THE IRON K-LINE AS A PROBE OF BEAMED X-RAY-EMISSION IN ACTIVE GALACTIC NUCLEI

We consider the use of the Fe K line in active galactic nuclei (AGNs) as a test of whether significant beaming of the hard X-ray emission is important or not. if the emission is highly anisotropic a narrow Fe K line is expected due to fluorescence in the broad-line region (BLR), with an equivalent width comparable to that expected from fluorescence in an X-ray illuminated accretion disk, even if the covering factor of the BLR is only approximately 10%. In that case some of the brighter AGNs will have a resolvable two-component Fe K line composed of a narrow and broad feature, whilst the fainter AGNs will be observed to have predominantly narrow lines. The apparent width of the composite line may vary since the transfer function for the anisotropically illuminated BLR component has a lack of response on timescales smaller than a few light days. On the other hand, if the X-ray emission is essentially isotropic then the Fe K line will be undetected in faint AGNs in which the disk is observed at high inclination angles. For the brighter AGNs there should be a general trend of lower centroid energies with narrower widths. We discuss the extent to which observations of the Fe K line in the near future will be able to provide information on the angular distribution of the X-ray emission in AGNs.