We identify a halo substructure in the Tycho Gaia Astrometric Solution ( TGAS ) dataset , cross-matched with the RAVE-on data release .
After quality cuts , the stars with large radial action ( J _ { R } > 800 kms ^ { -1 } kpc ) are extracted .
A subset of these stars is clustered in longitude and velocity and can be selected with further cuts .
The 14 stars are centered on ( X,Y,Z ) \approx ( 9.0 , -1.0 , -0.6 ) kpc and form a coherently moving structure in the halo with median ( v _ { R } ,v _ { \phi } ,v _ { z } ) = ( 167.33 , 0.86 , -94.85 ) kms ^ { -1 } .
They are all metal-poor giants with median [ Fe/H ] = -0.83 .
To guard against the effects of distance errors , we compute spectrophotometric distances for the 8 out of 14 stars where this is possible .
We find that 6 of the stars are still comoving .
These 6 stars also have a much tighter [ Fe/H ] distribution \sim - 0.7 with one exception ( [ Fe/H ] = -2.12 ) .
We conclude that the existence of the comoving cluster is stable against changes in distance estimation and conjecture that this is the dissolving remnant of a long-ago accreted globular cluster .