The ringdown is the final bit of a gravitational-wave signal, after the two black holes have merged. It’s nice because it’s clean; GR is so powerful that all that comes out after a black hole merger has specific frequencies, the fantastic “quasi-normal modes.” While the frequencies only depend on that final BH (thanks Kerr!), the excitations of those frequencies depend on all that happened before, i.e. the merger process itself. In this summer paper by Costantino and the rest of us, we present a new accurate approximant to those amplitudes. Now go home and test GR.
Costantino Pacilio, Swetha Bhagwat, Francesco Nobili, Davide Gerosa
arXiv:2408.05276 [gr-qc].