We undertake the first high resolution spectroscopic study of the
Triangulum-Andromeda (TriAnd) star cloud --- an extended, mid-latitude Milky
Way halo substructure about 20 kpc away in the second Galactic quadrant ---
through six M giant star candidates selected to be both spatially and
dynamically associated with this system. The abundance patterns of [Ti/Fe],
[Y/Fe] and [La/Fe] as a function of [Fe/H] for these stars support TriAnd as
having an origin in a dwarf galaxy with a chemical enrichment history somewhat
similar to that of the Sagittarius dwarf spheroidal (dSph) galaxy. We also
investigate the previously proposed hypothesis that TriAnd is an outlying,
dynamically older piece of the Monoceros Stream (also known as the Galactic
Anticenter Stellar Structure, "GASS") under the assumption that both features
come from the tidal disruption of the same accreted Milky Way satellite and
find that net differences in the above abundance patterns between the TriAnd
and GASS stars studied suggest that these two systems are independent and
unrelated.Comment: Accepted for publication in ApJ Letter
