Abstract

Contributed Talk - Splinter CloseBinaries   (MW-0250)

Quantitative spectroscopic analysis of He-sdO stars

Zoë Kaffarnik, Dr. Matti Dorsch
Institute for Physics and Astronomy, University of Potsdam

Hot subdwarf stars are core helium-burning objects located at the extreme blue end of the horizontal branch. Helium-rich subdwarf O (He-sdO) stars constitute a rare subclass characterized by helium-dominated atmospheres and complex chemical abundance patterns, whose evolutionary origin remains under debate. Mergers involving helium white dwarfs as well as late hot helium flashes of stripped stars are the currently favoured scenarios. Determining the abundances of heavy elements provides important constraints on the interplay of diffusion processes and stellar evolution. In this project, we perform a quantitative spectroscopic analysis of He-sdO stars using ultraviolet spectra obtained with the Hubble Space Telescope (HST). Atmospheric parameters and elemental abundances are derived by comparing the observations with non-local thermodynamic equilibrium (non-LTE) synthetic spectra computed with TLUSTY and SYNSPEC.