Hair imprints of the gravitational decoupling and hairy black hole spectroscopy

Hairy black holes by gravitational decoupling (GD) are probed to derive the gravitational waveform produced by perturbation theory applied to these compact objects. Using the Regge–Wheeler and Zerilli equations governing the metric perturbations and applying a higher-order WKB method, the quasinormal modes (QNMs) are computed and discussed. Compared to the QNMs produced in the ringdown phase of Reissner–Nordström black hole solutions, it yields a clear physical signature of primary hair imprinting the hairy GD black hole gravitational waveforms.