Die Entstehung He-dominierter post-AGB Sterne
Zusammenfassung der Projektergebnisse
So far, no systematic search for close binaries amongst He-rich post-AGB stars was made. Based on the previous analyses we estimate the close binary fraction of these objects to be higher than 5%, which leads to a detection probability of 1 of 20. To detect other close binary systems, we aim to search for RV shifts on short time scales (hours to a few days) in medium-resolution spectra in a large sample of the brightest O(He), He-rich PG1159 stars and DO WDs. The detection of these RV shifts would identify those stars as close binaries and thus provide valuable information on their evolutionary history. We performed long-slit spectroscopy with TWIN at the 3.5m telescope at Calar Alto Observatory using grating No. T08 for the blue channel and grating No. T04 for the red channel to achieve a good resolution for all optical He II lines. In total, 51 spectra of ten different objects were taken. Three nights had good weather conditions, the last night was too cloudy to obtain spectra. The data is currently being analysed.
