Accretion processes in magnetically and tidally perturbed Schwarzschild
  black holes
  We study the accretion process in the region of the Preston-Poisson
space-time describing a Schwarzschild black hole perturbed by asymptotically
uniform magnetic field and axisymmetric tidal structures. We find that the
accretion disk shrinks and the marginally stable orbit shifts towards the black
hole with the perturbation. The radiation intensity of the accretion disk
increases, while the radius where radiation is maximal remains unchanged. The
spectrum is blue-shifted. Finally, the conversion efficiency of accreting mass
into radiation is decreased by both the magnetic and the tidal perturbations.
