Ultra-hard fluid and scalar field in the Kerr-Newman metric
  An analytic solution for the accretion of ultra-hard perfect fluid onto a moving Kerr-Newman black hole is found. This solution is a generalization of the previously known solution by Petrich, Shapiro and Teukolsky for a Kerr black hole. Our solution is not applicable for an extreme black hole due to violation of the test fluid approximation. We also present a stationary solution for a massless scalar field in the metric of a Kerr-Newman naked singularity. 
E. Babichev, S. Chernov, V. Dokuchaev, Yu. Eroshenko