Radiative transfer in black hole systems
  We present a convariant formulation for radiative transfer in curved space time and demonstrate some applications in the black-hole systems. We calculate the emission from semi-transparent accretion tori around black holes, for opacity provided by the Fe K lines and for opacity dominated by electron scattering. We also calculate the emission from radiative inefficient accretion flow in black holes with opacity provided by electron-positron annihilation lines. Finally we show shadows cast by accreting black holes with different spins and with different distribution of warm material around them. 
Kinwah Wu (1), Warrick Ball (2), Steven V. Fuerst (3) ((1) Mullard   Space Science Laboratory, University College London, UK...