GD-1: the relic of an old metal-poor globular cluster
  Combining data from Gaia DR2, SDSS DR14 and LAMOST DR6, we update the fit to
model of the properties of the stellar stream GD-1 and find that it has an age
of $\sim 13$ Gyr, [Fe/H] of $-2.2\pm 0.12$, and a distance from the sun of
$\sim 8$ kpc. We tabulate 6D phase-space fiducial points along the GD-1 stream
orbit over a 90$^\circ$ arc. The fitted orbit shows that the stream has an
eccentricity $e \sim 0.3$, perigalacticon of 14.2 kpc, apogalacticon of 27.0
kpc and inclination $i \sim 40^{\circ}$. There is evidence along the arc for 4
candidate stellar overdensities, one candidate gap, two candidate stellar
underdensities and is cut off at $\phi_1 \sim 2^{\circ}$ (in the stream-aligned
$(\phi_1,\phi_2)$ coordinate system of \citet{kop10}). The spur originating at
$\phi_1 \sim -40^{\circ}$ implies stars were pulled away from the stream trace
by an encounter (potentially a dark matter subhalo). The narrowest place ( FWHM
$\sim 44.6$ pc) of the GD-1 trace is at $(\phi_1, \phi_2^c) \sim (-14^{\circ},
0.15^{\circ})$, which is $\sim (178.18^{\circ}, 52.19^{\circ})$ in (R. A.,
Decl.), where the progenitor is possibly located. We also find six BHB and 10
BS spectroscopic stars in the GD-1 stream.
