Investigating the Fidelity of the QNM Amplitudes in Ringdown Fitting

Considering aspects of multimodes ringdown fitting, increasing the number of QNMs and overtones is a frequent approach to improve the quality of multimode ringdown fitting. However, the fidelity of the QNM amplitudes obtained from fitting is not fully understood. In other words, some QNMs in the model are not fit robustly even though the fitting quality of some other quantities, like the mismatch and remnant parameters, has improved. To explore the robustness of QNM fitting, a method resembling the greedy algorithm is applied to a multimode QNM-fitting approach. The QNM coefficients in this technique tend to be fixed iteratively as the program runs.