The binary black hole signal GW250114, the clearest gravitational wave detected to date, offers a unique opportunity to test general relativity in the relativistic strong-gravity regime. How well does GW250114 agree with Einstein's predictions in the plunge-merger-ringdown stage? To address this point, we constrain deviations from general relativity across the plunge-merger-ringdown stage of spin-precessing binaries with a parametrized waveform model within the effective-one-body formalism. We find that deviations from the peak gravitational-wave amplitude and instantaneous frequency of the (ℓ,∣m∣)=(2,2) mode are constrained to about 10% and 4%, respectively, at 90% credible level. These constraints are, respectively, two and four times more stringent than those obtained by analyzing GW150914. We also constrain, for the first time, the instantaneous frequency of the (ℓ,∣m∣)=(4,4) mode at merger to about 6%, and the time at which the gravitational-wave amplitude peaks to about 5ms. These results are the most precise tests of general relativity in the nonlinear regime to date, and can be employed to constrain extensions of Einsten's theory.
@article{arxiv.2601.13173,
title = {Plunge-Merger-Ringdown Tests of General Relativity with GW250114},
author = {Leonardo Grimaldi and Elisa Maggio and Lorenzo Pompili and Alessandra Buonanno},
journal= {arXiv preprint arXiv:2601.13173},
year = {2026}
}