The general relativistic Poynting-Robertson effect. II: A photon flux   with nonzero angular momentum
  We study the motion of a test particle in a stationary, axially and reflection symmetric spacetime of a central compact object, as affected by interaction with a test radiation field of the same symmetries. Considering the radiation flux with fixed but arbitrary (non-zero) angular momentum, we extend previous results limited to an equatorial motion within a zero-angular-momentum photon flux in the Kerr and Schwarzschild backgrounds. While a unique equilibrium circular orbit exists if the photon flux has zero angular momentum, multiple such orbits appear if the photon angular momentum is sufficiently high. 
Donato Bini, Andrea Geralico, Robert T. Jantzen, Oldrich Semer\'ak,   Luigi Stella
gr-qc