Neutron Star with Dark Matter Admixture: A Candidate for Bridging the Mass Gap

Abstract

Neutron stars, white dwarfs and black holes are the after death remnants of massive stars. However, according to the most recent observations, the neutron stars maximum mass is between $2.0-2.5 M_{\odot}$ while black holes of less than 5 $M_{\odot}$ has not yet been observed. The region between the most massive neutron star and the least massive black hole is called the mass-gap. If indeed its existence is confirmed by future observations, that indicates a gap in our understanding which seeks for explanation. In addition, the existence of compact objects within the mass-gap should also be supported with the help of possible new theoretical scenarios. In this study, we propose a possible explanation for the existence of compact objects within the mass-gap region. Specifically, we propose that the mass-gap region could be bridged by the existence of a hybrid compact object, composed of hadronic and self interacting and non-annihilating fermionic dark matter, considering that the interaction between these two fluids it is only gravitational. Fundamental questions about how these objects form and how they can be detected are also addressed.