Publikace ÚTF

Motivated by the picture of a thin accretion disc around a black hole, radiating mainly in
the direction perpendicular to its plane, we study the motion of test particles interacting with
a test geodesic radiation flux originating in the equatorial plane of a Schwarzschild space–
time and propagating initially in the perpendicular direction. We assume that the interaction
with the test particles is modelled by an effective term corresponding to the Thomson-type
interaction which governs the Poynting–Robertson effect. After approximating the individual
photon trajectories adequately, we solve the continuity equation approximately in order to find
a consistent flux density with a certain plausible prescribed equatorial profile. The combined
effects of gravity and radiation are illustrated in several typical figures which confirm that the
particles are generically strongly influenced by the flux. In particular, they are both collimated
and accelerated in the direction perpendicular to the disc, but this acceleration is not enough to
explain highly relativistic outflows emanating from some black hole–disc sources. The model
can however be improved in a number of ways before posing further questions which are
summarized in concluding remarks.