A search for previously unrecognized metal-poor subdwarfs in the Hipparcos astrometric catalogue |
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| Authors: | I Neill Reid F van Wyk F Marang G Roberts D Kilkenny S Mahoney |
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| Institution: | 1Department of Physics and Astronomy, University of Pennsylvania, 209 S. 33rd Street, Philadelphia, PA 19104-6396, USA;2South African Astronomical Observatory, PO Box 9, Observatory 7935, South Africa;3Hinman Box 1709, Dartmouth College, Hanover, NH 03755, USA |
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| Abstract: | 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 ( 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 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 R C I C 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. |
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| Keywords: | stars: abundances subdwarfs Galaxy: halo |
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