CONTACT BINARIES AND SX PHE VARIABLES IN THE GLOBULAR-CLUSTER NGC-4372

NGC 4372, a southern globular cluster of very low metallicity and very low central concentration, was chosen for a CCD photometric search for short-period binaries and SX Phe variables. We report the discovery of 19 variable stars with well-determined light curves and periods. Eight of these belong to the SX Phe class, and eight are contact binaries. All the SX Phe variables are concentrated towards the centre of the cluster and are blue stragglers, while contact binaries occupy various locations in the cluster colour-magnitude diagram. Half of the SX Phe stars pulsate in the fundamental mode, and the other half probably pulsate in the first overtone. An eclipsing variable that is either a short-period detached main-sequence binary or a cataclysmic binary is discovered. The photometry confirms earlier findings of variable reddening within the cluster area.