Prospects for Direct Detection of Black Hole Formation in Neutron Star Mergers with Next-Generation Gravitational-Wave Detectors

TL;DR

This paper investigates the potential for next-generation gravitational-wave detectors to directly observe black hole formation in neutron star mergers, analyzing simulation data to identify characteristic signals and assess detection prospects up to 100 Mpc.

Contribution

It introduces a detailed analysis of gravitational-wave signatures from black hole formation in neutron star mergers using extensive numerical relativity simulations, highlighting detection strategies with future detectors.

Findings

Black hole formation signals show excess high-frequency power and quasinormal mode damping.

Long-lived remnants have reduced power above 4 kHz in gravitational-wave spectrum.

Detection of such signals is feasible up to 100 Mpc with next-generation detectors.

Abstract

A direct detection of black hole formation in neutron star mergers would provide invaluable information about matter in neutron star cores and finite temperature effects on the nuclear equation of state. We study black hole formation in neutron star mergers using a set of 190 numerical relativity simulations consisting of long-lived and black-hole-forming remnants. The postmerger gravitational-wave spectrum of a long-lived remnant has greatly reduced power at a frequency $f$ greater than $f_{\rm peak}$, for $f \gtrsim 4\,\rm kHz$, with $f_{\rm peak} \in [2.5, 4]\,\rm kHz$. On the other hand, black-hole-forming remnants exhibit excess power in the same large $f$ region and manifest exponential damping in the time domain characteristic of a quasinormal mode. We demonstrate that the gravitational-wave signal from a collapsed remnant is indeed a quasinormal ringing. We report on the opportunity for direct detections of black hole formation with next-generation gravitational-wave detectors such as Cosmic Explorer and Einstein Telescope and set forth the tantalizing prospect of such observations up to a distance of 100 Mpc for an optimally oriented and located source with an SNR of 4.