  We present the analysis of Lick absorption-line indices from three separate
long-slit spectroscopic observations of the nearby isolated elliptical galaxy
NGC 821. The three data sets present a consistent picture of the stellar
population within one effective radius, in which strong gradients are evident
in both luminosity-weighted age and metallicity. The central population
exhibits a young age of ~4 Gyr and a metallicity ~3 times solar. At one
effective radius the age has risen to ~12 Gyr and the metallicity fallen to
less than 1/3 solar. The low metallicity population around one effective radius
appears to have an exclusively red horizontal branch, with no significant
contribution from the blue horizontal branch evident in some globular clusters
of the same age and metallicity. Despite the strong central age gradient, we
demonstrate that only a small fraction (<10%) of the galaxy's stellar mass can
have been created in recent star formation events. We consider possible star
formation histories for NGC 821 and find that the most likely cause of the
young central population was a minor merger or tidal interaction that caused
NGC 821 to consume its own gas in a centrally concentrated burst of star
formation 1 to 4 Gyr ago.
