SIMBAD references

New accurate CCD photometry in the u, v, b and y bands of the Stroemgren system filters has been obtained for 17640 stars to V∼20^m in a ∼21'x21' field centered on the intermediate-age open cluster IC 4651. The resulting color-magnitude diagram (CMD) is substantially improved in completeness and accuracy compared to previous studies of IC 4651. Specifically, this study has: 1) more than doubled the known size of the cluster area on the sky, 2) more than doubled the number of stars brighter than V∼14^m, 3) added 160 ``new" candidate member stars to the turn-off region of the CMD, 4) identified ∼600 fainter stars that trace a previously undetected and well-defined main-sequence down to V∼18^m, and 5) enabled a very accurate determination of true distance modulus ((m-M)₀=10.03±0.1) by fitting the Hyades main-sequence over the long stretch of the cluster main-sequence. The (v-y)-V CMD defines the main-sequence significantly better than the traditional (b-y) or (B-V) CMDs. These findings make IC 4651 a perfect target for testing stellar evolution models. A correlation is found between the CMD and the radial distance of the stars to the cluster center. The fainter main-sequence stars are less centrally concentrated, as predicted by theory. Overall, IC 4651 appears to be a moderately dynamically evolved cluster ideally suited for testing of dynamical models.