1999A&AS..136..461A

We have obtained CCD UBVRI photometry of 3620 stars in the globular cluster NGC 6723, one of the few globular clusters with a horizontal branch well-populated on both sides of the instability strip. This is the first deep five-color study of NGC 6723. We have determined several important parameters for this cluster. Its color excess is E(B-V)=0.11±0.01. The most plausible value of metallicity is [Fe/H]=-1.22±0.15; even lower values are possible. The apparent distance modulus of the cluster is (m-M)_V,6723=14.76. From isochrone analysis, we prefer the NGC 6723 age in the range between 15 and 16 Gyr, in the scale of Bergbusch & VandenBerg (1992ApJS...81..163B). We find a close similarity of the shape and slope of the red giant branch in NGC 6723 and M 3 and of the magnitude difference between the main-sequence turnoff and the horizontal branch in NGC 6723, M 3, and M 5.