With the increasing number of astronomical observational data, it becomes feasible to constrain the equation of state of neutron star matter via data-driven method.

Constrain nuclear EOSs (Equation of State) with massive neutron stars in the framework of relativistic mean field (RMF) models according to various astrophysical observations on neutron star properties.

This study investigated the nuclear EOS and neutron star structures using RMF models constrained by Bayesian inference and astrophysical observations.

By analyzing density-dependent coupling constants across different critical densities, the work demonstrates that higher critical densities tighten constraints on the EOS, leading to softer intermediate-density behavior and increased central energy densities for massive neutron stars. Key ?ndings include a high probability of the squared sound speed exceeding the conformal limit (vs2>1/3) in massive neutron star cores. The inferred maximum neutron star masses (M_max≥2.5 M_⊙) align with interpretations of gravitational wave events like GW190814, where secondary components may represent massive neutron stars. The symmetry energy and pressure profiles at supranuclear densities exhibit critical-density dependence, consistent with multi-messenger constraints.

These findings highlight the interplay between EOS stiffness, phase transitions, and observational constraints, providing critical insights for future studies to refine nuclear matter properties through multi-messenger data and advanced density functional analyses.