We present observational confirmation of Hawking's black-hole area theorem based on data from GW150914, finding agreement with the prediction with 97% (95%) probability when we model the ringdown including (excluding) overtones of the quadrupolar mode. We obtain this result from a new time-domain analysis of the pre- and postmerger data. We also confirm that the inspiral and ringdown portions of the signal are consistent with the same remnant mass and spin, in agreement with general relativity.
@article{arxiv.2012.04486,
title = {Testing the black-hole area law with GW150914},
author = {Maximiliano Isi and Will M. Farr and Matthew Giesler and Mark A. Scheel and Saul A. Teukolsky},
journal= {arXiv preprint arXiv:2012.04486},
year = {2021}
}