Astronomy and Astrophysics – Astronomy
Scientific paper
May 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011aas...21833402b&link_type=abstract
American Astronomical Society, AAS Meeting #218, #334.02; Bulletin of the American Astronomical Society, Vol. 43, 2011
Astronomy and Astrophysics
Astronomy
Scientific paper
Two fields in the central regions of the Small Magellanic Cloud have had the metallicities of their RR Lyr stars determined using Caby photometry. The first field, Field 1, was located at 00h 38m, -73o 08', with about 17 useful RR Lyr stars, while the second field, Field 3, was located at 01h 02m, -72o 24' with about 13 useful stars. Metallicities were determined for both fields using two different estimates of the reddening, and reddening uncertainty was shown to have little effect on the derived abundances. The best weighted mean values of [Fe/H] were -1.25 +0.15 for Field 1, -1.23 +0.19 for Field 3, and -1.24 +0.11 for the combined fields. The actual spread in the metallicities of the RR Lyr stars in the fields ran from -2.09 to -0.05, significantly larger than the calculated [Fe/H] uncertainties for the individual stars and the standard deviations from the weighted means for the fields. The crowded nature of the fields led to substantial blending difficulties. A subgroup of 9 stars from Field 1 with σ[Fe/H] < 0.30 dex was used as a sample of unblended stars, which gave the weighted mean value of [Fe/H] of -1.38 +0.20: all stars in this group but one had metallicities between -2.1 and -0.9, and when the single outlier was dropped as a possible unresolved blend the result of [Fe/H] = -1.52 +0.16 was considered the most reliable. These results indicate a true spread in the metallicities of the RR Lyr stars, suggesting that early in the history of this galaxy there were at least some regions, perhaps very small and localized, perhaps coming from a merger, that had higher than average chemical enrichment.
Baird Scott R.
Cook Kem H.
Keller Stefan Claude
Smith Harold A.
Walker Alistair R.
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