Hercules stream K giants analysis

The giants have compositions spanning the interval [Fe/H] from -0.17 to +0.42 with a mean value of +0.15 and relative elemental abundances [El/Fe] representative of the Galactic thin disc. Selection effects may have biased the selection from the Hipparcos catalogue against the selection of metal-poor stars.

Our reconsideration of the recent extensive survey by Bensby et al. of FG dwarfs, including metal-poor stars, provides a [Fe/H] distribution for the Hercules stream, which is similar to that from the 58 giants. It appears that the stream is dominated by metal-rich stars from the thin disc. We discuss suggestions in the literature that the stream includes metal-poor stars from the thick disc.