  In the course of a large intervening MgII survey of 25 quasars, the CIV
emission lines of six (three radio-loud and three radio-quiet) were observed
serendipitously. In four of these six quasars, we detected associated narrow
absorption lines. Three of these four quasars are radio-quiet while the other
is radio-loud. As a result of the original target selection, the small sample
of six quasars is unbiased towards finding associated CIV absorption lines. In
three of these four cases, the absorption line optical-depth ratios deviate
from the prediction based on atomic physics, suggesting that the background
photon source(s) are only partially covered by the absorbing medium and, by
extension, that the absorption lines are intrinsic to the quasar. We have used
the method of Barlow & Sargent to determine the effective coverage fraction of
background source(s) and we have extended it to constrain the coverage fraction
of the continuum and broad-emission line sources separately. We have also
applied this refined method to the narrow intrinsic absorption lines in three
additional quasars for which the necessary data were available from the
literature. We find that in two objects from our sample, the continuum source
must be partially covered regardless of the covering factor of the
emission-line source. We discuss these results in the context of the properties
of absorption lines observed in different types of active galaxies and related
outflow phenomena. We cannot distinguish between possible mechanisms for the
origin of the partial coverage signature although we do consider possible
observational tests. Finally, we speculate on how the gas responsible for the
narrow lines may be related to the accretion disk wind that may be responsible
for the broad absorption lines observed in some quasars.
