In previous work [1] we proposed an improvement of the Wentzel-Kramers-Brillouin (WKB)-based semianalytic technique of Iyer and Will for calculation of the quasiormal modes of black holes by constructing the Padé approximants of the formal series for ${\omega }^2$. It has been demonstrated that (within the domain of applicability) the Padé transforms ${\mathcal{P}}_6^6$ and ${\mathcal{P}}_7^6$ are always in a very good agreement with the numerical results. In this paper we present a further extension of the method. We show that it is possible to reproduce many known numerical results with a great accuracy (or even exactly) if the Padé transforms are constructed from the perturbative series of a really high order. In our calculations the order depends on the problem but it never exceeds 700. For example, the frequencies of the gravitational mode $l=2$, $n=0$ calculated with the aid of the Padé approximants and within the framework of the continued fractions method agree to 24 decimal places. The use of such a large number of terms is necessary as the stabilization of the quasinormal frequencies can be slow. Our results indicate that the WKB-based approximations may be used for the accurate calculations of the frequencies of the overtones.

• Received 25 August 2019

DOI:https://doi.org/10.1103/PhysRevD.100.124006