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Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Discovery of a super-Li-rich turnoff star in the metal-poor globular cluster NGC 6397
AU - Koch, Andreas
AU - Lind, Karin
AU - Rich, R. Michael
PY - 2011/8/23
Y1 - 2011/8/23
N2 - We report on the discovery of a super-Li-rich turnoff (TO) star in the old (12 Gyr), metal-poor ([Fe/H] = –2.1 dex) globular cluster (GC) NGC 6397, based on high-resolution MIKE/Magellan spectra. This star shows an unusually high lithium abundance of A(Li)NLTE = 4.03 ± 0.06 ± 0.14 dex (or, 4.21, accounting for possible contamination from a binary companion) that lies above the canonical Li-plateau by a factor of 100. This is the highest Li enhancement found in a Galactic GC dwarf star to date. We discuss several enhancement mechanisms, but none can unambiguously explain such a high overabundance. The spectrum of the star shows a possible indication of binarity, but its line strengths and chemical element abundance ratios are fully compatible with other TO stars in this GC, seemingly ruling out mass transfer from an asymptotic giant branch companion as origin of the high A(Li). A possible cause is an interaction with a red giant that has undergone cool bottom processing.
AB - We report on the discovery of a super-Li-rich turnoff (TO) star in the old (12 Gyr), metal-poor ([Fe/H] = –2.1 dex) globular cluster (GC) NGC 6397, based on high-resolution MIKE/Magellan spectra. This star shows an unusually high lithium abundance of A(Li)NLTE = 4.03 ± 0.06 ± 0.14 dex (or, 4.21, accounting for possible contamination from a binary companion) that lies above the canonical Li-plateau by a factor of 100. This is the highest Li enhancement found in a Galactic GC dwarf star to date. We discuss several enhancement mechanisms, but none can unambiguously explain such a high overabundance. The spectrum of the star shows a possible indication of binarity, but its line strengths and chemical element abundance ratios are fully compatible with other TO stars in this GC, seemingly ruling out mass transfer from an asymptotic giant branch companion as origin of the high A(Li). A possible cause is an interaction with a red giant that has undergone cool bottom processing.
U2 - 10.1088/2041-8205/738/2/L29
DO - 10.1088/2041-8205/738/2/L29
M3 - Journal article
VL - 738
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
SN - 2041-8205
IS - 2
M1 - L29
ER -