOS agnostic. This framework demonstrates that higher-order terms neglected in linear expansion methods do not significantly affect $\Lambda_{1.4}$ estimates under current observational uncertainties. As gravitational-wave detectors improve in sensitivity and more binary neutron-star mergers are discovered, our purely data-driven strategy can serve as a robust standard baseline for extracting neutron-star interior properties without relying on unverified EOS models.