AAS 205th Meeting, 9-13 January 2005
Session 22 Open Clusters Young and Old
Poster, Monday, January 10, 2005, 9:20am-6:30pm, Exhibit Hall

[22.06] Oxygen in Hyades G & K Dwarfs

S.C. Schuler (Clemson Univ.), A.P. Hatzes (Tautenburg Observatory), J.R. King (Clemson Univ.), M. Kürster (Max Planck Inst. Astronomie)

Deriving accurate O abundances in various collections of Galactic stellar populations is critical to our understanding of Galactic chemical evolution. Unfortunately, measurable OI lines in the visible spectral region are limited to two sets of features. The first is the strong, high-excitation \lambda \; 7775 triplet, which is known to be affected by NLTE conditions. The second is the pair of [OI] forbidden lines at 6300 and 6363 \; \mathrm{Å}, which are quite weak in solar-type stars (~5 \; \mathrm{and} \; ~3 \; \mathrm{mÅ}, respectively, in the Sun) and are blended with other absorption features. Abundances derived from the triplet are seen to be discrepantly high compared to those derived from the [OI] \lambda 6300 forbidden line, which have been shown to be immune from NLTE effects, in dwarfs with T\mathrm{eff} greater than ~6300 \; \mathrm{K}. Indeed, current NLTE calculations predict such behavior. More recently, our study of cool Pleiades and M34 dwarfs (T\mathrm{eff} < 5600 \; \mathrm{K}) revealed a trend of increasing O abundances derived from the triplet with \textit{decreasing} T\mathrm{eff}, contrary to current NLTE predictions. We have continued our investigation of dwarf O abundances with the Hyades open cluster and present our preliminary results.

This work was supported by the South Carolina Space Grant Consortium through the Graduate Student Research Fellowship awarded to S.C.S., and by grants AST 00-86576 and AST 02-39518 to J.R.K. from the National Science Foundation.