Astronomy and Astrophysics – Astronomy
Scientific paper
Feb 2004
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004apj...602l.117s&link_type=abstract
The Astrophysical Journal, Volume 602, Issue 2, pp. L117-L120.
Astronomy and Astrophysics
Astronomy
24
Galaxy: Open Clusters And Associations: Individual: Messier Number: M34, Galaxy: Open Clusters And Associations: Individual: Name: Pleiades, Stars: Abundances, Stars: Atmospheres, Stars: Late-Type, Stars: Population Ii
Scientific paper
We analyze the high-excitation O I λ7774 triplet in high-resolution, moderate signal-to-noise ratio spectra of 15 Pleiades and eight M34 open cluster dwarfs over the effective temperature range of 5048-6172 K. Relative O abundances have been derived using model atmospheres interpolated from four different sets of ATLAS9 grids. In contrast to existing non-LTE (NLTE) predictions, a dramatic increase in the O I triplet abundance with decreasing temperature is seen for both clusters, regardless of the atmospheric model. S I abundances of three Pleiades stars derived from the high-excitation λ6053 feature mimic the O I abundance behavior. O abundances have also been derived from the [O I] λ6300 feature in three Pleiades stars; the abundances exhibit a much lower mean value than do the cool dwarf triplet results. Inasmuch as the [O I] abundances are presumed to be free from NLTE effects, their mean values ([O/H]6300=+0.14) provide the current best estimate of the Pleiades O abundance. Spreads in [O/H]Trip at a given temperature are also seen in both clusters; no correlation is found between the spreads and the chromospheric emission measures.
Based on observations obtained with the High Resolution Spectrograph on the Hobby-Eberly Telescope, which is operated by McDonald Observatory on behalf of the University of Texas at Austin, Pennsylvania State University, Stanford University, the Ludwig-Maximillians-Universitaet, Munich, and the George-August-Universitaet, Goettingen. Public Access time is available on the Hobby-Eberly Telescope through an agreement with the National Science Foundation.
Hobbs Lew M.
King Jeremy R.
Pinsonneault Marc H.
Schuler Simon C.
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