Astron. Astrophys. Suppl. Ser.
Volume 136, Number 3, May I 1999
|Page(s)||461 - 470|
|Published online||15 May 1999|
Deep multicolor CCD photometry of the globular cluster NGC 6723 *
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
Send offprint request to: G. Alcaíno
Accepted: 23 March 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 . The most plausible value of metallicity is ; even lower values are possible. The apparent distance modulus of the cluster is . 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)
© European Southern Observatory (ESO), 1999