The close-limit approximation to Neutron Star Collisions

TL;DR

This paper introduces a close-limit approximation method for modeling head-on neutron star collisions, providing a simplified framework to study gravitational waves and the post-merger object, useful for benchmarking complex simulations.

Contribution

It extends the close-limit approximation technique to neutron star mergers, offering a new approach to analyze gravitational radiation and post-merger dynamics.

Findings

Merged neutron stars excite fluid pulsation modes

Approximation can serve as a benchmark for nonlinear studies

Initial data construction is physically plausible

Abstract

We develop a close-limit approximation to the head-on collision of two neutron stars similar to that used to treat the merger of black hole binaries . This approximation can serve as a useful benchmark test for future fully nonlinear studies. For neutron star binaries, the close-limit approximation involves assuming that the merged object can be approximated as a perturbed, stable neutron star during the ring-down phase of the coalescence. We introduce a prescription for the construction of initial data sets, discuss the physical plausibility of the various assumptions involved, and briefly investigate the character of the gravitational radiation produced during the merger. The numerical results show that several of the merged objects fluid pulsation modes are excited to a significant level.