Reducing orbital eccentricity in initial data of binary neutron stars

TL;DR

This paper presents a new iterative method to generate low-eccentricity initial data for binary neutron star simulations, significantly reducing orbital eccentricity for more realistic modeling.

Contribution

The authors develop an iterative approach that adjusts orbital parameters to achieve low eccentricity in binary neutron star initial data, improving simulation accuracy.

Findings

Eccentricity reduced from ~0.01 to <0.001 after three iterations

Method achieves an order of magnitude reduction in eccentricity

Applicable to equal-mass binaries over ~10 orbits before merger

Abstract

We develop a method to compute low-eccentricity initial data of binary neutron stars required to perform realistic simulations in numerical relativity. The orbital eccentricity is controlled by adjusting the orbital angular velocity of a binary and incorporating an approaching relative velocity of the neutron stars. These modifications improve the solution primarily through the hydrostatic equilibrium equation for the binary initial data. The orbital angular velocity and approaching velocity of initial data are updated iteratively by performing time evolutions over ~3 orbits. We find that the eccentricity can be reduced by an order of magnitude compared to standard quasicircular initial data, specifically from ~0.01 to <~0.001, by three successive iterations for equal-mass binaries leaving ~10 orbits before the merger.