Hybrid stars with large strange quark cores constrained by GW170817

TL;DR

This study explores how multi-quark interactions influence hybrid star properties, demonstrating that certain interactions can lead to large strange quark cores consistent with GW170817 constraints.

Contribution

It introduces a detailed analysis of multi-quark interactions within the NJL model to understand their effects on hybrid star structure and strangeness content.

Findings

Large strange quark cores are possible in hybrid stars with specific interactions.

Low mass stars can contain small quark cores with minimal strangeness.

GW170817 constraints allow for hybrid stars with significant quark cores and strangeness.

Abstract

We analyze the impact of several multi-quark interaction channels on the properties of hybrid stars. Four and eight vector interactions were included in the $SU(3)$ NJL model to describe the quark matter, and all vector like interactions were investigated. The hybrid stars were built starting from an hadronic EoS that satisfy presently accepted nuclear matter properties and considering the quark model constrained by the vacuum properties of several light mesons. The interplay between the 8-quark vector interaction and the 4-quark isovector-vector interaction determine the size of the quark core and its strangeness content. The inclusion of a isovector-vector interaction is essential to obtain large $s$-quark contents and a smaller central speed of sound, although this interaction pushes the onset of quarks to larger densities. It is observed that low mass stars, with a mass below 1.4$M_\odot$, may contain a quark core but with small strangeness content. It is shown that the presently existing mass and tidal deformability constraints from NS observations allow for the existence of hybrid stars with a large strangeness content and large quark cores for binary mass ratios $q=M_2/M_1\gtrsim 0.85$.