NOAO >   Observing Info >   Approved Programs >   2004B-0175

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Proposal Information for 2004B-0175


PI: Simon C. Schuler, Clemson University, sschule@ces.clemson.edu
Address: Physics Department, 118 Kinard Laboratory, Clemson, SC 29634-0978, USA

CoI: Jeremy R. King, Clemson University

Title: Observing the (lambda) 7774 Oxygen Triplet in Hyades Dwarfs

Abstract: The high-excitation (lambda) 7774 \ionO1 triplet is often used for the derivation of stellar oxygen abundances; however, there are theoretical and observational data suggesting triplet abundances increase with increasing temperature for solar-type stars with T_\mathrmeff > 6100 \; \mathrmK. These triplet overabundances are believed to be due to NLTE effects in the warm stars. Our recent study of the triplet in NOAO/HET Pleiades (100 Myr) and Keck M34 (250 Myr) spectra has revealed an increase in triplet abundance with \textitdecreasing temperature for stars with T_\mathrmeff < 5700 \; \mathrmK, in stark disagreement with current NLTE calculations. While this is not understood, one possibility is that the trend is produced by local photospheric inhomogeneities due to spots and/or other activity-related phenomena. If true, the presumed decline in activity (e.g. spot coverage) with age would point to a similar reduction in the triplet abundance trend. We propose to observe 25-30 cool Hyades dwarfs (600 Myr) with the KPNO 4-m telescope to investigate the behavior of triplet abundances in these stars. These observations will allow us to place important constraints on the possible correlation between cluster age and observed triplet abundance trends.


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NOAO >   Observing Info >   Approved Programs >   2004B-0175

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