Other
Scientific paper
May 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994aj....107.1773s&link_type=abstract
The Astronomical Journal, vol. 107, no. 5, p. 1773-1785
Other
84
Abundance, Astronomical Models, Giant Stars, Globular Clusters, Halos, M Stars, Metallicity, Oxygen, Stellar Spectra, Astronomical Observatories, Data Reduction, Echelle Gratings, High Dispersion Spectrographs, Signal To Noise Ratios, Spectral Line Width, Telescopes
Scientific paper
We present oxygen, sodium, silicon, calcium, scandium, titanium, vanadium, iron, and nickel abundances for bright giants in M71, a relatively metal-rich globular cluster having a space motion like that of the thick disk. The abundances were obtained from analysis of Lick Observatory Hamilton Echelle spectra centered on the (O I) doublet. We find (Fe/H) = -0.79 +/- 0.01 from ten giants covering a range of 400 K in effective temperature. Iron peak and traditional alpha elements show no significant variations from one star to another. Oxygen and sodium appear to vary, but the range is barely significant, and is smaller than found earlier in M92, M13, M3, and M5. Two of the three stars with low oxygen have higher than average sodium abundances, but one low oxygen star also has relatively low sodium. Whether there exists an anticorrelation between (Na/Fe) and (O/Fe) is much less clear in the case of M71 than in the halo clusters studied in earlier papers of this series. For M71 giants, the combination of literature and present results confirms the existence of first dredge-up convective envelope mixing of C-12 yields C-13 and C yields N, but evidence for very deep mixing to O-depleted and Na-enhanced burning layers remains marginal. Primordial abundance fluctuations probably also play a role in the M71 light element abundances. Although most traditional alpha elements are slightly overabundant relative to Fe as expected, M71 giants are unusual in that the mean (Ti/Fe) ratio of +0.5 appears to be quite large, a property shared in common with a sample of giants in the region of the galactic bulge (McWilliam & Rich, (1993)).
Kraft Robert P.
Langer Edward G.
Prosser Charles F.
Shetrone Matthew D.
Sneden Christopher
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