We present a search for new members of the 300 km s ^ { -1 } stream ( 300S ) near the dwarf galaxy Segue 1 using wide-field survey data .
We identify 11 previously unknown bright stream members in the APOGEE-2 and SEGUE-1 and 2 spectroscopic surveys .
Based on the spatial distribution of the high-velocity stars , we confirm for the first time that this kinematic structure is associated with a 24 \degr -long stream seen in SDSS and Pan-STARRS imaging data .
The 300S stars display a metallicity range of -2.17 < { [ Fe / H ] } < -1.24 , with an intrinsic dispersion of 0.21 _ { -0.09 } ^ { +0.12 } dex .
They also have chemical abundance patterns similar to those of Local Group dwarf galaxies , as well as that of the Milky Way halo .
Using the open-source code galpy to model the orbit of the stream , we find that the progenitor of the stream passed perigalacticon about 70 Myr ago , with a closest approach to the Galactic Center of about 4.5 kpc .
Thus , 300S may be the most recent Milky Way satellite to be tidally disrupted .
Using Pan-STARRS DR1 data , we obtain an integrated stream luminosity of 4 \times 10 ^ { 3 } L _ { \odot } .
We conclude that the progenitor of the stream was a dwarf galaxy that is probably similar to the satellites that were accreted to build the present-day Milky Way halo .