Abundances in Stars from the Red Giant Branch Tip to Near the Main-Sequence Turnoff in M71. II. Iron Abundance
We present [Fe/H] abundance results that involve a sample of stars with a wide range in luminosity, from luminous giants to stars near the turnoff in a globular cluster. Our sample of 25 stars in M71 includes 10 giant stars more luminous than the RHB, three horizontal branch stars, nine giant stars less luminous than the RHB, and three stars near the turnoff. We analyzed both Fe I and Fe II lines in high-dispersion spectra observed with HIRES at the W. M. Keck Observatory. We find that the [Fe/H] abundances from both Fe I and Fe II lines agree with each other and with earlier determinations. Also the [Fe/H] obtained from Fe I and Fe II lines is constant within the rather small uncertainties for this group of stars over the full range in T_(eff) and luminosity, suggesting that non-LTE effects are negligible in our iron abundance determination. In this globular cluster, there is no difference among the mean [Fe/H] of giant stars located at or above the RHB, RHB stars, giant stars located below the RHB and stars near the turnoff.
Additional Information© 2001 The American Astronomical Society. Received 2001 March 29; accepted 2001 May 18. Based on observations obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The entire Keck/HIRES and LRIS user community owes a huge debt to Jerry Nelson, Gerry Smith, Steve Vogt, Bev Oke, and many other people who have worked to make the Keck telescope and HIRES and LRIS a reality and to operate and maintain the Keck Observatory. We are grateful to the W. M. Keck Foundation for the vision to fund the construction of the W. M. Keck Observatory. We thank R. Gratton for providing a detailed description of his automatic equivalent width measuring program and R. Pogge for providing the Gaussian profile-fitting routine. Partial support to M. M. B. was provided by a Theodore Dunham, Jr., grant for research in astronomy and by the National Science Foundation under grant AST 96-24680 to M. M. B. and grant AST 98-19614 to J. G. C.
Published - Ramírez_2001_AJ_122_1429.pdf
Accepted Version - 0103494.pdf