BVRI photometry of the galactic globular cluster NGC 6779.
Croke, B. F. W.
Monthly Notices of the Royal Astronomical Society; 3/11/2004, Vol. 348 Issue 4, p1157-1163, 7p
We present B, V, R and I photometry for NGC 6779 (M56), a metal-poor globular cluster in the galactic halo. The observations were performed using the 1.3-m telescope at Skinakas Observatory, in Crete. The reddening of the cluster was found to be , significantly higher than previous estimates. The metal abundance of the cluster was derived from various parametrizations of red giant branch characteristics and it was found to be dex on the Zinn–West metallicity scale, or dex on the Carretta–Gratton scale. The distance modulus of the cluster is estimated to be (or 14.62, if we correct for the reddening to the cluster). The horizontal branch of NGC 6779 shows a clear gap at . Finally, the revised value for the metallicity of NGC 6779 led to a revision of its age to 13 Gyr, using the age-index calibrations of Salaris & Weiss. [ABSTRACT FROM AUTHOR]
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