2004/10/21 by Barbara J. Anthony-Twarog, B. J. Anthony-Twarog, J. Atwell +3
Physics and Astronomy · #Astronomical and nuclear sciences #Astrophysics and Star Formation Studies #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/426752
21 pg postscript, latex to preprint format, 15 eps figures, 2 tables. Accepted for publication in the Astronomical Journal Feb. 2005
arxiv created 2004/10/21 · openalex publication_date 2005/01/31 · arxiv updated 2009/12/01 · openalex created_date 2022/05/12 · openalex updated_date 2026/07/31
CCD photometry on the intermediate-band uvbyCa Hβ system is presented for the metal-deficient open cluster NGC 2243. Restricting the data to probable single members of the cluster using the color-magnitude diagram (CMD) and the photometric indices alone generates a sample of 100 stars at the cluster turnoff. The average E ( b - y ) = 0.039 ± 0.003 (s.e.m.) or E ( B - V ) = 0.055 ± 0.004 (s.e.m.), where the errors refer to internal errors alone. With this reddening, [Fe/H] is derived from both m 1 and hk , using b - y and Hβ as the temperature index. The agreement among the four approaches is excellent, leading to a final weighted average of [Fe/H] = –0.57 ± 0.03 (s.e.m.) for the cluster, on a scale where the Hyades has [Fe/H] = +0.12. Using a combination of photometric and spectroscopic data, 27 probable cluster members are identified and used to delineate the red giant branch and a well-defined clump at V = 13.70, while eliminating the so-called second clump at V = 14.1. Interpolation between isochrones of appropriate [Fe/H] leads to an apparent modulus of m - M = 13.15 ± 0.1 and an age of 3.8 ± 0.2 Gyr. A differential CMD comparison with Ber 29, a cluster with a galactocentric distance almost twice that of NGC 2243, constrains Ber 29 to be at least as young and as metal-rich as NGC 2243.