An Orbit Fit for the Grillmair Dionatos Cold Stellar Stream
  We use velocity and metallicity information from SDSS and SEGUE stellar
spectroscopy to fit an orbit to the narrow $63^\circ$ stellar stream of
Grillmair and Dionatos. The stars in the stream have a retrograde orbit with
eccentricity $e = 0.33$ (perigalacticon of 14.4 kpc and apogalacticon of 28.7
kpc) and inclination approximately $i \sim 35^\circ$. In the region of the
orbit which is detected, it has a distance of about 7 to 11 kpc from the Sun.
Assuming a standard disk plus bulge and logarithmic halo potential for the
Milky Way stars plus dark matter, the stream stars are moving with a large
space velocity of approximately $276 \rm km s^{-1}$ at perigalacticon. Using
this stream alone, we are unable to determine if the dark matter halo is oblate
or prolate. The metallicity of the stream is [Fe/H] $= -2.1\pm0.1$. Observed
proper motions for individual stream members above the main sequence turnoff
are consistent with the derived orbit. None of the known globular clusters in
the Milky Way have positions, radial velocities, and metallicities that are
consistent with being the progenitor of the GD-1 stream.
