MOTION OF ACCRETING MATTER NEAR LUMINOUS SLOWLY ROTATING RELATIVISTICSTARS

In a previous paper, we reported test particle calculations showing th at the behavior of accretion flows near uniformly emitting, nonrotatin g, relativistic stars is affected significantly by radiation forces if the luminosity is greater than similar to 1% of the Eddington critica l luminosity L(E). Here, using a numerical code that can follow the mo tion of a test particle in any stationary axisymmetric spacetime, we i nvestigate the effects of nonuniform emission and of slow rotation of the gravitating mass and radiation source, when their rotation axes ar e co-aligned. We find that for emission from a bright, thin ring, accr eting particles are braked sharply near the radiation source, which ma y be favorable for the development of shock waves. We also show that i f the particle orbit is prograde with respect to the rotation of the r adiation source, the rates at which energy and angular momentum are lo st to the radiation held are less than the rates for a nonrotating sou rce. The diminished loss rates lead to a lower inward radial velocity, which increases the infall time. Surprisingly, if the radiation flux is sufficiently small, the increase in the infall time more than compe nsates for the decrease in the loss rates, so the total energy and ang ular momentum transferred to the radiation held during particle inspir al are actually greater than for a nonrotating radiation source. We al so discuss some of the effects of radiation forces on accreting fluid. We show that the angular, special relativistic, and general relativis tic effects that augment radiation drag on test particles near radiati ng relativistic stars also increase the fraction of angular momentum a nd energy that can be transferred from the accretion flow to the radia tion field. This may affect the maximum rotation rate of neutron stars and the prospects for observing gravitational radiation from rapidly rotating neutron stars.