High-mass twin stars with a multipolytrope equation of state

摘要

We show that in the three-polytrope model of Hebeler et al. [Astrophys. J. 773, 11 ( 2013)] for the neutron star equation of state (EoS) at supersaturation densities a third family of compact stars can be obtained which confirms the possibility of high-mass twin stars that have coincident masses M-1 = M-2 approximate to 2M(circle dot) and significantly different radii |R-1 - R-2| > 2-3 km. We show that the causality constraint puts severe limitations on the maximum mass of the third family sequence which can be relaxed when this scheme is extended to four polytropes thus mimicking a realistic high-density matter EoS.