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Monthly Notices of the Royal Astronomical Society


We have identified 317 stars included in the Hipparcos astrometric catalogue that have parallaxes measured to a precision of better than 15 per cent, and the location of which in the (MV,(B−V)T) diagram implies a metallicity comparable to or less than that of the intermediate‐abundance globular cluster M5. We have undertaken an extensive literature search to locate Strömgren, Johnson/Cousins and Walraven photometry for over 120 stars. In addition, we present new UBV(RI)C photometry of 201 of these candidate halo stars, together with similar data for a further 14 known metal‐poor subdwarfs. These observations provide the first extensive data set of RCIC photometry of metal‐poor, main‐sequence stars with well‐determined trigonometric parallaxes. Finally, we have obtained intermediate‐resolution optical spectroscopy of 175 stars.

47 stars still lack sufficient supplementary observations for population classification; however, we are able to estimate abundances for 270 stars, or over 80 per cent of the sample. The overwhelming majority have near‐solar abundance, with their inclusion in the present sample stemming from errors in the colours listed in the Hipparcos catalogue. Only 44 stars show consistent evidence of abundances below [Fe/H]=−1.0. Nine are additions to the small sample of metal‐poor subdwarfs with accurate photometry. We consider briefly the implication of these results for cluster main‐sequence fitting.