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A search for previously unrecognised metal-poor subdwarfs in the Hipparcos astrometric catalogue

I. Neill Reid·F. van Wyk·F. Marang·G. Roberts·D. Kilkenny·S. Mahoney
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Abstract

We have identified 317 stars included in the Hipparcos astrometric catalogue which have parallaxes measured to a precision of better than 15%, and whose location in the (M_V, (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 Stromgren, Johnson/Cousins and Walraven photometry for over 120 stars. In addition, we present new UBVRI photometry of 201 of these candidate halo stars, together with similar data for a further 14 known metal-poor subdwarfs. Those observations provide the first extensive dataset of RI photometry of metal-poor, main-sequence stars with well-determined trigonometric parallaxes. Finally, we have obtained intermediate-resolution optical spectroscopy of 175 stars. We are able to estimate abundances for 270 stars. 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.

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I. Neill Reid, F. van Wyk, F. Marang, G. Roberts, D. Kilkenny, S. Mahoney. 2000-12-12. A search for previously unrecognised metal-poor subdwarfs in the Hipparcos astrometric catalogue. https://doi.org/10.1046/j.1365-8711.2001.04350.x

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