Constraining exotic compact stars composed of bosonic and fermionic dark matter with gravitational wave events

Abstract

ABSTRACTWe investigate neutron star–black hole (NS–BH) merger candidates as a test for compact exotic objects. Using the events GW190814, GW200105, and GW200115 measured by the LIGO-Virgo collaboration, which represent a broad profile of the masses in the NS mass spectrum; we demonstrate the constraining power for the parameter spaces of compact stars consisting of dark matter for future measurements. We consider three possible cases of dark matter stars: self-interacting, purely bosonic or fermionic dark matter stars, stars consisting of a mixture of interacting bosonic and fermionic matter as well as the limiting case of self-bound stars. We find that the scale of those hypothetical objects are dominated by the one of the strong interaction. The presence of fermionic dark matter requires a dark matter particle of the GeV mass scale, while the bosonic dark matter particle mass can be arbitrarily large or small. In the limiting case of a self-bound constant speed of sound parametrization, we find that the vacuum energy of those configurations has to be similar to the one of QCD.