CCD PHOTOMETRY IN THE GLOBULAR-CLUSTER NGC-288 .1. BLUE STRAGGLERS AND MAIN-SEQUENCE BINARY STARS

Photometry based on a mosaic of CCD images in B and V is presented for the globular cluster NGC 288. The spatial coverage ranges from the cluster core to approximately 6 core radii, and stars have been measured over the absolute visual magnitude range -1.2 less than or similar M(v) less than or similar 8.4. The cluster is shown to contain a significant number of blue straggler stars in the central regions, and there is an excess of objects brighter and redder than the single-star main-sequence in the color-magnitude plane. These objects are interpreted as a population of main-sequence binary stars. With this interpretation, the explicitly measured fraction of binary stars is 10%, which sets a lower limit for the total binary population.