A NEW VISIT TO THE VARIABLE STARS IN M56 AND ITS COLOUR-MAGNITUDE DIAGRAM STRUCTURE

We present a $VI$ CCD photometric study and membership analysis of the globular cluster M56 (NGC 6779). This produced decontaminated CMD from field stars, which enabled better confrontation with theoretical isochrones; Zero-Age Horizontal Branches (ZAHB) post-ZAHB evolutionary tracks. Post He-flash models He-core mass 0.5 M$_\odot$ envelopes 0.04 - 0.18 M$_\odot$, cover complete Branch. Models total $\sim$ 0.68 explain RR Lyrae, while those 0.56 very subtle envelope, Pop II cepheids progenitor in blue tail HB. %Using mean $(V-I)$ at minimum color curve for RRab we derived value reddening $E(B-V)$ = 0.26 $\pm$ 0.02. Based on Fourier decomposition $V$ light single member RRc star, determined metallicity $\rm [Fe/H]_{ ZW}$ -1.96 0.09. Several independent distance determination approaches lead to $\big< d \big>$ 9.4 0.4 kpc. Finally, report 5 new variables: 1 SX Phe, 3 EB, RRc.