Observations of extreme horizontal branch stars in the globular cluster M13

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We will conduct spectroscopic observations of extreme horizontal branch (EHB) stars in the globular cluster M13 using the 3.5m telescope at the Calar Alto Observatory. Optical spectra are most important for deriving atmospheric parameters which in turn allows to characterize the horizontal branch (HB) population and relate it to the other cluster's properties. Despite their relative brightness, EHB stars in M13 have never been observed in spectroscopy. Our observations will allow us to have a first glance at their spectroscopic properties and compare them to that of similar stars in other globular clusters.