The Age of Old Magellanic Cloud Clusters . I : NGC 2257
نویسندگان
چکیده
Deep CCD photometry down to V 24:5 is presented for the old globular cluster NGC 2257 in the Large Magellanic Cloud. The main results of this study can be summarized as follows: i) the Red Giant Branch (RGB) Bump has been detected at V = 18:70:1, and it is compatible with determination of this feature in Galactic Globular Clusters; ii) using the currently accepted methods of dating Globular Clusters, NGC 2257 seems to be 2-3 Gyrs younger than a typical Galactic Globular; iii) the Helium abundance has been estimated to be Y = 0:210:03 using the R-method as calibrated by Buzzoni et al. (1983).
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