On gravito-magnetic time delay by extended lenses
  Gravitational lensing by rotating extended deflectors is discussed. Due to spin, corrections on image positions, caustics and critical curves can be significant. In order to obtain realistic quantitative estimates, the lens is modeled as a singular isothermal sphere. Gravito-magnetic time delays of nearly 0.2 days between different images of background sources can occur. 
M. Sereno (DFS, Universita` di Napoli "Federico II"; INAF - OAC; INFN   - Sez. Napoli)