Multiple X-ray reflection from ionized slabs
  Multiple reflection of X-rays may be important when an accretion disc and its hot corona have a complicated geometry, or if returning radiation due to gravitational light bending is important, or in emission from a funnel such as proposed in some gamma-ray burst models. We simulate the effects of multiple reflection by modifying the boundary condition for an X-ray illuminated slab. Multiple reflection makes the soft X-ray spectrum steeper (softer) and strengthens broad emission and absorption features, especially the K-shell features of iron. This may be important in explaining the spectra of sources such as the Narrow-Line Seyfert 1 galaxy 1H0707-495. 
R.R. Ross (1), A.C. Fabian (2) & D.R. Ballantyne (2) ((1) Holy Cross   USA, (2) IoA, Cambridge, UK)