Poster abstract details

Extended Horizontal Branch (EHB) stars are observed in many globular clusters and as field stars in the Galactic halo. Their evolutionary status is unclear, and a subject of debate. Current interest in these stars arise from their association with the discoveries of helium abundance inhomogeneities in the globular clusters $\omega$ Cen and NGC 2808. The origin of the inhomogeneities is not yet understood.

In order to shed light on the internal structure and evolutionary status of EHB stars, we explore the evolution of standard blue HB models using up-to-date physics. We present a grid of post-ZAHB evolutionary tracks that cover the EHB. We follow the stars to the termination of the nuclear burning phases of helium and hydrogen shell burning and associated shell flashes. The detailed properties of the sequence of helium shell flashes are described. We compare our models to observations of EHB stars by the FUSE mission.