Evidence of enrichment by individual supernova from elemental abundance
  ratios in the very metal-poor dSph galaxy Bootes I
  Aim: We establish the mean metallicity from high-resolution spectroscopy for
the recently found dwarf spheroidal galaxy Bootes I and test whether it is a
common feature for ultra-faint dwarf spheroidal galaxies to show signs of
inhomogeneous chemical evolution (e.g. as found in the Hercules dwarf
spheroidal galaxy). Methods: We analyse high-resolution, moderate
signal-to-noise spectra for seven red giant stars in the Bootes I dSph galaxy
using standard abundance analysis techniques. In particular, we assume local
thermodynamic equilibrium and employ spherical model atmospheres and codes that
take the sphericity of the star into account when calculating the elemental
abundances. Results: We confirm previous determinations of the mean metallicity
of the Bootes I dwarf spheroidal galaxy to be -2.3 dex. Whilst five stars are
clustered around this metallicity, one is significantly more metal-poor, at
-2.9 dex, and one is more metal-rich at, -1.9 dex. Additionally, we find that
one of the stars, Boo-127, shows an atypically high [Mg/Ca] ratio, indicative
of stochastic enrichment processes within the dSph galaxy. Similar results have
previously only been found in the Hercules and Draco dSph galaxies and appear,
so far, to be unique to this type of galaxy.
