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 .