Prospect of Constraining the EoS of Neutron Stars Using Post-Merger Signals

Abstract

Post-merger gravitational-wave emission from a binary neutron star merger carries crucial information about the equation of state (EoS) of matter at high temperatures. Current gravitational wave detectors have limited sensitivities at post-merger frequencies in the range [1.5, 4] kHz. Therefore, valuable inferences can only be made after combining information from multiple (BNS) events. Criswell et al. [Phys. Rev. D 107, 043021 (2023)] carries out an injection study to infer the radius posterior for a $1.6 M_{\odot}$ NS by combining the information from injected BNS events via the hierarchical Bayesian inference (HBI) formulation. This formulation utilizes empirical relations that connect the peak frequency of the post-merger remnant with the chirp mass of the system, and the EoS proxy parameter $R_{1.6}$. In this work, we extend the HBI formulation to other EoS proxy parameters (i.e., the radius of (NS), $R_{1.X}$, with masses 1.2, 1.4, and 1.8 $M_{\odot}$) and combine the four $R_{1.X}$ posteriors through the piecewise polytropic EoS model to obtain measurable constraints on the EoS of the NS. We show that the NS radii can be constrained to within $\sim$1 km ( $\sim$0.55 km) assuming uniform (astrophysical) prior on $R_{1.X}$ for injections in the A+ noise. We also study systematic biases in the analysis coming from the limitations of empirical relations.