Up: Deep multicolor CCD photometry NGC 6723
From our CCD photometry of 3620 stars in the globular cluster
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. Note that the method suggested
by Sarajedini (1994) leads to an unacceptably low metallicity for
NGC 6723. The apparent distance modulus of the
cluster is (m-M)V,6723=14.76. From isochrone analysis,
we prefer the NGC 6752 age in the range between 15 and 16 Gyr,
in the scale of
Bergbusch & VandenBerg (1992). We have found an interesting
separation of blue and red horizontal branches, near the
region of the instability strip, by U magnitude in the
diagram.
The shape and slope of the RGB in NGC 6723 which we derive are
practically the same as in M 3. Remarkably, our value
for NGC 6723 is almost exactly the
same as those found by other authors for M 3 (3.52;
Ferraro et al. 1996)
and for M 5 (3.47; Sandquist et al. 1996). This similarity of the three clusters with
intermediate morphology of the horizontal branch should be
taken into account when analyzing the "second parameter''
problem.
Acknowledgements
We wish to thank Mr. Oleg Lahtionov for assistance during this
study.
Up: Deep multicolor CCD photometry NGC 6723
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