The Blue Hook Populations of Massive Globular Clusters
Abstract
We present new HST ultraviolet color-magnitude diagrams of 5 massive Galactic globular clusters: NGC 2419, NGC 6273, NGC 6715, NGC 6388, and NGC 6441.  These observations were obtained in order to investigate the "blue hook" phenomenon previously observed in HST ultraviolet images of the globular clusters omega Cen and NGC 2808.  Blue hook stars are a class of hot (approximately 35,000 K) subluminous horizontal branch stars that occupy a region of the HR diagram that is unexplained by canonical stellar evolution theory.  By coupling new stellar evolution models to appropriate non-LTE synthetic spectra, we investigate various theoretical explanations for these stars.  Specifically, we compare the color-magnitude diagrams to stellar models that assume normal evolution at cluster abundances, models with enhanced helium resulting from cluster self-enrichment, and flash-mixed models formed via late helium core flash on the white dwarf cooling curve.
- Publication:
-
American Astronomical Society Meeting Abstracts #215
- Pub Date:
- January 2010
- Bibcode:
- 2010AAS...21542516B