Search for an intrinsic metallicity spread in old globular clusters of
  the Large Magellanic Cloud
  We report for the first time on the magnitude of the intrinsic [Fe/H] spread
among ten old globular clusters (GCs) of the Large Magellanic Cloud (LMC). Such
spreads are merely observed in approximately five per cent of the Milky Way GCs
and recently gained more attention in theoretical models of GC evolution. We
derived metallicities with a typical precision of 0.05 dex < sigma[Fe/H] < 0.20
dex for an average of 14 red giant branch stars per GC from Str\"omgren
photometry. The respective, metallicity-sensitive indices have been calibrated
to precise and accurate high-dispersion spectroscopy. For all clusters we found
null [Fe/H] spreads with a typical uncertainty of 0.04 dex, with the possible
exception of NGC1786 that shows an intrinsic dispersion of 0.07+-0.04 dex. The
mean, observed standard deviation of the derived metallicities for nearly 40
per cent of our GC sample amounted to smaller than 0.05 dex. At present, we
cannot exclude that the remaining GCs also have intrinsic Fe-abundance
variations in excess of 0.05 dex, but in order to significantly detect those,
the measurement errors on individual [Fe/H]-values would need to be lowered to
the 0.03--0.07 dex level. These findings suggest, along with those from ages
and light-element abundances, that the LMC GCs studied here are alike to the
majority of Galactic GCs.
