  We present line-of-sight stellar velocity distributions of elliptical galaxy
NGC 821 obtained to approximately 100 arcsec (over 2 effective radii) with
long-slit spectroscopy from the Hobby-Eberly Telescope. Our measured stellar
line-of-sight velocity distributions are larger than the planetary nebulae
measurements at similar radii. We fit axisymmetric orbit-superposition models
with a range of dark halo density profiles, including two-dimensional
kinematics at smaller radii from SAURON data. Within our assumptions, the
best-fitted model gives a total enclosed mass of 2.0x10^11 M_sun within 100
arcsec, with an accuracy of 2%; this mass is equally divided between halo and
stars. At 1R_e the best-fitted dark matter halo accounts for 13% of the total
mass in the galaxy. This dark halo is inconsistent with previous claims of
little to no dark matter halo in this galaxy from planetary nebula
measurements. We find that a power-law dark halo with a slope 0.1 is the
best-fitted model; both the no dark halo and NFW models are worse fits at a
greater than 99% confidence level. NGC 821 does not appear to have the expected
dark halo density profile. The internal moments of the stellar velocity
distribution show that the model with no dark halo is radially anisotropic at
small radii and tangentially isotropic at large radii, while the best-fitted
halo models are slightly radially anisotropic at all radii. We test the
potential effects of model smoothing and find that there are no effects on our
results within the errors. Finally, we run models using the planetary nebula
kinematics and assuming our best-fitted halos and find that the planetary
nebulae require radial orbits throughout the galaxy.
