Gravitational waves from supermassive stars collapsing to a supermassive black hole

TL;DR

This paper models gravitational waves from the collapse of rapidly rotating supermassive stars into black holes, predicting detectable signals for space-based interferometers, which could test SMBH formation theories.

Contribution

It provides the first axisymmetric numerical-relativity simulations of gravitational waves from supermassive star collapse to SMBH seeds, including waveform predictions and detectability analysis.

Findings

Peak strain amplitude of ~5×10⁻²¹ at 5 mHz

Detectable by eLISA with SNR ≈ 10 at z=3

Gravitational waves can test SMBH seed formation scenarios

Abstract

We derive the gravitational waveform from the collapse of a rapidly rotating supermassive star (SMS) core leading directly to a seed of a supermassive black hole (SMBH) in axisymmetric numerical-relativity simulations. We find that the peak strain amplitude of gravitational waves emitted during the black-hole formation is $\approx 5 \times 10^{-21}$ at the frequency $f \approx 5$\,mHz for an event at the cosmological redshift $z=3$, if the collapsing SMS core is in the hydrogen-burning phase. Such gravitational waves will be detectable by space laser interferometric detectors like eLISA with signal-to-noise ratio $\approx 10$, if the sensitivity is as high as LISA for $f=1$--10\,mHz. The detection of the gravitational-wave signal will provide a potential opportunity for testing the direct-collapse scenario for the formation of a seed of SMBHs.