Quasinormal resonances of near-extremal Kerr–Newman black holes

We study analytically the fundamental resonances of near-extremal, slowly rotating Kerr–Newman black holes. We find a simple analytic expression for these black-hole quasinormal frequencies in terms of the black-hole physical parameters: ω=mΩ−2iπTBH(l+1+n), where TBH and Ω are the temperature and angular velocity of the black hole. The mode parameters l and m are the spheroidal harmonic index and the azimuthal harmonic index of a co-rotating mode, respectively. This analytical formula is valid in the regime ℑω≪ℜω≪M−1, where M is the black-hole mass.