A Broad-Band Photometric Survey of the Open Cluster NGC 7789
ORAL
Abstract
We have used approximately 200 frames of the open cluster NGC 7789 on the UBVRI system taken with the 0.9m WIYN telescope over four years to survey the cluster and to define its fundamental properties, in conjunction with a complementary study based on extended Stromgren, intermediate-band CCD data. Removing probable radial-velocity and proper-motion non-members, the color-magnitude diagram (CMD) for the cluster core is extremely well matched by Yale-Yonsei isochrones with an age of 1.5 $+$ - 0.1 Gyr for a derived solar [Fe/H] and E(B-V) $=$ 0.26 $+$ - 0.02, as well as an apparent distance modulus of (m-M) $=$ 12.2 $+$ - 0.1. The lower reddening and slightly younger age compared to previous work can be attributed to spatially dependent offsets in the published VI photometry of the cluster. The main sequence approximately one magnitude below the turnoff appears to exhibit a narrow break aligned with the predicted location of the blue edge of the Li-dip among main sequence stars.
*We gratefully acknowledge support from the National Science Foundation for S.B. as part of the REU program at San Diego State University under grant AST-0850564.
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