We present a study of the recently discovered compact stellar system Triangulum II .
From observations conducted with the DEIMOS spectrograph on Keck II , we obtained spectra for 13 member stars that follow the CMD features of this very faint stellar system and include two bright red giant branch stars .
Tri II has a very negative radial velocity ( \langle v _ { r } \rangle = -383.7 ^ { +3.0 } _ { -3.3 } { km s ^ { -1 } } ) that translates to \langle v _ { r, \mathrm { gsr } } \rangle \simeq - 264 { km s ^ { -1 } } and confirms it is a Milky Way satellite .
We show that , despite the small data set , there is evidence that Tri II has complex internal kinematics .
Its radial velocity dispersion increases from 4.4 ^ { +2.8 } _ { -2.0 } { km s ^ { -1 } } in the central 2 ^ { \prime } to 14.1 ^ { +5.8 } _ { -4.2 } { km s ^ { -1 } } outwards .
The velocity dispersion of the full sample is inferred to be \sigma _ { vr } = 9.9 ^ { +3.2 } _ { -2.2 } { km s ^ { -1 } } .
From the two bright RGB member stars we measure an average metallicity \langle { [ Fe / H ] } \rangle = -2.6 \pm 0.2 , placing Tri II among the most metal-poor Milky Way dwarf galaxies .
In addition , the spectra of the fainter member stars exhibit differences in their line-widths that could be the indication of a metallicity dispersion in the system .
All these properties paint a complex picture for Tri II , whose nature and current state are largely speculative .
The inferred metallicity properties of the system however lead us to favor a scenario in which Tri II is a dwarf galaxy that is either disrupting or embedded in a stellar stream .