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In this paper, a matrix method is employed to study the scalar quasinormal modes of Kerr as well as Kerr–Sen black holes. Discretization is applied to transfer the scalar perturbation equation into a matrix form eigenvalue problem, where the resulting radial and angular equations are derived by the method of separation of variables. The eigenvalues, quasinormal frequencies Formula: see text and angular quantum numbers Formula: see text, are then obtained by numerically solving the resultant homogeneous matrix equation. This work shows that the present approach is an accurate, as well as efficient method for investigating quasinormal modes.
Lin et al. (Mon,) studied this question.