Assessment of Proposed Equations of State for Neutron Stars Using Multi-Messenger Astronomy

Neutron stars (NS) are the densest known objects in the universe with its central density is hypothesized to reach as high as 6-10 times nuclear density. At such densities the strong nuclear interaction plays a crucial role. Our lack of understanding of the strong interaction not only limits our ability to explain the physics of NSs, but it is also the biggest hurdle in our goal of describing dense matter. This elusive mathematical description of matter is called the equation of state (EoS), which is a relationship between pressure and energy density of matter. In the absence of a complete theoretical understanding of the EoS, numerous models have been proposed. None of these theories can be tested in laboratories since we cannot create matter at such extreme conditions. A manifestation of this description is in the physical properties of the NSs, namely how big a NS should be for a given mass (Mass-Radius relation) and how much can a NS deform due to tidal forces (Mass-Tidal deformability relation). In this work, we showcase a Bayesian inference technique we developed to combine the mass-radii and mass-tidal deformability observations from NICER telescope observations of pulsars, and LIGO observations of colliding NSs respectively to put constraints on the EoS.