  We provide semi-analytic expressions for quasinormal mode frequencies of
slowly rotating Kerr black holes to the quadratic order in the rotation
parameter. We apply the parametrized black hole quasinormal mode ringdown
formalism to the Chandrasekhar-Detweiler equation and the Sasaki-Nakamura
equation instead of the Teukolsky equation, and compare our result with the
previous numerical calculations.
