Constraining strangeness in dense matter with GW170817

TL;DR

This paper investigates how strangeness in dense matter influences neutron star properties and gravitational wave signals, using various models to constrain the presence of hyperons and phase transitions in neutron stars based on GW170817 data.

Contribution

It models the effects of strangeness on neutron star structure and gravitational waves, providing constraints on phase transitions and the existence of hybrid stars from GW170817 observations.

Findings

Hybrid stars require low-density phase transitions near saturation.

Strangeness content affects tidal deformability and gravitational wave signatures.

Constraints on hyperon interactions from GW data.

Abstract

Particles with strangeness content are predicted to populate dense matter, modifying the equation of state of matter inside neutron stars as well as their structure and evolution. In this work, we show how the modeling of strangeness content in dense matter affects the properties of isolated neutrons stars and the tidal deformation in binary systems. For describing nucleonic and hyperonic stars we use the many-body forces model (MBF) at zero temperature, including the $\phi$ mesons for the description of repulsive hyperon-hyperon interactions. Hybrid stars are modeled using the MIT Bag Model with vector interaction (vMIT) in both Gibbs and Maxwell constructions, for different values of bag constant and vector interaction couplings. A parametrization with a Maxwell construction, which gives rise to third family of compact stars (twin stars), is also investigated. We calculate the tidal contribution that adds to the post-Newtonian point-particle corrections, the associated love number for sequences of stars of different composition (nucleonic, hyperonic, hybrid and twin stars), and determine signatures of the phase transition on the gravitational waves in the accumulated phase correction during the inspirals among different scenarios for binary systems. On the light of the recent results from GW170817 and the implications for the radius of $\sim1.4\,\mathrm{M_{\odot}}$ stars, our results show that hybrid stars can only exist if a phase transition takes place at low densities close to saturation.