Spin-1 Quasi-normal Frequencies in Schwarzschild space-time for Large   Overtone Number
  We analytically investigate the spin-1 quasinormal mode frequencies of Schwarzschild black hole space-time. We formally determine these frequencies to arbitrary order as an expansion for large imaginary part (i.e., large-n, where n is the overtone number). As an example of the practicality of this formal procedure, we explicitly calculate the asymptotic behaviour of the frequencies up to order $n^{-5/2}$. 
Marc Casals and Adrian C. Ottewill
gr-qc hep-th