MULTI-WAVELENGTH HUBBLE SPACE TELESCOPE PHOTOMETRY OF STELLAR POPULATIONS IN NGC 288

We present new UV observations for NGC 288, taken with the WFC3 detector on board the Hubble Space Telescope, and combine them with existing optical data from the archive to explore the multiple-population phenomenon in this globular cluster (GC). The WFC3's UV filters have demonstrated an uncanny ability to distinguish multiple populations along all photometric sequences in GCs thanks to their exquisite sensitivity to the atmospheric changes that are telltale signs of second-generation enrichment. Optical filters, on the other hand, are more sensitive to stellar-structure changes related to helium enhancement. By combining both UV and optical data, we can measure the helium variation. We quantify this enhancement for NGC 288 and find that the variation is typical of what we have come to expect in other clusters. © 2013. The American Astronomical Society. All rights reserved.