The 300km/s stellar stream near Segue 1: Insights From high-resolution
  spectroscopy of its brightest star
  We present a chemical abundance analysis of 300S-1, the brightest likely
member star of the 300 km/s stream near the faint satellite galaxy Segue 1.
From a high-resolution Magellan/MIKE spectrum we determine a metallicity of
[Fe/H] = -1.46 +- 0.05 +- 0.23 (random and systematic uncertainties) for star
300S-1, and find an abundance pattern similar to typical halo stars at this
metallicity. Comparing our stellar parameters to theoretical isochrones, we
estimate a distance of 18 +- 7 kpc. Both the metallicity and distance estimates
are in good agreement with what can be inferred from comparing the SDSS
photometric data of the stream stars to globular cluster sequences. While
several other structures overlap with the stream in this part of the sky, the
combination of kinematic, chemical and distance information makes it unlikely
that these stars are associated with either the Segue 1 galaxy, the Sagittarius
stream or the Orphan stream. Streams with halo-like abundance signatures, such
as the 300 km/s stream, present another observational piece for understanding
the accretion history of the Galactic halo.
