We have numerically investigated close scattering processes of two black holes (BHs). Our careful analysis shows for the first time a non-merging ringdown gravitational wave coming from dynamical tidal deformations of individual BHs during their close encounter. The ringdown wave frequencies turn out to agree well with the quasi-normal ones of a single BH in perturbation theory, despite its distinctive physical context from the merging case. Our study shows a new type of gravitational waveform and opens up a new exploration of strong gravitational interactions using BH encounters.
@article{arxiv.2310.18686,
title = {Ringdown gravitational waves from close scattering of two black holes},
author = {Yeong-Bok Bae and Young-Hwan Hyun and Gungwon Kang},
journal= {arXiv preprint arXiv:2310.18686},
year = {2023}
}