Direct Measurement of the Accretion Disk Formed in Prompt Collapse Mergers with Future Gravitational-Wave Observatories

TL;DR

This paper demonstrates that future gravitational-wave observatories can directly measure the mass of accretion disks formed during prompt collapse neutron star mergers, improving understanding of heavy element production and gamma-ray burst mechanisms.

Contribution

It introduces a novel method to directly measure accretion disk mass from gravitational-wave signals, based on numerical relativity simulations, with potential for high precision.

Findings

Accretion disk influences the gravitational-wave ringdown signal.

Method can measure disk mass with 10% error at 30 Mpc.

Event rate estimated at 0.001 to 0.25 per year.

Abstract

The production site of heavy r-process elements, such as Gold and Uranium, is uncertain. Neutron star mergers are the only astrophysical phenomenon in which we have witnessed their formation. However, the amount of heavy elements resulting from the merger remains poorly constrained, mainly due to uncertainties on the mass and angular momentum of the disk formed in the merger remnant. Matter accretion from the disk is also thought to power gamma ray-bursts. We discover from numerical relativity simulations that the accretion disk influences the ringdown gravitational-wave signal produced by binaries that promptly collapse to black-hole at merger. We propose a method to \emph{directly} measure the mass of the accretion disk left during black hole formation in binary mergers using observatories such as the Einstein Telescope or Cosmic Explorer with a relative error of 10\% for binaries at a distance of up to 30~Mpc, corresponding to an event rate of 0.001 to 0.25 events per year.