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Astron. Astrophys. 361, 929-936 (2000)

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New color-magnitude diagram for the open cluster IC 4651

Deep Strömgren uvby CCD photometry in a large field * **

S. Meibom 1,2

1 Niels Bohr Institute for Astronomy, Physics, and Geophysics, Astronomical Observatory, Juliane Maries Vej 30, 2100 Copenhagen, Denmark
2 Astronomy Department, University of Wisconsin, Madison, WI-53706, USA (meibom@astro.wisc.edu)

Received 20 March 2000 / Accepted 26 July 2000


New accurate CCD photometry in the u, v, b and y bands of the Strömgren system filters has been obtained for 17640 stars to [FORMULA] in a [FORMULA] 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 [FORMULA], 3) added 160 "new" candidate member stars to the turn-off region of the CMD, 4) identified [FORMULA] fainter stars that trace a previously undetected and well-defined main-sequence down to [FORMULA], and 5) enabled a very accurate determination of true distance modulus [FORMULA]) by fitting the Hyades main-sequence over the long stretch of the cluster main-sequence. The [FORMULA] CMD defines the main-sequence significantly better than the traditional [FORMULA] or [FORMULA] 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.

Key words: Galaxy: open clusters and associations: individual: IC 4651 – stars: Hertzsprung – Russel (HR) and C-M diagrams

* Based on observations obtained with the Danish 1.5-m telescope at the European Southern Observatory, La Silla, Chile.
** Tables 1, 2 and 3 are only available in electronic form at the CDS via anonymous ftp to ftp://cdsarc.u-strasbg.fr/pub/cats/J/A+A/361/929 ( or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/361/929

SIMBAD Objects


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© European Southern Observatory (ESO) 2000

Online publication: October 10, 2000