Can quasi-universal relations be used in the future of Neutron Star's detections ?

The dependence of neutron stars’s astrophysical features on the description of their interior is key to our understanding of isospin asymmetric and dense matter. There exists a series of almost equation of state independent relations reported in the literature, called quasi-universal relations, that were used to extract constraints on radii in the famous double neutron star binary merger GW170817 [Abbott et al. 2018].

Using sets of equations of state constrained by multi-messenger astronomy and nuclear-physics theory, we discuss quasi-universal relations in the context of future gravitational-wave detectors.

We focus on the relation between the tidal deformability Λ and the compactness C. A gravitational-wave signal is simulated with the sensitivity of Cosmic Explorer and Einstein Telescope detectors, and the radius of the stars inferred using quasi-universal relations. We then use the information in this simulated signal to obtain a simulated set of signal-constrained equations of state.

We find that direct equation of state constraints offer a significantly better precision in the extraction of the radius than the quasi-universal relations C(Λ) when applied to next-generation analyses.