2026/06/21 by Jia-Ning Chen, Liang-Bi Wu, Zong-Kuan Guo · 1 citation
#gr-qc
Parameterized descriptions of black-hole quasinormal-mode spectra are essential for testing gravity with ringdown observations. We extend the Parameterized Spin Expansion Coefficients (ParSpec) formalism by simultaneously sampling the characteristic length scale ℓ and the scaling index p, rather than fixing p to a theory-motivated integer and constraining ℓ. Physically, this extension promotes the scaling of the spectral corrections coming from higher-curvature operators to an observable quantity. Methodologically, it enables us to investigate the enlarged ParSpec parameter space and identify the prior geometry induced by conditions on the effective coupling γ. We examine the robustness of the framework by using the 220 and 220+221 ringdown models over different start times with informative priors on mass and luminosity for GW250114, and further study a joint constraint with GW231123. We find that p remains prior dominated and that the data show no evidence for deviations from general relativity (GR). Among the coupling prescriptions considered, γ<1 avoids an artificial correlation between p and ℓ. At the current signal-to-noise ratio, the results based on the Kullback-Leibler divergence show that the 220-only model provides more informative constraints than the 220+221 model. Higher-SNR ringdowns and hierarchical analyses of a larger event population will be required to break the p-ℓ degeneracy and directly probe the scaling structure of corrections to GR.