Volume 393, Number 2, October II 2002
|Page(s)||617 - 628|
|Section||Stellar structure and evolution|
|Published online||23 September 2002|
Lithium 6104 Å in Population II stars
Department of Physics, Keele University, Keele, Staffordshire, ST5 5BG, UK e-mail: email@example.com; firstname.lastname@example.org; email@example.com
2 Department of Physics and Astronomy, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK e-mail: firstname.lastname@example.org
3 National Astronomical Observatory of Japan, Mitaka, Tokyo, 181-8588 Japan e-mail: email@example.com; firstname.lastname@example.org
4 School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9SS, UK
5 Laboratoire d'Astrophysique, Observatoire de Grenoble, BP 53, 38041 Grenoble, Cedex 9, France e-mail: email@example.com
6 Observatoire de Genève, 51 Chemin des Maillettes, 1290 Sauverny, Switzerland
Corresponding author: A. Ford, firstname.lastname@example.org
Accepted: 11 July 2002
We have obtained échelle spectroscopy of 14 Population II objects selected from those previously observed by Bonifacio & Molaro (1997). For one object, HD 140283, we obtained exquisite data with the High Dispersion Spectrograph on the Subaru Telescope, with exceeding 1000 per 0.018 Å pixel. Li abundances have been determined by spectral synthesis from both the 6708 Å resonance line and also from 6104 Å subordinate feature. Firm detections of the weak line have been made in seven objects, and upper limits are reported for the remainder. Our 6708 Å abundances agree with those reported by Bonifacio & Molaro with a mean difference of only 0.019 ± 0.009 dex. Abundances from the 6104 Å line hint at a higher Li abundance than that determined from the resonance feature, but this evidence is mixed; the weakness of the 6104 Å line and the large number of upper limits make it difficult to draw firm conclusions. NLTE-corrections increase (rather than eliminate) the size of the (potential) discrepancy, and binarity appears unlikely to affect any abundance difference. The effect of multi-dimensional atmospheres on the line abundances was also considered, although it appears that use of 3-D (LTE) models could again act to increase the discrepancy, if one is indeed present.
Key words: stars: abundances / stars: Population II / stars: interiors
© ESO, 2002
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