Gravitational waves from very massive stars collapsing to a black hole

TL;DR

This paper models gravitational waves from the collapse of very massive, rotating stars into black holes, predicting their detectability with current and future gravitational wave detectors and offering a way to identify such stars.

Contribution

It presents axisymmetric numerical-relativity simulations of collapsing very massive stars, providing predictions for gravitational wave signals and their detectability.

Findings

Gravitational waves peak at strain amplitude ~10^{-22} and frequency 300-600 Hz for events at 50 Mpc.

Second-generation detectors can detect these signals only within 10 Mpc.

Third-generation detectors could detect such signals up to 100 Mpc.

Abstract

We compute gravitational waves emitted by the collapse of a rotating very massive star (VMS) core leading directly to a black hole in axisymmetric numerical-relativity simulations. The evolved rotating VMS is derived by a stellar evolution calculation and its initial mass and the final carbon-oxygen core mass are $320M_\odot$ and $\approx 150M_\odot$, respectively. We find that for the moderately rapidly rotating cases, the peak strain amplitude and the corresponding frequency of gravitational waves are $\sim 10^{-22}$ and $f \approx 300$--600\,Hz for an event at the distance of $D=50$~Mpc. Such gravitational waves will be detectable only for $D \lesssim 10$~Mpc by second generation detectors, advanced LIGO, advanced VIRGO, and KAGRA, even if the designed sensitivity for these detectors is achieved. However, third-generation detectors will be able to detect such gravitational waves for an event up to $D \sim 100$~Mpc. The detection of the gravitational-wave signal will provide a potential opportunity for verifying the presence of VMSs with mass $\gtrsim 300M_\odot$ and their pair-unstable collapse in the universe.