Stellar properties indicating the presence of hyperons in neutron stars

Abstract

We describe distinctive stellar features indicating the presence of hyperons in neutron stars as compared to purely nucleonic systems. A strongly negative curvature of the mass-radius relation $R(M)$ is characteristic of hyperons, which can be determined from measurements of neutron stars with three different masses. Similarly, a reduced second derivative of the tidal deformability as function of mass \lambda(M) points to hyperonic degrees of freedom in NS matter. The slopes of such curves R(M) and \lambda(M) can distinguish a hyperonic equation of state from purely nucleonic models if they appear increased (decreased for \lambda(M)) relative to the maximum mass of neutron stars.