Differentially Rotating Relativistic Stars beyond the J-Constant Law

Abstract

The merger of a binary neutron star (BNS) system can lead to different final states, depending on the total mass of the binary and the equation of state (EOS). One of the possible outcomes of the merger is a long-lived (lifetime > 10ms), compact and differentially rotating remnant.The Komatsu, Eriguchi and Hachisu (1989) differential rotation law (KEH) has been used almost exclusively in the literature to describe such configurations, despite the tension with corresponding rotational profiles reported from numerical simulations. New rotation laws suggested by Uryu et al.(2017) aspire to ease this tension and provide more realistic choices to describe the rotational profiles of BNS merger remnants. We have recently started constructing equilibrium models with one of the new rotation laws proposed, and comparing their physical properties to the KEH rotation law counterpart models. In addition, building on earlier work, the accuracy of the IWM-CFC conformal flatness approximation with the new differential rotation law has been confirmed.