Simulations of rotating neutron star collapse with the puncture gauge: end state and gravitational waveforms

TL;DR

This paper uses advanced numerical relativity simulations to study the collapse of rotating neutron stars into black holes, analyzing the end state and gravitational waveforms with improved techniques.

Contribution

It introduces new 3+1 numerical relativity simulations with the Z4c formulation and moving puncture gauge for rotating neutron star collapse.

Findings

The end state matches vacuum spacetime from spinning puncture data.

Gravitational waveforms are consistent with black hole perturbation theory.

Collapse dynamics are linked to radiation emission patterns.

Abstract

We reexamine the gravitational collapse of rotating neutron stars to black holes by new 3+1 numerical relativity simulations employing the Z4c formulation of Einstein equations, the moving puncture gauge conditions, and a conservative mesh refinement scheme for the general relativistic hydrodynamics. The end state of the collapse is compared to the vacuum spacetime resulting from the evolution of spinning puncture initial data. Using a local analysis for the metric fields, we demonstrate that the two spacetimes actually agree. Gravitational waveforms are analyzed in some detail. We connect the emission of radiation to the collapse dynamics using simplified spacetime diagrams, and discuss the similarity of the waveform structure with the one of black hole perturbation theory.