Was GW190814 a black hole -- strange quark star system?

TL;DR

This paper explores the hypothesis that the low mass companion in GW190814 was a strange quark star within a two-families scenario, allowing for massive quark stars and small-radius neutron stars with realistic equations of state.

Contribution

It introduces a two-families model where neutron stars and strange quark stars coexist, explaining GW190814's observations without extreme sound speeds.

Findings

Strange quark stars can reach masses of 2.5-2.67 M_ with realistic equations of state.

Neutron stars can have radii less than 11 km at 1.4 M_, consistent with constraints.

The two-families scenario satisfies both high mass and small radius requirements.

Abstract

We investigate the possibility that the low mass companion of the black hole in the source of GW190814 was a strange quark star. This possibility is viable within the so-called two-families scenario in which neutron stars and strange quark stars coexist. Strange quark stars can reach the mass range indicated by GW190814, $M\sim (2.5-2.67) M_\odot$ due to a large value of the adiabatic index, without the need for a velocity of sound close to the causal limit. Neutron stars (actually hyperonic stars in the two-families scenario) can instead fulfill the presently available astrophysical and nuclear physics constraints which require a softer equation of state. In this scheme it is possible to satisfy both the request of very large stellar masses and of small radii while using totally realistic and physically motivated equations of state. Moreover it is possible to get a radius for a 1.4 $M_\odot$ star of the order or less than 11 km, which is impossible if only one family of compact stars exists.