NOAO >   Observing Info >   Approved Programs >   2009B-0078

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Proposal Information for 2009B-0078


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

CoI: Hannes Richter, University of Vienna
CoI: Alessandro Bressan, INAF, Astronomical Observatory Padova
CoI: Ken Hinkle, NOAO

Title: The role of stellar variability in mid-IR circumstellar spectra

Abstract: Theoretical investigations of the mass loss process in M giants stress the need of suitable observations that are able to clarify the role of dust in the circumstellar envelopes. Such an observational picture has been recently provided by Lebzelter et al. (2006) who showed that there is a well defined sequence of circumstellar dust along the AGB of the globular cluster 47 Tuc. The proposed evolutionary scenario, however, was based on spectra from only one epoch while previous investigations indicated possible variations of the shape of the dust features with pulsation phase. As discussed in Lebzelter et al. (2006) stellar variability would allow us to understand part of the scatter in the observed mid-IR spectra of AGB stars in this cluster. Here we propose testing this hypothesis by re-observing these stars in this cluster using T-ReCS at Gemini South. Our aim is a thorough sampling of the dust sequence along the AGB that serves as a solid basis for theoretical investigations.


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