Intervening BLR Clouds' Effects on Optical/UV Spectrum
  Recent x-ray observations of Mrk 766 suggest that broad emission line region
clouds cross our line of sight and produce variable x-ray absorption. Here we
investigate what optical/ultraviolet spectroscopic features would be produced
by such "Intervening BLR Clouds" (IBC) crossing our line of sight to the
accretion disk, the source of the optical/UV continuum. Although the emission
spectrum produced by intervening clouds is identical to the standard BLR model,
they may produce absorption features on the optical or UV continuum. Single
clouds will have little effect on the optical/UV spectrum because BLR clouds
are likely to be much smaller than the accretion disk. This is unlike the X-ray
case, where the radiation source is considerably smaller. However, an ensemble
of intervening clouds will produce spectroscopic features in the FUV including
a strong depression between the Lyman limit and Ly{\alpha}. The amount of the
depression will indicate the line-of-sight covering factor of clouds, an
unknown quantity that is important for the ionization of the intergalactic
medium and the energy budget of AGN. Comparison with observations suggests that
the SED of Mrk 766 may be affected by intervening BLR clouds and IBC may exist
in most of AGNs.
