We present BV photometry for 54 variables in the metal-rich inner halo globular cluster NGC 6723 .
With the discovery of new RR Lyrae variables ( RRLs ) , we obtain \langle P _ { ab } \rangle = 0.541 \pm 0.066 and \langle P _ { c } \rangle = 0.292 \pm 0.030 day , n ( c ) /n ( ab+c ) = 0.167 , and \langle V \mathrm { ( RR ) } \rangle _ { \mathrm { int } } = 15.459 \pm 0.055 .
We carry out the Fourier decomposition analysis and obtain [ Fe/H ] _ { \mathrm { ZW } } = - 1.23 \pm 0.11 and E ( B - V ) = 0.063 \pm 0.015 for NGC 6723 .
By calibrating the zero-point from the recent absolute trigonometric parallax measurements for RR Lyr , we derive the revised M _ { V } ( \mathrm { RR } ) - [ Fe/H ] relation , providing M _ { V } ( \mathrm { RR } ) = 0.52 at [ Fe/H ] = - 1.50 and ( m - M ) _ { 0 } = 18.54 for Large Magellanic Cloud ( LMC ) , in excellent agreement with others .
We obtain ( m - M ) _ { 0 } = 14.65 \pm 0.05 , equivalent to the distance from the Sun of 8.47 \pm 0.17 kpc , for NGC 6723 from various distance measurement methods using RRLs .
We find that RRLs in NGC 6723 do not have magnitude dependency on the radial distance , due to a not severe degree of the apparent crowdedness .
Finally , we show that there exists a relation between the degree of photometric contamination and the apparent crowdedness of the central region of globular cluster systems , | \bar { \mu } - \mu _ { r } | \propto \log \rho _ { c } d ^ { 2 } .
The use of this relation can play a significantly role on mitigating the discrepancy to establish a cosmic distance scale using RRLs in resolved stellar populations in the near-field cosmology .