Disks Irradiated by Beamed Radiation from Compact Objects

Abstract

We examine the reprocessing of X-radiation from compact objects by accretion disks when the X-ray emission from the star is highly beamed. The reprocessed flux for various degrees of beaming and inclinations of the beam axis with respect to the disk is determined. We find that, in the case where the beam is produced by a nonrelativistic object, the intensity of the emitted spectrum is highly suppressed if the beam is pointing away from the disk. However, for beams produced by compact objects, general relativistic effects cause only a small reduction in the reradiated flux even for very narrow beams oriented perpendicularly to the disk. This is especially relevant in constraining models for anomalous X-ray pulsars, whose X-ray emission is highly beamed. We further discuss other factors that can influence the emission from disks around neutron stars.