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Differentially rotating relativistic stars with post-merger-like rotational profiles
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1  Aristotle University of Thessaloniki

Published: 22 February 2021 by MDPI in 1st Electronic Conference on Universe session Compact Objects

Numerical simulations have been the primary tool to study compact binary coalescences in the last two decades, supplying a wealth of information. Depending primarily on the total mass of the binary, a possible outcome of a binary neutron star merger is a long-lived (with a lifetime > 10ms) compact remnant supported by differential rotation. In this work, we present equilibrium sequences of rotating relativistic stars, constructed with a new differential rotation law that was proposed by Uryu et al. (2017). We choose rotational parameters motivated by numerical simulations of binary neutron star merger remnants, but otherwise adopt a cold, relativistic N=1 polytropic equation of state, in order to perform a detailed comparison to published equilibrium sequences that used the Komatsu, Eriguchi and Hachisu (1989) differential rotation law. We find a small influence of the choice of rotation law on the mass of the equilibrium models and a somewhat larger influence on their radius. The versatility of the new rotation law allows us to construct models that have a similar rotational profile and axis ratio as observed for merger remnants, while at the same time being quasi-spherical. While our models are highly accurate solutions of the fully general relativistic structure equations, we demonstrate that for models relevant to merger remnants the IWM-CFC approximation still maintains an acceptable accuracy.

Keywords: neutron stars; differential rotation; compact remnants