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Session 107 - Open Clusters.
Display session, Thursday, January 18
North Banquet Hall, Convention Center

[107.07] CCD Photometry of the Old Open Cluster 092-SC18

M. Kassis (CTIO/Boston U.), E. D. Friel (CTIO/MMO), R. L. Phelps (OCIW)

We present deep VI_c CCD photometry for the open cluster 092-SC18 collected at the CTIO 1.5 meter telescope in April, 1994 as part of a program of photometric studies of old open clusters. VandenBerg (1985) isochrone fits to a V, V-I color-magnitude diagram yield estimates of cluster parameters of 4-6 Gyrs, with a range in metallicity of -0.23 to -0.75 dex. Based on the best fit isochrone, 092-SC18 is 5 Gyrs old, has an abundance of [Fe/H] = -0.45 dex, reddening of E(V-I) = 0.32, and (m-M)_0 of 14.88 mag. With the current determination of the cluster's distance modulus, 092-SC18 is at a distance of 9.5 kpc, with a Galactocentric radius of 10.5 kpc, and lies 1.2 kpc below the Galactic plane. By extrapolating the main-sequence mass calculations to low-mass stars and accounting for a typical concentration of binaries, we place a lower limit to the cluster mass of \sim4200 M_ødot. From an exponential fit to the stellar surface density of the cluster field, we find a linear diameter of 18 pc for 092-SC18.

Program listing for Thursday