Tidal deformability with sharp phase transitions in (binary) neutron stars

TL;DR

This paper investigates how sharp phase transitions in neutron star matter affect tidal deformability, revealing that such transitions cause minimal deformability and disrupt universal relations, impacting gravitational-wave analysis.

Contribution

It provides a detailed analysis of the impact of sharp phase transitions on neutron star tidal deformability and the validity of universal relations.

Findings

Sharp phase transitions lead to minimal tidal deformabilities.

Discontinuities occur in the tidal deformability-mass relation.

Universal relations are less accurate with sharp phase transitions.

Abstract

The neutron star tidal deformability is a critical parameter which determines the pre-merger gravitational-wave signal in a neutron star merger. In this article, we show how neutron star tidal deformabilities behave in the presence of one or two sharp phase transition(s). We characterize how the tidal deformability changes when the properties of these phase transitions are modified in dense matter equation of state (EoS). Sharp phase transitions lead to the smallest possible tidal deformabilities and also induce discontinuities in the relation between tidal deformability and gravitational mass. These results are qualitatively unmodified by a modest softening of the phase transition. Finally, we test two universal relations involving the tidal deformability and show that their accuracy is limited by sharp phase transitions.