Poster abstract details
Evolution and Internal Structure of Extended Horizontal Branch Stars
Abstract
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.
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.