The Properties of the Large Magellanic Cloud Based on OGLE III
  Photometry of RR Lyrae Stars
  We present results from a study of ab-type RR Lyrae variables in the Large
Magellanic Cloud using the extensive dataset from phase III of the Optical
Gravitational Lensing Experiment (OGLE). The metallicities of the RR Lyraes,
determined from the periods and amplitudes of their light curves, reveal a
statistically significant radial abundance gradient that is approximately
one-half of what is seen in the disks of the Milky Way and M33. The RR Lyrae
abundance gradient agrees with that of the old and metal-poor LMC globular
clusters. The reddenings of the OGLE RR Lyraes have been calculated using their
minimum light colors and reveal a mean value of E(V-I) = 0.12 +/- 0.05, where
the quoted uncertainty represents the standard deviation of the mean. The
distribution of RR Lyrae extinctions across the face of the LMC is
well-correlated with the distribution and emission intensity of CO clouds based
on recent millimeter wave surveys. In addition, we find that the old LMC
globulars tend to be located in regions of low extinction. This underscores the
need to survey the higher extinction regions with the specific aim of
increasing the sample of old LMC globular clusters. Finally, we examine the
distance distribution of the RR Lyraes in order to probe the structure of the
LMC and investigate the possibility that some of the RR Lyraes may reside in a
kinematically hot halo population. In addition to calculating a mean LMC
distance of (m-M)o = 18.55 +/- 0.10 mag, we conclude that some fraction of the
RR Lyraes in our sample could be members of the LMC halo.
