The Metallicity of the Open Cluster Tombaugh 2
  We investigate the nature of the chemical composition of the outer disc open
cluster Tombaugh 2, that a recent study by Frinchaboy et al. (2008) suggested
to possess an intrinsic metal abundance dispersion. We aim to investigate such
claims by high resolution spectra obtained for a number of stars in the
Tombaugh 2 field, together with independent UBVIc photometry. The spectra,
together with input atmospheric parameters and model atmospheres, are used to
determine detailed chemical abundances for a variety of elements in 13 members
having good spectra. We find the mean metallicity to be [Fe/H]=-0.31+-0.02 with
no evidence for an intrinsic abundance dispersion, in contrary to the recent
results of Frinchaboy et al. (2008). We find Ca and Ba to be slightly enhanced
while Ni and Sc are solar. The r-process element Eu was found to be enhanced,
giving an average [Eu/Ba]=+0.17. The Li abundance decreases with Teff on the
upper giant branch and maintains a low level for red clump stars. The mean
metallicity we derive is in good agreement with that expected from the radial
abundance gradient in the disc for a cluster at its Galactocentric distance.
The surprising result found by Frinchaboy et al. (2008), that is the presence
of 2 distinct abundance groups within the cluster, implying either a completely
unique open cluster with an intrinsic metallicity spread, or a very unlikely
superposition of a cold stellar stream and a very distant open cluster, is not
supported by our new result.
