Free Access
Astron. Astrophys. Suppl. Ser.
Volume 136, Number 3, May I 1999
Page(s) 461 - 470
Published online 15 May 1999
DOI: 10.1051/aas:1999228

Astron. Astrophys. Suppl. Ser. 136, 461-470

Deep multicolor CCD photometry of the globular cluster NGC 6723[*]

G. Alcaíno1 - W. Liller1 - F. Alvarado 1 - A. Mironov2 - A. Ipatov3 - A. Piskunov3 - N. Samus3 - O. Smirnov3

Send offprint request: G. Alcaíno

1 - Isaac Newton Institute, Ministry of Education of Chile, Casilla 8-9, Correo 9, Santiago, Chile
2 - Sternberg Astronomical Institute and Isaac Newton Institute Moscow Branch, 13 University Ave., Moscow 119899, Russia
3 - Institute of Astronomy of Russian Acad. Sci. and Isaac Newton Institute Moscow Branch, 48 Pyatnitskaya Str., Moscow 109017, Russia e-mail:,,,

Received November 17, 1998; accepted March 23, 1999


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 $E(B-V) =0.11\pm{}0.01$. The most plausible value of metallicity is $\rm [Fe/H]=-1.22\pm{}0.15$;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 (1992). 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.

Key words: globular clusters: individual (NGC 6723)

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