Multi-wavelength Hubble Space Telescope photometry of stellar populations in NGC288

TL;DR

This study uses combined UV and optical Hubble Space Telescope photometry to identify and quantify helium variation among multiple stellar populations in the globular cluster NGC288.

Contribution

It demonstrates the effectiveness of combining UV and optical data to measure helium enrichment in globular cluster populations, providing new insights into stellar population complexity.

Findings

Helium variation in NGC288 is typical of other globular clusters.

UV filters effectively distinguish multiple stellar populations.

Optical data reveal helium enhancement related to stellar-structure changes.

Abstract

We present new UV observations for NGC288, 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 tell-tale 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 helium variation. We quantify this enhancement for NGC288 and find that its variation is typical of what we have come to expect in other clusters.