  NGC 6819 is an open cluster of age 2.4 Gyr that was in the NASA Kepler
spacecraft field of view from 2009 to 2013. The central part of the cluster was
observed in a 200 x 200 pixel `superstamp' during these four years in 30-minute
cadence photometry, providing a unique long time-series high-precision data
set. The cluster contains 'blue straggler' stars, i.e., stars on the main
sequence above the cluster turnoff that should have left the main sequence to
become red giants. We present light curves and pulsation frequency analyses
derived from custom photometric reductions for five confirmed cluster
members--four blue stragglers and one star near the main-sequence turnoff. Two
of these stars show a rich spectrum of $\delta$ Scuti pulsation modes, with 236
and 124 significant frequencies identified, respectively, while two stars show
mainly low-frequency modes, characteristic of $\gamma$ Doradus variable stars.
The fifth star, a known active x-ray binary, shows only several harmonics of
two main frequencies. For the two $\delta$ Scuti stars, we use a frequency
separation--mean-density relation to estimate mean density, and then use this
value along with effective temperature to derive stellar mass and radius. For
the two stars showing low frequencies, we searched for period-spacing sequences
that may be representative of gravity-mode or Rossby-mode sequences, but found
no clear sequences. The common age for the cluster members, considered along
with the frequencies, will provide valuable constraints for asteroseismic
analyses, and may shed light on the origin of the blue stragglers.
