METAL-POOR LITHIUM-RICH GIANTS IN THE RADIAL VELOCITY EXPERIMENT SURVEY

Journal Article · Tue Dec 20 04:00:00 EST 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/743/2/107· OSTI ID:22004462

Ruchti, Gregory R; Fulbright, Jon P; Wyse, Rosemary F. G. ^[1]; Gilmore, Gerard F ^[2]; Grebel, Eva K ^[3]; Bienayme, Olivier; Siebert, Arnaud ^[4]; Bland-Hawthorn, Joss ^[5]; Freeman, Ken C ^[6]; Gibson, Brad K ^[7]; Munari, Ulisse ^[8]; Navarro, Julio F ^[9]; Parker, Quentin A; Watson, Fred G ^[10]; Reid, Warren ^[11]; Seabroke, George M ^[12]; Siviero, Alessandro ^[13]; Steinmetz, Matthias; Williams, Mary ^[14]; Zwitter, Tomaz ^[15]

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1. Bloomberg Center for Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States)
2. Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom)
3. Astronomisches Rechen-Institut, Zentrum fuer Astronomie der Universitaet Heidelberg, Moenchhofstr. 12-14, D-69120 Heidelberg (Germany)
4. Observatoire de Strasbourg, 11 Rue de l'Universite, F-67000 Strasbourg (France)
5. Sydney Institute for Astronomy, School of Physics A28, University of Sydney, NSW 2006 (Australia)
6. RSAA Australian National University, Mount Stromlo Observatory, Cotter Road, Weston Creek, Canberra, ACT 2611 (Australia)
7. Jeremiah Horrocks Institute for Astrophysics and Super-computing, University of Central Lancashire, Preston PR1 2HE (United Kingdom)
8. INAF Osservatorio Astronomico di Padova, Via dell'Osservatorio 8, I-36012 Asiago (Italy)
9. Department of Physics and Astronomy, University of Victoria, P.O. Box 3055, Station CSC, Victoria, BC V8W 3P6 (Canada)
10. Australian Astronomical Observatory, Coonabarabran, NSW 2357 (Australia)
11. Department of Physics and Astronomy, Macquarie University, Sydney, NSW 2109 (Australia)
12. Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking RH5 6NT (United Kingdom)
13. Department of Astronomy, Padova University, Vicolo dell'Osservatorio 2, I-35122 Padova (Italy)
14. Leibniz-Institut fuer Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam (Germany)
15. Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, SK-1000 Ljubljana (Slovenia)

We report the discovery of eight lithium-rich field giants found in a high-resolution spectroscopic sample of over 700 metal-poor stars ([Fe/H] < -0.5) selected from the Radial Velocity Experiment survey. The majority of the Li-rich giants in our sample are very metal-poor ([Fe/H] {approx}< -1.9), and have a Li abundance (in the form of {sup 7}Li), A(Li) = log (n(Li)/n(H)) + 12, between 2.30 and 3.63, well above the typical upper red giant branch (RGB) limit, A(Li) < 0.5, while two stars, with A(Li) {approx} 1.7-1.8, show similar lithium abundances to normal giants at the same gravity. We further included two metal-poor, Li-rich globular cluster giants in our sample, namely the previously discovered M3-IV101 and newly discovered (in this work) M68-A96. This comprises the largest sample of metal-poor Li-rich giants to date. We performed a detailed abundance analysis of all stars, finding that the majority of our sample stars have elemental abundances similar to that of Li-normal halo giants. Although the evolutionary phase of each Li-rich giant cannot be definitively determined, the Li-rich phase is likely connected to extra mixing at the RGB bump or early asymptotic giant branch that triggers cool bottom processing in which the bottom of the outer convective envelope is connected to the H-burning shell in the star. The surface of a star becomes Li-enhanced as {sup 7}Be (which burns to {sup 7}Li) is transported to the stellar surface via the Cameron-Fowler mechanism. We discuss and discriminate among several models for the extra mixing that can cause Li production, given the detailed abundances of the Li-rich giants in our sample.

• OSTI ID: 22004462
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 743; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABUNDANCE
BERYLLIUM 7
GRAVITATION
LITHIUM
RADIAL VELOCITY
STAR EVOLUTION
STARS