Hierarchical triple mergers: testing Hawking's area theorem with the inspiral signals

TL;DR

This paper proposes a new method to test Hawking's black hole area theorem using hierarchical triple mergers, leveraging inspiral signals to infer properties of progenitor and remnant black holes, and confirms the law for some simulated events.

Contribution

It introduces a novel approach to test Hawking's area theorem through hierarchical triple mergers using inspiral data, enhancing existing testing methods.

Findings

The area law can be confirmed for some hierarchical triple merger events.

Simulations show the method's effectiveness in LIGO/Virgo/KAGRA/O4/O5.

The approach complements previous tests of the black hole area theorem.

Abstract

Hawking's area theorem is one of the fundamental laws of black holes (BHs), which has been tested at a confidence level of $\sim 95\%$ with gravitational wave (GW) observations by analysing the inspiral and ringdown portions of GW signals, independently. In this work, we propose to carry out the test in a new way with the hierarchical triple merger (i.e., two successive BH mergers occurred sequentially within the observation window of GW detectors), for which the properties of the progenitor BHs and the remnant BH of the first coalescence can be inferred from the inspiral portions of the two mergers. As revealed in our simulations, the BH area law can be well confirmed for some plausible hierarchical triple merger events detectable in LIGO/Virgo/KAGRA/LIGO-India's O4/O5 runs. Our proposed method provides significant facilitation for testing the area law and complements previous methods.