THE OPTICAL GRAVITATIONAL LENSING EXPERIMENT - VARIABLE-STARS IN GLOBULAR-CLUSTERS - IV - FIELDS 104A-E IN 47-TUCANAE

Five fields located close to the center of the globular cluster NGC 10 4 = 47 Tuc were surveyed in a search for variable stars. We present V- band light curves for 42 variables. This sample includes 13 R.R Lyr st ars - 12 of them belong to the Small Magellanic Cloud (SMC) and 1 is a background object from the galactic halo. Twelve eclipsing binaries w ere identified - 9 contact systems and 3 detached/semi-detached system s. Seven eclipsing binaries are located in the blue straggler region o n the cluster color-magnitude diagram (CMD) and four binaries can be c onsidered main-sequence systems. One binary is probably a member of th e SMC. Eight. contact binaries are likely members of the cluster and o ne is most probably a foreground star. We show that for the surveyed r egion of 47 Tuc, the relative frequency of contact binaries is very lo ur as compared with other recently surveyed globular clusters. The sam ple of identified variables also includes 15 red variables with period s ranging from about 2 days to several weeks. A large fraction of thes e 15 variables probably belong to the SMC but a few stars are likely t o be red giants in 47 Tuc. VI photometry for about 50 000 stars from t he cluster fields was obtained as a by product of our survey(1).