Modeling a 2.5M⊙ compact star with quark matter

Abstract

The detection of an unexpected [Formula: see text] component in the gravitational wave event GW190814 has puzzled the community of high-energy astrophysicists, since in the absence of further information it is not clear whether this is the heaviest “neutron star” ever detected or either the lightest black hole known, of a kind absent in the local neighborhood. We show in this work a few possibilities for a model of the former, in the framework of three different quark matter models with and without anisotropy in the interior pressure. As representatives of classes of “exotic” solutions, we show that even though the stellar sequences may reach this ballpark, it is difficult to fulfill simultaneously the constraint of the radius as measured by the NICER team for the pulsar PSR J0030+0451. Thus, and assuming both measurements stand, compact neutron stars cannot be all made of self-bound quark matter, even within anisotropic solutions which boost the maximum mass well above the [Formula: see text] figure. We also point out that a very massive compact star will limit the absolute maximum matter density in the present universe to be less than 6 times the nuclear saturation value.