NOAO >   Observing Info >   Approved Programs >   2009B-0083

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Proposal Information for 2009B-0083


PI: Thomas Lebzelter, University of Vienna, lebzelter@astro.univie.ac.at
Address: Department of Astronomy, Tuerkenschanzstrasse 17, Vienna A1180, Austria

CoI: Kenneth Hinkle, NOAO
CoI: Oscar Straniero, INAF Teramo
CoI: Michael Lederer, University of Vienna

Title: A taste of the interior: oxygen abundances in cluster red giants

Abstract: In our current understanding fo stellar evolution mixing processes play a key role. The mixing processes also are a critical step in the cosmic matter cycle. The surface abundance of stars is modified by a series of mixing events during the advanced stages of stellar evolution. This can be studied best by measurements in cluster AGB stars. Many aspects of the mixing are not yet fully understood. Here we want to focus on understanding the role of non-convective (`extra') mixing. We propose to observe the isotopic ratios of oxygen, which are expected to be very sensitive to the depth reached by the mixing events, in a sample of AGB stars from the cluster 47 Tuc. While third dredge up should not occur due to the low mass of these stars, extra-mixing is expected to have affected the surface abundances both during the RGB and AGB phase. Furthermore, our studies will provide a highly needed data point at the low mass end for testing the predicted relation between mass and isotopic ratios.


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NOAO >   Observing Info >   Approved Programs >   2009B-0083

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