Fundamental parameters of hot subdwarf stars from the Tycho-Gaia sample

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The fundamental parameters of hot evolved stars, like masses and radii, are poorly constrained. Hot subdwarf stars (sdO/B) are compact helium stars and constitute an important population of hot evolved stars. They dominate old stellar populations in the ultraviolet and are key objects to study peculiar events in stellar evolution as diverse as the interaction of stars and planets or the progenitors of type Ia supernovae. With accurate distances from the Gaia mission available from 2016 we will be able to determine the fundamental parameters of those stars and study their formation. To achieve this, we have to improve the atmospheric models for those peculiar objects and minimize systematics using a homogeneous dataset of high quality. We were granted five nights with the IDS spectrograph at the Isaac Newton telescope for this project. Here propose funds to cover the expenses of this observing run.