Discriminate among spin-dependent quadratic-mode amplitude models

Determine which of the competing spin-dependent theoretical models for the $220\times220$ quadratic-mode amplitude ratio best describes GW250114.

Background

The paper measures the amplitude ratio between the $220\times220$ quadratic quasi-normal mode and its parent $220$ linear mode in GW250114, comparing the result with several predictions based on numerical-relativity fits and second-order black-hole perturbation theory. The inferred posterior is broad and consistent with all considered predictions, so the observation does not yet identify a preferred model for the remnant-spin dependence of the coupling coefficient.